Klairs Freshly Juiced Vitamin C Drop Review

Klairs Freshly Juiced Vitamin C Drop Review

15 Foods High in Vitamin C

Fact Checked Updated: Mar 2, 2021

Vitamin C keeps the immune system healthy, helping treat infections, viruses, and other conditions. Although research has not proven that vitamin C prevents the common cold, it can help people recover more quickly, and it may reduce the severity of the virus. Though most people think of oranges and orange juice, vitamin C is in many common foods.

Chili Peppers

Chili peppers can be used to spice up just about any dish, and they up your vitamin C intake, too. In addition to burning your tongue, a half cup of diced chili peppers contains more than 100 percent of your recommended daily vitamin C. They also have plenty of other nutrients, like vitamins A and B6 and potassium. To add chili peppers to your diet, try dicing and putting them into soups, curries or meat dishes for a little extra spice. In addition to vitamin C's effects on viruses, the capsaicin in chili peppers can help to clear nasal passages and relieve headaches during cold season, too.

Strawberries

Strawberries are not just delicious; they are one of the best sources of vitamin C, containing even more than oranges. They're also a great source of folate, antioxidants, manganese, and potassium. Strawberries are easy to add to your diet; they can top yogurt or cereal, sweeten smoothies, make a great, simple snack.

Mangos

If you want to consume more vitamin C, turn to mangos. One cup of diced mango pieces can meet your daily recommended intake of vitamin C. Due to their size, eating an entire mango can provide nearly twice the recommended amount. That boost may help to keep you healthy and decrease viral recovery time. Mangos might not be as popular as apples and oranges in the produce section, but given how much protein, potassium, and vitamins are packed into these fruits, maybe they should be!

Sweet Peppers

If chili peppers are too much, sweet peppers can also provide vitamin C. A half cup of chopped green peppers has up to three times the daily recommended intake of vitamin C, and the more colorful sweet peppers contain more than 100%. Raw vegetables contain the most nutrients, so try snacking on raw slices and low-fat dip or dicing them up for salads. Even cooked peppers retain a lot of their nutritional benefits.

Kohlrabi

This turnip-looking green root vegetable is a member of the cabbage family and a cup gives you more than the recommended daily amount of Vitamin C. Kohlrabi contains many key nutrients, including vitamin C, fiber and antioxidants, potassium, magnesium, and vitamin B6. The sweet, crunchy, lightly flavored veggie is delicious raw, but can also be steamed as a side dish.

Kale

Kale is a superfood because of high levels of vitamin K and vitamin A, but it's also a great source of vitamin C, containing about 130% of the daily recommended amount in every cup. In addition, kale is full of iron, omega-3 fatty acids, and other important nutrients. It's easy to add more kale to your diet by swapping it for lettuce in salads or adding it to smoothies.

Pineapple

A cup of pineapple has more than 75 mg of vitamin C. Pineapples have a lot of bromelain, an enzyme that can help with food breakdown during digestion, improving the body;'s ability to absorb nutrients. Pineapple is available fresh, frozen, dried, and canned. Many studies suggest frozen fruit has as much, if not more, nutritional value as fresh, though it may affect the flavor.

Kiwi

Kiwi is a great snack for anyone on the go, and it's packed with vitamins C, K, and E, fiber, and potassium. Although you can eat the peel safely, the best way to eat kiwi is to cut it in half and use a spoon to scoop out the center. Kiwi also has lots of antioxidants and anti-inflammatory properties. These fruits are small and easy to prepare, so pack one to eat at your desk at work, or add them to fruit salad.

Grapefruit

The grapefruit diet might not be as trendy as it once was, but grapefruit is still an excellent source of nutrients. A great source of vitamin C, of course, the citrus fruit also contains vitamin A, potassium, and fiber. Grapefruits also offer lycopene, which has been shown to fight cancer-causing cells and reduce the risk of developing tumors. Research shows that grapefruit improves heart health, making it a good option for those with cardiovascular issues. You can drink grapefruit juice and get many of the same health benefits, but eating half a fruit for breakfast or as a mid-afternoon snack is ideal.

Cauliflower

A cup of cauliflower can meet about 85 percent of your recommended daily intake of vitamin C. This vegetable from the brassica family is a healthy way to get vitamin B6, fiber, and potassium into your diet. A cup of cauliflower only has about 25 calories. For maximum nutrients, try raw cauliflower pieces with yogurt dip. You can also steam or boil cauliflower for a healthy side dish.

Broccoli

Broccoli is packed with nearly 135 percent of the recommended daily intake of this important nutrient in a single-cup serving. It also has lots of other healthy components, like vitamin B6, vitamin A, and plenty of fiber. Both the stems and the flowering heads are edible, and the cruciferous veggie can be served cooked or raw.

Brussels Sprouts

Brussels sprouts might not be at the top of everyone's list, but they're full of vitamin C and have fewer than 40 calories per cup. They're also bursting with potassium, vitamin B6, and vitamin A, and a healthy dose of fiber. Steam or roast Brussels sprouts for a healthy, vitamin C-filled side dish with your next meal.

Guava

Guava grows primarily in Central and South America and is not always well-known to North Americans. However, just one cup of the pretty pink fruit contains a whopping 625 percent of your recommended daily vitamin C. It includes 36 percent of recommended fiber, and 20 percent of vitamin A, too. Guava has been known to help with everything from common colds to high blood pressure.

Papaya

The papaya is another tropical fruit full of vitamins and minerals. It makes a great ingredient for smoothies, salads, and other delicious dishes, and delivers about 150 percent of daily vitamin C in every cup. That amount also has less than half a gram of total fat and just 62 calories. Papaya has a sweet, tropical taste with a very smooth consistency.

