Could soy isoflavones extend life?
Scientists at the university’s Human Nutrition Research Centre and Institute for Cell and Molecular Biosciences at Newcastle University report that the soy isoflavone daidzein may activate a protein called sirtuin1 (Sirt1), previously linked to the regulation of ageing and longevity.
“The concentration of daidzein that elicited [the Sirt1] response (100 mmol) exceeds achievable plasma concentrations but is not unrealistic with respect to local intestinal concentrations following consumption of isoflavone-rich foods or isoflavone supplements,” wrote the researchers in Nutrition Bulletin.
“The long life expectancy and healthy ageing observed in the inhabitants of Okinawa Island in Japan, who in past years consumed a low-energy diet, is often cited as evidence supporting a longevity effect of energy restriction in humans,” they added.
“It is of interest to note that soya provided the principal source of protein in this diet, raising the possibility that some beneficial effects of the diet relevant to healthy ageing and long lifespan may, speculatively, have been the result of soybean isoflavones potentiating effects mediated through the activity of Sirt1.”
Despite these feasible links, the researchers stressed that “extensive further investigation is required to confirm such effects”.
Less is more
Calorie restriction, while avoiding malnutrition, has already been reported to extend lives and reduce the risk of chronic disease in certain species, including monkeys.
Scientists from the University of Wisconsin-Madison published findings in Science showing that 80 per cent of rhesus monkeys who consumed a calorie restricted diet were still alive after 20 years, compared to only 50 per cent of control animals who ate freely.
Certain compounds found in the diet may also activate Sirt1, with the most focus being on resveratrol, a polyphenol found in red wine. David Sinclair and his team from Harvard reported in Nature in 2003 that resveratrol increased the survival of yeast cells.
Hints towards soy’s potential
Laura Ions, Luisa Wakeling and Dianne Ford from Newcastle University report that early observations from their work indicate that soy isoflavones may share many of the functional properties of resveratrol, “and so highlight the potential for a diet rich in these compounds to promote healthy ageing”.
According to the researchers, isoflavones and resveratrol share a degree of structural similarity. They have also been reported to have effects on DNA methylation.
“A recent report providing evidence that daidzein can increase Sirt1 activity suggests to us that the isoflavones may potentially increase DNA methylation through the same hypothetical mechanism we propose for effects of resveratrol and energy restriction - that is, through the removal of acetyl groups from histone proteins by the activity of Sirt1,” wrote the researchers.
“Our preliminary data lend some support to such a mechanism, but extensive further investigation is required to confirm such effects and to elucidate in detail the underlying mechanisms before giving dietary advice concerning potential beneficial effects of soya consumption outwith its probable cardioprotective effect,” they concluded.
The study was supported by an Alpro Foundation Masters Award (UK) and the BBSRC.
Source: Nutrition Bulletin
September 2009, Volume 34, Issue 3, Pages 303-308, doi: 10.1111/j.1467-3010.2009.01764.x
“Can soyabean isoflavones mimic the effects of energy restriction on healthy ageing?”
Authors: L. Ions, L. Wakeling, D. Ford