Vitamin C is found in nature in fruits and other plant material. However, humans can synthesise vitamin C in the laboratory.
Research has demonstrated a number of health benefits from doses of vitamin C above and beyond those required for the reversal of scurvy. Linus Pauling was a strong advocate of high doses of vitamin C. If you have read his unified theory of cardiovascular disease (here) you will already know that his recommendations to those at most risk of heart disease were to consume vitamin C in the dose range of 10 to 20 grams per day. Many nutritionists recommend vitamin C in the range of 1 to 5 grams a day for basic long term health maintenance. However, even a very high fruit diet may only be able to supply a level of vitamin C in the hundreds of milligrams range. Therefore, some health benefits of ascorbic acid may not be possible to attain from food sources alone.
For example a study published in the British Journal of Nutrition1 demonstrated that a kg of oranges and strawberries contains roughly 540 and 770 mg of vitamin C respectively. Apples provided just 60 mg of vitamin C per kg and plums just 40 mg per kg. The best vegetable sources of vitamin C were mange-tout and broccoli which contained 540 and 870 mg per kg respectively but carrots only provided 60 mg per kg. Trying to obtain the health benefits of gram quantities of vitamin C by eating fruit and vegetables alone is therefore not possible. On top of a variety of plant based foods, it would appear that supplementation with vitamin C is necessary. But is the synthetic ascorbic acid in tablet form really as effective as getting your vitamin C from foods?
A study published in the American Journal of Nutrition in 19932 measured the bioavailability of vitamin C from tablets (with or without iron), as orange segments, orange juice, or as raw or cooked broccoli. All of the different regimes provided 108 mg of ascorbic acid. For all subjects plasma ascorbic acid rose equally during treatment and fell equally when a depletion phase was introduced, except when they consumed raw broccoli. The raw broccoli treatment produced a response in plasma levels that was around 20 % lower than the other treatment. This is likely because the cooking process breaks down the cell walls of the broccoli making more of the intracellular vitamin C available for absorption. Other studies have supported the notion of cooking food to increase the bioavilability of nutrients such as flavonoids and carotenoids.
This study also measured the total antioxidant ability of the fruit and found that this was much higher than could be accounted for by the vitamin C content alone. Fruit contains many other compounds that work in the body as antioxidants, the most common of these being flavonoids and carotenoids. For example, onions may contain only around 80 mg of ascorbic acid but also contain roughly 100 mg of the flavonoid quercetin, which is an excellent scavenger of free radicals. So these foods have an important place in our diets. Eating a diet containing as many different varieties of plant material incorporating as many different colours as possible seems a very prudent step on the way to optimum nutrition, supplemented of course with extra gram quantities of vitamin C.