Cantaloupe

Cantaloupe is a great source of vitamin C. The melon exceeds the recommended daily value for vitamin A and contains plenty of potassium, too. Because vitamin C is very beneficial to immune system function and heart health, cantaloupe is a good choice for those at risk for cardiovascular concerns. Eating a dish of cantaloupe every day can also help fend off viruses and other illnesses by strengthening the immune system.

Klairs Freshly Juiced Vitamin C Drop Review

Source: https://facty.com/food/nutrition/15-foods-high-in-vitamin-c/

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Is It Ok To Take Vitamin C And Iron Together

Is It Ok To Take Vitamin C And Iron Together

Witthaya Prasongsin / Getty Images

Key Takeaways

• It's common practice to take vitamin C with iron supplements to help with absorption.
• New research says there's not enough evidence to definitively support a need to take vitamin C with iron in people with iron deficiency anemia.
• You should still avoid taking iron with any food, antacids, or calcium to achieve the best absorption.

According to a new study, people with iron deficiency anemia (IDA) might not need to take supplemental vitamin C along with oral iron supplements to help with absorption, despite longstanding advice to do so.

The standard practice for managing IDA has been for a person to increase dietary sources of iron and take an iron supplement, as well as supplemental vitamin C or foods rich in vitamin C, Nicole DeMasi Malcher, MS, RDN, CDCES, registered dietitian and founder of DeMasi Nutrition, tells Verywell. But now, Malcher confirms that recent data "suggests vitamin C might not be necessary to absorb non-heme [not animal based] iron supplements in the body."

What Is Iron Deficiency Anemia (IDA)?

Iron deficiency anemia (IDA) occurs when the body does not have enough iron. It can be diagnosed with a simple blood test. If untreated, IDA can cause a variety of symptoms, including chronic fatigue, headaches, and an irregular heartbeat.

Anyone can become iron deficient, but some people are more likely to develop the condition. For example, pregnant people are more at risk for developing IDA because iron needs increase throughout pregnancy.

Iron and Vitamin C

Traditionally, healthcare providers have suggested that people take iron along with vitamin C to help create an acidic gastrointestinal environment, which is thought to help dissolve the iron adequately for absorption.

The new study, which was published in the November issue of the Journal of the American Medical Association, notes that there has not been a randomized clinical trial (RCT) to assess whether vitamin C supplements are necessary for patients with IDA taking iron tablets.

The Study

In the randomized clinical trial, 440 adult participants with newly-diagnosed IDA were randomly assigned to two groups. Participants in one group took oral iron supplements (in the form of ferrous succinate) plus vitamin C, and participants in the other took only oral iron supplements.

The participants who were in the iron-only group took 100-milligram (mg) iron tablets every 8 hours for three months. The participants in the iron-vitamin C group took the same dose of iron supplement plus an additional 200 mg of vitamin C.

During the several months of treatment, the researchers periodically evaluated blood samples taken from the subjects to check their iron levels.

Based on their findings, the researchers concluded that taking oral iron supplements alone provided hemoglobin level and iron storage recovery efficacy equivalent to that of oral iron supplemented with vitamin C.

It does not appear that the vitamin C boost offered benefits in terms of iron absorption.

The only possible benefit the researchers observed was that vitamin C might have a positive effect on changes in mean corpuscular volume (MCV)—the measure of the mean size of red blood cells. The researchers thought that the finding could be important because patients with IDA typically have lower than normal MCV values.

Iron Supplements

Iron supplements have been used as a standard practice for treating iron deficiency anemia. The logic behind supplementing with higher doses of iron is that the nutrition gap is filled and the deficiency can be resolved.

There are different forms of iron supplements—including ferrous succinate, the kind used in the recent study—that have been shown to be effective.

While the study suggests that combining iron supplements with vitamin C offers no clinical benefit in terms of iron absorption, other research has found otherwise.

In a 2019 article published in Geriatric Nursing, the author noted that in one study, taking 100 mg of vitamin C with a meal was found to increase iron absorption by 67%.

However, the dose matters when it comes to the data surrounding supplementation. In the recent study, "the participants took 100 mg of iron every 8 hours, which would be 300 mg per day total," Grace Goodwin Dwyer, MS, MA, RD, LDN, a registered dietitian based in Nashville, Tennessee, tells Verywell. "In contrast, people taking over-the-counter iron supplements are probably taking 30 to 60 mg per day if they're following the instructions on the packages on most major brands."

Dwyer says "it would be interesting to see in a follow-up study about how vitamin C applies to lower dosages, like many of our patients are taking."

Dietary Sources of Iron

While taking iron supplements is one way to treat IDA, including food sources of iron in your diet can also help you meet your needs.

There are two main types of iron that come from your diet:

• Heme iron is found in foods like beef and seafood options
• Non-heme iron is found in foods like vegetables, beans, and whole grains. Certain foods are also fortified with non-heme iron.

Heme iron appears to be better absorbed in the body than non-heme iron. Taking vitamin C with non-heme sources of iron may help maximize iron absorption with little risk.

Tips to Support Iron Absorption

If you're supplementing with iron, there are also some things you can do to help ensure that it's properly absorbed and used by your body—or at least, you can avoid doing things that would make it harder for your body to absorb and use the important mineral.

Take Iron Every Other Day

Data published in The Lancet in 2019 suggested that giving iron-depleted women daily iron supplements as divided doses reduced iron absorption. On the other hand, providing iron supplements in single doses on alternate days appeared to optimize iron absorption and might be a preferable dosing regimen.

Choose Your Dietary Sources Wisely

"If you're looking to boost iron absorption in your body through food, it's helpful to focus on animal sources," Dwyer says. This is because of the heme form of the iron that these foods contain. Red meat, chicken, and shellfish can be helpful additions to your diet.

If you follow a vegetarian or vegan lifestyle, know that while there are dietary iron sources that are animal-free, you may need to consider taking a supplement to prevent anemia.

