The Paleo Diet and Thyroid Disease
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"Caveman diets" may trigger unexpected problems in some
Mary Shomon
Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."
Medically reviewed by Lindsey Waldman, MD, RD on November 08, 2019
Lindsey Waldman, MD, RD, is a board-certified pediatrician and pediatric endocrinologist.
Lindsey Waldman, MD, RD
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For those who have autoimmune thyroid conditions such as Hashimoto's disease and Graves' disease, the Paleo diet has been touted as a lifestyle approach to modifying the effects of the illness. But, while there are certainly some advantageous features of the Paleo style of eating, evidence regarding its benefits is unclear. Experts warn that some aspects of the Paleo diet—namely, recommendations to limit salt and dairy—can be harmful to your thyroid hormone function, especially if you have thyroid disease.
Paleo Diet Guidelines
As the role of inflammation in many health conditions is gaining attention, diets such as the Paleo diet have become an increasingly popular strategy for reducing inflammation. Paleo diets, also known as "ancestral eating" or "caveman diets," have varying interpretations. These diets generally emphasize:
Whole foods in their original, unprocessed forms
Grass-fed, hormone-free meats, eggs, and seafood
Pesticide-free and otherwise organic vegetables
Some fruit, nuts, and seeds
Paleo diets usually recommend avoiding foods that commonly trigger inflammation, allergies, food sensitivities, and other reactions, including:
Grains, especially gluten
Legumes and beans
While reducing salt intake or cutting back on some dairy could have benefits for health and weight loss, excessively low amounts can be problematic, impacting both iodine levels and, subsequently, thyroid hormone levels.
Impact on Thyroid Hormone Levels
Iodine is a raw material that is essential for the production of thyroid hormone by the thyroid gland.
Iodine deficiency is linked to hypothyroidism, thyroid enlargement, and, interestingly, hyperthyroidism. A goiter, which is an enlarged but low-functioning thyroid, can develop as a result of excessive TSH, which is produced in response to low thyroid hormone levels.
Iodine Deficiency and Your Thyroid
Worldwide, table salt and dairy are the largest sources of iodine in one's diet. And that is why Paleo and other caveman-style diets can pose a concern. With these foods essentially eliminated on these plans, it's very likely that someone could drastically lower their overall iodine intake, resulting in the above concerns.
Though iodine deficiency was previously thought to be eliminated in many countries, including the United States (where most table salt is iodized), low levels of iodine are being noted.
While there is an idea that attempts to replicate the diet of our ancestors should be healthy, researchers have found that changes in agriculture and human metabolic requirements have increased our need for iodine in comparison to the needs of our ancestors, possibly making a caveman-type diet harmful.
At the other end of the spectrum, excessive iodine intake—both severe and moderate—is also associated with hypothyroidism and goiter, and with worsening of Hashimoto's autoimmune thyroid disease.
Notable Research
Researchers in Sweden studied the effects of the Paleo style diet on iodine levels. In the study, healthy women were divided into two groups that either ate a modified Paleo diet or a Nordic Nutrition (NNR) guidelines-based diet over a two-year period.
The NNR diet recommends:
Sufficient intake of monounsaturated fats
Limiting of saturated fats
25 to 35 grams of dietary fiber a day
Sufficient, but not excessive protein
Limited added sugars
Increased vitamin D and selenium-rich foods
Regular moderate-intensity activity weekly
The Paleo dieters ate a high-protein, high-fat, low-carbohydrate diet focusing on lean meat, fish, fruits and vegetables, eggs, and nuts. They excluded all gluten, grains, beans, refined foods, sugar, salt, and sodas.
Both groups had equivalent baseline iodine levels before the study began. After two years the Paleo group's iodine levels decreased significantly, while the NNR group maintained the same iodine levels throughout the study.
In addition, the Paleo group had higher levels of thyroid stimulating hormone (TSH) after two years and decreased free triiodothyronine (FT3) after six months, while those in the Nordic diet group did not experience any changes in their thyroid hormones.
Elevated TSH levels indicate that the body is trying to increase thyroid hormone levels, while FT3 is one of the thyroid hormones. These results suggest that the diet's effect on iodine deficiency began to have an impact on thyroid hormones.
How to Get More Iodine in Your Diet
Modified Paleo diets can be healthy, may lower inflammation, and may help with weight loss. You should, however, ensure that you are getting enough iodine. If you eliminate iodized salt and dairy products from your diet, you may want to make sure that you are taking a multivitamin that includes iodine, or include some iodine-rich foods in your diet.
Some of the most iodine-rich, non-dairy foods include:
Sea vegetables, including kombu, wakame, and seaweed
The Paleo diet has some advantages in that the emphasis is on foods that are not processed. However, there are some concerns for people who have certain underlying conditions, such as thyroid disease. If you are planning on starting a new diet, you should consult with your doctor or a dietician first to ensure that the diet is right for you.
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Kopp W. Nutrition, evolution and thyroid hormone levels - a link to iodine deficiency disorders? Med Hypotheses. 2004;62(6):871-5.
Manousou S, Stål M, Larsson C, et al. A Paleolithic-type diet results in iodine deficiency: a 2-year randomized trial in postmenopausal obese women. Eur J Clin Nutr. 2018 Jan;72(1):124-129. doi: 10.1038/ejcn.2017.134. Epub 2017 Sep 13.
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