Absorption in humans of isoflavones from soy and red clover is similar.Author: Tsunoda N, Pomeroy S, Nestel P. Publication: J Nutr 2002 Aug;132(8):2199-201.
Isoflavones are increasingly used as food supplements. The two main sources of isoflavones are soy and red clover. The aim of this study was to investigate if there's a difference in the absorption of isoflavones originating from soy and those from red clover. Soy and red clover have different combinations of isoflavones.
For this study 14 persons were used in a single-blind, randomized, placebo-controlled, crossover trial. Soybean isoflavone glycosides (group 1) and red clover isoflavone aglycones (group 2) were incorporated into a breakfast cereal and eaten daily for 2 weeks, separated by a 2 week control period.
The isoflavones levels in the urine were measured. In both groups about 25% of the isoflavones was recovered in urine which indicates that in both groups same amounts of isoflavones are absorbed. It can be concluded the type of isoflavones (isoflavones glycosides and isoflavone aglycones) have minimal influence in the absorption rates.
Dietary isoflavones: biological effects and relevance to human health. J Nutr. 1999 Mar;129(3):758S-767S