Take Iron On An Empty Stomach

Iron is best absorbed when taken on an empty stomach with a full 8-ounce glass of water or orange juice. If you get an upset stomach, you can take your iron with food or immediately after meals; however, know that taking an iron supplement with food will decrease absorption to 40%.

Avoid Taking Iron With Phytate-rich and/or Polyphenol-rich Foods

You also need to be mindful of the foods and drinks you consume when you take your iron. Absorption of oral iron is inhibited by phytates (which are found in cereals and certain vegetables) and polyphenols (which are found in some vegetables, fruits, cereals, legumes, tea, coffee, and wine).

Tea has been shown to reduce iron absorption by 90%.

Do Not Take Antacids Or Calcium Supplements With Iron

Antacids or calcium supplements can decrease iron absorption and should not be taken at the same time as iron supplements. It is best to space doses of these products out. Take antacids or calcium 12 hours apart from your iron.

Ensure You Are Not Deficient in Copper

Copper is a mineral that plays a key role in helping the body absorb iron. If your copper levels are low, your body might have a hard time absorbing iron.

Consider The Pros and Cons of Taking Vitamin C With Iron

Data appears to be mixed when it comes to the benefits of taking vitamin C with iron to support absorption. If you do choose to take a vitamin C supplement, make sure that you know how much vitamin C is in the product you've chosen.

It appears that vitamin C needs to be taken in a dose of 200 mg to reap the potential benefit.

While taking supplemental vitamin C is low-risk, it's not risk-free. For example, if you don't tolerate the dose, you might experience gastrointestinal symptoms like nausea and diarrhea. You should also know that some prescription and over-the-counter (OTC) medications don't mix with vitamin supplements, including vitamin C. If you're considering trying a supplement, talk to your healthcare provider.

What This Means For You

If you have iron deficiency anemia, your provider might recommend that you increase sources of heme and non-heme iron in your diet, as well as take an iron supplement. But despite the standard practice, you may not need to pair iron with vitamin C to help with absorption. Talk to your doctor before starting any kind of vitamin supplement.

Is It Ok To Take Vitamin C And Iron Together

Source: https://www.verywellhealth.com/vitamin-c-iron-supplement-study-5087131

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How Long Does Vitamin C Stay In The Body

How Long Does Vitamin C Stay In The Body

Vitamin C in human health and disease is still a mystery ? An overview

K Akhilender Naidu

¹Department of Biochemistry and Nutrition, Central Food Technological Research Institute, Mysore 570 013, India

Received 2003 May 13; Accepted 2003 Aug 21.

This article has been cited by other articles in PMC.

Abstract

Ascorbic acid is one of the important water soluble vitamins. It is essential for collagen, carnitine and neurotransmitters biosynthesis. Most plants and animals synthesize ascorbic acid for their own requirement. However, apes and humans can not synthesize ascorbic acid due to lack of an enzyme gulonolactone oxidase. Hence, ascorbic acid has to be supplemented mainly through fruits, vegetables and tablets. The current US recommended daily allowance (RDA) for ascorbic acid ranges between 100–120 mg/per day for adults. Many health benefits have been attributed to ascorbic acid such as antioxidant, anti-atherogenic, anti-carcinogenic, immunomodulator and prevents cold etc. However, lately the health benefits of ascorbic acid has been the subject of debate and controversies viz., Danger of mega doses of ascorbic acid? Does ascorbic acid act as a antioxidant or pro-oxidant ? Does ascorbic acid cause cancer or may interfere with cancer therapy? However, the Panel on dietary antioxidants and related compounds stated that the in vivo data do not clearly show a relationship between excess ascorbic acid intake and kidney stone formation, pro-oxidant effects, excess iron absorption. A number of clinical and epidemiological studies on anti-carcinogenic effects of ascorbic acid in humans did not show any conclusive beneficial effects on various types of cancer except gastric cancer. Recently, a few derivatives of ascorbic acid were tested on cancer cells, among them ascorbic acid esters showed promising anticancer activity compared to ascorbic acid. Ascorbyl stearate was found to inhibit proliferation of human cancer cells by interfering with cell cycle progression, induced apoptosis by modulation of signal transduction pathways. However, more mechanistic and human in vivo studies are needed to understand and elucidate the molecular mechanism underlying the anti-carcinogenic property of ascorbic acid. Thus, though ascorbic acid was discovered in 17^th century, the exact role of this vitamin/nutraceutical in human biology and health is still a mystery in view of many beneficial claims and controversies.

Historical perspective

The sea voyager/sailors developed a peculiar disease called scurvy when they were on sea. This was found to be due to eating non-perishable items and lack of fresh fruits and vegetables in their diet. A British naval Physician, Lind [1] documented that there was some substance in citrus fruits that can cure scurvy. He developed a method to concentrate and preserve citrus juice for use by sailors. British Navy was given a daily ration of lime or lemon juice to overcome ascorbic acid deficiency. Ascorbic acid was first isolated from natural sources and structurally characterized by Szent-Gyorgyi, Waugh and King [2,3]. This vitamin was first synthesized by Haworth and Hirst [4]. Currently ascorbic acid is the most widely used vitamin supplement through out the world.

Sources of Ascorbic acid

Ascorbic acid is widely distributed in fresh fruits and vegetables. It is present in fruits like orange, lemons, grapefruit, watermelon, papaya, strawberries, cantaloupe, mango, pineapple, raspberries and cherries. It is also found in green leafy vegetables, tomatoes, broccoli, green and red peppers, cauliflower and cabbage.

Most of the plants and animals synthesize ascorbic acid from D-glucose or D-galactose. A majority of animals produce relatively high levels of ascorbic acid from glucose in liver (Fig ​ 1).

