Do Polyunsaturated Fats Decrease Thyroid Function?

by Jackie Wicks

We’ve all heard the benefits of consuming a diet rich in omega-3s, a type of polyunsaturated fat (PUFA for short). Some internet nutrition writers have been blasting PUFAs, though, for causing thyroid function to decrease.

Want to learn the truth? Watch the video below!

This question comes from Tara.

Tara writes, “I just read that polyunsaturated fats are actually depressive of thyroid function, so if you have gained weight due to thyroid issues, you want to avoid foods high in these fats. I’ve been trying to increase my fat intake–are saturated fats the only acceptable fats? Now, I’m thouroughly confused!”

(If you have a nutrition question you’d like to ask me, click here to submit it!)

Are Polyunsatured Fats Bad for the Thyroid?

Short Answer:

  • NO!

Long Answer:

  • Diets high in PUFAs decrease thyroid hormone levels, but INCREASE the body’s sensitivity to thyroid hormone!
  • This could be no change in overall metabolism, or could even mean metabolism goes up.
  • Omega-3s, in particular, boost sensitivity to thyroid hormone in the liver, increasing fat burning.
  • There is no evidence omega-6s cause any form of harm to thyroid function.
  • At worst, we can argue the science hasn’t revealed the exact effect of high-PUFA diets on thyroid function.
  • More likely: PUFAs, especially omega-3s, increase sensitivity, thereby lowering the need for large amounts of thyroid hormone to be secreted.
  • Some evidence even shows omega-3s helping to prevent against hypothyroidism!

If you have experience with polyunsaturated fats affecting your thyroid function (either good or bad), please let me know if the comments!

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  1. Souza LL, Nunes MO, Paula GS, et al. Effects of dietary fish oil on thyroid hormone signaling in the liver. J Nutr Biochem. 2010 Oct;21(10):935-40. doi: 10.1016/j.jnutbio.2009.07.008.
  2. Makino M, Oda N, Miura N, et al. Effect of eicosapentaenoic acid ethyl ester on hypothyroid function. J Endocrinol. 2001 Nov;171(2):259-65.
  3. Deshpande N, Hulbert AJ. Dietary omega 6 fatty acids and the effects of hyperthyroidism in mice. J Endocrinol. 1995 Mar;144(3):431-9.
  4. Clarke SD, Hembree J. Inhibition of triiodothyronine’s induction of rat liver lipogenic enzymes by dietary fat. J Nutr. 1990 Jun;120(6):625-30.

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