I was bothered by eczema for decades. I never had it bad – and it can get bad. Instead, every winter, like clockwork, itchy dry areas on my skin would breakout. All the dermatologist could do was tell me to use moisturizing lotion, but that never really helped much. But just as it appeared like clockwork in winter, it disappeared like clockwork in the spring. Then, when I began taking 10,000 IU/day (250 mcg) of vitamin D3, my eczema disappeared, never to return.
But my case doesn’t interest scientists. They want “proof.” Mendelian randomization (MR) analyses are all the “proof” rage; some say they are more accurate than randomized controlled trials. They are being used to disprove vitamin D is involved in various diseases, even when randomized controlled trials and meta-analyses show a direct cause/effect treatment relationship.
Cannell, JJ., MD. Eczema and problems with vitamin D Mendelian randomization studies. The Vitamin D Council Blog & Newsletter, February 5, 2018.
 Kim MJ, Kim SN, Lee YW, Choe YB, Ahn KJ. Vitamin D Status and Efficacy of Vitamin D Supplementation in Atopic Dermatitis: A Systematic Review and Meta-Analysis. Nutrients. 2016 Dec 3;8(12). pii: E789. Review.
 Manousaki D, Paternoster L, Standl M, Moffatt MF, Farrall M, Bouzigon E, Strachan DP, Demenais F, Lathrop M, Cookson WOCM, Richards JB. Vitamin D levels and susceptibility to asthma, elevated immunoglobulin E levels, and atopic dermatitis: A Mendelian randomization study. PLoS Med. 2017 May 9;14(5):e1002294.
 Beckett EL, Jones P, Veysey M, Duesing K, Martin C, Furst J, Yates Z, Jablonski NG, Chaplin G, Lucock M. VDR gene methylation as a molecular adaption to light exposure: Historic, recent and genetic influences. Am J Hum Biol. 2017 Sep 10;29(5).