Soy protein: myths and real benefits

Soy protein: myths and real benefits

If word of mouth and some scientific studies are to be believed, soy-based foods have estrogen-like properties that slow down anabolic and growth processes in bodybuilders. Unfortunately, the problem with information is that there are two types of information: Information and misinformation.

This article will look at the pros and cons of soy-based foods and consult scientific studies and expert information to clarify whether soy is a bodybuilder's friend or foe.

Often new trends in the fitness industry are based on a distortion of the facts. For example, you can find a positive aspect and interpret it in such a way that it becomes something good. A good example of this would be obesity, which is known to have a negative impact on general wellbeing. However, one could also argue that being overweight is an effective protection against osteoporosis. The same distortion of facts can also be observed with soy.

Opponents of soy protein claim that plant estrogens, also known as phytoestrogens, lower testosterone levels and link this to soy bringing out the feminine characteristics in men by increasing estrogen levels.

It is very likely that many of these cynics are not steroid-free bodybuilders, which is funny because excess testosterone (or other anabolic steroids) has been shown in studies to be responsible for the emergence of feminine traits in men.

Furthermore, it is modern myth at best that soy-based foods, or any foods for that matter, have estrogenic properties associated with feminine characteristics or hormonal changes.

The support for this magical food source that this article will provide is scientifically, logically and rationally based and some readers may be surprised at how good soy foods can be in reality.

The following sections present the unbiased view from both sides, which is unusual in that most articles and even scientific reviews will only focus on support for their claims.

Myth 1: Soy suppresses testosterone production

Some studies have shown that the consumption of soy products may be associated with a reduction in testosterone levels. However, there are also a number of studies that show no changes in testosterone levels when eating soy products. Here is a small selection of studies on the topic:

One study (1), which observed the strong association of soy protein consumption with a reduced risk of prostate cancer through modulation of serum hormones, did observe a slight reduction in testosterone levels, but this slight reduction was not associated with feminine changes or negative health consequences.

Another study (2) also concluded that soy has benefits in protecting against prostate disease and heart disease. The idea that the slight reduction in testosterone levels could make men less masculine or less muscular did not occur to anyone here.

One study (3) did observe a link between soy consumption and reduced testosterone levels, but the authors of the study concluded that this relationship was only of minor significance. In a follow-up study by the same research team (4), no changes in testosterone levels were observed when soy products were consumed.

A closer look at the studies that observed a slight reduction in testosterone levels shows that this reduction was classified as a correlation. This does not mean that the result is based on causation, only that there is a relationship, but the logic underlying this relationship is not yet fully understood.

In other words, this means that these lower testosterone levels could just as well have another cause, such as a diet that included less saturated fat and more fiber. It is well known that diets low in fat and/or high in fiber are associated with lower testosterone levels.

For a bodybuilder who consumes a variety of different protein sources such as lean red meat, dairy and poultry in moderate amounts in conjunction with intense training, the minor testosterone-lowering properties of soy would most likely be offset while still benefiting from the positive effects on the prostate and other health benefits.

Another factor to consider when looking at claims of suppression of testosterone production is the methodology of the supporting study. In some of these studies, the subjects consumed only soy products or at least used very high amounts of soy products to isolate the effects of soy.

In the real world, most people would not eat soy products exclusively, so the results of these studies are not really transferable to the real world.

So there are some problems with the claim that soy protein reduces testosterone levels:

1. A skewed and biased view to make meat or dairy protein a better sell.
2. Studies that show the opposite are ignored
3. Insignificant results are extrapolated to support an irrelevant claim
4. A distortion of the facts and a one-sided focus on hormonal changes while ignoring all health-promoting aspects.

Myth 2: Soy protein does not support muscle growth

A study conducted on pigs suggested that eating soy protein induced protein breakdown. However, other studies show otherwise. Here is a brief overview of some studies:

A study conducted with rats (5) was able to show that soy protein prevented protein breakdown. However, a human study (6), which showed that there were no significant differences in strength, hypertrophy, muscle cross-sectional area or muscle creatine levels when comparing the consumption of meat protein with soy protein in combination with resistance training, is probably more significant.

