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.

Seiichiro Aoe,Hirofumi Ohtoshi,Chiemi Yamanaka,Fumiko Nakamura,Suguru Fujiwara

doi:10.3390/md19070352

Seiichiro Aoe, Hirofumi Ohtoshi + Show 3 more

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https://doi.org/10.3390/md19070352

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Abstract

To investigate whether supplementation with iodine-reduced kelp (Laminaria japonica) powder decreases body fat composition in overweight Japanese subjects, a randomized, double-blind, placebo-controlled intervention study was conducted in 50 Japanese subjects with body mass index (BMI) ≥25 and <30 kg/m2. Subjects were randomly assigned to consume thirty tablets/d (10 tablets orally, 3 times/d) containing either iodine-reduced kelp powder (test, 6 g kelp powder corresponding to 3 g alginate/d) or kelp-free powder (placebo) for 8 weeks. Anthropometric measurements, blood lipids, and serum thyroid hormone levels were obtained before and after the trial. Body fat percentage was significantly decreased in male subjects from the test group compared with the placebo group. 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. Serum thyroid hormone concentrations did not increase after 1.03 mg/d of iodine supplementation through kelp intake. The intake of iodine-reduced kelp powder led to significant and safe reductions in body fat percentage in overweight male subjects. The consumption of kelp high in alginate may contribute to preventing obesity without influencing thyroid function in Japanese subjects with a relatively high intake of iodine from seaweed.

Highlights

Dietary fiber is one of the candidates for improving nutrient intake: epidemiological evidence has shown a negative relationship between dietary fiber intake and the incidence of type 2 diabetes [3,4], hypertension, dyslipidemia [5], and coronary heart disease [6]
The two groups were similar in age, body weight, body mass index (BMI), body fat percentage, and visceral fat area
Other adverse events corresponding to the intake of the kelp supplement, such as gastrointestinal problems, were not observed during the trial

Summary

Introduction

Obesity is a severe health problem and a key risk factor for other diseases, including type 2 diabetes, hypertension, dyslipidemia, and coronary heart disease [1]. Metabolic syndrome (MS) is a cluster of symptoms, including abdominal obesity, dyslipidemia, hypertension, and glucose intolerance [2]. Improving nutrient intake is a key factor in reducing the risk of MS. Dietary fiber is one of the candidates for improving nutrient intake: epidemiological evidence has shown a negative relationship between dietary fiber intake and the incidence of type 2 diabetes [3,4], hypertension, dyslipidemia [5], and coronary heart disease [6]. The average daily fiber intake in the Japanese population has been low for many years (

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