MD-Writer Blog

When young, I was told by my mom (a dietician) and my teachers that vitamin D was necessary for strong healthy bones. If you didn’t get enough, you might get rickets, a softening of bones that leads to fractures. That was pretty much the story about it until recently. I wouldn’t have guessed that Vitamin D might turn out to be one of the most important vitamins for many bodily functions.

Last March, I wrote in a post that British medical researchers had found that people with higher vitamin D levels had lower rates of cardiovascular disease and diabetes. Danish and Canadian researchers found that vitamin D is necessary for the proper functioning of both innate and adaptive immune systems. And Dutch researchers found that the vitamin may counter mental depression in regions with where winters are long and dark, like the Netherlands.

But vitamin D may have more benefits still. An article yesterday in USA Today described a study by British scientists on cognitive impairment, which they presented at the Alzheimer’s Association international conference now underway in Honolulu. Using data on cognitive functioning and vitamin D levels from 3000 Americans aged 65 and older, who had participated in a U.S. national health survey, the researchers found that rates of cognitive impairment were more than 40% higher in people with deficiency of the vitamin and nearly 400% higher in those with severe deficiency.

Also, medical scientists at the University of Rochester and University of Chicago investigated the roles of the vitamin D receptor, the site where the vitamin binds to the cell and exerts its effect, in the health and disease of the intestines. The results of their work appeared in the American Journal of Pathology online last month and were reported in ScienceDaily on Thursday.

The researchers studied mice that had been engineered to lack the vitamin D receptor (VDR knockout mice) and compared them with normal mice. They found that Salmonella bacteria were much more virulent when infecting the intestines of the knockout mice than the normal ones. The knockout mice would lose weight more quickly and succumb to infection more often. But even when the knockout mice were free of germs, they had higher levels of inflammatory molecules in their intestines than the normal mice.

The findings indicated that the activity of the vitamin D receptor, which is stimulated by vitamin D, plays a major role in protecting the animals from intestinal infection and maintaining their intestines in a normal state free from inflammation. The findings suggest also that besides helping to limit infections, the activity of vitamin D and its receptor may play an important role in preventing inflammatory bowel disease and cancer.

Addendum: While I was composing this post, I received an email from Scientific American reporting two more studies on the benefits of vitamin D. So I’m updating the post now, several hours later.

A study of Parkinson’s disease incidence among 3000 Finnish men and women aged 50-79 determined the subjects’ blood levels of vitamin D and followed them for 29 years. All participants were free of the disease at the start of the study. Those the highest levels of vitamin D (above 50 nmol/L) had a 65% lower rate of developing Parkinson’s disease than those with the lowest levels (below 25 nmol/L). That country’s National Institute for Health and Welfare conducted the investigation, which was reported this week in the Archives of Neurology.

Another study by the University of Exeter in the U.K. determined the vitamin D levels of more than 800 Italian men and women. More than half the subjects who had dementia were deficient in the vitamin, with levels below 50 nmol/L. Moreover, those with levels below 25 nmol/L were 60% more likely to experience cognitive impairment during a 6-year follow-up period. The study was reported this week in the Archives of Internal Medicine.

The SciAm article also notes that three-quarters of American adults and teenagers are believed to be vitamin D deficient. According to the U.S. Institute of Medicine, daily vitamin intake should range between 200-600 IU per day. The article noted that the optimal blood level of the vitamin is above 75 nmole/L.

Can we improve our mood, ward off three serious diseases, and avoid infections by taking a single inexpensive pill? Perhaps we can with vitamin D. The buzz about the vitamin seems to get louder by the day. The fact that this subject of medical news is a cheap, widely available tablet suggests it’s not just hype spun a company seeking to boost sales.

Several reports on possible benefits of the vitamin have appeared in just the last few weeks. In late February, medical researchers in the U.K. published a meta-analysis of research on the relationship of vitamin D blood levels to a group of illnesses they called “cardiometabolic disorders,” which included cardiovascular disease, diabetes, and metabolic syndrome. The scientists pooled 28 studies involving 100,000 middle-aged and elderly adults and found a 43% reduction in these of illnesses among those with the highest levels of the vitamin.

This week, doctors and scientists in Copenhagen showed that vitamin D supports the immune response of T-cells to cellular antigens. T-cells are white blood cells involved in cellular immunity, the part of the immune system that recognizes and eliminates invasive organisms, such as viruses, that reside within the body’s cells. T-cells can also distinguish and destroy cancer cells.

The Danish research, which was covered by both Scientific American and ScienceDaily, found that vitamin D participates in a critical step in transforming T-cells from silent sentinels on the watch for invasive organisms into messengers that sound the alarm and killers that attack compromised cells. As explained by one of the scientists who did the research:

When a T cell is exposed to a foreign pathogen, it extends a signaling device or ‘antenna’ known as a vitamin D receptor, with which it searches for vitamin D. This means that the T cell must have vitamin D or activation of the cell will cease. If the T cells cannot find enough vitamin D in the blood, they won’t even begin to mobilize.

A T-cell recognizes danger when it contacts a foreign antigen on the surface of another type of white cell, called a macrophage, which ingests invaders or cancer cells. The contact then triggers the gene for the antenna, which forms a complex with vitamin D. If the T cell has sufficient quantities of the vitamin, then another gene gets triggered, and its product activates the T-cell and transforms it into an immune fighter.

In January, scientists in Montreal reported that the vitamin also participates in another crucial immune function. It supports the recognition of harmful bacteria by monocytes, epithelial cells and macrophages in the intestine. These important components of the immune system secrete an antibacterial substance in response to contact with muramyl dipeptide, a chemical pattern found on the surface of many bacteria.

There’s also evidence that vitamin D counters depression. Two years ago, researchers in Amsterdam reported that vitamin D levels averaged 14% lower in people with minor and major depression among a large Dutch cohort of more than 1000 persons participating in a long-term epidemiological survey. In line with this discovery, medical researchers at the Loyola University Health System in Chicago announced plans this week for a trial to learn whether vitamin D supplements would improve the mood of women in that city, where harsh winters often keep people indoors and out of the sun.

Vitamin D is synthesized in the skin in response to sunlight. But in America (as well as much of the rest of the developed world), exposure to sunlight is insufficient to produce enough of the vitamin. As a result, three-quarters of Americans may be vitamin D deficient, according to research done as part of a national survey of Americans’ health.