Biosynthesis of L-Ascorbic acid in animals

However, guinea pigs, fruit eating bats, apes and humans can not synthesize ascorbic acid due to the absence of the enzyme L-gulonolactone oxidase. Hence, in humans ascorbic acid has to be supplemented through food and or as tablets.

Ascorbic acid is a labile molecule, it may be lost from foods during cooking/processing even though it has the ability to preserve foods by virtue of its reducing property. Synthetic ascorbic acid is available in a wide variety of supplements viz., tablets, capsules, chewable tablets, crystalline powder, effervescent tablets and liquid form. Buffered ascorbic acid and esterfied form of ascorbic acid as ascorbyl palmitate is also available commercially. Both natural and synthetic ascorbic acid are chemically identical and there are no known differences in their biological activities or bio-availability.

Chemistry of ascorbic acid

L-ascorbic acid (C₆H₈O₆) is the trivial name of Vitamin C. The chemical name is 2-oxo-L-threo-hexono-1,4-lactone-2,3-enediol. L-ascorbic and dehydroascorbic acid are the major dietary forms of vitamin C [5]. Ascorbyl palmitate is used in commercial antioxidant preparations. All commercial forms of ascorbic acid except ascorbyl palmitate are soluble in water. L-ascorbic acid and its fatty acid esters are used as food additives, antioxidants, browning inhibitors, reducing agents, flavor stabilizers, dough modifiers and color stabilizers. Ascorbyl palmitate has been used for its greater lipid solubility in antioxidant preparations. In foods, pH influences the stability of ascorbic acid. It exhibits maximal stability between pH 4 and 6 [5]. Cooking losses of ascorbic acid depend on degree of heating, surface area exposed to water, oxygen, pH and presence of transition metals.

Catabolism of Ascorbic acid

Ascorbic acid present in foods is readily available and easily absorbed by active transport in the intestine [6]. Most of it (80–90%) will be absorbed when the in take is up to 100 mg/day, whereas at higher levels of intake (500 mg/day) the efficiency of absorption of ascorbic acid rapidly declines. Ascorbic acid is sensitive to air, light, heat and easily destroyed by prolonged storage and over processing of food.

Ascorbic acid being a water soluble compound is easily absorbed but it is not stored in the body. The average adult has a body pool of 1.2–2.0 g of ascorbic acid that may be maintained with 75 mg/d of ascorbic acid. About 140 mg/d of ascorbic acid will saturate the total body pool of vitamin C [7]. The average half life of ascorbic acid in adult human is about 10–20 days, with a turn over of 1 mg/kg body and a body pool of 22 mg/kg at plasma ascorbate concentration of 50 μmol/ L [8,9]. Hence ascorbic acid has to regularly supplemented through diet or tablets to maintain ascorbic acid pool in the body.

The major metabolites of ascorbic acid in human are dehydroascorbic acid, 2,3-diketogulonic acid and oxalic acid (Fig ​ 2). The main route of elimination of ascorbic acid and its metabolites is through urine. It is excreted unchanged when high doses of ascorbic acid are consumed. Ascorbic acid is generally non-toxic but at high doses (2–6 g/day) it can cause gastrointestinal disturbances or diarrhea [10,11]. The side effects are generally not serious and can be easily reversed by reducing intake of ascorbic acid. Furthermore, there is no consistent and compelling data on serious health effects of vitamin C in humans [11].

Catabolism of Ascorbic acid

A deficiency of ascorbic acid leads to scurvy. It is characterized by spongy swollen bleeding gums, dry skin, open sores on the skin, fatigue, impaired wound healing and depression [13]. Scurvy is of rare occurrence nowadays due to adequate intake ascorbic acid through fresh vegetables and fruits and or supplementation as tablets.

Dietary recommendations of Ascorbic acid

The new average daily intake level that is sufficient to meet the nutritional requirement of ascorbic acid or recommended dietary allowances (RDA) for adults (>19 yr) are 90 mg/day for men and 75 mg/day for women [14]. Consumption of 100 mg/day of ascorbic acid is found to be sufficient to saturate the body pools (neutrophils, leukocytes and other tissues) in healthy individuals. Based on clinical and epidemiological studies it has been suggested that a dietary intake of 100 mg/day of ascorbic acid is associated with reduced incidence of mortality from heart diseases, stroke and cancer [15]. However, stress, smoking, alcoholism, fever, viral infections cause a rapid decline in blood levels of ascorbic acid.

Smoking is known to increase the metabolic turnover of ascorbic acid due to its oxidation by free radicals and reactive oxygen species generated by cigarette smoking [16]. It has been suggested that a daily intake of at least 140 mg/day is required for smokers to maintain a total body pool similar to that of non-smokers consuming 100 mg/day [17]. Based on latest literature reports, it has been recommended that the RDA for ascorbic acid should be 100–120 mg/day to maintain cellular saturation and optimum risk reduction of heart disease, stroke and cancer in healthy individuals [18]. There is no scientific evidence to show that even very large doses of vitamin C are toxic or exert serious adverse health effects [11,19]. Furthermore, the panel on dietary antioxidants and related compounds suggested that in vivo data do not clearly show a relationship between excess vitamin C intake and kidney stone formation, pro-oxidant effects, excess iron absorption [20].

Physiological functions of Ascorbic acid

The physiological functions of ascorbic acid are largely dependent on the oxido-reduction properties of this vitamin. L-ascorbic acid is a co-factor for hydroxylases and monooxygenase enzymes involved in the synthesis of collagen, carnitine and neurotransmitters [21]. Ascorbic acid accelerates hydroxylation reactions by maintaining the active center of metal ions in a reduced state for optimal activity of enzymes hydroxylase and oxygenase.

