BY: Mir Nelofar Nazir
Vitamins are essential to maintain normal metabolic processes and homeostasis within the body. The amount of a specific vitamin required by an individual varies considerably and it is influenced by such factors as body size, growth rate, physical activity, and pregnancy. Most vitamins are stored minimally in human cells, but some are stored in liver cells to a greater extent. Vitamins A and D, for example, may be stored in sufficient amounts to maintain an individual without any intake for 5 to 10 months and 2 to 4 months, respectively. However, a deficiency of vitamin B compounds (except vitamin B12) may be noted within days, and the lack of vitamin C will manifest within weeks and may result in death in 5 to 6 months. The current recommended dietary allowance (RDA) of vitamin C is 75 mg for woman and 90 mg for men, based on the vitamin’s role as an antioxidant as well as protection from deficiency. High intakes of the vitamin are generally well tolerated, however, a Tolerable Upper Level (TUL) was recently set at 2 g based on gastrointestinal upset that sometimes accompanies excessive dosages. Several populations warrant special attention with respect to vitamin C requirements. These include patients with periodontal disease, smokers, pregnant and lactating women, and the elderly.
Vitamin C or 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.
Foods high in Vitamin C:-
- Chili peppers:
One green chili pepper contains 109 mg of vitamin C, . In comparison, one red chili pepper delivers 65 mg.
A single guava contains 125 mg of vitamin C. It’s particularly rich in the antioxidant lycopene.
A 6-week study involving 45 young, healthy people found that eating 400 grams of peeled guava per day, or around 7 pieces of this fruit, significantly lowered their blood pressure and total cholesterol levels .
- Sweet yellow peppers:
The vitamin C content of sweet or bell peppers increases as they mature.
One large yellow pepper provides 342 mg of vitamin C which is over twice the amount found in green peppers.
Consuming enough vitamin C is important for your eye health and may help protect against cataract progression.
A study in over 300 women found that those with higher vitamin C intakes had a 33% lower risk of cataract progression, compared with those with the lowest intakes.
One-half cup (56 grams) of blackcurrants (Ribes nigrum) contains 102 mg of vitamin C.
Antioxidant flavonoids known as anthocyanins give them their rich, dark color.
Studies have shown that diets high in antioxidants like vitamin C and anthocyanins may reduce oxidative damage associated with chronic diseases, including heart disease, cancer, and neurodegenerative diseases.
This sweet, high-fiber fruit is packed with vitamin A.
Cantaloupe is also a good source of Vitamin C.
One cup of cantaloupe slices contains 17.4 mg of Vitamin C, which is 19% of what is recommended for adults daily .
Two tablespoons (8 grams) of fresh parsley contain 10 mg of vitamin C, providing 11% of the recommended DV .
Parsley is a significant source of vitamin K, antioxidants, and vitamin C.
Eating foods rich in vitamin C may reduce your risk of cancer.
A 2018 study found that increasing vitamin C by 100 mg per day reduced the risk of cancer by 7% .
Additionally, increasing dietary vitamin C by 150 mg per day was shown to lower prostate cancer risk by up to 5% in cohort studies and by 21% in case-control studies.
- Mustard spinach:
One cup of raw chopped mustard spinach provides 195 mg of vitamin C.
Even though heat from cooking lowers the vitamin C content in foods, one cup of cooked mustard greens still provides 117 mg of vitamin C.
As with many dark, leafy greens, mustard spinach is also high in vitamin A, potassium, calcium, manganese, fiber, and folate.
One medium kiwi packs 56 mg of vitamin C.
Research shows that kiwis can have an inhibitory effect on blood platelets, which may help reduce the risk of blood clots and stroke .
Kiwi consumption may also benefit the immune system.
A study involving 14 men with vitamin C deficiency found that eating two kiwis daily for 4 weeks increased white blood cell activity by 20%. Blood levels of vitamin C normalized after just 1 week.
Broccoli is a cruciferous vegetable. One-half cup of cooked broccoli provides 51 mg of vitamin C.
Numerous observational studies have shown a possible association between eating plenty of vitamin-C–rich cruciferous vegetables and a decreased risk of cancer .
One study found that 30 grams a day of broccoli sprouts decreased markers of the inflammatory marker C-reactive protein in overweight adults.
- Brussels sprouts:
One-half cup of cooked Brussels sprouts provides 49 mg of Vitamin C.
Like most cruciferous vegetables, Brussels sprouts are also high in fiber, vitamin K, folate, vitamin A, manganese, and potassium.
Both vitamins C and K are important for your bone health. In particular, vitamin C aids the formation of collagen, which is the fibrous part your bones.
A large 2018 review found that a high dietary intake of vitamin C was associated with a 26% reduced risk of hip fractures and a 33% reduced risk of osteoporosis.
Lemons were given to sailors during the 1700s to prevent scurvy. One whole raw lemon provides 45 mg of vitamin C.
The vitamin C in lemon juice also acts as an antioxidant, evident through its ability to prevent other fruits and foods from browning.
When fruits and vegetables are cut, the enzyme polyphenol oxidase is exposed to oxygen. This triggers oxidation and turns the food brown. Applying lemon juice to the exposed surfaces acts as a barrier, preventing the browning process .
Lemon juice has also been found to reduce blood pressure and lower the effects of bread on blood sugar.
One lychee provides nearly 7 mg of vitamin C, or 7.5% of the DV.
Research shows that lychees contain polyphenol compounds including gallic acid, rutin, epicatechin, chlorogenic acid, caffeic acid, kaempferol, quercetin, luteolin, and apigenin .
One cup (145 grams) of papaya provides 88 mg of vitamin C.
Vitamin C also aids memory and has potent anti-inflammatory effects in your brain .
In one study, 20 people with mild Alzheimer’s were given a concentrated papaya powder for 6 months. The results showed decreased inflammation and a 40% reduction in oxidative stress.
One cup of sliced strawberries (166 grams) provides 97 mg of vitamin C.
Strawberries contain a diverse and potent mix of vitamin C, manganese, flavonoids, folate, and other beneficial antioxidants.
Studies suggest that, because of their high content of nutrients and beneficial plant compounds, regularly eating strawberries may help reduce the risk of several health conditions.
One medium-sized orange provides 83 mg of vitamin C, which is 92% of the DV .
Widely eaten, oranges make up a significant portion of dietary vitamin C intake.
Other citrus fruits can also help you meet your vitamin C needs. For example, half a pink grapefruit contains 46 mg, or 51% of the DV, a medium sized mandarin 24 mg, or 27% of the DV, and the juice of one lime 13 mg.
Vitamin C in health and disease:
1.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 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. 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.
- 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 . Hence, administration of 500 mg to 1.0 g/day of ascorbic acid are recommended to accelerate the healing process.
- Ascorbic acid and atherosclerosis:
Lipid peroxidation and oxidative modification of low density lipoproteins (LDL) are implicated in development of atherosclerosis. Vitamin C protects against oxidation of isolated LDL by different types of oxidative stress,including metal ion dependent and independent processes. 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. Similarly, when ascorbic acid was added to human serum supplemented with Cu2+,antioxidant activity rather than pro-oxidant effects were observed.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 . In addition, in vitro studies have shown that physiological concentrations of ascorbic acid strongly inhibit LDL oxidation by vascular endothelial cells . 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 or oxidized LDL .Further, lipophilic derivatives of ascorbic acid showed protective effect on lipid-peroxide induced endothelial injury.
- 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 . 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.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 . Cameron and Pauling 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 .
Author is PG scholar Dietics Tutor Sr technologist at Kidney hospital Srinagar.
Can be reached at [email protected]