Do Dietary Supplements Affect Inflammation, Oxidative Stress, and Antioxidant Status in Adults with Hypothyroidism or Hashimoto's Disease?-A Systematic Review of Controlled Trials.

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• Selenium supplementation, especially at doses of 200 µg/day, was associated with significant reductions in thyroid-stimulating hormone (TSH) levels and improvements in markers of oxidative stress, such as glutathione peroxidase (GPx).
• Further research is needed to support the effects of selenium and other nutrients in patients with hypothyroidism (HT) or Hashimoto’s thyroiditis (AIT).

Introduction

A comprehensive systematic review was conducted to investigate the effects of dietary supplements (DS) on inflammation, oxidative stress, and antioxidant status in adults (>18 years old) with hypothyroidism (HT) or Hashimoto’s thyroiditis (AIT).

Method

The review was conducted following the PRISMA guidelines, reviewing 22 controlled trials. The primary outcomes assessed were inflammatory markers, oxidative stress, antioxidant levels, and thyroid function parameters. The supplements reviewed were primarily selenium and vitamin D, alongside others like Nigella sativa and genistein.

Results

Selenium Supplementation:

• Six studies indicated selenium's beneficial effects on inflammation, including decreased levels of pro-inflammatory markers. For example, Sun et al. demonstrated a significant reduction in IL-2 and TNF-α after 3 months of selenium yeast supplementation (p = 0.001).
• Selenium supplementation significantly improved antioxidant markers like glutathione peroxidase (GPx) and superoxide dismutase (SOD). In one study, GPx activity rose from 58.4 ± 23.2 to 80.2 ± 12.1 U/gHB (p = 0.001).
• Seven studies demonstrated improvements in thyroid function. For instance, Chakrabarti et al. reported a significant reduction in TSH levels after selenium supplementation, dropping from 25.8 ± 9.5 to 1.7 ± 0.7 µIU/mL (p = 0.001).

Vitamin D supplementation:

• There were no significant differences in inflammatory or thyroid function markers between intervention and control groups post-supplementation.
• None of the vitamin D studies assessed oxidative stress markers.

Other Supplements:

• Nigella sativa demonstrated a decrease in Thyroid-stimulating hormone (TSH) levels (p = 0.03), as well as improvements in thyroid antibodies such as TPO-Ab (p = 0.019).
• In one study, genistein showed effects on thyroid antibodies (p= 0.01).

Conclusion

This review suggests that selenium supplementation may help reduce inflammation and improve thyroid function in HT/AIT patients. While vitamin D supplementation raised serum 25-hydroxy levels, it had minimal effects on inflammatory and thyroid parameters.

• Selenium supplementation may help reduce inflammation and improve thyroid function in patients with Hashimoto’s thyroiditis and hypothyroidism.
• Clinicians could therefore consider selenium for patients with nutrition deficiencies and elevated TSH.
• Vitamin D did not seem to be effective, and further research is needed for other noted supplements.

• Many of the studies were limited by small sample sizes (<50 participants) and methodological weaknesses (conducted only among women). Future research should prioritize larger, well-controlled randomised trials to better assess the efficacy of additional supplements like zinc, iodine, magnesium, and omega-3 in hypothyroidism and Hashimoto’s thyroiditis.
• Understanding how supplements affect inflammation, oxidative stress, and thyroid autoimmunity at a mechanistic level is crucial. Future research should explore the biological pathways, particularly for selenium, to clarify its role in immune modulation and thyroid health.