BACKGROUND AND OBJECTIVES: Diet is one of the major risk factors for thyroid diseases. It has been shown that high or excessive iodine intake is more likely to be a health concern in iodine-sufficient regions or regions where iodine deficiency previously existed due to the emergence of iodine-induced hypothyroidism or hyperthyroidism. Therefore, this review investigates the occurrence of thyroid diseases, and particularly hypothyroidism and hyperthyroidism, in populations with different levels of iodine intake and other dietary factors in various geographic regions. MATERIALS AND METHODS: A total of 856 articles published between January 1st, 1990 and March 31st, 2015, were identified. Epidemiological studies that showed an association between dietary factors and thyroid diseases were selected, yielding a total of 21 articles. RESULTS: Due to a sudden increase in iodine supplementation (i.e., via salt iodization), regions such as Denmark and China, where insufficient iodine intake previously existed, showed a significant increase in the occurrence of hypothyroidism compared with that of hyperthyroidism. Other dietary factors, such as nitrate intake, may increase the risk of the diseases, whereas a vegan diet and alcohol intake may lower the risk. CONCLUSION: The level of iodine intake is quite variable between individuals in different geographic regions, and the risk of thyroid diseases may also vary by age and gender. Therefore, monitoring of safe levels of iodine intake should be performed to prevent iodine-induced thyroid diseases.
China ; Denmark ; Diet ; Diet, Vegan ; Epidemiologic Studies ; Hyperthyroidism ; Hypothyroidism ; Iodine ; Risk Factors ; Thyroid Diseases* ; Thyroid Gland*

This study examined the effects of a brown rice vegetarian diet and outdoor walking exercise program on body composition and blood lipid parameters in collegians. The mean age of respondents was 21.8 yrs (males) and 21.7 yrs (females). During the ten-day program, the respondents lived in a dormitory and had three meals. The respondents exercised one hour in the morning (6:20~7:20 am) and attended one and a half hour evening lecture (7:00~8:30 pm) everyday. The brown rice vegetarian diet consisted of brown rice, whole grain bread, beans, fresh vegetables, and fresh fruits contained 2043.2+/-112.7 kcal (97.3% of RNI), 66.7 g protein (133.3% of RNI), 33.6 g dietary fiber (168.2% of RNI), vitamin A (194.2% of RNI), vitamin B1 (245.5% of RNI), vitamin B2 (225.1% of RNI), niacin (233.7% of RNI), vitamin B6 (277.1% of RNI), folic acid (128.4% of RNI), vitamin C (334.6% of RNI), iron (131.9% of RNI), zinc (112.4% of RNI) and calcium (60.3% of RNI). The results showed that there were significant increases in body weight (P<0.05) and BMI (P<0.05) in males and body weight (P<0.05) and lean body mass (P<0.01) in females. In addition, there were significant decreases in total cholesterol (P<0.001), LDL cholesterol (P<0.001), TG (P<0.05), and HDL-cholesterol (P<0.001) in males and total cholesterol (P<0.01) and LDL-cholesterol (P<0.01) in female. The ten day brown rice vegetarian diet rich in fiber and outdoor walking exercise program significantly increased body weight and decreased total cholesterol and LDL-cholesterol in collegians.
Ascorbic Acid ; Body Composition ; Body Weight ; Bread ; Calcium ; Edible Grain ; Cholesterol ; Cholesterol, LDL ; Surveys and Questionnaires ; Diet, Vegan ; Dietary Fiber ; Fabaceae ; Female ; Folic Acid ; Fruit ; GTP-Binding Proteins ; Humans ; Iron ; Male ; Meals ; Niacin ; Riboflavin ; Thiamine ; Vegetables ; Vitamin A ; Vitamin B 6 ; Walking ; Zinc