Vitamin C and Diabetes

A new study has added to the growing amount of research showing that vitamin C- as well as a high intake of vegetables and fruits- may have protective effects against diabetes.

This makes more than a little intuitive sense- after all Diabetes is a disease marked by a good amount of oxidative damage- damage done to your cells and DNA by rogue molecules called free radicals. Antioxidants- like vitamin C- can help protect against this. A cornerstone of the Atkins program has always been a diet high in antioxidants such as vitamin C, vitamin E, zinc and selenium, precisely because of their multiple protective benefits.

In the current study, published in the July 28 edition of the Archives of Internal Medicine, researchers collected food questionnaires from over 21,000 subjects. The researchers also measured blood levels of vitamin C in all the participants. The subjects were then followed up for 12 years during which 735 individuals were diagnosed with diabetes (about .4% of the population studied).

There was a significant inverse association between vitamin C levels in the blood and the risk of getting diabetes. In other words those patients with the highest blood levels of vitamin C at the beginning of the study were the least likely to be among those who developed diabetes.

Since vitamin C is often a “marker” for fruit and vegetable intake- after all, we get 90% of our vitamin C from vegetables and fruits- the researchers decided to investigate the effect of fruit and vegetable consumption independently from blood levels of vitamin C. Using the questionnaires, they determined that indeed, fruit and vegetable consumption did protect against diabetes to some degree. But surprisingly, the protection was not nearly as dramatic as the protection obtained by high blood levels of vitamin C. Those who ate the most fruits and vegetables had a 22% reduction in their risk of developing the disease, while those with the most vitamin C in their blood had a 62% reduction.

Other studies have shown a connection between low levels of vitamin C in the blood and higher risks for diabetes. One important 16-year study of 85,000 women of whom 2% were diabetic found that 400mg or more of daily vitamin C supplements was associated with significant reductions in the risk of both fatal and nonfatal coronary heart disease in both the women with diabetes and those without(2). However an earlier study showed just the opposite: Postmenopausal diabetic women taking 300mg or more a day of vitamin C supplements had a suprising (and unexplained) increase in their risk for death from coronary heart disease and stroke than those who were not taking the supplements.(3)

It’s entirely possible that a genetic factor comes into play here and that there may be a small subpopulation of diabetics that would not benefit from vitamin C supplements above 250mg a day (though many others would benefit greatly). But while the researchers sort it all out, one conclusion is shared by all- there is no potential damage (and a wealth of potential benefit) from consuming as much vitamin C (and other antioxidants) as possible from foods.

A single kiwifruit has 70 mg of vitamin C, an orange has 63% and both are relatively low-sugar fruits that can easily be incorporated into the Atkins Advantage plan. Atkins Advantage shakes contain 30% of the daily recommended allowance of vitamin C, while both the caramel cookie dough and caramel chocolate peanut nougat bars each have 25% of the RDA while also providing plenty of protein and fiber (and not a gram of sugar), all important components of an “anti-diabetic” diet strategy!


Ref:
1) “Plasma Vitamin C Level, Fruit and Vegetable Consumption, and the Risk of New-Onset Type 2 Diabetes Mellitus: The European Prospective Investigation of Cancer–Norfolk Prospective Study” Harding, Wareham, et al. Arch Intern Med. 2008; 168(14):1493-1499.
http://archinte.ama-assn.org/cgi/content/abstract/168/14/1493
2) “Vitamin C and risk of coronary heart disease in women”. Osganian SK, Stampfer MJ, Rimm E, et al. J Am Coll Cardiol. 2003;42(2):246-252  
http://www.ncbi.nlm.nih.gov/pubmed/12875759?dopt=Abstract
3) “Does supplemental vitamin C increase cardiovascular disease risk in women with diabetes?” Lee, Folsom, et al Am J Clin Nutr. 2004;80(5):1194-1200.
http://www.ncbi.nlm.nih.gov/pubmed/15531665?dopt=Abstract
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