Inadequate levels of vitamin D are associated with an increase in the risk of cardiovascular disease and death, as reported at the American Heart Association 2009 Scientific Sessions. Results from 27 000 people 50 years or older with no history of cardiovascular disease for just over a year, found that those with very low levels of vitamin D (<15>30 ng/mL). Those deficient in vitamin D were also twice as likely to develop heart failure as those with normal levels.
"We concluded that even a moderate deficiency of vitamin D was associated with developing coronary artery disease, heart failure, stroke, and death," said coauthor Dr Heidi May (Intermountain Medical Center).
Deficiency in vitamin D is generally agreed to be a blood level of <20>150 ng/mL indicating excessive vitamin D. Data suggest that many people are likely getting inadequate vitamin D, he said, with studies showing that black Americans have blood levels ranging from 6-18 ng/mL and that white Americans have levels ranging from 16-25 ng/mL. In general, a supplement of 100 IU of vitamin D per day will increase blood levels of vitamin D by 1 ng/mL, Rimm said. Those taking 1000 IU per day should have blood levels in the range of 25-32 ng/mL and those taking 4000 IU should have levels of 40-50 ng/mL.
During the right times of year, five to 10 minutes a day of sunlight is sufficient is to make enough vitamin D. I do hear the concerns about skin cancer and I think people should wear suntan lotion, but it's probably better to put it on 10 minutes after you've been in the sun." Researchers cautioned that "in northern climes, even if you go out in the sun in January, you're not going to make much vitamin D, so there you would need supplementation to get adequate levels." One of the best dietary sources of vitamin D is fish. People should remember that diet is an important source of vitamin D, too, he noted. "One of the best dietary sources of vitamin D is fish. We already suggest people eat a couple of servings a week, but having three or four servings a week of fish can get you a fair bit of vitamin D, and would represent an additional 300 to 500 IU of vitamin D. This still might not be sufficient so you might need a little bit of sunlight or to take a vitamin D supplement. It's really a combination of things, that's probably the best approach."
Both Rimm and Dobnig said it is nearly impossible for anyone to suffer adverse effects from too much vitamin D. Those who spend whole days in the sun, such as lifeguards, have vitamin D levels ranging from 45 to 65 ng/mL, said Rimm. "Vitamin D is safe. Hypercalcemia is not a problem, with the rare exception of granulomatous disease," said Dobnig. He added that because vitamin D is a fat-soluble vitamin, it can be given weekly, or even monthly.