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Iodine Status and Thyroid Function of Vegans versus Non-Vegan Adults

Iodine Status and Thyroid Function of Vegans versus Non-Vegan Adults. Kristen, Tony, Kelly, and Kelsie. Overview and Physiology. Essential for normal development and metabolism Controlled by thyroid gland Major component of thyroid hormones (T3 & T4) BMR Macronutrient metabolism

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Iodine Status and Thyroid Function of Vegans versus Non-Vegan Adults

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  1. Iodine Status and Thyroid Function of Vegans versus Non-Vegan Adults Kristen, Tony, Kelly, and Kelsie

  2. Overview and Physiology • Essential for normal development and metabolism • Controlled by thyroid gland • Major component of thyroid hormones (T3 & T4) • BMR • Macronutrient metabolism • Muscle contraction • Developmental growth • Sexual maturation • Low hormone TSH release overstimulation of thyroid increased gland size (goiter)

  3. Iodine Deficiency • Symptoms: • Apathy • Reduced mental functioning • Lack of physical energy • During pregnancy: • Spontaneous abortion • Increase infant mortality • Cretinism • Cognitive defects • “Single most important preventable cause of brain damage worldwide” –World Health Organization

  4. Dietary Source • Fairly limited… • Table salt • Sea-grown plants and animals • Dairy products • Some bread products • Vegetables grown in soil w/ high iodine levels

  5. Significance • Lack of primary research regarding US iodine status • Damaging effects of iodine deficiency • Can be easily prevented with adequate intake • Our study will: • Expand current findings • Increase understanding of iodine status • Study relationship between dietary choice and iodine status • Raise awareness of iodine status in developed countries (US)

  6. Significance

  7. Hypothesis • Healthy vegan (diet excluding meat and dairy) adults aged 20-45 years will have poorer iodine status than non-vegan adults of similar age, gender and BMI. • This population may be at risk for negative subclinical effects on metabolic rate.

  8. Objectives • Recruiting subjects from Missouri, we will test the above hypothesis by comparing iodine status and metabolic rate between young adult vegans and non-vegans. • Observational study

  9. Specific Aims • 24 hour urine iodine excretion • Anthropometrics (body weight, height, waist circumference, body composition) • Fasting serum T3 and T4 levels • Basal metabolic rate (indirect calorimetry) • Dietary intake (24 hr diet record, food frequency questionaire) • Physical activity (Int’l Physical Activity Questionaire)

  10. Subjects • Sample size =133 per group (between 20-45yrs old) • Vegan: actively and consciously avoiding meat/dairy/eggs and meat derivatives of any kind including fish and shellfish. For at least 6 months prior to study selection. • Non-Vegan: standard Midwestern diet (no required or voluntary dietary restrictions of meat, eggs, or milk food sources. • Location: Recruitment will occur in the city of Columbia, Missouri. Lab and anthropometric testing will occur in the McKee research laboratory site under supervision of professionals.

  11. Recruitment/Selection • Flyers posted at local grocery stores and college campuses • $20.00 monetary incentive per subject upon completion • Testing will be in the winter • College students would be gone in the summer • Milk has more iodine in the winter due to shift from grass feeding to iodine-enriched grain feeding of livestock • Gives opportunity to exacerbate any differences between the two groups

  12. Exclusion Criteria • Vegan subject doesn’t meet all of criteria of vegan diet for at least 6 months prior to recruitment • Standard diet subject self imposes dietary restrictions of meat, eggs, or milk (or had in last 6 months) • Subject is diagnosed with a thyroid or iodine related illness in the last 5 yrs • Subject using vitamin/mineral supplements • Female subjects who are pregnant or lactating

  13. Screening/Methods • Baseline assessment (signing consent document) • Answer food/medical history questions • Food frequency questionnaire • Height, weight, waist circumference, DXA, BMR (indirect calorimeter), International PA Questionnaire, 10mL blood draw (fasting serum T3 and T4 levels) • Subject will consume an iodine supplement, take home a 24hr urine iodine loading kit, and return after a recorded supplement ingestion time • 24hr dietary recall using 5-step, multi-pass approach

  14. Expected Results • Hypothesis: “Healthy vegan adults aged 20-45 years will have poorer iodine status than non-vegan adults of similar age and gender; and thus may be at risk for subclinical malnutrition”

  15. Expected Results • Related Studies: • Thomas Remer, Annette Neubert and Friedrich Manz. British Journal of Nutrition 1999 • Pearce EN, Pino S, He X, et al. Journal of Clinical Endocrinology and Metabolism 2004 • Swanson CA, Zimmermann MB, Skeaff S, et al. Journal of Nutrition 2012

  16. Limitations/ Confounders • Sample will come from Columbia, MO and may not be representative of total population • Urinary iodine test efficacy depends on adherence by subjects • Self-reporting subjectivity/ inaccuracy is possible

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