Soybeans are seeds of the legume Soya plant, and like other seeds, they contain an abundance of nutrition. Yet the protein in soybeans is unique, as are the Phytochemicals (like Isoflavones and saponins). Soy is easy to grow in good yield making it the most efficient protein source from an ecological standpoint. More than $15 billion worth of soybeans per year are grown in the United States alone, a huge source of foodstuffs for animals and people. Most common is soybean oil, which is usually hydrogenated into shortening and margarine. Other familiar soy products are lecithin, tofu, miso, termpeh, textured vegetable protein (TVP) and many real food look-alikes.

Whole soybeans are about 42% protein, 33% carbohydrate, 20% fat and 5% fiber by weight. Soy flour is 50% protein, but has some indigestible fibers that may cause gastrointestinal back talk. Soy concentrate , or TVP, is 70% protein; soy protein isolate is 90% - 92% protein. The remainder of soy protein isolate consists of Phytochemicals

Soy protein has been around for a long time, but public perception of soy has been generally negative, thanks to failed attempts to promote healthy soy-based imitation foods on the public. The marketing push that tried to make us think soy burgers were better than good ol' hamburgers has tainted our perception of soy proteins. The time has come to change this image -- soy is now more American than apple pie.

In a quest for the most efficient protein, bodybuilders have enshrined milk and egg proteins as the ultimate in protein nutrition. Low-fat tissue proteins (such as chicken or tuna) run a close second. Anything else isn't going to help muscles grow their best, and soy has been lumped in this category. Well, think again.

Overlooked in the protein fray is the huge but quiet industry that has successfully fed human infants soy protein-based formulas instead of milk for several generations. Since infants have a much higher amino-acid requirement per pound of body weight than adults, soy protein has already passed the most stringent test of all -- growing a healthy baby. The infant-formula industry has had to jump through so many regulatory hoops that the enormity of soy protein benefits has been lost in paperwork and bureaucracy.

But what about the protein-rating scales that show soy protein is inferior ? True, the PROTEIN EFFICIENCY RATIO (PER) has been used for so many years as the benchmark for rating protein quality. Soy protein PER doesn't look good compared to milk and egg protein. But look at the facts: The PER is determined by how well newly weaned baby rats grow, not by how well a human being grows.

If you think you're equivalent to a rat, then by all means believe the PER. Rats , however, require extra sulfur amino-acids (methionine) to make sulfur-rich hair proteins (keratins). Think about it-- rats have a whole-body coat of hair, so they need much more methionine than humans. Thus the PER makes soy protein look low in methionine compared to milk or egg proteins. The PER is at best a crude estimate of protein quality, and doesn't relate to protein needs of humans.

Other protein-quality scales have been proposed, but the latest and greatest is the PROTEIN DIGESTIBILITY- CORRECTED AMINO ACID SCORE. Established in 1990 and directly applicable to humans , the PDCAAS is patterned after the amino-acid needs of 2-5 year olds, since this group matches or exceeds amino-acid requirements for older children and adults (who require less than infants). Corrections for digestibility of protein are applied to give a protein-quality rating that's much closer to reality. A PDCAAS can't be higher than 1.0 , so any protein with a rating of 1.0 is complete for humans. Soy protein isolate has a PDCAAS rating of 1.0.

Astoundingly, scientists had to prove that adults could survive on soy protein as a sole dietary-protein source , even though infants (with higher requirements) have been thriving on soy protein alone for decades. A series of studies, some performed at the Massachusetts Institute of Technology, found that soy protein as the only dietary protein for adults was equivalent to milk and egg proteins, and could maintain body weight for at least 84 days when the Recommended Dietary Allowance (RDA) of 0.8 grams per 2.2 pounds of body weight was consumed per day. Nitrogen balances were slightly positive with soy protein, and no tolerance problems were seen.

Another important point on the completeness of soy protein is that fortification with the limiting amino-acid (methionine) didn't change nitrogen balance in adults or growth in infants, as long as protein consumption was near or above the RDA. Thus, fortifying soy protein with metgionine is neither advantageous nor required. Soy protein is good enough on its own, doing just as well as chicken meat in a low-calorie, weight-reducing diet given to obese subjects.

All this shows that soy is a good protein, but still doesn't prove if soy protein is good for athletes and body- builders. After all, protein demands during resistance training are known to exceed requirements for healthy adults. Mounting evidence indicates that soy indeed works well for athletes when used as a protein supplement.

Studies with Romanian athletes who supplemented with soy protein at 1.5 grams per 2.2 pounds of body weight a day for up to 12 weeks found increased lean body mass (more muscle), less body fat , more hemoglobin in the blood (the better to carry oxygen with, my dear) and less fatigue after exercise. Decreased excretion of mucoproteins in the urine was also seen, which is a marker of less kidney stress. These results were repeated half a world away with Chinese national teams, including weightlifting teams. Again, strength was improved, along with resistance to fatigue.

