There’s a reason depressed people stay indoors: it’s easier to stay depressed when you’re not out in the sun. Sun rays have a way of penetrating clouds of gloom and lifting mood. Today’s research excerpt explains why.

A study of more than 81,000 women found those with the highest intake of vitamin D from food sources had a significantly lower prevalence of depressive symptoms.

The researchers suggested that vitamin D may affect the function of dopamine and norepinephrine. These are neurotransmitters that are likely involved in depression, while also modulating the relationship between depression and inflammation

The connection between vitamin D and depression is not new. In 2006, scientists evaluated the effects of vitamin D on the mental health of 80 elderly patients and found those with the lowest levels of vitamin D were 11 times more prone to be depressed than those who received healthy doses.

In the current study, researchers found that intake of more than 400 IU of vitamin D from food sources was associated with a 20 percent lower risk of depressive symptoms compared with intake of less than 100 IU. This was a significant benefit from a very small amount of vitamin D — as 400 IU is far too low to benefit most people (not to mention your body is made to get vitamin D primarily from the sun, not food or supplements, as I’ll explain below).

It now appears as though most adults need about 8,000 IU’s of vitamin D a day in order to get their serum levels above 40 ng/ml, which is the lowest they should be. Ideally your serum levels should be between 50-70 ng/ml, and up to 100 ng/ml to treat cancer and heart disease.

It’s likely that vitamin D fights depression via several pathways, not only directly in your brain but also via inflammation. Vitamin D receptors have been identified throughout the human body, and that includes in your brain. Researchers have located metabolic pathways for vitamin D in the hippocampus and cerebellum of the brain, areas that are involved in planning, processing of information, and the formation of new memories.

Source: “New Study Shows Vitamin D Helps Prevent Depression.” By Dr. Mercola.