There's a reason why vitamin D now outsells vitamin C in some stores. Starting in 2008, a corona’s worth of research began showing vitamin D is good for most everything under the sun. Study after study has come out documenting vitamin D's benefits on everything from colon, prostate and breast cancer to blood pressure and heart disease to insulin sensitivity and glucose tolerance to psoriasis and dermatitis.1-4
Vitamin D and bone health
And of course, vitamin D might be best known for its bone-health bona fides. Vitamin D supplementation reduces the number of fractures and directly improves neuromuscular function, thus helping to prevent falls and subsequent fractures.5
In September of 2008, with such incontrovertible evidence, the FDA amended its health claim for calcium and osteoporosis prevention, adding that the combination of calcium with vitamin D was even better because vitamin D helps calcium get absorbed. In fact, the two have a complementary relationship so that any study on calcium should also include vitamin D, and vice versa, says vitamin D researcher Robert Heaney, MD, from Creighton University in Nebraska.
“Each nutrient is necessary for the full expression of the effect of the other, and where their actions are independent, their effects on skeletal health are complementary,” said Heaney. “Nutrient status for both tends to be deficient in the adult population of the industrialized nations. Hence, supplementation or food fortification with both nutrients is appropriate and, given contemporary diets and sun exposure, probably necessary.”6
Vitamin D and immunity
How can a humble little vitamin be responsible for so many seemingly divergent health conditions? For one, most organs, including the gut, brain, heart, pancreas, skin, kidneys, and immune system have receptors for vitamin D.6 But it’s more than that. It’s because of the way vitamin D helps cells perform. Before all this recent vitamin D research came out, researchers believed cells would size up pathogens and then build an ad hoc defense to counter each one.
But then it was discovered that actually inside every cell is a sort of file cabinet that contains the blueprints for any invader a cell might expect. And vitamin D holds the key to the file cabinet. In essence, vitamin D makes cells more efficient with cellular communication and performance.
In October/November 2010, the Institute of Medicine has said it will come out with revised vitamin D recommendations, probably at least a conservative 1,000 IU a day, though most researchers say the evidence shows that 2,000 IU a day is more appropriate. Scientists worldwide are making repeated calls for this to happen, as the studies showing vitamin D's profound effects on health keep pouring in. This will give more media attention to the cheap hormone – it's really not a vitamin, which, by definition, can be attained only through the diet, and vitamin D is manufactured by the skin after direct exposure to the sun. No mastication required.
Even if it’s only 1,000 IU a day, one human clinical trial on cancer incidence used 1,100 IU per day of vitamin D along with 1,500 milligrams a day of calcium. The postmenopausal women who took both had a 77 percent reduction in the risk of all-cancer incidence.7
Vitamin D and eye health
A 2011 study of 1,300 elderly women (under 75) found that those who got the most vitamin D had a 59 percent decreased risk of developing age-related macular degeneration, compared to women with the lowest vitamin D intake.10 Age-related macular degeneration is the most common cause of blindness in the world.
Researchers also found that the women who had a blood vitamin D level higher than 38 nmol/L had a 48% decreased risk of early age-related macular degeneration (AMD). A blood level of 50 nmol/L is considered sufficient, according to the Institute of Medicine.
The top food sources of vitamin D among women in the study were milk, fish, fortified margarine and fortified cereal. No correlation was found between self-reported time in direct sunlight, which is also a source of vitamin D, and AMD.
Study author Amy E. Millen, PhD, of the University of Buffalo, and colleagues studied data from 1,313 women to investigate whether a well-known blood test for vitamin D status might be associated with early age-related macular degeneration.
And here’s one final tidbit: Virtually every person in North America is deficient in vitamin D. One population study measured vitamin D status of blacks, whites and Hispanics in North America and found 60 percent of Caucasians were deficient – and that was the best of the lot! At the other end, 98 percent of black teenage girls had suboptimal values.8
As vitamin-D levels were found to be 24 per cent lower during winter compared with summer, could vitamin-D deficiencies be the reason people get sicker in wintertime?
Vitamin D and pregnancy
Recent research in the Netherlands11 suggests that infants born with low levels of vitamin D may be at higher risk for lung infections caused by a common respiratory syncytial virus (RSV). The researchers measured concentration of vitamin D in the babies' cord blood at birth. This echoes the results of an earlier study that found newborns with low vitamin D count were more likely to wheeze and develop respiratory infections than those with higher levels.
The researchers wrote “Especially during pregnancy, doses up to 4000 IU per day may be needed to maintain optimal maternal and neonatal health,” which leads us to ...
Vitamin D dosage
As for how much to take, well, that gets a little controversial. First, vitamin D3, not D2, is the supplementation that is currently thought of as best. Next, the Institute of Medicine (a branch of the National Institutes of Health) government came out with a report in 2010 that recommended only 600IU/day for adults up to age 70, a number that shocked most researchers who are involved in vitamin D studies because it was so low. After age 70, the number goes up to 800 IU/day.The report also said most people are getting enough vitamin D from their diet and sunlight. We at WellWise seriously doubt that.
Many others in the know recommend 4,000 IU/day. Most seem to agree that you can take up to 10,000 IU/day before there is any danger of getting too much.
10. Millen, Amy E. et al. Arch Ophthalmol. 2011;129(4):481-489. doi:10.1001/archophthalmol.2011.48
11. Belerbos, Mirjam E, et al. Cord Blood Vitamin D Deficiency is Assoicated With Respiratory Syncytial Vius Bronchiolitis; Pediatrics, published online ahead of print.
Disclaimer: The information provided in this section is a public service of WellWise.org, and should not in any way substitute for the advice of a qualified healthcare professional and is not intended to constitute personal medical advice.