title: Iodine status and thyroid function of Boston-area vegetarians and vegans.
abstract: BACKGROUND
  Adequate dietary iodine is required for normal thyroid function. The iodine status and thyroid function of U.S. vegetarians and vegans have not been previously studied. Environmental perchlorate and thiocyanate (inhibitors of thyroid iodine uptake) exposures may adversely affect thyroid function.
  
  
  OBJECTIVE
  The objective of the study was to assess the iodine status and thyroid function of U.S. vegetarians (consume plant based products, eggs, milk; abstain from meat, poultry, fish, shellfish) and vegans (avoid all animal products) and whether these may be affected by environmental perchlorate and thiocyanate exposures.
  
  
  METHODS
  This was a cross-sectional assessment of urinary iodine, perchlorate, and thiocyanate concentrations and serum thyroid function in Boston-area vegetarians and vegans.
  
  
  METHODS
  One hundred forty-one subjects (78 vegetarians, 63 vegans) were recruited; one vegan was excluded.
  
  
  RESULTS
  Median urinary iodine concentration of vegans (78.5 μg/liter; range 6.8-964.7 μg/liter) was lower than vegetarians (147.0 μg/liter; range 9.3-778.6 μg/liter) (P < 0.01). Adjusted for cigarette smoking (confirmed by urinary cotinine levels) and thiocyanate-rich food consumption, median urinary thiocyanate concentration of vegans (630 μg/liter; range 108-3085 μg/liter) was higher than vegetarians (341 μg/liter; range 31-1963 μg/liter) (P < 0.01). There were no between-group differences in urinary perchlorate concentrations (P = 0.75), TSH (P = 0.46), and free T(4) (P = 0.77). Urinary iodine, perchlorate, and thiocyanate levels were not associated with TSH (P = 0.59) or free T(4) (P = 0.14), even when adjusted for multiple variables.
  
  
  CONCLUSIONS
  U.S. vegetarians are iodine sufficient. U.S. vegans may be at risk for low iodine intake, and vegan women of child-bearing age should supplement with 150 μg iodine daily. Environmental perchlorate and thiocyanate exposures are not associated with thyroid dysfunction in these groups.
authors: Section of Endocrinology, Diabetes, and Nutrition, Boston Medical Center, Boston, Massachusetts 02118, USA. angela.leung@bmc.org
authors: Angela M
authors: AM
authors: Leung
authors: Andrew
authors: A
authors: Lamar
authors: Xuemei
authors: X
authors: He
authors: Lewis E
authors: LE
authors: Braverman
authors: Elizabeth N
authors: EN
authors: Pearce
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