(NaturalNews) High-dose vitamin D supplements may help increase the body's sensitivity to the blood sugar-regulating hormone insulin, thus reducing the risk of diabetes, researchers have found.
Insulin resistance (or insensitivity) occurs when the body's tissues stop responding as strongly to the presence of insulin. As a consequence, the cells uptake less sugar from the bloodstream, producing the elevated glucose levels characteristic of diabetes.
In the current study, conducted by researchers from Massey University and published in the British Journal of Nutrition, researchers randomly assigned 81 South Asian women between the ages of 23 and 68 to take either a placebo or 4,000 IU of vitamin D once per day. All participants suffered from insulin sensitivity at the start of the study, but none were taking diabetes drugs or vitamin D supplements larger than 1,000 IU per day.
At the start of the study, the average participant had vitamin D blood levels of approximately 50 nanomoles per liter, slightly lower than the average levels in a U.S. adult (60-75 nmol/L). After six months, women in the vitamin D group exhibited significantly more insulin sensitivity and less insulin resistance than women who had received a placebo. The largest effect was seen in women whose vitamin D blood levels had reached 80 to 119 nmol/L.
According to the Vitamin D Council, blood levels should be at least 125 nmol/L for optimal health.
Vitamin D has long been known to play an important role in bone and tooth health, and recommended daily intakes were originally calculated for these functions. Yet a growing body of research suggests that much higher intakes may be required to gain protection against cancer, autoimmune diseases, cardiovascular disease, diabetes and other chronic illnesses.
Health professionals currently debate what daily intakes are ideal, with the U.S. government recommending 200 IU for adults between the ages of 19 and 50, 400 IU for those aged 51 to 70, and 600 IU for those over the age of 70. The British government recommends that those at high risk of deficiency take a daily supplement of 1,000 IU. Yet studies such as the Massey University one keep pointing up the benefits of higher doses.
The study is not the first to connect vitamin D and diabetes. A 2009 meta-analysis published in the Journal of Clinical Endocrinology & Metabolism found that higher blood levels of vitamin D lowered diabetes risk. Likewise, in a study published in the journal Diabetic Medicine, researchers from the Sitaram Bhartia Institute of Science and Research in New Delhi found that a large dose of vitamin D significantly improved insulin sensitivity after meals in 71 men who were healthy except for central obesity.
Central obesity -- along with high blood pressure and high levels of fasting blood glucose, triglycerides and LDL cholesterol -- is a symptom of the condition known as metabolic syndrome, a significant risk factor for cardiovascular disease and diabetes.
Diabetes is widespread in the United States, with 24 million people diagnosed and 5.6 million undiagnosed, according to the U.S. Centers for Disease Control and Prevention. The National Institute of Health estimates that a further 70 to 80 million people suffer from metabolic syndrome or other "pre-diabetic" conditions. Some researchers have suggested that the nation's high rate of vitamin D deficiency might be partially to blame for this phenomenon.
Exposure to sunlight is still considered the healthiest way to get vitamin D, as the body can synthesize all it needs in only a fraction of the time it takes to acquire a tan. Health professionals recommend 15 minutes of sun every day on at least the face and hands for light-skinned people, and up to three times as much for people with dark skin. More time in the sun or some form of dietary supplementation may be necessary during the winter for people living far from the equator, especially those with dark skin.