Three paradoxes of vitamin D


Three paradoxes of vitamin D and how to overcome them.
1. The paradox of vitamin D supplements.
In many studies, high levels of vitamin D are associated with a reduced risk of many diseases, from cancer and autoimmune diseases to obesity and diabetes. The quality and reliability of these studies are beyond doubt. However, conversely, vitamin D supplements do not reduce the risks of diseases almost anywhere. Why? Two possible explanations for the paradox:
1. Vitamin D is a surrogate marker of health, meaning it is higher in those who spend more time outdoors, meaning they are more physically active, socialize more, etc.
2. Sunlight (ultraviolet) induces the formation of about a dozen beneficial compounds besides vitamin D (such as nitric oxide, beneficial for lowering blood pressure and for erection, or proopiomelanocortin, etc.) – one supplement cannot replicate their synergistic effect. What to do? Prefer sunlight, even in winter countries.

2. The Mediterranean paradox of vitamin D.
Vitamin D deficiency in sunny countries such as Greece, Cyprus, or Australia is observed unusually often (39.5% of our population was severely vitamin D deficient (levels below 12.5 ng/mL, despite the high percentage of sunny days in Athens). What is the reason? There are changes in lifestyle (indoor lifestyle), such as when people work in offices, relax at home or on terraces, and travel by car. 
Vitamin is produced in the skin only when your shadow is equal to or shorter than your height - due to the angle of sunlight. An evening walk will not help you maintain your vitamin D level. Active use of sunscreen, demonization of the sun as an oncogen, and air pollution reduce vitamin D production, even in very sunny countries. What to do? Be more often in safe sunlight.
3. The fat paradox of vitamin D.
The more fat you have, the lower your vitamin D level. As a fat-soluble compound, it accumulates in adipose tissue, and decreased fat-burning reduces the availability of vitamin D. Evolutionarily, it was intended that during a hungry winter, you lose weight - and as you lose weight, vitamin D comes out into the blood. But alas, nowadays we gain weight in winter. For example, a person weighing 100 kg with 40% fat reserves of vitamin D in fat will last for 2000 days, taking into account the recommended daily dose! A six-year supply! But the person himself may suffer from vitamin D deficiency! The higher the level of physical activity, the higher the vitamin D level in the blood. What to do? Physical activity and normal body weight will give you an optimal vitamin D level. 
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): 3759-3769.).
The vitamin D paradox: high prevalence of deficiency in sunny Athens (Greece) Ann Res Hosp 2019;3:
Paradoxical suboptimal vitamin D levels in a Mediterranean area: a population-based study Sci Rep 2022 Nov 16;12(1):19645.
Mobilising vitamin D from adipose tissue: The potential impact of exercise Nutrition Bulletin 18 December 2019 Pages 25-35