Diabetics shouldn't forget their antioxidants: study

Vitamins C and E supplements may reduce memory loss in type-2 diabetics, a population at risk of increased impaired memory, suggests a new study from Canada.

Daily doses of 1000 mg of vitamin C and 800 IU of vitamin E improved mental function after carbohydrate-rich meals and may protect against memory loss, according to a small study with 16 diabetics published in the journal Nutrition Research.

"Results from this study suggest that postprandial oxidative stress is a potential contributor because deficits in [cognitive performance] after test meal consumption could be minimized by co-consumption of the test meal with high doses of antioxidant vitamins," wrote Michael Chui and Carol Greenwood from the University of Toronto.

The results may have significant benefits for the growing number of diabetes across the world. An estimated 19 million people are affected by diabetes in the EU 25, equal to four per cent of the total population. This figure is projected to increase to 26 million by 2030.

In the US, there are over 20 million people with diabetes, equal to seven per cent of the population. The total costs are thought to be as much as $132 billion, with $92 billion being direct costs from medication, according to 2002 American Diabetes Association figures.

According to Chui and Greenwood: "Type 2 diabetes mellitus is associated with chronic oxidative stress, a major contributor to cognitive decline and Alzheimer disease. Meal ingestion can induce acute elevations of free radicals, with higher susceptibility observed in patients with type-2 diabetes compared with healthy individuals."

Study details

The Toronto-based researchers recruited 16 type-2 diabetes with an average age of 63.5 and fed them a high-fat meal (50.4 g fat, 63 g carbohydrate, and 25.4 g protein), the same meal plus the vitamins, or just water. The meals were fed on three separate occasions and none of the subjects were regular consumers of high-dose antioxidant supplements.

The results of a battery of cognitive tests showed that consumption of the high-fat meal produced poor performance in verbal recall and working memory, compared to water consumption.

Consumption of antioxidant vitamins attenuated the detrimental effects of the high-fat meal and cognitive performance was "indistinguishable from that after water intake," wrote Chui and Greenwood.

Interestingly, a "small but significant improvement" in certain tests (word and colour classification) was observed after consumption of both meals, regardless of antioxidant intake, compared to water, "demonstrating the specificity of meal-induced impairments to memory function," they added.

"Results from this study can only provide indirect evidence that meal-induced oxidative stress may contribute to postprandial changes in cognitive performance," wrote the researchers.

"Nevertheless, the results are consistent with an animal-based study, which demonstrates that acute exposure of rats to low-dose ozone induces deficits in short- and long-term memory and that administration of vitamin E before or after exposure prevents these deficits."

Chui and Greenwood do note that the doses used were higher than current RDAs (vitamin C in the EU is 80 mg per day, while vitamin E is about 18 IU), but stated that these high doses have previously been reported to "effectively prevent the meal-induced elevations in circulating pro-inflammatory cytokines in subjects with type-2 diabetes and were selected on this basis."