Further evidence that soy protein aids athletes comes from a study with seven top women gymnasts (14 years old) who were given a supplement of soy protein (1 gram per 2.2 pounds of body weight per day) for four months during heavy training. Lean body mass was slightly improved, and thyroxine (a thyroid hormone associated with protein synthesis) increased. A control group saw a decline in thyroxine and an increase in urine mucoproteins.

Anabolic Stimulators. Diadzein, one of the Isoflavones in soy and soy protein, was injected under the skin of rats for 16 days at a dose of 30 mg per 2,2 pounds of body weight a day. Muscle weight increased, body weight increased 15%, efficiency of converting food to muscle improved 12%, and growth hormone, endorphin and testosterone levels all increased. Estrogen levels increased in both genders, likely in relation to the rise in testosterone, suggesting that Diadzein may have a normalizing effect on estrogenic activity

Of course eating soy protein with much lower amounts of Diadzein may not have the same effects, but a recent human study suggests it could. Daily doses of 80 mg of soy Isoflavones from soy protein raised growth hormone and prolactin in 20 menopausal women while decreasing hot flashes, luteinizing hormone (LH) and serum cholesterol -- an overall potentially anabolic effect. Something to look forward to when soy Isoflavones become increasingly available in pure form.

Over fat rats who were fed a diet containing 35% protein, either as casein or soy protein, lost more body fat and body weight and less nitrogen on the soy protein diet, suggesting that soy protein functions as more of a fat burner than other proteins. This new finding echoes extensive and consistent results of soy protein lowering cholesterol in humans when switched with animal proteins. Many studies show that the composition of amino acids in soy protein, not Isoflavones, is what lowers cholesterol and fat. Apparently, the amino acids in soy protein are converted in the liver to organic acids and ketone bodies that enter energy pathways in a way that simultaneously burns fat.

Soy protein peptides bind cholesterol and bile acids in the gut, preventing their absorption. Soy protein metabolates also interact with LDL ("bad") cholesterol receptors to clear LDL ("bad") cholesterol out of the blood faster. That means soy protein offers a unique benefit unmatched by animal proteins: lower fat and cholesterol levels.

In corroboration with results seen in athletic studies, switching renal-failure patients from animal to soy protein lead to dramatic benefits such as 30% less protein in the urine and lowered blood cholesterol and fats. Simply trading half of the animal protein with soy protein in the diet of diabetics with kidney damage decreased markers of kidney damage in the blood. Finally, the effects of genistein and equol, two soy Isoflavones, were equivalent to those of furosemide (a diuretic drug) on isolated rat kidneys. A vasodilatory effect (expansion of blood vessels) accounted for the results. So it seems from these and other studies that soy protein is kidney-friendly and may have diuretic actions.

The presence of soy Isoflavones in soy protein has come under suspicion for being estrogenic, since some estrogenic activity in post menopausal women has been attributed to soy Isoflavones (this may be why they protect against osteoporosis). Obviously, enhanced estrogenic activity would be counterproductive to using soy protein supplements to support muscle mass.

Fortunately, soy protein with Isoflavones doesn't have etrogenic activity in males. Consuming enough soy protein or soy milk to deliver more than 1 gram daily of soy Isoflavones didn't change blood levels of testosterone, estrogen, 1.11 or follicle-stimulating hormone. In one study, large amounts of genistein from soy milk (more than 1 gram daily) reduced dihydrotestosterone by 13% and DHEA- sulfate by 14% after 4 weeks. This level of soy Isoflavones is extremely difficult to reach with soy protein supplements, so even consuming 200-300 grams of sot protein a day shouldn't have antianabolic effects.

The increases in muscle mass and decreases in body fat seen in soy protein supplementation studies with athletes further support the case that soy protein won't counteract anabolic processes in exercising individuals. No evidence exists that soy protein has estrogenic effect in athletes, and it may even have anabolic effects greater than milk proteins (the usual control-group supplement in these studies).

Thanks to an intensification of research efforts in the last few years, we now have an abundance of information on soy protein isolates being good for protein quality, muscle support, body fat reduction and improved exercise performance, not to mention the already significant effects on cholesterol lowering, prevention of cancer and other possible benefits. Soy protein is healthy and potentially anabolic, with no concerns about estrogenic activity. It deserves more respect as an ideal protein for all humans, including hard-lifting bodybuilders.

FOR MORE INFORMATION:

Henley, EC, Kuster, J.M. Protein quality evaluation by protein digestibility-corrected amino acid scoring. Food Technology, April 1994.

Exercise
Level

Activity

Protein Requirement
per Pound of
Lean Body Mass

Daily Protein
Requirement
for 150 Pounds
of Lean Mass

ESSENTIAL Protein
Required
to Fulfill
Daily Protein Need

Heavy

Heavy weight training
or
twice a day exercise

1.0 grams  

150 grams

9 scoops

Very
Active

Two hours a day,
five times per week

0.9 grams

135 grams

8 scoops

Active

One hour per day,
five times per week

0.8 grams

120 grams

7 scoops

Moderate

30 minutes per day,
five times per week

0.7 grams

105 grams

6 scoops

Light

Walking

0.6 grams

90 grams

5 scoops

Sedentary

Inactive

0.5 grams

75 grams

4 scoops