Ascorbic acid plays an important role in the maintenance of collagen which represents about one third of the total body protein. It constitutes the principal protein of skin, bones, teeth, cartilage, tendons, blood vessels, heart valves, inter vertebral discs, cornea and eye lens. Ascorbic acid is essential to maintain the enzyme prolyl and lysyl hydroxylase in an active form. The hydroxylation of proline and lysine is carried out by the enzyme prolyl hydroxylase using ascorbic acid as co-factor. Ascorbic acid deficiency results in reduced hydroxylation of proline and lysine, thus affecting collagen synthesis.

Ascorbic acid is essential for the synthesis of muscle carnitine (β-hydroxy butyric acid). [22]. Carnitine is required for transport and transfer of fatty acids into mitochondria where it can be used for energy production. Ascorbic acid acts as co-factor for hydroxylations involved in carnitine synthesis. Further, ascorbic acid acts as co-factorfor the enzyme dopamine-β-hydroxylase, which catalyzes the conversion of neurotransmitter dopamine to norepinephrine. Thus ascorbic acid is essential for synthesis of catecholamines. In addition, ascorbic acid catalyzes other enzymatic reactions involving amidation necessary for maximal activity of hormones oxytocin, vasopressin, cholecystokinin and alpha-melanotripin [23].

Ascorbic acid is also necessary for the transformation of cholesterol to bile acids as it modulates the microsomal 7 α-hydroxylation, the rate limiting reaction of cholesterol catabolism in liver. In ascorbic acid deficiency, this reaction becomes slowed down thus, resulting in an accumulation of cholesterol in liver, hypercholesterolemia, formation of cholesterol gall stones etc [24].

Ascorbic acid and iron

Ascorbic acid is known to enhance the availability and absorption of iron from non-heme iron sources [25]. Ascorbic acid supplementation is found to facilitate the dietary absorption of iron. The reduction of iron by ascorbic acid has been suggested to increase dietary absorption of non-heme iron [26]. It is well known that in the presence of redox-active iron, ascorbic acid acts as a pro-oxidant in vitro and might contribute to the formation of hydroxyl radical, which eventually may lead to lipid, DNA or protein oxidation [27]. Thus, ascorbic acid supplementation in individuals with high iron and or bleomycin-detectable iron (BDI) in some preterm infants could be deleterious because it may cause oxidative damage to biomolecules [28-31]. However, no pro-oxidant effect was observed on ascorbic acid supplementation on DNA damage in presence or absence of iron [32].

Ascorbic acid in health and disease

Ascorbic acid and common cold

The most widely known health beneficial effect of ascorbic acid is for the prevention or relief of common cold. Pauling [33] suggested that ingestion of 1–2 g of ascorbic acid effectively prevents/ ameliorate common cold. The role of oral vitamin C in the prevention and treatment of colds remains controversial despite many controlled trials. Several clinical trails with varying doses of ascorbic acid showed that ascorbic acid does not have significant prophylactic effect, but reduced the severity and duration of symptoms of cold during the period of infection. Randomized and non-randomized trials on vitamin C to prevent or treat the common cold showed that consumption of ascorbic acid as high as 1.0 g/day for several winter months, had no consistent beneficial effect on the incidence of common cold. For both preventive and therapeutic trials, there was a consistent beneficial but generally modest therapeutic effect on duration of cold symptoms. There was no clear indication of the relative benefits of different regimes of vitamin C doses. However, in trials that tested vitamin C after cold symptoms occurred, there was some evidence of greater benefits with large dose than with lower doses [34].

There has been a long-standing debate concerning the role of ascorbic acid in boosting immunity during cold infections. Ascorbic acid has been shown to stimulate immune system by enhancing T-cell proliferation in response to infection. These cells are capable of lysing infected targets by producing large quantities of cytokines and by helping B cells to synthesize immunoglobulins to control inflammatory reactions. Further, it has been shown that ascorbic acid blocks pathways that lead to apoptosis of T-cells and thus stimulate or maintain T cell proliferation to attack the infection. This mechanism has been proposed for the enhanced immune response observed after administration of vitamin C during cold infections [35].

Ascorbic acid and wound healing

Ascorbic acid plays a critical role in wound repair and healing/regeneration process as it stimulates collagen synthesis. Adequate supplies of ascorbic acid are necessary for normal healing process especially for post-operative patients. It has been suggested that there will be rapid utilization of ascorbic acid for the synthesis of collagen at the site of wound/ burns during post-operative period [36]. Hence, administration of 500 mg to 1.0 g/day of ascorbic acid are recommended to accelerate the healing process [8].

Ascorbic acid and atherosclerosis

Lipid peroxidation and oxidative modification of low density lipoproteins (LDL) are implicated in development of atherosclerosis [37]. Vitamin C protects against oxidation of isolated LDL by different types of oxidative stress, including metal ion dependent and independent processes [38]. Addition of iron to plasma devoid of ascorbic acid resulted in lipid peroxidation, whereas endogenous and exogenous ascorbic acid was found to inhibit the lipid oxidation in iron-over loaded human plasma [39]. Similarly, when ascorbic acid was added to human serum supplemented with Cu²⁺, antioxidant activity rather than pro-oxidant effects were observed [40].

Ascorbic acid is known to prevent the oxidation of LDL primarily by scavenging the free radicals and other reactive oxygen species in the aqueous milieu [41]. In addition, in vitro studies have shown that physiological concentrations of ascorbic acid strongly inhibit LDL oxidation by vascular endothelial cells [42]. Adhesion of leukocytes to the endothelium is an important step in initiating atherosclerosis. In vivo studies have demonstrated that ascorbic acid inhibits leukocyte-endothelial cell interactions induced by cigarette smoke [43,44] or oxidized LDL [45]. Further, lipophilic derivatives of ascorbic acid showed protective effect on lipid-peroxide induced endothelial injury [46].

