Effects of calorie-restricted diet on health state and intestinal flora in Hashimoto's thyroiditis patients: Study protocol for a randomized controlled trial.

Background and objectives: Hashimoto's thyroiditis (HT) is an autoimmune disease, characterized by abnormal elevation in thyroid peroxidase antibody and/or thyroglobulin antibody. In recent decades, HT disease has become more and more widespread. Patients always report multiple symptoms, even though their thyroid hormone levels are kept in normal ranges. However, no treatment exists to effectively reduce the levels of thyroid antibodies. Our study aims to determine whether calorie-restricted diet is helpful in improving health of HT patients.

Methods and study design: This is a 3-month randomized controlled trial. HT patients will be randomized into a calorie-restricted (CR) group or a calorie-unrestricted control group. All the participants will be instructed to consume a diet that includes a combination of 45-55% calories from carbohydrates, 20-30% from fats, and 15-25% from proteins, according to current Chinese Dietary Guidelines. Participants in CR group need to limit their calories intake equal to their basal energy expenditure, which means that their daily caloric intake will be limited by about 20-30%.

Results: The study population is planned to be 66 HT patients aged 18 to 65 years. The primary outcome is change of thyroid antibody levels from baseline. Secondary outcomes include the changes of non-hypothyroid symptoms scores, thyroid function indexes, morphology of thyroid, T lymphocyte subpopulations, inflammatory biomarkers and lipids from baseline to 12 weeks.

Conclusions: This trial will have implications for nutrition treatment policy in regard to thyroid antibodies control, immune dysfunction and related non-hypothyroid symptoms improvement among HT patients.