New Study Shows Antioxidant-Rich Foods Diminish Diabetes Risk

Veronica Hackethal

November 10, 2017

Consuming a diet rich in antioxidant foods may help decrease the risk of type 2 diabetes, according to a new study published November 9 in Diabetologia.

The trial is the first prospective investigation into the link between total antioxidant consumption and risk of type 2 diabetes, say the researchers.

"This work complements our current knowledge of the effect of isolated foods and nutrients and provides a more comprehensive view of the relationship between food and type 2 diabetes," senior author Guy Fagherazzi, PhD, of the University Paris-Sud, Villejuif Cedex, France, said in a press release.

Prior research has suggested that oxidative stress may contribute to the development of type 2 diabetes. While some studies have found that the antioxidant vitamin E may help decrease the risk of type 2 diabetes, others have not confirmed this effect for the antioxidants vitamin C, flavonoids, and lycopene.

However, these studies looked only at isolated nutrients, and there is some evidence to suggest that ingredients in the diet may have a cumulative or synergistic effect and that the total antioxidant capacity may help reduce the risk of type 2 diabetes.

In particular, fruits, vegetables, wine, coffee, and tea have been identified as important sources of antioxidants.

"Ceiling Effect" for Total Antioxidant Intake and Diabetes Risk

To examine whether overall antioxidant content in the diet has an impact on diabetes risk, Dr Fagherazzi and colleagues analyzed data from the large E3N-EPIC prospective cohort study, begun in France in 1990 with the aim of studying risk factors for cancer and severe chronic conditions in women born between 1925 and 1990.

The current analysis included a subset of 64,223 women who had a mean age of 52 years and were free of diabetes and cardiovascular disease at the beginning of the study. At baseline (1993), women self-reported their typical diet for the past year on a detailed questionnaire that asked about over 200 foods and was specific to the French population.

The researchers used this information, along with a database of antioxidant capacity for a large variety of foods, to calculate the total antioxidant capacity score for each woman. Then they looked at the relationship between this score and risk for type 2 diabetes.

They decided to exclude coffee from the calculations, so as not to obscure associations between other antioxidants and type 2 diabetes risk. Coffee is rich in antioxidants and has already been shown to be associated with a reduced risk of type 2 diabetes.

Over 15 years of follow-up, 1751 women developed diabetes.

Results adjusted for important diabetes risk factors, including smoking, education level, hypertension, high cholesterol, and family history of diabetes showed that women who consumed higher levels of total antioxidants had a lower risk of type 2 diabetes.

Women who ate the most antioxidants (highest quintile) had a 39% lower risk of type 2 diabetes than women who ate the least amount (lowest quintile; hazard ratio [HR], 0.61).

After further adjustment for body mass index (BMI), one of the most important contributors to diabetes risk, the magnitude of the risk decreased slightly but remained statistically significant. Women who ate the most antioxidants had a 27% lower risk of type 2 diabetes, compared with those who ate the least (HR, 0.73).

The effect seemed to be directly proportional to increasing intake of total antioxidants, up to a level of 15 mmol/day. After that, the effect plateaued, so that increasing total antioxidant consumption above that level had no further beneficial effect on type 2 diabetes risk.

Study limitations include the use of a single dietary assessment at the beginning of the study and the fact that dietary patterns may change over time. Also, the fact that only women were studied — who may have been more health conscious than average — may mean the results are not generalizable to a wider population, say the authors.

Fruit and Vegetables Contribute to Reduced Risk; Still a Question Mark on Wine

Foods that contributed the most to high total antioxidant scores included fruit (23%), vegetables (19%), alcoholic beverages (15%), and tea and other hot beverages (12%).

Women with high total antioxidant scores drank more wine than women with lower antioxidant scores, but the authors stress the importance of moderation with regard to wine consumption.

Consuming high quantities of alcohol has been linked to increased diabetes risk. And only wine — not beer or spirits — has been associated with decreased diabetes risk.

While the study cannot provide information on the mechanisms via which total antioxidant consumption may decrease the risk of diabetes, it paves the way for future studies to look at the issue, say the authors.

"We know that these molecules counterbalance the effect of free radicals, which are damaging to cells, but there are likely to be more specific actions in addition to this — for example, an effect on the sensitivity of cells to insulin. This will need to be confirmed in future studies," said first author Francesca Romana Mancini, DVM, PhD, also of the University Paris-Sud.

The study was funded by the World Cancer Research Fund, the Agence Nationale de Recherche, and the European Union. The authors report no relevant financial relationships.

Diabetologia. Published online on November 9, 2017. Abstract

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