This randomized, double-blind, placebo-controlled intervention study was conducted in 50 overweight Japanese subjects receiving either iodine-reduced Laminaria japonica boiled kelp powder (6 g/d = 3 g alginate/d) or placebo for 8 weeks.

Results indicate that body fat percentage was significantly decreased in male subjects compared with placebo (p < 0.05). The same tendency was observed for body weight (p = 0.065) and BMI (p = 0.072) in male subjects. No significant changes in anthropometric measurements or visceral fat area were observed in female subjects. In addition, kelp powder may reduce serum LDL cholesterol concentrations in non-hyperlipidemic subjects.

Serum thyroid hormone concentrations did not increase after 1.03 mg/d of iodine supplementation through kelp intake. This means that additional supplementation of iodine from kelp powder is safe in Japanese subjects with already a relatively high intake of iodine from seaweed consumption.

In conclusion, intake of iodine-reduced kelp powder is safe and leads to significant reductions in body fat percentage in overweight male subjects without influencing thyroid function.

Aoe S, Yamanaka C, Ohtoshi H, Nakamura F, Fujiwara S. Effects of Daily Kelp (Laminaria japonica) Intake on Body Composition, Serum Lipid Levels, and Thyroid Hormone Levels in Healthy Japanese Adults: A Randomized, Double-Blind Study. Mar Drugs. 2021 Jun 22;19(7):352.

Photo by Anika Mikkelson on Unsplash