Metabolic syndrome is a combination of disorders that includes abdominal obesity, hypertension, hyperglycemia, and disorder of lipid metabolism, which increases the risk for arteriosclerotic diseases such as cardiac disease and stroke. Based on the National Health and Nutrition Survey Japan, 2014 (by the Ministry of Health, Labour and Welfare), 16.3% of people aged 20 years or more are highly suspected to have metabolic syndrome. By including “those with potential metabolic syndrome,” the percentage increases to 30.7%, which reveals that about one third of individuals aged 20 years or more are highly suspected to have or develop metabolic syndrome.
The most important factor in treating suspected metabolic syndrome appropriately is to change to a healthier lifestyle, and the common health guidance includes exercise and diet therapy. However, many difficulties arise in continuation of the therapy. Supplemental intake of healthy foods as a part of the diet therapy is one of the easiest ways.
Therefore, routine intake of healthy foods to suppress the increase in the levels of blood pressure, glucose, and triglycerides is of great importance in preventing metabolic syndrome. Indeed, many studies have been published about the various functions of foods, such as the efficacy of indigestible dextrin or dietary fiber on postprandial glucose 1 and triglyceride levels2, and the efficacy of gamma-aminobutyric acid (GABA) on blood pressure 3, 4. These food components have specific health benefits.
Kale (Brassica oleracea var acephala, hagoromokanran in Japanese) used in this study is a cruciferous vegetable, which is originally from southern Europe; it has been cultivated as one of the edible vegetables since a long time ago. Currently, it is rarely consumed as an edible vegetable in Japan. However, kale is rich in β-carotene, vitamin C, calcium, and dietary fiber. Therefore, various age groups consume it as a useful food for comprehensive health management or for beauty purposes. It is generally consumed in the form of juice or dry powder for the daily supply of nutrients.
Additionally, kale is rich in various functional ingredients with diverse effects. Its effects on various lifestyle-related diseases have been recognized; for example, the effects of kale powder on blood cholesterol 5, blood sugar, and blood pressure 6 have been reported. However, only a few studies have been conducted regarding the effects on lifestyle-related diseases. Additionally, no study has currently been published for the effect of kale powder on metabolic syndrome.
In general, a randomized, placebo-controlled, and double blind study is conducted for foods with specified health use that require verification of effects. Although a similar study design is desirable for healthy foods, it is difficult to conduct an effective nutrient management intervention in many subjects. Furthermore, it is well known that various factors, such as mealtime and habits, influence the endpoint evaluation. To resolve these issues, a prospective intervention study is necessary under non-blinded conditions and randomization in an appropriate, large-scale population.
In this study, the prospective, single arm, intervention study of kale powder was conducted to investigate the effect on metabolic syndrome in male and female subjects with potential metabolic syndrome in Arita-cho, Saga in Japan.