Vitamin D, known as the “sunshine vitamin” because it is only produced by the human body when exposed to sunlight, is essential for heath. We have known for years that vitamin D deficiency leads to a weakening of the bones, but more research is suggesting that vitamin D has links to cardiovascular health and depression as well.

During the last century, depression has increased, and vitamin D deficiency has increased as well. And although this correlation may not mean that a lack of vitamin D leads to depression, there is enough evidence mounting to support getting the 10-15 minutes of sunlight a day needed to product vitamin D, or to at least take it in supplement form.

A recent study looked at individuals who had experienced some type of heart disease or stroke, measures their vitamin D levels, and assessed them for depression. Interestingly, those with lower levels of vitamin D were more likely to be depressed than individuals with normal levels of vitamin D.

So as we approach winter and the sun gets dimmer and the days get shorter, remember that the seasonal depression many people experience may just be your body telling you it needs more vitamin D. Do yourself a favor a take a multivitamin and see if you feel better!

For more details on vitamin D and health, visit a story on vitamin D on CNN Health.

Future posts will examine the scientific evidence behind these claims.

Correlation Between Fish Consumption and Major Depression

In this classic article to the Lancet, JR Hibbeln demonstrated that there was an inverse correlation between annual fish consumption in a country, and that country’s incidence of depression (Hibbeln, 1998.)  As you can see from the graph, those countries that consumed the most fish per capita, such as Japan, had the lowest rates of depression.  Vice versa, those countries where people consumed the lowest amount of fish, such as the United States, had the highest rates of depression per capita.  Of course, correlation is not causation – the fact that two things are linked does not mean one causes the other.  For that reason, epidemiological studies such as this one must be confirmed by other methodologies: mechanistic studies in cell cultures, animal models of illness, and randomized clinical trials.  Research on why fish consumption might help prevent depression has focused on omega-3 fatty acids.  Cellular studies have confirmed that Omega-3 fatty acids, found mostly in certain kinds of fish, but also in walnuts, soybeans, flaxseed, and some other plants, are integral components of the cell membrane of brain cells.  Without adequate omega-3’s, membrane dysfunction may lead to cellular dysfunction, and from cellular dysfunction to conditions such as depression.

Next week: what randomized clinical trials show about omega-3 consumption and depression!