In a previous post, I mentioned that morning sunlight exposure correlated to a lower body-mass index (BMI), a measurement which is used to assess whether a person is obese, normal weight, overweight, etc. It was obvious that production of vitamin D was not the mechanism that led to the slimmer bodies, because D production is greatest at midday.
The relationship of weight to sunlight has again been assessed in an impressive animal study. The researchers fed mice a high-fat diet to investigate the effects of vitamin D and/or ultraviolet radiation (UVR) (such as that in sunlight) on the potential to develop obesity, diabetes and other measures—a cluster of maladies known as the metabolic syndrome (MetS). Long-term UVR exposure significantly suppressed weight gain, glucose intolerance, insulin resistance, and fatty liver disease. It also suppressed blood levels of fasting insulin, glucose and cholesterol. Interestingly, those benefits were not reproducible by vitamin D supplementation. However, when nitric oxide (NO) was increased by UVR exposure, many of the positive benefits were indeed duplicated.
The authors make a profound statement to conclude their research: “These studies suggest that UVR (sunlight exposure) may be an effective means of suppressing the development of obesity and MetS, through mechanisms that are independent of vitamin D but dependent on other UVR-induced mediators such as NO.”
The takeaway from this research is that we cannot simply throw a vitamin D capsule at a problem and expect it to take the place of the sun. That marvelous hormone, vitamin D, is critically important to human health, and the information here does not denigrate its importance; nevertheless, there are many other important sunlight products such as NO, serotonin, and endorphins that are essential to wellbeing. We need them all, and sunlight is the best source.
Stay slim and stay healthy by enjoying safe, non-burning sunlight.
 Geldenhuys S, Hart PH, Endersby R, Jacoby P, Feelisch M, Weller RB, Matthews V, Gorman S. Ultraviolet radiation suppresses obesity and symptoms of metabolic syndrome independently of vitamin D in mice fed a high-fat diet. Diabetes. 2014 Nov;63(11):3759-69.