Muscle: Vegetarians vs. Meat Eaters

You rarely see an elite bodybuilding champion who’s also a vegetarian. There are, however, some notable exceptions. One is Andreas Cahling of Sweden, who won the IFBB Mr. International title in 1980. Another is Bill Pearl, who won the AAU Mr. America in 1953 and four NABBA Mr. Universe titles (’53, ’61, ’67, ’71). On the other hand, neither Cahling or Pearl were vegans, who eat no animal products. Pearl ate milk and eggs, the two best animal-protein sources. Andreas favored fish, another top-notch animal protein. At the other extreme, French-based pro bodybuilder Serge Nubret claimed to have downed up to 12 pounds of horse meat daily. Horse meat is popular in France, although the idea would likely turn off most Americans.

From a purely objective scientific view, a bodybuilder doesn’t need to eat red meat to make gains in muscle size and strength. Meat is a good source of nutrients that have an anabolic connection. It provides a generous supply of essential amino acids, as well as creatine and such nutrients as the trace mineral zinc, which is required for insulin, growth hormone and testosterone metabolism. The high creatine content of beef makes it stand out among protein sources. Many studies show that creatine aids in muscle size and strength gains. Interestingly, habitual meat eaters get a lesser response with creatine supplements than nonmeat eaters do. In fact, those who eschew all sources of beef often show the greatest response. That’s because habitual meat eaters are constantly loading their muscles with creatine from their diets. Those who abstain from meat have considerably less creatine stored in their muscles. Creatine supplements are suitable for vegetarians because they are synthetic, not derived from meat.

While eating meat doesn’t appear to be a necessity for producing muscle gains, several studies have compared bodybuilders who eat meat to those who abstain. The meat eaters usually make better gains and have more muscle mass than the nonmeat eaters. Subjects in the latest study were middle-aged women: 21 omnivores—those who eat both meat and plant foods—and 19 vegetarians. One was a vegan; 10 were lacto-vegetarians who drank milk but ate no beef or eggs; and eight were lacto-ovo vegetarians, meaning they ate milk and eggs. The vegetarians had been off meat for a minimum of two years, with most averaging 12 years. Some were sedentary, and others were moderately active. None were athletes or bodybuilders.

The researchers determined the women’s muscle mass by measuring urinary creatinine levels; the dietary intake was obtained through five-day records of everything the women ate. Other measurements recorded hormone levels and the natural phytoestrogens in the subjects’ diets. There were no differences in hormone levels between the groups, with the exception of sex-hormone-binding globulin, which was lower in the omnivores. SHBG binds active sex hormones in the blood, including estrogen and testosterone. Only the free, or unbound, hormone is considered biologically active. The most significant finding of the study was that muscle mass was strongly associated with animal-protein intake but not with the amount of protein taken in.

The women who ate more animal foods—the omnivores—had more muscle mass than the vegetarians. So, although both groups ate the same amount of protein, the omnivores had more muscle. Why? It has to do with the richer content of essential amino acids found in animal foods, which are vital for helping boost muscle mass gains. While vegetarians could theoretically offset the deficit by eating a greater variety of plant-based proteins—soy, for example—the women in this study didn’t eat all that many isoflavones, which are plant-based phytoestrogens. That means the vegetarians weren’t eating higher-quality plant proteins, such as those found in soy, so they weren’t getting enough essential amino acids to support added muscle mass, even though they were eating just as much protein as their omnivorous counterparts—indeed, more than the recommended daily intake of protein.

Plant protein sources are generally harder to digest and absorb than animal proteins. They tend to be high in fiber, which, while offering health benefits, also significantly slows uptake. Much of the protein isn’t digested at all, which explains why the subjects had amino acid deficits despite the protein they ate.

One perplexing question is why the vegetarian women who ate high-quality animal protein sources, such as milk and eggs, didn’t show muscle mass comparable to the omnivores. There are two possibilities: One, the women didn’t eat enough—a distinct possibility, given concerns about excess calories from eggs and dairy. Two, there’s something special about eating a greater variety of animal proteins, including red meat. Greater variety would ensure an optimal intake of essential amino acids for building and supporting muscle mass.

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Aubertain-Leheudre, M., et al. (2009). Relationship between animal protein intake and muscle mass index in healthy women. Br J Nutr. 102(12):1803-10.