Isoflavones are the hot new supplement these days, with purported health benefits from fighting cancers to protecting from heart disease. In general, these
compounds are a type of phytoestrogen, with very weak estrogenic activity. You can find them in their greatest amounts in soy; hence, the push for soy
protein. Okay, enough health talk. The question here is this: Do isoflavones confer any anabolic effects?
Possible Anabolic Role
To date, most research involving isoflavones has been performed in animals, petri dishes and test tubes - not exactly your typical bodybuilding conditions.
Yet recent information does suggest a possible anabolic role of one of these isoflavones. And best of all, it was in active human beings! But more on that
As for animal studies, Chinese scientists from Nanjing Agricultural University examined the effects of daidzein (a type of isoflavone) on various hormonal
parameters in rats. In the male rats, bodyweight as well as hind-leg muscle weight increased more in the daidzein rats than the control rats. Another study
from the Applied Research Institute in Japan found that soy protein (which, of course, contains boatloads of isoflavones) might reduce bodyfat in obese
Besides all the natural isoflavones in foods, man-made versions have been formulated and patented. According to, United States Patent #4,163,746, the
following compounds are "particularly active as anabolic agents": 5-methyl-7-methoxy-isoflavone, 5-methyl- ethoxy-isoflavone,
5-methyl-7-(2-hydroxy-ethoxy)-isoflavone and 5-methyl-7-isopropoxy-isoflavone. Sounds like gobbledy-gook so far, but we'll soon narrow down the players.
What's intriguing about these compounds is that data exist (in the patent) to support a possible anabolic effect, yet none of this has appeared as
scientific publication in any form. The patent reports that these compounds are useful in promoting weight gain in domestic animals, particularly in
"fattening pigs." I doubt that you'd want to be fattened like a pig, but let's examine the data and you can decide for yourself.
Using broiler chickens as their test animals, researchers gave two doses of the isoflavones (2 g and 5 g per 100 kg of fodder) in their feed. The
isoflavone-supplemented broilers gained roughly 12% more bodyweight than the controls, regardless of dose. When the researchers tested each compound
separately, they found that the different isoflavones induced varying amounts of weight gain.
The researchers suggest that a dose of 20 mg per kg (or 9.1 mg per pound bodyweight) of 5-methyl-7- methoxy-isoflavone is effective in broiler chickens. This
is an important point to which I'll refer to later, so keep it in mind.
What About Us Homo Sapiens?
Of course, little in the way of hard data is available regarding an anabolic effect of these isoflavones in humans. But let's just say that I'm privy to some
very interesting data regarding the efficacy of these compounds in humans. I can't provide detailed information, but I can give you the nuts and bolts.
In a recent pilot study done at a major university and sponsored by a product manufacturer, active men (not necessarily bodybuilders, just guys who exercised
regularly with both cardio and weight training) were given a placebo or a liquid mixture that contained a daily dose of 800 mg 5-methyl-7-methoxy-isoflavone.
Remember, according to the patent data, this was the most anabolic of the tested isoflavones.
Subjects were allowed to perform their regular exercise routine but were asked to keep a training diary. After eight weeks of supplementation, the
isoflavone-supplemented group had roughly a 2% increase in lean body mass while the control group didn't change. Although statistically significant, that 2%
may not seem '/ like much. Is it worth it?
For a 200-pound guy who's 10% fat (and therefore has 180 pounds of lean mass), a 2% increase translates roughly into a 3.6- pound gain. It's good, but nothing
to bungee-jump over. Yet the dosage suggested in the patent was 9.1 mg per pound of bodyweight; in this study (details to come at a major sports-medicine
conference), the actual dosage was 4.1 mg per pound of bodyweight. So would doubling the dose help?
Whether increasing the dose would cause a greater effect in humans isn't known. After all, on a bodyweight basis, the dose for chickens is more than double
that used on humans. While simply multiplying doses used in animal studies by a human's bodyweight seems reasonable, in practice it just doesn't work - the
active dose per pound of bodyweight differs from one species to the next. The effective dose per pound often varies more than tenfold between mice and humans,
for example. Mice and chickens have bigger livers than humans for their body size and very different drug-metabolizing enzymes.
Peer review is another unknown regarding the new human data. Until these early data are evaluated by other experts, we can't be sure if the effect is real or
not. Usually scientists at other labs must test the supplement on humans and get the same results before we can have confidence in the effect. Until then,
it's up in the air whether bodybuilders and other athletes should take 5-methyl-7-methoxy-isoflavone, but so far it looks promising and the compound probably
What are phytoestrogens?
A broad group of plant compounds ("phyto" means plant in Greek) that are nonsteroidal in structure (aka dietary estrogens).
What are isoflavones?
A type of phytoestrogen found in particularly high concentrations in soy. Daidzein and genistein are specific types of isoflavones. The
following synthetic compounds are also purported to be anabolic isoflavones: 5-methyl-7-methoxy-isoflavone 5-methyl-ethoxy-isoflavone
How much of these "anabolic" isoflavones should you consume?
The exact dose isn't clear at this time, but approximately 9 mg per pound of bodyweight seems to be
a good place to start.