Fewer cases of flu and colds thanks to artificial sunlight
For healthy people, colds and flu are relatively harmless, but that doesn't take away from the fact that infection with such a sneaky virus can be quite unpleasant. Fortunately, there is a simple way to significantly reduce the misery of colds and flu, according to recent research by the US military. Artificial UV light and vitamin D supplements can drastically reduce the number of days you have to stay home sick during the winter months.
The study we are referring to, which was published in Medicine and Science in Sports and Exercise in July 2021, involved 250 soldiers. The study was conducted during the winter months.
The researchers already knew that soldiers' vitamin D levels drop significantly during this period. The average American soldier has vitamin D levels of 80 nanomoles/L in the summer. However, during the winter months, those levels drop by half to 40 nanomoles/L. That is not low enough to pose an acute health risk, but it is far from optimal. The immune system cannot function properly at such low levels.
Low vitamin D levels in the winter months partly explain why so many people are struck down by flu and colds during that season. The researchers wanted to know whether supplements with extra vitamin D or artificial UV light could prevent this.
The researchers divided the soldiers into four groups. One group received a vitamin D3 supplement for 12 weeks, another group received a placebo (without vitamin D), another group received weekly treatments with artificial UV light, and a final group received treatments with light that did not stimulate the production of vitamin D by the skin.
In both the supplement groups and the light groups, the treatment consisted of two parts. First, the researchers built up the vitamin D levels over a period of 4 weeks, then they kept them stable for 8 weeks. During this period, the supplement users took 1,000 IU (or 25 micrograms) of vitamin D3 per day, while the soldiers in the artificial UV light group received three treatments per week.
In the eight weeks that followed, the researchers switched to a maintenance dose. The daily dose of vitamin D in the supplement group was reduced to 400 IU (or 10 micrograms) of vitamin D3 per day, while the soldiers in the artificial UV light group received only one session per week.
Both artificial sunlight and vitamin D3 pills increased winter vitamin D levels from 40 nanomoles/L to the summer level of 80 nanomoles/L. Both treatments were therefore equally effective.
When the researchers looked at flu and colds, they came to the same conclusion. Compared to the soldiers in the placebo groups, the subjects who had taken vitamin D3 or been treated with artificial sunlight were sick 36 percent fewer days as a result of a cold or flu. And if the latter group of subjects did become ill, their symptoms were 15 percent less severe than those of the soldiers in the placebo groups.
