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Eating a couple of citrus fruits every day will exceed your Recommended Dietary Allowance (RDA) for vitamin C o​r ascorbic acid. 

For men aged 19 and above, the RDA is 90 mg; for women, it is 75 mg.

So is there any benefit in taking a vitamin C supplement as the body only absorbs the vitamin C it needs?

If your diet already includes a few servings of fruits and vegetables every day, taking a separate vitamin C supplement may not be necessary. Any excess is excreted in the urine.​ In fact, ingesting more than 2,000 mg of vitamin C every day may cause nausea, diarrhoea and kidney stones, said pharmacists from Changi G​eneral Hospital​ (CGH), a member of the SingHealth​ group.

All about vitamin C

Our bodies do not produce or store the water-soluble vitamin C. We need to replenish our supply of vitamin C every day – and the best source is from fruits and vegetables.

Best food sources of vitamin C

Citrus fruits such as orange, kiwi, lemon, guava, grapefruit, and vegetables such as broccoli, cauliflower, Brussel sprouts and capsicums are rich, natural sources of vitamin C. Other vitamin C-rich fruits include papaya, cantaloupe and strawberries.

One cup of raw capsicums will provide 117mg of vitamin C, which exceeds the RDA for both men and women. 

A combination of a kiwi fruit (75mg of vitamin C) and a vegetable will provide all the vitamin C you need in a day.

Why you need vitamin C

1. It protects your cells from free radical damage

Vitamin C is a powerful antioxidant that protects your cells from being damaged by free radicals produced by cigarette smoke, air pollution, excessive sunlight and normal metabolism. Free radicals are thought to play a role in rapid ageing and diseases such as cancer and heart disease.

2. It is needed to make collagen

Vitamin C is essential for the synthesis of collagen which is needed to support new tissue growth. It promotes a healthy skin as well as the healing of cuts and wounds. Collagen is also found in the connective tissues of healthy gums, bones, muscles, cartilage, and blood vessels.

3. It improves iron absorption

Vitamin C increases the absorption of non-heme iron found in vegetables, fruits and nuts.

Potential interactions with vitamin C

Excessive doses of vitamin C from over-supplementation may interfere with certain medications or conditions.

Too much ascorbic acid or vitamin C (2000mg/day) may increase the amount of aluminium absorbed from aluminium compounds. Patients with kidney impairment on long term use of aluminium-containing compounds should avoid high dose of vitamin C supplements.

Concurrent administration of oestrogen and large doses of vitamin C (1g daily) may increase oestrogen levels, so high dose vitamin C supplementation should be avoided. Women on oestrogen therapy should not substantially vary their intake of vitamin C supplements.

Patients with diabetes, kidney stones or kidney dysfunction should avoid prolonged use of high-dose vitamin C supplementation.

You should always talk to your doctor first before taking any high dose vitamin C supplementation on a long-term basis, especially if you have any other underlying medical conditions.

Signs of vitamin C deficiency

Vitamin C deficiency is rare, but its signs are bleeding gums, easy bruising, dry scaly skin, muscle weakness, and joint and muscle aches.

In extreme cases, a vitamin C deficiency may lead to scurvy, a disease characterised by bleeding, bruising, anaemia and weakness. Such a case, involving a 37-year-old woman with underlying obsessive-compulsive and eating disorders, was actually reported in the Singapore Medical Journal in 2006.

A deficiency in vitamin C may also impair wound healing. Patients recovering from injuries, surgeries, burns and wounds may benefit from a short-term use of vitamin C supplement as it can promote the healing process.

When buying supplements, consumers should look for products from reliable sources to ensure quality and safety and evaluate the manufacturer’s health claims carefully.

Mayo Clinic
Harvard School of Medicine

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Check out our other vitamin-related articles:

Vitamin A: Benefits and Best Food Sources

Vitamin B: Why You Need It and Best Food Sources

Vitamin D: Recommended Daily Allowances (RDA), Food Sources and Side Effects

Other Essential Vitamins: Iron, Zinc and More

Can You Overdose on Vitamins?