Abstract
Diets eliminating animal products have rarely been associated with hypothyroidism but may protect against autoimmune disease. Thus, we investigated whether risk of hypothyroidism was associated with vegetarian compared to omnivorous dietary patterns. The Adventist Health Study-2 was conducted among church members in North America who provided data in a self-administered questionnaire. Hypothyroidism was queried at baseline in 2002 and at follow-up to 2008. Diet was examined as a determinant of prevalent (n = 4237 of 65,981 [6.4%]) and incident cases (1184 of 41,212 [2.9%]) in multivariate logistic regression models, controlled for demographics and salt use. In the prevalence study, in addition to demographic characterstics, overweight and obesity increased the odds (OR 1.32, 95% CI: 1.22–1.42 and 1.78, 95% CI: 1.64–1.93, respectively). Vegan versus omnivorous diets tended to be associated with reduced risk (OR 0.89, 95% CI: 0.78–1.01, not statistically significant) while a lacto-ovo diet was associated with increased risk (OR 1.09, 95% CI: 1.01–1.18). In the incidence study, female gender, white ethnicity, higher education and BMI were predictors of hypothyroidism. Following a vegan diet tended to be protective (OR 0.78, 95% CI: 0.59–1.03, not statistically significant). In conclusion, a vegan diet tended to be associated with lower, not higher, risk of hypothyroid disease.
Highlights
There is a growing awareness that a plant-based diet decreases morbidity and mortality associated with a range of chronic disease
Vegans may be at risk of inadequate iodine intake as animal products tend to be rich in iodine [4,6]
The purpose of this study was to see if vegetarian diets including vegan, lacto-ovo, pesco or semi-vegetarian were associated with prevalence and incidence of hypothyroidism compared to omnivore diets
Summary
There is a growing awareness that a plant-based diet decreases morbidity and mortality associated with a range of chronic disease. There are concerns that vegetarian diets may be low in calcium, vitamin D, vitamin B12, and zinc [1]. Another critical nutrient is iodine which is found mainly in iodized salt, breads and dairy sources in the U.S Since 2000 the U.S population generally has demonstrated adequate iodine nutriture [2]. The American Dietetic Association recommends that those consuming vegetarian diets be cognizant of the need of iodine supplementation [1]. Lacto-ovo vegetarians in the U.K. appear to have adequate iodine intake [5]. Vegans may be at risk of inadequate iodine intake as animal products tend to be rich in iodine [4,6]. Study of British, and recently, U.S vegetarians indicated that vegans are at risk of iodine deficiency [7,8]
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