Spotlight on diet

Diet and diabetes were the focus of two recent large studies—one an umbrella review of the impact of diet patterns on diabetes incidence and the other a prospective study of fat intake and mortality among patients with type 2 diabetes.

Recent studies analyzed connections between diet and development of and mortality from type 2 diabetes.

The first study was an umbrella review of 53 systematic reviews with meta-analyses (75% of high methodological quality) that included prospective observational studies focused on type 2 diabetes' association with dietary behaviors or diet quality indices, food groups and foods, beverages, alcoholic beverages, macronutrients, and micronutrients.

Overall, the review found relatively few associations supported by high-quality evidence: an inverse association with increased intake of whole grains and cereal fiber, as well as moderate intake of total alcohol, and a positive association with higher intake of red meat, processed meat, and sugar-sweetened beverages. There was moderate-quality evidence supporting lower incidence of diabetes with consumption of chocolate, wheat bran, vegetable fat, yogurt, coffee, and tea. The other studied associations only had low or very low evidence support, “which might be explained by the high proportion of meta-analyses that included fewer than five studies, had high heterogeneity, or had moderate effect sizes,” said the study authors, who called for additional research on diet and diabetes. They also noted that the review's findings generally support existing dietary guidelines.

The other study used data from 11,264 participants with type 2 diabetes from the Nurses' Health Study and Health Professionals Follow-Up Study to compare mortality and consumption of polyunsaturated fatty acids (PUFAs). During follow-up, 2,502 died, 646 due to cardiovascular disease. After multivariate adjustment, compared with total carbohydrate consumption, total PUFA intake (as well as intake of marine n-3 PUFAs, α-linolenic acid, and linoleic acid individually) was associated with lower cardiovascular disease mortality. Inverse associations with total mortality were also observed for total PUFAs, n-3 PUFAs, and linoleic acid. Higher consumption of monounsaturated fatty acids from animal sources was associated with a higher mortality. Using a model, study authors calculated that replacing 2% of energy from saturated fatty acids with PUFAs or linoleic acid would be associated with 13% or 15% lower cardiovascular disease mortality, respectively. They noted that the benefits are mostly attributable to linoleic acid. “Our results suggest that dietary PUFAs, in replacement of saturated fatty acids or carbohydrates, may facilitate long term survival among adults with type 2 diabetes,” they concluded.

Both studies were limited by their observational design, the study authors noted, and they were published by The BMJ on July 3 and July 2, respectively.