Mark Pine

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.