A number of studies have been carried out in humans to determine the protective effect of ascorbic acid supplementation (500–100 mg/day) on in vivo and ex vivo lipid peroxidation in healthy individuals and smoker. The findings are inconclusive as ascorbic acid supplementation showed a reduction or no change in lipid peroxidation products [10,47-50]. In this context, it is important to note that during ex vivo LDL oxidation studies, water soluble ascorbic acid is removed during initial LDL isolation step itself. Therefore, no change in ex vivo would be expected [15]. Overall, both in vitro and in vivo experiments showed that ascorbic acid protects isolated LDL and plasma lipid peroxidation induced by various radical or oxidant generating systems. However, a recent report demonstrated that large doses of exogenous iron (200 mg) and ascorbic acid (75 mg) promoted the release of iron from iron binding proteins and also enhanced in vitro lipid peroxidation in serum of guinea pigs. This finding supports the hypothesis that high intake of iron along with ascorbic acid could increase in vivo lipid peroxidation of LDL and therefore could increase risk of atherosclerosis [51]. However, Chen et al., [52] demonstrated that ascorbic acts as an antioxidant towards lipids even in presence of iron over load in in vivo systems.

Numerous studies have looked at the association between ascorbic acid intake and the risk of developing cardiovascular disease (CHD). A large prospective epidemiological study in Finnish men and women suggested that high intake of ascorbic acid was associated with a reduced risk of death from CHD in women and not in men [53]. Similarly, another study showed that high intake of ascorbic acid in American men and women appeared to benefit only women [54,55]. A third American cohort study suggested that cardiovascular mortality was reduced in both sexes by vitamin C [56]. In the UK, a study showed that the risk of stroke in those with highest intake of vitamin C was only half that of subjects with the lowest intake and no evidence suggestive of lower rate of CHD in those with high vitamin C intake [57]. However, a recent meta analysis on the role of ascorbic acid and antioxidant vitamins showed no evidence of significant benefit in prevention of CHD [58]. Thus, no conclusive evidence is available on the possible protective effect of ascorbic acid supplementation on cardiovascular disease.

Ascorbic acid and Cancer

Nobel laureate Pauling and Cameron advocated use of high doses of ascorbic acid (> 10 g/day) to cure and prevent cold infections and in the treatment of cancer [34,59]. The benefits included were increased sense of well being/ much improved quality of life, prolongation of survival times in terminal patients and complete regression in some cases [60-62]. However, clinical studies on cancer patients carried out at Mayo Clinic showed no significant differences between vitamin C and placebo groups in regard to survival time [63]. Cameron and Pauling [23] believed that ascorbic acid combats cancer by promoting collagen synthesis and thus prevents tumors from invading other tissues. However, researchers now believe that ascorbic acid prevents cancer by neutralizing free radicals before they can damage DNA and initiate tumor growth and or may act as a pro-oxidant helping body's own free radicals to destroy tumors in their early stages [64-66].

Extensive animal, clinical and epidemiological studies were carried out on the role of ascorbic acid in the prevention of different types of cancers. A mixture of ascorbic acid and cupric sulfate significantly inhibited human mammary tumor growth in mice, while administered orally [67]. Ascorbic acid decreased the incidence of kidney tumors by estradiol or diethylstilbesterol in hamsters due to decrease in the formation of genotoxic metabolites viz., diethylstilbesterol-4'-4"-qunione [68]. Ascorbic acid and its derivatives were shown to be cytotoxic and inhibited the growth of a number of malignant and non-malignant cell lines in vitro and in vivo [69-72]. Ascorbic acid has been reported to be cytotoxic to some human tumor cells viz., neuorblastoma [73], osteosarcoma and retinoblastoma [74]. A number of ascorbic acid isomers/ derivatives were synthesized and tested on tumor cell lines. Roomi et al., 1998 [75] demonstrated that substitution at 2- or 6- and both at 2,6-positions in ascorbic acid have marked cytotoxicity on malignant cells. Ascorbate-6-palmitate and ascorbate-6-stearate, the fatty acid esters of ascorbic acid were found to be more potent inhibitors of growth of murine leukemia cells compared to ascorbate 2-phosphate, ascorbate 6-phosphate and or ascorbate 6-sulfate respectively [75].

Among ascorbic acid derivatives, fatty acid esters of ascorbic acid viz., ascorbyl palmitate and ascorbyl stearate have attracted considerable interest as anticancer compounds in view of their lipophilic nature as they can easily cross cell membranes and blood brain barrier [76]. Ascorbic acid and ascorbyl esters have been shown to inhibit the proliferation of mouse glioma and human brain tumor cells viz., glioma (U-373) and glioblastoma (T98G) cells and renal carcinoma cells [77-79]. Ascorbyl stearate was found to be more potent than sodium ascorbate in inhibiting proliferation of human glioblastoma cells [80]. Ascorbyl-6-O-palmitate and ascorbyl-2-O-phosphate-6-O-palmitate also showed anti-metastatic effect by inhibiting invasion of human fibrosarcoma HT-1080 cells through matrigel and pulmonary metastasis of mouse melanoma model systems [81].

Numerous reports are available in literature on cytotoxic and anti-carcinogenic effect of ascorbic acid and its derivatives in different tumor model systems. However, the molecular mechanisms underlying the anti-carcinogenic potential of ascorbic acid are not completely elucidated. Recently, Naidu et al [80] demonstrated that ascorbyl stearate inhibited cell proliferation by interfering with cell cycle, reversed the phenotype and induced apoptosis by modulation of insulin-like growth factor 1-receptor expression in human brain tumor glioblastoma (T98G) cells. They also studied the effect of ascorbyl stearate on cell proliferation, cell cycle, apoptosis and signal transduction in a panel of human ovarian and pancreatic cancer cells. Treatment with ascorbyl stearate resulted in concentration-dependent inhibition of cell proliferation and also clonogenicity of ovarian/ pancreatic cancer cells [82,83]. The anti-proliferative effect was found to be due to the arrest of cells in S/G2-M phase of cell cycle, with increased fraction of apoptotic cells. The cell cycle perturbations were found to be associated with ascorbyl stearate induced reduction in the expression and phosphorylation of IGF-I receptor, while the expression of EGFR and PDGFR remained unchanged. These changes were also associated with activated ERK1/2 but late reduction in AKT phosphorylation. Overexpression of IGF-I receptor in OVCAR-3 cells had no protective effect, however ectopic expression of a constitutively active AKT2 did offer protection from the cytotoxic effects of ascorbyl stearate. In conclusion, ascorbyl stearate-induced anti-proliferative and apoptotic effects in ovarian cancer were found to be mediated through cell cycle arrest and modulation of the IGF-IR and PI3K/AKT2 survival pathways [83].

