Vitamin D has an important role in regulating cell growth. Laboratory experiments suggest that it helps prevent the unrestrained cell multiplication that characterizes cancer by reducing cell division, restricting tumor blood supply (angiogenesis), increasing the death of cancer cells (apoptosis), and limiting the spread of cancer cells (metastasis). Like many human tissues, the prostate has an abundant supply of vitamin D receptors. And, like some other tissues, it also contains enzymes that convert biologically inactive 25(OH)D into the active form of the vitamin, 1,25(OH)2D. These enzymes are much more active in normal prostate cells than in prostate cancer cells. _Harvard Health
Vitamin D has come a long way since its discovery in 1920. Once seen mainly as a cure and preventative for rickets, and later seen as an adjunct to prevent osteoporosis of ageing, Vitamin D is now considered an important ingredient in the overall quest for lifelong health. Vitamin D may even turn out to be a preventative for heart disease, cancer, viral infections, dementia, multiple sclerosis, and allergic disorders.
Image: Harvard Health
Low levels of vitamin D lead to low bone calcium stores, increasing the risk of fractures. If vitamin D did nothing more than protect bones, it would still be essential. But researchers have begun to accumulate evidence that it may do much more. In fact, many of the body’s tissues contain vitamin D receptors, proteins that bind to vitamin D. In the intestines, the receptors capture vitamin D, enabling efficient calcium absorption. But similar receptors are also present in many other organs, from the prostate to the heart, blood vessels, muscles, and endocrine glands. And work in progress suggests that good things happen when vitamin D binds to these receptors. The main requirement is to have enough vitamin D — but many Americans don’t… even in healthy people, advancing age is linked to an increased risk of vitamin D deficiency. _Harvard Health
One of the most intriguing areas of Vitamin D research is in connection to its possible role in preventing cancer:
… Evidence for some cancers, he [Michael Holick] says, is better than others. “If I were to pick one cancer where vitamin D is sure to matter, it would be colon,” he says. “The second would be breast cancer.”
… The vitamin appears to defend against viral infections, too. The annual winter flu season comes at a time when people garner little vitamin D from sunshine and blood levels fall. The timing may not be a coincidence, says Reinhold Vieth, a biochemist at the University of Toronto. Low vitamin D levels might offer the virus the edge it needs to gain a foothold in the population and spread from person to person.
… Another study in the United States showed that substantially more people with low vitamin D develop upper respiratory infections than do people with more of the vitamin, and taking up to 2,000 IU a day reduced such infections by two-thirds in one trial. A Dutch research team also reported online in May in Pediatrics that babies with low levels of vitamin D at birth were several times as prone to develop a severe respiratory viral infection in the first year of life as were newborns with ample amounts.
… Asthma, another immune malfunction that can wreak havoc in the lungs, also shows links to low vitamin D levels. In a study conducted at National Jewish Health respiratory hospital in Denver, researchers found that people with asthma who also had low levels of vitamin D had poorer lung function than asthmatics who had higher levels of the vitamin. _Science News
What about Vitamin D toxicity? That is not a danger for people who take around 1,000 IU or less per day. Many people require more — much more. The only way to know is to have your Vitamin D level measured. And even then, you may be given the wrong advice, because of the way that laboratory norms are calculated in clinical medicine.
The older you are, the more Vitamin D you are likely to need. And the farther from the equator you live, and the fewer days of direct sunshine you are exposed to, the more Vitamin D you will need.
Medical science knows very little about optimum human nutrition. But as we learn more about individual genetic function and more about the mysteries of cell and tissue biology, we will almost certainly learn that everything we now think we know, just ain’t so.