It’s a well-known nutrient that many people may assume they’re consuming enough of.
Yet the main dietary source of vitamin C – fruits and vegetables – is a food group that most Canadians fall short on. And that’s concerning.
Beyond its role in immunity, vitamin C is critical for healthy blood vessels, wound healing, antioxidant protection and much more. Here’s a primer on vitamin C, why you need it and how to get more of it every day.
What vitamin C does
Vitamin C supports the immune system by stimulating the production and function of white blood cells that destroy infection-causing microbes.
The nutrient is also needed to make collagen, a vital protein for wound healing, skin health and maintaining healthy blood vessel walls. And it’s used to synthesize L-carnitine, an amino acid that transports fat into cells for energy.
Vitamin C also acts as a powerful antioxidant, neutralizing harmful free radicals. (Free radicals are unstable oxygen molecules that, if left unchecked, can contribute to illness and aging.)
Studies suggest that higher vitamin C intakes may help prevent cataracts, macular degeneration, hypertension and cardiovascular disease, as well as promote healthy brain aging.
How much you need
Your body doesn’t produce or store vitamin C, so you need to consume it every day.
The official daily recommended intake for adults is 75 mg for females and 90 mg for males. Smokers need an additional 35 mg each day, since smoking can deplete vitamin C in the body.
Some experts contend that a higher daily intake of 200 mg is needed to ensure the body’s cells and tissues are adequately supplied with vitamin C. Because some people may absorb the nutrient less efficiently, the Linus Pauling Institute recommends adults aim for 400 mg.
Vitamin C in foods
You can get 150 to 200 mg of vitamin C by eating at least 2.5 cups of fruit and vegetables each day, including ones that are rich sources of the nutrient.
Fruits high in vitamin C include strawberries (85 mg per one cup), pineapple (80 mg per one cup), citrus fruit (70 mg per one medium orange; 70 to 90 mg per one grapefruit), kiwifruit (65 mg each) and mango (60 mg per one cup).
One-half of a raw large yellow, red and green pepper each supply 171 mg, 105 mg and 65 mg of vitamin C, respectively. Other good sources include broccoli (81 mg per one cup raw), cauliflower (52 mg one cup raw), Brussels sprouts (48 mg per one half-cup cooked) and tomato juice (170 mg per one cup).
Vitamin C is water-soluble and sensitive to heat, so a large amount is lost when vegetables are boiled. Steaming minimizes vitamin C loss.
Who’s at risk for getting too little?
People who are more likely to have an inadequate level of vitamin C include those who eat a narrow diet, those who follow a restrictive diet (e.g., low carbohydrate, low calorie), smokers and heavy drinkers. People with certain medical conditions, including severe malabsorption, are also at risk.
A 2009 study conducted by researchers from the University of Toronto revealed that, among 979 young adults, 47 per cent had inadequate blood levels of vitamin C, with 14 per cent classified as deficient. One in four participants did not consume the daily recommended intake for vitamin C.
A severe vitamin C deficiency causes scurvy. Early signs are fatigue, malaise and inflamed gums. As the deficiency progresses, collagen synthesis becomes impaired causing weak blood vessels.
Symptoms include bleeding under the skin, poor wound healing, bruising, hair and tooth loss and joint pain. If left untreated, scurvy is fatal.
While scurvy is rare in North America, cases have been reported in people with poor nutrition caused by restrictive diets, mental illness and social isolation.
Should you supplement?
Get your vitamin C from fruits and vegetables, which also deliver plenty of other protective nutrients and phytochemicals. That said, there’s no harm in boosting your vitamin C intake from a supplement.
Multivitamins typically contain 60 to 100 mg of vitamin C, but some may have more. Single supplements of vitamin C are also available.
There’s little scientific evidence that one form of vitamin C is better absorbed than another (e.g., ascorbate versus Ester-C). At vitamin C doses above 1,000 mg, absorption falls to less than 50 per cent.
A safe upper daily limit of 2,000 mg has been established to prevent diarrhea and digestive upset.
People predisposed to calcium oxalate kidney stones should not consume more that 1,000 mg of vitamin C a day; vitamin C increases oxalate excretion in the urine.
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD
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