There is a solid body of evidence in the scientific literature to support the notion of Vitamin D supplementation positively affecting health outcomes from respiratory infections.
As a supporter of holistic health, we here at Mossy Tonic tend to highlight a whole herb, whole food approach to well being over supplementation. That being said, Vitamin D is a nutrient that is hard to come by in our modern diet at sufficient amounts (see below), and the benefits from sunshine have real limitation.
Note the discrepancy of the RDA (recommended daily amount) of Vitamin D, at 600 IU (international units) and the much higher therapeutic daily dose of Vitamin D in the study, at 4,000 IU/day.
Natural sources of Vitamin D include beef liver, fish and egg yolk. While some traditional foods (like organ meet) contain higher amounts of Vitamin D, more modern diets can be lacking in vitamins and do not get anywhere close to the therapeutic doses of Vitamin D seen in these studies.
Sunlight also helps our bodies produce Vitamin D, however variations in latitude, season and skin color affect how much we make. People living in middle and high latitudes (farther from the equator) have less sunlight and it’s limited even more during the winter months. Those will darker skin need more sunlight to produce Vitamin D because of the sun-protective quality of melanin. Because of these factors, sunlight cannot always be relied on to supply adequate amounts of Vitamin D.
That being said, I want to stress that is IS good to “soak up the sun” when you can and in healthy moderation as it still can be a good source of Vitamin D.
“Vitamin D Supplementation to Prevent Acute Respiratory Tract Infections: Systematic Review and Meta-Analysis of Individual Participant Data” declares that “Vitamin D supplementation reduced the risk of acute respiratory tract infection among all participants”.