Study Shows Women Who Follow a Paleolithic Diet May Experience Iodine Deficiency

Swedish women who followed a modified Paleolithic diet for two years experienced a nearly 50% decrease in iodine levels, accompanied by an increase in thyroid-stimulating hormone and a decrease in FT3 levels.

Results from a recent study indicate that women who followed a modified Paleolithic diet for two years experienced mild to moderate iodine deficiency, compared to subjects on a diet that followed the Nordic Nutrition Recommendations. The study was a two-year prospective randomized trial in healthy postmenopausal, overweight women who were recruited for a dietary weight reduction program.

A group of researchers from Sweden presented these results at the 83rd Annual Meeting of the American Thyroid Association, held in San Juan, Puerto Rico, during a poster session on October 17, 2013. The researchers conducted this study at Sahlgrens' Academy, Skaraborgs Hospital, University of Gothemburg, Umeå University, and Sahlgrenska University Hospital.

For the study, researchers monitored subjects’ median 24-hour urinary iodine concentration (24-UIC) and 24-hour urinary iodine excretion (24-UIE) over the course of three days, and also measured thyroid hormone levels at baseline and at six and 24 months. Urine sampling was monitored via para-aminobenzoic acid (PABA) and salt intake was monitored by urinary sodium levels. The researchers kept a record of participants’ dietary habits.

Paleolithic dieters exclude two of the larger iodine sources—table salt and dairy products—from their diet. This study gave the opportunity for the first time to study patients’ iodine metabolism on a “Stone Age” diet. The paleolithic diet consumed by study participants consisted of a high-protein, high-fat, and low-carbohydrate diet that included lean meat, fish, fruit, vegetables, root vegetables, eggs and nuts. Dairy products, cereals, beans, refined fats and sugars, added salt, bakery products, and soft drinks were excluded. Processed, canned and preserved foods, as well as foods with any degree of manufacturing, were also avoided.

After six months, subjects on a paleolithic diet had doubled their reported intake of foods containing fish and seafood, and reduced their intake of dairy products from 269 to 7.4 grams per day and cheese from 28.9 to 1.6 grams per day. Products such as bread, cereals, and ice cream were also severely reduced. The changed diet pattern was sustained at 24 months, but figures were slightly higher. The group that followed Nordic Nutrition Recommendations kept their intake of iodine relatively constant throughout the study.

The group following a paleolithic diet showed a decrease in iodine level after six months. Compared to baseline 24-UIC and 24-UIE levels of 72&thinsp;μg/L and 24-UIE 134&thinsp;μg/L, respectively, at six months the Paleolithic diet group’s levels had decreased to 24-UIC of 36&thinsp;μg/L (p<0.001) and 24-UIE of 77&thinsp;μg (p<0.001). Iodine levels in the group following a Nordic Nutrition Recommendations diet held constant.

Median thyroid-stimulating hormone level at 24 months was higher than at baseline in both groups. FT3 levels decreased in the paleolithic diet group after six months and were lower than in the group following Nordic nutrition recommendations.