It is well known that diet plays an important role in the development of type 2 diabetes, but less is known about the influence of specific nutrients on non-Western populations. A report published in the March 2009 issue of the American Journal of Clinical Nutrition revealed a protective effect of calcium and magnesium against diabetes in a large group of Chinese women.

The study involved 64,191 women participated in the Shanghai Women’s Health Study, living in Shanghai,China. Analysis of dietary questionnaire responses determined calcium and magnesium intake.

Women whose intake was in the highest group at an average of 649.6 milligrams per day had a 27 percent lower risk of diabetes than those whose intake was in the lowest group at 277.5 milligrams. Women whose intake of magnesium was highest at an average of 318.1 milligrams per day experienced a 20 percent lower risk compared with those in the lowest category of intake. Dairy intake was also related to a lower risk of type 2 diabetes.

The researchers did not have information on vitamin D intake, but the protective effect of dairy products could be partly due to their vitamin D content as well as calcium. The combination of vitamin D and calcium has been associated with a reduction in the risk of type 2 diabetes in previous research.

Source: Am J Clin Nutr 89: 1059-1067, 2009.

An article published in the British Journal of Nutrition summarizes the roles of select vitamins and trace elements in immune function. Adequate intakes of micronutrients are required for the immune system to function efficiently. Micronutrient deficiency suppresses immunity by affecting antibody responses, leading to imbalances in the immune system. This situation increases susceptibility to infections, which increases disease and death risk. In addition, infections aggravate micronutrient deficiencies by reducing nutrient intake, increasing losses, and interfering with utilization by altering metabolic pathways. Inadequate intakes of micronutrients are common in people with eating disorders, smokers (active and passive), individuals with chronic alcohol abuse, certain diseases, during pregnancy and lactation, and in the elderly.

Micronutrients contribute to the body’s natural defenses on three levels by supporting physical barriers (skin/mucosa), cellular immunity, and antibody production. Vitamins A, C, E, and the mineral zinc assist in enhancing the skin barrier function. Vitamins A, B6, B12, C, D, E, and folic acid, and the minerals iron, zinc, copper and selenium work synergistically to support the protective activities of the immune cells. Finally, all these micronutrients, with the exception of vitamin C and iron, are essential for the production of antibodies.

Overall, inadequate intake and status of these vitamins and minerals may lead to a suppressed immune system, which increases the risk of infections and aggravates malnutrition. Therefore, supplementation with a multivitamin that includes these micronutrients can support the body’s natural defense system by enhancing all three levels of immunity.

It has been hypothesised that dietary changes associated with a westernised lifestyle may have contributed to the increase in asthma in the developed world. Epidemiological evidence of an inverse association of dietary fruit intake with pulmonary function and respiratory symptoms suggests that dietary antioxidants may modify the development of respiratory disease in susceptible individuals.

Previous studies found that symptomatic asthma in adults is associated with a low dietary intake of fruit, the antioxidant nutrients vitamin C and manganese, and low plasma vitamin C levels.

A new meta-analysis review also suggests that a low dietary intake of vitamin A and C increases the risk of asthma. 40 studies (up to November 2007) of asthma, wheeze, or airway responsiveness in relation to intakes and serum concentrations of vitamins A, C and E were included in this latest review.

Dietary vitamin A intake was significantly (182µg/day) lower at in people with asthma compared to those without asthma; and vitamin A intake was 344µg/day lower in patients with severe asthma compared to those with mild asthma. Lower serum levels of vitamin C were also associated with an increased occurrence of asthma. Vitamin E intake was generally unrelated to asthma status but was significantly lower in people with severe asthma compared to people with mild asthma.

These findings suggest that diet may be a potentially modifiable risk factor for the development of asthma.

Sources: Thorax April 2009 online; Thorax 2006;61;388-393