By Joseph E. Scherger, MD, MPH
Core Faculty, Eisenhower Health Family Medicine, Residency Program, Eisenhower Health Center, La Quinta, CA; Clinical Professor, Keck School of Medicine, University of Southern California, Los Angeles
SYNOPSIS: A randomized, controlled trial that included older adults showed vitamin D3 2,000 units daily or n-3 fatty acids 1,000 mg daily over five years reduced the incidence of autoimmune diseases 25% to 30%.
SOURCE: Hahn J, Cook N, Alexander E, et al. Vitamin D and marine n-3 fatty acid supplementation and prevention of autoimmune disease in the VITAL randomized controlled trial. American College of Rheumatology Meeting Abstracts. Nov. 7, 2021.
In a randomized, controlled trial, Hahn et el recruited almost 26,000 adults with a mean age of 67.1 years (71% non-Hispanic whites, 20% Black, and 9% other racial/ethnic groups; 51% women). Participants took vitamin D3 2,000 units daily and/or n-3 fatty acids (i.e., omega-3 fatty acids) 1,000 mg daily, or placebo.
During a median follow-up of 5.3 years, there were 117 confirmed cases of autoimmune diseases in the vitamin D3 group vs. 150 in the placebo group. In the n-3 fatty acids group, there were 123 confirmed cases. The autoimmune diseases included psoriasis, rheumatoid arthritis, autoimmune thyroid disease, polymyalgia rheumatic, and others. The authors reported the number needed to treat with both supplements for five years to prevent one autoimmune disease was 167.
COMMENTARY
Although these results are modest, they reached statistical significance. Notably, one of the authors of this study previously wrote that vitamin D supplementation beyond 800 units daily was not of benefit in preventing disease.1 The causes of autoimmune diseases remain a mystery, but the leading postulation today implicates a leaky gut and an unhealthy microbiome.2 Vitamin D is a prohormone that is not readily available in food unless we consume organs from animals.3 While vitamin D may be obtained through the skin by sunshine converting cholesterol to the vitamin, this conversion declines with age.4 Hence, vitamin D deficiency is common in seniors.5 This study provides welcome evidence suggesting vitamin D supplementation is of benefit in preventing disease. Omega-3 fatty acids (called n-3 fatty acids in this trial) have a history similar to vitamin D. We know they are important for health, but there is little evidence indicating their supplementation provides benefit.6
Although the strength of these findings does not confirm that all or most adults should take vitamin D or omega-3 fatty acids as supplements, this study shows these supplements may be of benefit in preventing autoimmune diseases. I take these supplements and recommend them to my patients older than age 50 years.
REFERENCES
- Manson JE, Cook NR, Lee IM, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. N Engl J Med 2019;380:33-44.
- Kinashi Y, Hase K. Partners in leaky gut syndrome: Intestinal dysbiosis and autoimmunity. Front Immunol 2021;12:673-708.
- Borel P, Caillaud D, Cano NJ. Vitamin D bioavailability: State of the art. Crit Rev Food Sci Nutr 2015;55:1193-1205.
- MacLaughlin J, Holick MF. Aging decreases the capacity of human skin to produce vitamin D3. J Clin Invest 1985;76:1536-1538.
- Boucher BJ. The problems of vitamin D insufficiency in older people. Aging Dis 2012;3:313-329.
- Tomdio A, Ritchie M, Miller AC. Omega-3 fatty acids and cardiovascular disease prevention. Am Fam Physician 2019;100:209-210.
A randomized, controlled trial that included older adults showed vitamin D3 2,000 units daily or n-3 fatty acids 1,000 mg daily over five years reduced the incidence of autoimmune diseases 25% to 30%.
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