A plethora of epidemiological studies were carried out to find out the association of ascorbic acid with various types of cancers including breast, esophageal, lung, gastric, pancreatic, colorectal, prostate, cervical and ovarian cancer etc. The results were found to be inconclusive in most types of cancers except gastric cancer [84]. One of the most consistent epidemiological findings on vitamin C has been an association with high intake of ascorbic acid or vitamin C rich foods and reduced risk of stomach cancer. Considerable biochemical and physiological evidence suggests that ascorbic acid functions as a free radical scavenger and inhibit the formation of potentially carcinogenic N-nitroso compounds from nitrates, nitrite in stomach and thus offer protection against stomach cancer [85-87].

Low intake of ascorbic acid and other vitamins was associated with an increased risk of cervical cancer in two of three studies reported [88-91]. This relationship needs further study because the results suggest that other nutrients including vitamin E, carotenoids, retinoic acid either individually or in synergy with ascorbic acid may impart a protective effect against various cancers. Current evidences suggest that vitamin C alone may not be sufficient as an intervention in the treatment of most active cancers, as it appears to be preventive than curative. However, vitamin C supplementation has shown to improve the quality of life and extend longevity in cancer patients, hence it could be considered as an adjuvant in cancer therapy.

Dehydroascorbic acid, the oxidized form of ascorbic acid was shown to cross the blood brain barrier by means of facilitative transport and was suggested to offer neuroprotection against cerebral ischemia by augmenting antioxidant levels of brain [92].

Controversies on health benefits of Ascorbic acid

Does ascorbic acid acts as antioxidant or pro-oxidant?

Vitamin C is an important dietary antioxidant, it significantly decreases the adverse effect of reactive species such as reactive oxygen and nitrogen species that can cause oxidative damage to macromolecules such as lipids, DNA and proteins which are implicated in chronic diseases including cardiovascular disease, stroke, cancer, neurodegenerative diseases and cataractogenesis [93].

As shown in Table ​ 2, ascorbic acid is a potent water soluble antioxidant capable of scavenging/ neutralizing an array of reactive oxygen species viz., hydroxyl, alkoxyl, peroxyl, superoxide anion, hydroperoxyl radicals and reactive nitrogen radicals such as nitrogen dioxide, nitroxide, peroxynitrite at very low concentrations [15]. In addition ascorbic acid can regenerate other antioxidants such as α-tocopheroxyl, urate and β-carotene radical cation from their radical species [94]. Thus, ascorbic acid acts as co-antioxidant for α-tocopherol by converting α-tocopheroxyl radical to α-tocopherol and helps to prevent the α-tocopheroxyl radical mediated peroxidation reactions [95].

Table 2

Reactive species scavenged by ascorbic acid

Chemical species	Reaction rate (M-1s-1)
Reactive oxygen species
Hydroxyl radical	1.1 × 1010
Alkoxyl radical	1.6 × 109
Peroxy radical	1.2 × 106
Superoxide anion/ hydroperoxy radical	1.0 × 105
Reactive nitrogen species
Dinitrogen trioxide/dinitrogen tetroxide	1.2 × 109
Peroxynitrite/peroxynitrous acid	235
Antioxidant derived radicals
Alpha-tocopherol radical	2 × 105
Urate radical	1 × 106
Thiyl/sulphenyl radical	6 × 108

Adapted from Carr and Frei [15]

AH^- + Fe ³⁺ - - - → A^{• -} + Fe ²⁺ + H⁺

AH^- + Cu ²⁺ - - - → A^{• -} + Cu⁺ + H ⁺

H₂O₂ + Fe ²⁺ - - - → HO^• + Fe ³⁺ + ^-OH

H₂O₂ + Cu ⁺ - - - → HO^• + Cu ²⁺ + ^-OH

LOOH + Fe ²⁺ - - - → LO• + Fe ³⁺ + ^-OH

LOOH + Cu ⁺ - - - → LO + Cu⁺ + ^-OH

HO^•, LO^• - - - → Lipid peroxidation

Adapted from Carr and Frei [15]

These radical species are highly reactive and can trigger lipid peroxidation reactions. Thus the question arises whether vitamin C acts as a pro-oxidant in in vivo conditions? The answer appears to be "no" as though these reactions occur readily in vitro, its relevance in in vivo has been a matter of debate concerning ready availability of catalytically active free metal ions in vivo [94]. In biological systems, iron is not freely available, but it is bound to proteins like transferrin, hemoglobin and ferretin. Mobilization of iron from these biomolecules may be required before it can catalyze lipid peroxidation. Further, the concentration of free metal ions in in vivo is thought to be very low as iron and other metals are sequestered by various metal binding proteins [94]. Another factor that may affect pro-oxidant vs antioxidant property of ascorbic acid is its concentration. The in vitro data suggest that at low concentrations ascorbic acid act as a pro-oxidant, but as an antioxidant at higher levels [96]. Moreover, a recent report demonstrated that large doses of exogenous iron (200 mg) and ascorbic acid (75 mg) promote the release of iron from iron binding proteins and also enhance in vitro lipid peroxidation in serum of guinea pigs. This finding supports the hypothesis that high intake of iron along with ascorbic acid could increase in vivo lipid peroxidation of LDL and therefore could increase risk of atherosclerosis [52]. However, another study demonstrated that in iron-overloaded plasma, ascorbic acid acts as an antioxidant and prevent oxidative damage to lipids in vivo [97].

