Effects of isoflavone‐rich red clover extract on blood glucose level: A randomized, double‐blind, placebo‐controlled trial

Abstract

High blood glucose is associated with increased risk of various diseases. Red clover (RC; Trifolium pratense L.) is an edible legume whose sprout is rich in isoflavones such as formononetin and biochanin A. We examined the effects of RC extract on postprandial and fasting blood glucose level, using a randomized, double-blind, placebo-controlled trial with 36 participants, aged 25 to 64 years, who were randomly assigned to receive either 1.91 g of RC extract (containing 8 mg formononetin and 1.8 mg biochanin A) or placebo. Each participant ingested the assigned test food daily for 8 weeks, and at the oral maltose tolerance test (OMTT). Initially, the two groups did not significantly differ in OMTT results. However, fasting insulin levels at 8 weeks were significantly lower in the RC group (4.76 μIU/ml at Week 0 to 4.01 μIU/ml at Week 8) with a significant interaction (P = 0.046). Subgroup analysis showed that change in blood glucose level (blood glucose ΔC) tended to decrease late in the trial period during OMTT in the ≤50-year-old RC group, as did fasting blood glucose and insulin levels at 8 weeks; hemoglobin A1c was also significantly reduced in this subgroup (5.36% at Week 0 to 5.28% at Week 8) with a significant interaction (P = 0.040). These results suggest that the daily intake of RC could reduce blood glucose, particularly for those ≤50 years old. Formononetin-an α-glucosidase inhibitor-is considered to be the major functional molecule for these effects. Therefore, intake of RC that contains formononetin might help blood glucose control.

Perspectives on the Combined Effects of Ocimum basilicum and Trifolium pratense Extracts in Terms of Phytochemical Profile and Pharmacological Effects

“…Due to some common compounds the extracts from the plants T. pratense and O. basilicum have been shown to have similar therapeutic effects [ 34 , 35 , 36 ]. The biological activities specific to the T. Pratense and O. basilicum , but also its common biological effects are presented in Figure 3 [ 11 , 28 ].…”

Multidirectional Effects of Red Clover (Trifolium pratense L.) in Support of Menopause Therapy

“…In leaves, we observe a correlation showing a dependence between the sum of polyphenols and antidiabetic activity. In the work of Masuda et al [ 9 ], formononetin, an α-glucosidase inhibitor, was suspected to be the main functional molecule responsible for the antidiabetic effect. Masuda et al [ 7 ] suggest that a daily intake of 1.91 g of red clover extract (containing 8 mg formononetin and 1.8 mg biochanin A) can lower blood glucose levels, especially in people aged ≤ 50 years.…”

“…There is also evidence of red clover being effective in lowering blood glucose and having beneficial effects on the prevention of cardiovascular disease [ 7 , 8 ]. In an in vitro model, its anti-inflammatory and antioxidant effects were documented in lipopolysaccharide-stimulated macrophages [ 9 , 10 ].…”

Clover microgreen incorporation in diet‐controlled diabetes and counteracted aflatoxicosis of rats

“…Red clover was reported before to have the potential of lowering the blood sugar level. This was attributed to its rich content of Formononetin‐an α‐glucosidase inhibitor (Masuda et al, 2021 ).…”