Friday, April 18, 2008

Long-term magnesium intake reduces the risk of symptomatic gallstone disease among men

About 10-15 percent of the U.S. population (20 million people) have gallstones, and 1 million new cases are diagnosed yearly, according to the US National Institutes of Health. New research indicates that higher magnesium intake may decrease the risk of gallstone disease.

Magnesium deficiency has been associated with alterations in blood lipids (cholesterol) and insulin hypersecretion, which can lead to formation of gallstones. In addition, gallstone disease is an important risk factor for gallbladder cancer. A recent study published in the American Journal of Gastroenterology analyzed the effect of long-term consumption of magnesium on the risk of gallstone disease.

Researchers studied magnesium consumption and risk of gallstone disease in a group of 42,705 U.S. men from 1986 to 2002. Magnesium intake was assessed using a food frequency questionnaire, and newly diagnosed gallstone disease was determined twice a year.

During 13 years of follow-up, 2,195 cases of gallstones were documented. The average intake of magnesium was calculated to 352.8 milligrams per day for the study population. Men with the highest average levels of magnesium intake (454 mg/d) were 28 per cent less likely to develop gallstones, compared to men with the lowest average intake (262 mg/d).

It is not yet known whether higher magnesium intake protects against initial formation of gallbladder stones, or whether it simply decreases the likelihood of the already existing gallstones becoming symptomatic. However, since surveys show that most adults do not meet the RDA for magnesium (320 mg per day for women and 420 mg per day for men), improving the diet and supplementing magnesium may prove to be an effective means of reducing the progression of gallstone disease.

Wednesday, April 09, 2008

Effect of low-glycemic cereals on glucose response at subsequent meals

High-glycemic diets and their impact on blood glucose levels are increasingly associated with a heightened risk of obesity, type-2 diabetes, and cardiovascular disease. New research has shown that eating a low-glycemic breakfast comprised of certain whole grains can help moderate blood glucose responses for the rest of the day.

Researchers recently studied the extent to which high blood sugar levels and after-meal blood sugar increases are adjusted by the characteristics of cereal foods, including their glycemic index (GI) and content of indigestible carbohydrates (dietary fiber).

Twelve healthy subjects consumed two different test meals. In series 1, the test meals were consumed at breakfast, and after-meal blood glucose levels were calculated after a test breakfast, standardized lunch, and standardized dinner. In series 2, the subjects consumed test evening meals, and blood sugar levels were calculated after a standardized breakfast the following morning.

Breakfasts comprised of low-glycemic grains (such as barley or rye kernel) lowered blood glucose response levels at breakfast, at the following lunch, and cumulatively throughout the day (breakfast + lunch + dinner) when compared with white-wheat bread. An evening meal of low-glycemic grains resulted in lower blood-glucose responses at the following morning's breakfast (again, when compared with white-wheat bread).

The study concluded that glucose tolerance and sensitivity at subsequent meals can be improved during the course of an entire day - or even overnight - by choosing specific low-glycemic, whole-grain cereal products.

Source: Effect of cereal test breakfasts differing in glycemic index and content of indigestible carbohydrates on daylong glucose tolerance in healthy subjects, Nilsson et al, American Journal of Clinical Nutrition, Vol. 87, No. 3, 645-654, March 2008

Thursday, April 03, 2008

Vitamin D insufficiency widespread even in sunny climates

It is well-established that vitamin D deficiency or insufficiency is very common among northern populations. However, there is little information on the prevalence of vitamin D deficiency in southern climates with high sun exposure. A recent study shows that adult residents of southern Arizona are commonly deficient in vitamin D despite living in an area with chronic sun exposure.

A new study published in the American Journal of Clinical Nutrition determined and analyzed blood vitamin D levels in a group of residents of southern Arizona (statistically representative of the larger population). Participants were categorized into 4 groups on the basis of serum vitamin D concentrations: The average vitamin D concentration for the total population was 26 ng/mL. Of 637 participants, 22.3% had vitamin D concentrations >30 ng/mL, 25.4% had concentrations Adult residents of southern Arizona are commonly deficient in vitamin D despite living in an area with chronic sun exposure. Adults with darker skin are particularly at risk for vitamin D insufficiency.