Think of a study of more than 81,000 women. How much time do you think such a study would take; how much effort from the scientists? Then say it was prospective, that is, it looked into the future from the past. Dr. Elizabeth Bertone-Johnson, from the University of Massachusetts, senior author JoAnn Manson, from Harvard, and 12 colleagues from the Women’s Health Initiative did just that in a paper published in October of 2011. They looked at vitamin D intake from foods and supplements and current and later symptoms of depression.
Bertone-Johnson ER, Powers SI, Spangler L, Brunner RL, Michael YL, Larson JC, Millen AE, Bueche MN, Salmoirago-Blotcher E, Liu S, Wassertheil-Smoller S, Ockene JK, Ockene I, Manson JE. Vitamin D intake from foods and supplements and depressive symptoms in a diverse population of older women. Am J Clin Nutr. 2011 Oct;94(4):1104-12
The authors begin,
“Vitamin D may affect the function of dopamine and norepinephrine, which are monoamine neurotransmitters that are likely involved in depression. Furthermore, vitamin D may modulate the relation between depression and inflammation.”
They assessed 81,000 women at baseline (1993 -1998) and 3 years later for depression, using a simple depression rating scale, and for total vitamin D intake from foods and supplements. Their finding:
“In cross-sectional analysis that used baseline data, women with the highest intake of vitamin D and vitamin D from food sources had a significantly lower prevalence of depressive symptoms. . . In women without depressive symptoms at baseline, a higher vitamin D intake from food as associated with a lower risk of depression at year 3.”
However, they added,
“We did not find supplemental vitamin D intakes to be consistently related to measures of depressive symptoms.”
Explaining that in their group of women, for surprising and unknown reasons, vitamin D levels were higher in women who did not use vitamin D supplements. Remember in 1998, vitamin D supplements were either cod liver oil or multivitamins, both of which contained little vitamin D and toxic amounts of preformed retinol in the 1990s.
They went on to quote studies indicating that not 90%, but only 30% of vitamin D currently comes from sunlight. “Recent evidence suggested that only ~30% of circulating 25(OH)D is the product of sunlight exposure.” The studies indicating 90% comes from sunlight expose were from the early 1980s, when 90% did come from sunlight. This change from 90% to 30% reflects just how much we have become sunless creatures. Nature must have been totally surprised, when one day in the late 1980s, we suddenly decided that the Nature’s gift of sunlight was evil.
The authors conclude,
“Our results support an inverse association of vitamin D intake from foods and the occurrence of depressive symptoms in older women.”
In other words, this means the higher vitamin D intake from food the less depression. This is a good reason to eat ocean-caught salmon and fresh tuna (also known as brain food) two or three time a week.