Soy-enriched protein blend lowers estrogen and raises testosterone in men

Vegan and vegetarian lifestyles may not be mainstream, other plant protein trends are slowly becoming just that. Depending on definition a majority of people qualifies as a ‘flexitarian’, opting for alternatives to animal protein on a regular basis.

Meanwhile industry is also flexing – they’re producing hybrid protein sources: not as bad, and just as good.

April 2011 something weird happened. During a hamburger taste test a panel of experts from the Dutch meat industry awarded the highest score to a hamburger that wasn’t even 100% meat. About a quarter of the protein in the winning hamburger came from wheat protein produced by the Dutch company Meatless.

‘Light hamburgers’ and sausages ‘enhanced’ with Meatless vegetable proteins are already on supermarket shelves. These products are low in fat and cholesterol and high in protein and fibres.

Another example: the Dutch supermarket leader Albert Heijn received a prize in 2010 for its ‘Extra Lean Meat’ products. These products are in the meat section of the supermarket, but they contain up to 30% vegetable protein. They contain less saturated fat and more protein than their regular counterparts, yet they taste the same.

All over Europe foods are starting to appear in which vegetable-based proteins have replaced animal proteins. In German supermarkets you can now buy Lupinesse Eis [ice cream] that contains no dairy products, but is based on a lupin-derived protein developed by Fraunhofer.

The biggest driver in the popularity of vegetable protein is the protein crisis. As food prices continue to rise, the price of animal protein is projected to go through the roof. For this reason alone vegetable proteins are the key to the future. But it’s also becoming clear that, by substituting plant proteins for animal proteins, the meat industry can not only save on its production costs, but it can also improve its products.

And research shows this may also hold true for the sports nutrition industry, which is slowly, but gradually waking up to the fact that some plant proteins add extra benefits to the athlete’s diet, as a product like Fast Matrix Protein Blend by Berry de Mey Nutrition shows – also a hybrid. It contains 67% soy protein isolate, and the other proteins are derived from whey.

Both soy and whey are ‘fast’ proteins – the amino acids are absorbed quickly into the blood. That’s why whey is used before or after training. Soy protein, rich in arginine [an amino acid with extra benefits for blood flow and muscle recovery – commonly found in sports supplements] should be equally well suited.

A source of concern to some, however, is that soy proteins contain mildly oestrogenic isoflavones. According to some studies, high doses of these could lower men’s testosterone levels and raise their oestrogen levels. Although meta-studies have shown that this is not the case, some strength athletes are still not keen on the idea of using soya proteins.

In 2008 the results of a study were published in the Journal of the International Society of Sports Nutrition, and they indicated that hybrid protein shakes at least do not have this side effect. According to the study, soy-whey combinations lower oestrogen levels and raise testosterone levels.

In this study 20 young men did weight training for 12 weeks. They drank two protein shakes a day, one an hour after finishing training and one later in the day. In total the shakes provided the men with 50 g protein extra each day.

Some of the men were given a soy-protein isolate [SI]; others were given a soy-protein concentrate [SC]. Yet another group were given a preparation containing 50% soy-protein isolate and 50% whey [SW]. A fourth group were given a whey preparation [WB].

The table below shows the nutritional value of the proteins that were tested. The graphs below show that each of the preparations resulted in approximately similar increases in lean body mass in the men.

Soy protein blend: hybrid proteins

Soy protein blend: hybrid proteins

Soy protein blend: hybrid proteins

Soy protein blend: hybrid proteins

The soy isolate and the hybrid mix both boosted the total testosterone level, but the effect was not significant. The decrease in estradiol level in the hybrid group was significant though. The researchers suspect that the combination of the whey proteins and isoflavones causes the enzyme aromatase to work more slowly. Aromatase is the enzyme that converts testosterone into estradiol.

It’s quite possible that the study underestimates the positive effect of the whey-soy combination on the testosterone level. During the experiment the energy intake of the SW group went down by over 1500 kcal/day. A drop like this usually also means a drop in the testosterone level.

Solae financed the research, and Solae is funded by soya producers.

© Willem Koert |

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