It may be hard to believe, but there is actually an anti-soy article that cites this exact study and claims that there is a 30% increase in muscle cross-sectional area when eating meat protein compared to soy protein. It is not clear where this claim comes from, as the authors of the study in the full text version showed both graphically and statistically that there were no significant differences in muscle cross-sectional area and concluded that the key factor in regulating muscle strength and hypertrophy is adequate protein intake regardless of the protein source (6). This example shows once again that one should not blindly rely on cited studies.

Another human study (7), which compared whey protein and soy protein in conjunction with resistance training, also concluded that protein supplementation increases muscle strength and muscle mass regardless of the protein source used.

A study (8) that looked at the effects of a whey and soy protein supplemented diet in mice concluded that both protein sources had positive effects on antioxidant status and resulted in better body composition.

Another study (9) showed that low-fat milk resulted in greater muscle growth compared to soy protein, although it was also shown that both milk and soy protein resulted in a positive protein balance.

Of course, low-fat milk is an excellent source of protein that should have its place in any diet, but the same is true for soy protein. A study (10) comparing whey protein and soy protein bars and their impact on lean body mass in college athletes in a weight training class concluded that both protein sources led to greater gains in lean body mass, but only soy protein was observed to have a significant positive antioxidant function, while whey protein was not nearly as effective in counteracting exercise-induced oxidative stress.

It's worth remembering that when it comes to gains in the gym, it's not necessarily the training itself that promotes growth - training sessions stimulate growth, while nutrients determine how effective the response to that stimulus is. Thus, you could achieve better and faster recovery with the help of soy protein, which would mean you can see better gains in the gym.

Is soy superior to other protein sources in terms of muscle building? Of course not. Studies show that whey protein and casein protein are best absorbed by the human body and give the best results, whereas soy protein as a plant protein is not digested and absorbed as well and has certain deficiencies in some amino acids.

However, when soy protein is combined with whey protein or casein, the lack of certain essential amino acids is no longer a problem (11). My point is that the inclusion of soy protein as a protein source in the diet can be an enrichment.

The benefits of soy protein

For the purpose of this discussion, I will use soy milk as an exemplary reference food for soy products and milk as an exemplary reference food for animal protein sources. This is an important comparison that is relevant to the concept of this article.

Over the last few years, milk has always been highlighted as an excellent food. The media kept mentioning that milk is good for your body, that milk is good for your bones and that milk will make you big and strong. I am in no way suggesting that whey protein and casein are not good sources of protein or that milk is not good in moderation. I am using the two foods mentioned above as an analogy, with soy symbolically representing those who support soy and milk representing those who are against soy products.

As an aside, it should be noted that even Arnold Schwarzenegger is convinced that a vegetarian can build big muscles and become a bodybuilding champion. This vegetarian is none other than Bill Pearl. A funny anecdote is Arnold's answer in the movie Pumping Iron to the question of whether he drinks milk: "No, I don't drink milk. Milk is for babies. When you grow up, you have to drink beer."

A good source of protein for bodybuilders

Soy milk contains a good amount of protein, which is around 7 grams per cup. If you look at the nutritional composition of soy products, in most cases you will find a wonderful macronutrient profile consisting mainly of protein, complex carbohydrates, healthy fats and fiber.

Additionally, there are different brands of soy milk that contain varying amounts of carbohydrates, fat, calories and fiber. Scientific research has shown that the brands with less carbohydrates and more fiber have a lower glycemic index and a lower insulin index.

Low glycemic index & insulin index and the fat-burning properties of soy

Many people know that low-fat milk has a low glycemic index, but not many people know that low-fat milk has a high insulin index. In other words, this means that milk causes insulin levels to rise, even though blood sugar levels remain within the normal range. At this point, let us briefly recall that insulin is an effective inhibitor of fat oxidation. Soy milk, on the other hand, has been shown to have both a low glycemic index and a low insulin index (12), allowing soy milk to stay in fat loss mode for longer.

In addition to this, there are studies showing that soy protein consumption is associated with an improvement in markers of fat oxidation. It has even been shown that soy protein leads to a greater reduction in body fat percentage and blood glucose levels than casein or whey protein (13, 14).

