The Influence of Nutritional Intervention in the Treatment of Hashimoto's Thyroiditis-A Systematic Review.

Karolina Osowiecka, Joanna Myszkowska-Ryciak

Journal: Nutrients 2023;15(4):1041

PMID: 36839399

Plain Language Summary

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Hashimoto’s thyroiditis is an autoimmune disorder characterized by the presence of antibodies in the thyroid gland such as thyroid peroxidase (TPO) and thyroglobulin (TG) antibodies. Immune-mediated inflammatory responses eventually lead to the progressive destruction of the gland and impaired thyroid function. The disease has a strong genetic disposition but is also influenced by environmental factors, including diet. Hence diet has been considered a complementary tool to manage thyroid function and disease progression by harnessing the benefits of certain nutrients and anti-inflammatory properties. This systematic review examined the effects of nutrients and dietary interventions on Hashimoto’s disease in current literature. Using antibody levels, thyroid hormone levels and body weight to measure outcomes. The review included 9 studies, all of which compared the intervention group to the control groups. The trials included looked at gluten-free, lactose-free and energy-restricted diets, with or without selected nutrients and foods supplements (ie. Nigella sativa, iodine). The intervention duration ranged from 3 weeks to 12 months. Despite the small number of trials, the data from those studies included in this review showed promising results. Improvements in disease parameters were observed in diets that were energy deficient, eliminated gluten, lactose and goitrogens or added Nigella sativa. Iodine restrictions did not show any improvements. In the discussion section, the authors presented the results in the wider context and the findings from other studies. Ultimately there appears to be a wide variance in outcomes, usually ranging from beneficial to neutral. The authors contributed to such variability due to the complexity of the condition and many influencing factors. Often participants in trials have highly variable thyroid status and function, and differences in regular dietary intakes of nutrients critical to thyroid health can easily distort the results. Hence much more specific research is needed to make firmer conclusions. Whereby no clear conclusions in larger groups could be drawn, potential benefits of dietary interventions in Hashimoto's disease may be much more apparent in clinical settings with personalized approaches that account for such individual variances.

Expert Review

Reviewer: Ana-Paula Agrela
9th Dec 2024
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Conflict of interest

None

Take home message

  • Diet, supplementation, and lifestyle factors play an important role in managing Hashimoto’s thyroiditis.
  • Tailored interventions based on individual dietary sensitivity, nutritional status and lifestyle factors are needed to optimise the effectiveness of the treatment and the patient’s well-being.

Evidence category

B: Systematic reviews including RCTs of limited number

Summary review

Introduction

A systematic review was conducted to investigate the impact of various nutritional interventions on anti-thyroid antibodies and thyroid hormone levels in participants with Hashimoto’s thyroiditis.

Method

The review followed the PRISMA checklist and PICO (population, intervention, comparative, outcome) Model. PubMed, Scopus and Web of Science databases were searched and nine studies were included. Nutritional interventions such as gluten or lactose-free diets, Nigella sativa, and iodine supplementation were examined. The primary outcomes related to thyroid function and autoimmune markers.

Results

Gluten and Lactose-Free Diets.

  • A gluten-free diet showed a decreased TSH in levothyroxine LT4-treated patients, (p = 0.044). However, there was no significant effect on thyroid hormones or anti-TPO and anti-TG antibodies.
  • Additionally, in women with Hashimoto’s disease, a gluten-free diet and vitamin D supplementation reported a decrease in thyroid antibodies anti-TPO (p=0.0017) and anti-TG (p=0.0056) and an increase in vitamin D concentrations (p= 0.0006) in the control group compared to the experimental group. No changes were observed in the case of TSH, fT4 and fT3 in the groups.
  • A lactose-free diet was reported to significantly decrease TSH after the intervention in LT4-treated patients with HT and lactose intolerance (p < 0.05).

