Higher Plasma Vitamin C LevelsLinked with Lower Diabetes Risk

Higher plasma vitamin C levels, an indicator of a high fruit and vegetable intake, is associated with a substantially decreased risk of type 2 diabetes, according to a European-based study of more than 20,000 middle-aged adults.

Between 1993 and 1997, 21,831 healthy, nondiabetic participants had their plasma vitamin C levels measured and their fruit and vegetable intake evaluated using food frequency questionnaires. Over a twelve-year follow-up period, 423 men and 312 women developed diabetes.

Analysis of the data revealed a strong protective effect of high vitamin C levels against diabetes. Participants in the top 20 percent of plasma vitamin C had a 62 percent lower adjusted risk of developing diabetes compared with those in the lowest 20 percent. In addition, those whose fruit and vegetable intake was in the top fifth had a 22 percent lower diabetes risk than subjects whose intake was lowest.

Fruits and vegetables are low in calories, high in fiber, and rich in phytochemicals, minerals, and vitamins (including vitamin C), all of which may be protective against diabetes. This study was the first to examine the association of plasma vitamin C and the development of diabetes. The findings suggest that low levels of vitamin C are present before the onset of diabetes.

“Our findings highlight a potentially important public health message on the benefits of a diet rich in fruit and vegetables for the prevention of diabetes,” the authors of the study write.

“The strong independent association observed in this prospective study, together with biological plausibility, provides persuasive evidence of a beneficial effect of vitamin C and fruit and vegetable intake on diabetes risk. Because fruit and vegetables are the main sources of vitamin C, the findings suggest that eating even a small quantity of fruit and vegetables may be beneficial and that protection against diabetes increases progressively with the quantity of fruit and vegetables consumed.”


Harding AH, Wareham NJ, Bingham SA. Plasma vitamin C level, fruit and vegetable consumption, and the risk of new-onset type 2 diabetes mellitus. Archives of Internal Medicine, 2008;168:1493-9.

Melissa’s Comments:

It’s difficult to accurately assess people’s fruit and vegetable intake because people often have trouble recalling what they ate. Researchers of this study didn’t rely on food frequency questionnaires alone; they also looked at levels of plasma vitamin C, a biomarker that is more strongly related to fruit and vegetable intake than is the level of plasma carotenoid or plasma vitamin E.

By looking at one of the most reliable indicators in the body of a high intake of fruits and vegetables, this study used another method to show that eating fruits and vegetables protects against the development of diabetes. As I have written in my books, that’s especially true when fruits and vegetables, but especially vegetables, are eaten in place of grains and sugars. It’s noteworthy that low levels of vitamin C come first before diabetes develops – just more evidence that you should be eating plenty of fruits and vegetables to prevent diabetes before it develops.

© Copyright 2008 Melissa Diane Smith

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