Previous literature has found potential association between selenium deficiency and inactivated glutathione peroxidase and deiodinase, which may contribute to subsequent elevation of T4 and ratio of T4/T3. Conduction of a case-control study (ID: Liuyanping3) has been applied on Clinicaltrials.gov to further elucidate effect of selenium deficiency on thyroid function. Based on its data, the investigators will perform a randomized, placebo-controlled,single-blinded crossover study on 20 participants with selenium deficiency to verify health consequence of selenium.

Inclusion Criteria:

• Clinical diagnosis of selenium deficiency through serum selenium test in previous phase (ID: Liuyanping3) of the study
• Should have stable body weight in the latest 3 months;
• Should be not prescribed with thyroid hormone replacement therapy
• Should be without medical history of thyroid surgery or iodine radiotherapy
• Should have normal FT3, FT4 and TSH.

Exclusion Criteria:

• Clinical diagnosis of acute critical illness in the latest 1 year
• Have had weight fluctuation by more than 5%
• Eating disorders
• Neuropsychological disorders
• Allergy to corn or yeast

All participants will be blinded. Both the selenium-rich corn powder and the ordinary corn powder (placebo) have the same smell, color and taste.