Diets and Supplements for Thyroid Disorders — British Thyroid Foundation
Source: https://www.btf-thyroid.org/diets-and-supplements-for-thyroid-disorders Authors: marian-ludgate (Prof Emerita, Cardiff University School of Medicine); jonathan-hayes (registered dietitian, NHS Lothian) Published: 2024-12-07 Publisher: british-thyroid-foundation
Summary
No specific foods or dietary supplements can treat a thyroid disorder. A balanced diet following NHS Eatwell Guide principles is the best approach: five portions of fruit/vegetables daily, high-fibre starchy foods, adequate protein, unsaturated fats, 6–8 glasses of fluid, and avoidance of processed foods and excess sugar.
Diet and Gut Microbiome
Emerging research links the gut-microbiome to thyroid disease. A diverse, plant-rich diet promotes a healthy microbiome. Mouse models of graves-disease showed gut bacteria influence disease symptoms; antibiotics improved disease while faecal transplants from Graves’ patients worsened it. However, evidence is insufficient to recommend specific antibiotics, prebiotics, or probiotics for thyroid conditions.
Specific Foods
- Brassicas (cabbage, cauliflower, kale): May contribute to goitre formation but only at very high consumption; not a concern under normal UK dietary conditions.
- kelp: High in iodine; marketed as a “thyroid booster” but provides no benefit and may interfere with thyroid function. Avoid kelp and sea moss supplements.
- soy: Interferes with levothyroxine absorption; leave at least four hours between soy consumption and levothyroxine dosing.
Supplements
| Supplement | Evidence for Thyroid | Notes |
|---|---|---|
| biotin (B7) | None — no clear benefit | Mega-doses (5,000–10,000 mcg) can falsely elevate/suppress TSH, FT4, FT3; stop 2 days before thyroid blood tests |
| calcium | Interferes with levothyroxine absorption | Four-hour gap required |
| carnitine | Improved hyperthyroidism symptoms (esp. irregular heartbeat) in one trial | No evidence for hypothyroidism |
| ginger | May alleviate some hypothyroid symptoms (pilot RCT) | Needs larger human trials; varies by brand |
| iodine | Essential for normal thyroid but harmful if supplemented when on treatment | Worsens hyperthyroidism; counteracts antithyroid drugs |
| Iron | Deficiency linked to hypothyroidism; ferrous sulphate interferes with thyroxine absorption | Four-hour gap required |
| lemon-balm | Case reports suggest benefit in graves-disease; no clinical trials | Needs controlled trials |
| magnesium | Deficiency linked to hypothyroidism; higher levels may help control Graves’; inconclusive | Found in legumes, nuts, seeds, leafy greens |
| resveratrol | No proper trials for thyroid disease | Anti-inflammatory/antioxidant |
| selenium | Strong evidence for thyroid eye disease; may reduce antibodies in Graves’; no effect on thyroid function itself | High-dose (>300 mcg/day) increases all-cause mortality |
| vitamin-b12 | Lower levels seen in hypothyroidism (not hyperthyroidism); no evidence supplementation improves thyroid function | Association with autoimmune thyroid disease via pernicious anaemia |
| vitamin-d | Low levels correlate with thyroid autoantibodies; NHS recommends 10 mcg/day for most people | Consider year-round if low sun exposure or dark skin |
| zinc | May improve outcomes in hypothyroidism alone or combined with other supplements | Needs large-scale trials |
Key Warning
Exceeding recommended supplement intakes can be harmful and may interfere with thyroid medication or test results. Always take supplements at least four hours apart from levothyroxine.
Key Concepts Mentioned
hyperthyroidism · graves-disease · iodine · selenium · zinc · vitamin-d · calcium · soy · levothyroxine · kelp · cruciferous-vegetables · gut-microbiome · biotin · carnitine · ginger · iron-and-thyroid · lemon-balm · magnesium · resveratrol · vitamin-b12 · thyroid-hormones · anti-inflammatory-diet
Key Entities Mentioned
marian-ludgate · jonathan-hayes · british-thyroid-foundation