A new randomized controlled trial determined if the Paleo diet results in a higher risk of developing iodine deficiency compared with the Nordic diet.
The Paleolithic diet, also known as the caveman diet or stone-age diet, is becoming increasingly popular for weight loss. People who follow the Paleo diet cut out modern foods from their diet and eat the same way as individuals from the Paleolithic era. Therefore, the Paleo diet mainly includes fresh fruits, vegetables, meats, and nuts. The grains, legumes, dairy, refined sugar, processed oils, and salt are excluded from the Paleo diet.
Research suggests that health claims of Paleo diet hold true
Some studies have shown that the Paleo diet can improve health by eliminating high-fat and processed foods. Since the Paleo diet emphasizes eating a lot of fruits, vegetables and meat, and restricts entire food groups such as carbohydrates, it can help reduce caloric intake.
Other studies have found that the Paleo diet leads to short-term improvements in waist circumference and blood glucose, which may cause certain chronic diseases. In other studies, researchers found positive long-standing effects of the Paleo diet on abdominal obesity, body fat, and serum triglycerides levels. On the other hand, many scientists suggest that there is not enough evidence to prove the beneficial effects of the Paleo diet.
Iodine is an essential nutrient
Iodine is an essential element needed for the production of thyroid hormones. Iodine is available in salt, seafood, dairy products, and some meats. A deficiency of iodine is a common nutritional disorder worldwide that is linked to the enlargement of the thyroid gland or goiter, hypothyroidism, and intellectual disabilities in infants born to mothers who were iodine deficient. Since the 1920s, most table salt in all developed countries has been fortified with iodine to address the high incidence of goiter in the early twentieth century.
The most common method to determine iodine deficiency in a population is the measurement of iodine in urine samples since iodine is released from the body through the urine.
A median iodine concentration of less than 50mg/L is defined as mild iodine deficiency in a population, whereas urine iodine concentration of less than 20mg/L is considered as severe iodine deficiency. Since the daily iodine uptake in an individual may vary, the calculation of urinary iodine excretion over multiple days provides an accurate estimate of the iodine status.
A new study compared iodine levels after the Paleo diet and after the Nordic diet
When people follow the Paleo diet, they switch from having table or iodized salt to sea salt or no salt. This takes away the richest source of iodine from their diet. In addition, dairy, which is the other significant source of iodine, is also excluded from the Paleo diet. The result is a possibility of developing iodine deficiency in people following this diet.
A recent study published in the European Journal of Clinical Nutrition determined if the Paleo diet results in a higher risk of developing iodine deficiency compared with a diet based on the Nordic Nutrition Recommendations.
The Nordic diet is a way of eating that focuses on the traditional foods of the Nordic countries, Norway, Denmark, Sweden. Finland, and Iceland. The Nordic diet recommends 150 mg/L iodine per day.
The researchers in Sweden compared the 24-hour urinary iodine concentration in participants on Paleo diet with the participants on a Nordic diet. The study, performed between 2007 to 2010, included 49 postmenopausal obese women that were assigned to either a Paleo diet or the Nordic diet. The researchers conducted clinical investigations at the start of the study, at 6 months, and 24 months.
The Paleo diet was mainly comprised of lean meat, fish, seafood, fruits, vegetables, eggs, and nuts. The diet provided 30% energy intake from protein, 40% energy intake from fat and 30% energy intake from carbohydrates. The diet did not include any dairy products, cereals, beans, refined fats, sugar, and added salt.
The Nordic diet included lower protein and fat intake but a higher carbohydrate intake compared with the Paleo diet. The participants on the Nordic diet got 15% energy intake from proteins, 25-30% from fat, and 55-60% from carbohydrates.
The participants in both the groups consumed food as needed and self-reported the food intake records. The researchers determine 24-hour urinary iodine concentrations, 24-hour urinary iodine excretion, and levels of thyroids hormones (free thyroxine or FT4, free Triiodothyronine or FT3, and thyrotropin or TSH) for all the participants at the start of the study, and at 6 and 24 months.
The Paleo diet is associated with inadequate iodine levels
The results of clinical investigations at the start of the study showed similar median 24-hour urinary iodine concentration (71 mg/L) and urinary iodine excretion (134 mg/d) levels in both the Paleo diet and Nordic diet groups. However, the researchers observed a decrease in 24-hour urinary iodine concentration to 36 mg/L and 24-hour urinary iodine excretion to 77 mg/d in the Paleo diet group at 6 months.
On the other hand, the iodine levels remain unchanged in the Nordic diet group. Moreover, the hormone FT3 also decreased at 6 months in the paleo diet group but the levels of FT4 and TSH were similar in both the groups.
A long-term use of Paleo diet may result in mild iodine deficiency
This study demonstrates that following the Paleo diet for a long time may result in the development of mild iodine deficiency. The participants who were iodine sufficient at the start of the study were iodine deficient after following the Paleo diet for 6 months.
Interestingly, the results showed that 24-hour urinary iodine levels increased in the Paleo diet group at 24 months. The researchers attributed this change to the possible difficulties faced by the participants in maintaining long-term Paleo diet. Additionally, consistent with mild iodine deficiency, the levels of FT4 and TSH was unaltered in this study.
This study is the first of its kind
The researchers claim that this is the first study that investigated the association between iodine deficiency and Paleo diet. Although the study had a small sample size, it finds strength in an increased precision of the sample collection methods. The researchers believe that the differences in the iodine levels between the Paleo diet and Nordic diet were based on the true effects of dietary changes.
Iodine supplementation may be necessary with the Paleo diet
The conclusion of this study points to the possible adverse effects of weight loss diets. The recurrence of iodine deficiency in the United Kingdom is an example of the iodine issue associated with the Paleo diet. The low 24-hour urinary iodine concentration observed in the participants following the Paleo diet in this study confirms that paleo diet results in a higher risk of developing iodine deficiency.
The researchers suggest that people following the Paleo diet should consider iodine supplementation to keep their iodine levels within healthy limits.
Written by Preeti Paul, MS Biochemistry
Reference: S Manousou et al. A Paleolithic-type diet results in iodine deficiency: a 2-year randomized controlled trial in postmenopausal obese women. European Journal of Clinical Nutrition (2018) 72, 124-129; doi:10.1038/ejcn.2017.134