Antioxidant capacity and healthy fats:

Soy milk and other soy products contain isoflavones, which have positive effects on reducing the risk of prostate cancer and heart disease and may lower cholesterol levels. In addition to this, soy milk also contains alpha-lipoic acid. Some soy milk products contain up to 300 mg of alpha-lipoic acid, whereas milk only provides around 20 mg of alpha-lipoic acid per serving. Scientific studies show that alpha-lipoic acid helps fight free radicals and oxidative stress.

Summary

If you ask me, soy milk (and of course other soy products) sounds like a bodybuilder's friend based on its benefits and nutritional value:

• Low sodium and high potassium, making soy a good food for contest prep. Interestingly, soy milk has an almost perfect ratio of these two electrolytes.
• Low calorie content, which is in the range of fat-free milk.
• Low glycemic index and low insulin index, which means you stay in a fat-burning state for longer with low insulin levels and higher glucagon levels.
• High protein content, which is important for bodybuilders.
• Promotes cardiovascular health, which can only be beneficial in a world where bodybuilding is often associated with poor health, not without reason, due to the use of numerous unhealthy performance enhancing pharmaceuticals.

The key to success is to use everything in moderation, which ultimately leads to balance. Of course, whey protein and casein are among the best sources of protein and lean meats and dairy products also have many benefits, which is why you should consume all of these protein sources on a regular basis. However, the real point of this article was to understand that soy protein also has a number of benefits and can therefore be a good regular addition to a bodybuilder's diet. So the next time you hear in the gym that soy protein is supposed to hinder gains, know that a varied diet that includes soy protein and soy products is something good for your body and health, while still allowing you to win bodybuilding competitions.

Sources:

1. Dillingham et al (2005). Soy protein isolates of varying isoflavone content exert minor effects on serum reproductive hormones in healthy young men, Journal of Nutrition, 135(3), 584-591.
2. Gardner-Thorpe et al (2003). Dietary supplements of soya flour lower serum testosterone concentrations and improve markers of oxidative stress in men, European Journal of Clinical Nutrition, 57(1), 100-106
3. Nagata et al (2000). Inverse association of soy product intake with serum androgen and estrogen concentrations in Japanese men, Nutrition and Cancer, 36(1), 14-18.
4. Nagata et al (2001). Effect of Soymilk Consumption on Serum Estrogen and Androgen Concentrations in Japanese Men, Cancer Epidemiology, Biomarkers, and Prevention, 10(3), 179-184.
5. Nikawa et al (2002). Effects of a Soy Protein Diet on Exercise-Induced Muscle Protein Catabolism in Rats, Nutrition, 18(6), 490-495.
6. Haub et al (2002). Effect of Protein Source on Resistive-Training-Induced Changes in Body Composition and Muscle Size in Older Men, American Journal of Clinical Nutrition, 76(3), 511-517.
7. Candow et al (2006). Effect of Whey and Soy Protein Supplementation Combined With Resistance Training in Young Adults, International Journal of Sport Nutrition and Exercise Metabolism, 16(3), 233-244.
8. Elia et al (2006). Effect of Soy- And Whey Protein-Isolate Supplemented Diet on the Redox Parameters of Trained Mice, European Journal of Nutrition, 45(5), 259-266.
9. Wilkinson et al (2007). Consumption of Fluid Skim Milk Promotes Greater Muscle Protein Accretion After Resistance Exercise Than Does Consumption of an Isonitrogenous and isoenergetic Soy-Protein Beverage, American Journal of Clinical Nutrition, 85(4), 1031-1040.
10. Brown et al (2004). Soy Versus Whey Protein Bars: Effects on Exercise Training Impact on Lean Body Mass and Antioxidant Status, Nutrition Journal, 3, 22.
11. Margen et al (1991). University of California, Berkley: The Wellness Encyclopedia. Houghton Mifflin Company, Boston, MA.
12. Manore & Thompson. (2000). Sport Nutrition for Health and Performance. Human Kinetics, Champaign, IL.
13. Morifuji et al (2006). Dietary Soya Protein Intake and Exercise Training Have an Additive Effect on Skeletal Muscle Fatty Acid Oxidation Enzyme Activities and mRNA Levels in Rats, British Journal of Nutrition, 96(3), 469-475.
14. Nagasawa et al (2002). Effects of Soy Protein Diet on Expression of Adipose Genes and Plasma Adiponectin, Hormone and Metabolic Research, 34(11-12), 635-639.

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