Weight and BMI

  • In a study where body weight, BMI, and percentage of body fat was observed, TSH, fT3, fT4, anti-TG, and anti-TPO levels showed a significant decrease in both the control and experimental groups ( p = 0.001). Changes in body weight, BMI, and adipose tissue were reported to be positively correlated with anti-TG levels (p = 0.001, p = 0.001, and p = 0.003).

Supplementation

  • Participants in a study group who consumed 2g of Nigella sativa, showed a significant improvement in TSH (p = 0.02), fT4 (p = 0.04), and anti-TPO (p = 0.01) compared to the control group.
  • An improvement in TSH (p = 0.02), fT4 (p = 0.04), and anti-TPO (p = 0.01) levels were reported in a region with excessive iodine intake (>1100 mcg/day).

Conclusion

Although previous studies have reported a positive or neutral impact on the biochemical parameters of Hashimoto's thyroiditis symptoms, this review found it challenging to present an unequivocal conclusion.

Clinical practice applications

  • For patients with Hashimoto’s thyroiditis who require high doses of levothyroxine, or struggle with TSH regulation, testing for gluten and lactose intolerance may be beneficial.
  • Monitoring and possibly supplementing with vitamin D might benefit patients with HT by potentially reducing antibody levels. Routine testing for vitamin D deficiency could help identify patients who may benefit from supplementation.
  • Assessing HT patient’s iodine levels to advise if levels are found to be higher or lower than recommended may be recommended.
  • Clinicians might also consider weight management and lifestyle counselling as part of a therapeutic plan.

Considerations for future research

  • The number of studies included in this review was small and the interventions were diverse. Further larger studies are needed to determine which type of nutritional intervention would be the most beneficial for patients with Hashimoto’s thyroiditis.
  • Hashimoto’s thyroiditis is not a homogeneous condition, and variability between patients is high. Future studies should aim to investigate tailored treatment protocols based on individual patient characteristics to help identify specific subgroups that respond differently to interventions.
  • Nutrient interventions such as iodine, selenium and iron were not addressed in the included studies. Further research is needed to determine if these nutrients may benefit individuals with Hashimoto’s thyroiditis.
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Abstract

Diet can be a complementary treatment for Hashimoto's disease by affecting thyroid function and anti-inflammatory properties. It is still unclear which dietary strategy would be the most beneficial. The aim of this systematic review is to examine all the data currently available in the literature on the effects of nutritional intervention on biochemical parameters (anti-thyroid antibody and thyroid hormones levels) and characteristic symptoms in the course of Hashimoto's thyroiditis. This systematic review was prepared based on PRISMA guidelines. Articles in PubMed and Scopus databases published up to November 2022 were searched. As a result of the selection, out of 1350 publications, 9 were included for further analysis. The nutritional interventions included the following: elimination of gluten (3 articles) or lactose (1 article), energy restriction with or without excluding selected foods ( = 2), consumption of ( = 2), or dietary iodine restriction ( = 1). The intervention duration ranged from 21 days to 12 months and included individuals with various thyroid function. Of the nine studies, three studies were female only. An improvement was observed during an energy deficit and after the elimination of selected ingredients (e.g., gluten, lactose, or goitrogens), as well as after the intervention of . These interventions improved antibody levels against peroxidase (anti-TPO), (thyrotropin) TSH, and free thyroxine (fT4). No improvement was seen on the iodine-restricted diet. Varied outcomes of analyzed dietary interventions may be due to the heterogeneous thyroid condition, high variability between patients, and differences in habitual intake of critical nutrients (e.g., iodine, selenium, and iron) in different populations. Therefore, there is a great need for further experimental studies to determine whether any nutritional interventions are beneficial in Hashimoto's disease.

Address: Doctoral School, Warsaw University of Life Sciences (WULS), 02-787 Warsaw, Poland.; Department of Dietetics, Institute of Human Nutrition Sciences, Warsaw University of Life Sciences (WULS), 02-776 Warsaw, Poland.
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