Isoflavones are a group of phytochemicals that are present in high amounts in legumes and their seeds. Soy, red clover and kudzu are plants that are high in isoflavones, usually in their glycated form. Isoflavones are often grouped with flavonoids, but chemically are distinct from this group. Isoflavones may have a low oestrogenic activity, but they may have other effects in humans and animals. The activity of isoflavones may depend on their metabolism in the gut, and in particular gut bacteria can alter their activity through metabolism of the parent compounds. Important dietary isoflavones include the glycosides genistin, daidzin, and glycitin which can be deglycosylated to form the aglycones genistein, daidzein, and glycitein, and this process may occur in the small intestine. Gut bacteria can metabolise daidzein to equol, and this may increase the oestrogenic activity of the compound. This process requires a specific gut microbiota, but only around a third of those living in Western nations have the desired gut bacteria to facilitate this conversion, and this may significantly modify the health of the individual, with high equol producers being protected from particular diseases.
Isoflavones may enhance metabolic rate when consumed as part of a diet in animal models. For example, in mice, a diet enriched with kudzu flowers reduced adiposity and the development of a fatty liver when combined with a high fat diet. In rats, daidzein was able to reduce the severity of weight gain and fatty liver accumulation when fed in combination. Analysis of the effects of daidzein in rats showed that its use was associated with changes to the liver including changes to transcription factors and the lipogenic enzymes stearoyl coenzyme A desaturase 1. As stearoyl coenzyme A desaturase 1 enzyme is considered to be pivotal in the formation of obesity, this suggests that daidzein was able to favourably reduce the metabolic milieu that might facilitate increases in adiposity. Another study found that isoflavones from sea buckthorn was able to significantly reduce appetite, body weight increases and epididymal fat pad mass in mice. Serum and total cholesterol was also reduced in the mice and levels of proliferator-activated receptor γ (PPAR-γ), a transcription factor associated with adipose tissue breakdown, was also increased. Levels of carnitine palmitoyltransferase 1 were also increased, suggesting that fatty acid oxidation may have increased.
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Stohs, S. J. and Badmaev, V. 2016. A review of natural stimulant and non‐stimulant thermogenic agents. Phytotherapy Research. 30(5): 732-740
