Daily consumption of magnesium-rich whole grains took a 30% bite out of the risk of diabetes among a cohort of more than 40,000 Black women, according to a recently published transatlantic study.

The 8-year study showed that the women who had the highest average intake of magnesium-containing whole grains (1–2 servings per day) had a 31% lower risk of developing type 2 diabetes compared with the women who ate the least amount of whole grain (less than one serving per week). These findings, published in the journal Diabetes Care, corroborate earlier studies showing similar levels of risk reduction among White women with the highest versus lowest magnesium intake.

Researchers from the Harvard School of Public Health, Boston University, and the Vrije Universiteit, Amsterdam, tracked 41,186 women of African descent, who had a mean age of 39, for 8 years, using a 68-item food frequency questionnaire. During the course of the study, 1,964 of the women were diagnosed with type 2 diabetes. In making their risk assessments, the investigators controlled for BMI, parental history of diabetes, smoking, alcohol consumption, soft drink consumption, calcium intake and other demographic/risk variables.

Both grain consumption and reduced risk of diabetes tracked closely with magnesium intake. The women with the highest average magnesium consumption (244 mg/day) had a 35% lower diabetes risk than those with the lowest magnesium intake (115 mg/day).

Bearing in mind the limitations of any risk-estimate study based on self-reporting, lead investigator Rob van Dam, MD, reported that, “These findings indicate that higher consumption of magnesium-rich foods, particularly whole grain products, is associated with a lower risk of type-2 diabetes in African-American women” (Van Dam RM, et al. Diabetes Care. 2006; 29(10): 2238–2243).

Magnesium is an important co-factor in enzyme-mediated metabolic reactions, and it may also have an influence on insulin secretion. A large and growing body of data indicate that magnesium, as well as other minerals like zinc and chromium, have salutary effects on glucose metabolism, and may play a role in diabetes prevention.

The authors stress, however, that their data pertain only to magnesium-rich foods, and strictly speaking, cannot be extrapolated to make a case for magnesium supplement use as a method of reducing diabetes risk.

Given the rampant rise of diabetes among African-Americans in particular, the findings are extremely timely. Whole grains are relatively inexpensive, widely available and extremely nutritious.