New research out of Australia has found that vitamin D may positively affect blood pressure. Though a cause-and-effect relationship was not established, after pooling data from a whopping 140,000 people, Australian scientists saw a clear trend: for every 10% increase in vitamin D blood levels, blood pressure declined. Even better, the team behind the study concluded that adequate vitamin D levels lowered the chances of even developing high blood pressure by 8%.
Researchers in Iran have found that supplementing with vitamin D--along with its old pal calcium--improves symptoms of gestational diabetes, a sometimes dangerous metabolic disorder during pregnancy. Supplementation appeared to reduce levels of glucose, insulin, and LDL ("bad") cholesterol, and insulin sensitivity and HDL ("good") cholesterol also improved.
On the flipside, according to the Journal of the American Medical Association (JAMA), D is not helpful for treating adult asthma. Though not previously associated with reducing asthma symptoms, this result is still surprising because low vitamin D levels in asthma patients have been linked to worse symptoms and a double-blind study of Japanese children found that supplementing with vitamin D reduced the incidence of asthma attacks compared with a placebo.
As the lead author in the Australian study put it, "In view of the costs and side effects associated with antihypertensive drugs, the potential to prevent or reduce blood pressure and therefore the risk of hypertension with vitamin D is very attractive." That logic may apply for other conditions as well.
As to the question of mandatory testing, Aisle7 Chief Science Editor Dr. Alan Gaby points out that questions remain about which reference ranges indicate deficiency, whether the screenings provide meaningful information, and whether low levels of certain vitamin D markers truly indicate low vitamin D status. Fortunately, he suggests, "There is a simple solution to this debate: average adults, with their doctor's approval, supplement with 800 to 1,200 IU per day, which is enough to realize the benefit in most cases, and not so much to risk toxicity."
Deficiencies are more common in winter, and seen more often in seniors, vegans, and people living in northern latitudes or those with malabsorption due to surgeries, celiac disease, or other intestinal condition.