Is ascorbic acid harmful to cancer patients?

Agus et al [98] have reported that the tumor cells contain large amounts of ascorbic acid, although the role of ascorbic acid in tumors is not yet known. They have established that vitamin C enters through the facilitative glucose transporters (GLUTs) in the form of dehydroascorbic acid, which is then reduced intracellularly and retained as ascorbic acid. It is speculated that high levels of ascorbic acid in cancer cells may interfere with chemotherapy or radiation therapy since these therapies induce cell death by oxidative mechanism. Thus, ascorbic acid supplementation might make cancer treatment less effective because, ascorbic acid being a strong antioxidant may scavenge or neutralize the oxidative stress induced by chemotherapy in cancer patients. However, more studies are needed to understand the role of ascorbic acid in tumors cells and the speculative contraindication of ascorbic acid for cancer chemotherapy.

Does ascorbic acid cause cancer ?

Recently, it has been reported that lipid hydroperoxide can react with ascorbic acid to form products that could potentially damage DNA, suggesting that it may form genotoxic metabolites from lipid hydroperoxides implicating that ascorbic acid may enhance mutagenesis and risk of cancer. Lee et al [99], demonstrated that ascorbic acid induces decomposition of lipid hydroperoxide (13-(S)-hydroperoxy-(Z,E)-9,11-octadecadienoic acid;(13-HPODE) in presence of transition metals to DNA-reactive bifunctional electro-philes namely 4-oxo-2-nonenal, 4,5-epoxy-2(E)-decenal and 4-hydroxy-2-nonenal. 4-oxo-2-nonenal being a genotoxin can react with DNA bases to form mutations [100] or apoptosis [101].

Thus, the above process can give rise to substantial amounts of DNA damage in vivo. However there are many questions, which need to be considered before we accept the hypothesis that ascorbic acid can cause cancer by producing genotoxic metabolites from lipids. The hydroperoxides formed through lipid peroxidation reaction are rapidly reduced to aldehydes by a number of enzymes. Further, ascorbic acid being a strong antioxidant effectively inhibits the formation of lipid peroxides as ascorbic acid forms the first line of antioxidant defense mechanism in human plasma. The formation of lipid hydroperoxides occur only after ascorbic acid has been exhausted. Hence, interaction of ascorbic acid and hydroperoxide may not arise in human plasma. Recently, high intracellular vitamin C was reported to prevent oxidation-induced mutations in human cells [102]. Thus, the physiological relevance of these results is yet to be established in in vivo experiments.

Conclusion

Ascorbic acid is one of the important and essential vitamins for human health. It is needed for many physiological functions in human biology. Fresh fruits, vegetables and also synthetic tablets supplement the ascorbic acid requirement of the body. However, stress, smoking, infections and burns deplete the ascorbic acid reserves in the body and demands higher doses of ascorbic acid supplementation. Based on available biochemical, clinical and epidemiological studies, the current RDA for ascorbic acid is suggested to be 100–120 mg/day to achieve cellular saturation and optimum risk reduction of heart diseases, stroke and cancer in healthy individuals. In view of its antioxidant property, ascorbic acid and its derivatives are widely used as preservatives in food industry. Many health benefits have been attributed to ascorbic acid namely antioxidant, anti-atherogenic and anti-carcinogenic activity. Lately some of these beneficial effects of ascorbic acid are contradicted. The relation between ascorbic acid and cancer is still a debatable as the molecular mechanism underlying anti-carcinogenic activity of ascorbic acid is not clearly elucidated. Regarding the pro-oxidant activity of vitamin C in presence of iron, there is compelling evidence for antioxidant protection of lipids by ascorbic acid both with and without iron co-supplementation in animals and humans. Current evidences also suggest that ascorbic acid protects against atherogenesis by inhibiting LDL oxidation. The data on vitamin C and DNA damage are conflicting and inconsistent. However, more mechanistic and human in vivo studies are warranted to establish the beneficial claims on ascorbic acid. Thus, though ascorbic acid was discovered in 17^th century, the role of this important vitamin in human health and disease still remains a mystery in view of many beneficial claims and contradictions.

Table 1

Ascorbic acid content in selected foods

Fruits	mg/100 g edible portion
Banana	8–16
Apple	3–30
Mango	10–15
Pineapple	15–25
Cherry	15–30
Papaya	39
Orange	30–50
Grape fruit	30–70
Lemon	40–50
Strawberry	40–70
Currant black	150–200
Rose hips	250–800
Vegetables
Onion	10–15
Tomato	10–20
Egg plant	15–20
Radish	25
Spinach	35–40
Cabbage	30–70
Cauliflower	50–70
Broccoli	80–90
Coriander	90
Brussels sprout	100–120
Pepper	150–200
Parsley	200–300

Adapted from Johnson et al [12]

Acknowledgements

Author gratefully acknowledges Dr.S.G.Bhat, Head, Department of Biochemistry and Nutrition and Dr.V.Prakash, Director, CFTRI, Mysore for their encouragement in preparing this review. The author also acknowledges Dr.Santo V.Nicosia and Dr. D.Coppola, Moffitt Cancer Research Center, University of South Florida, Tampa, FL, USA for supporting the work on ascorbyl stearate in his laboratory.

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How Long Does Vitamin C Stay In The Body

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC201008/#:~:text=The%20average%20half%20life%20of,acid%20pool%20in%20the%20body.

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