Multivitamins and Healthy Immune Function

A recent 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.

Br J Nutr. 2007 Oct;98 Suppl 1:S29-35.

High glycemic index diets increase the risk of age-related macular degeneration

Several dietary factors are known to be risk factors for age-related macular degeneration (AMD), the leading cause of blindness among persons over 65. New research indicates that high-glycemic-index diets may be a risk factor for early AMD and potential visual loss later in life.

A new study published in the American Journal of Clinical Nutrition examined the association between dietary glycemic index and the 10 year incidence of AMD in the Blue Mountain Eye Study population.

This was a population-based study with 3,654 participants over 49 years of age. Volunteers were examined at the beginning (1992-1994); then were reexamined after 5 years and again after 10 years.

Over 10 years, 208 of the participants developed early AMD. After adjusting for age, smoking, other risk factors, and dietary constituents, a higher average dietary glycemic index was associated with an increased 10 year risk of early AMD. Conversely, a greater consumption of cereal fiber and breads and cereals (predominantly lower glycemic index foods such as oatmeal) was associated with a reduced risk of early AMD. No relation was observed with advanced AMD.

The research suggests that a high-glycemic-index diet is a risk factor for early AMD, and low-glycemic-index foods such as oatmeal may protect against early AMD.

American Journal of Clinical Nutrition, Vol. 88, No. 4, 1104-1110, October 2008

Magnesium intake and risk of type 2 diabetes

A meta-analysis recently published in the Journal of Internal Medicine analyzed the association between magnesium intake and the risk of type 2 diabetes. The meta-analysis involved studies of magnesium intake (both from foods only and from foods and supplements) published between 1966 and 2007. Seven studies meeting the criteria were identified, and in total they included 286,668 participants and 10,912 cases. All but one study found an inverse relation between magnesium intake and risk of type 2 diabetes, and in four studies the association was statistically significant. Overall, an increase of 100 mg of magnesium per day resulted in a 15% reduction in overall risk of type 2 diabetes.

Based on these studies, magnesium intake is inversely associated with incidence of type 2 diabetes. This finding suggests that increased consumption of magnesium from supplements and foods such as whole grains, beans, nuts, and green leafy vegetables may reduce the risk of type 2 diabetes.