Athletic Anti-Nutrition: What a Vegan Diet Did to Carl Lewis

By: Dave Asprey

One of the most-cited vegan athlete success stories is of Carl Lewis, who credits his outstanding 1991 results in part to the vegan diet he adopted in 1990.(1) He says something that is often quoted in vegan propaganda,

“My best year of track competition was the first year I ate a vegan diet.”

The biohacker in me read that and said, “but what about the year after that?” The results are predictable, at least if you’ve read a previous post about measuring power in vegetarian athletes.  It’s also a little known fact that a high omega-6 diet masks cellular energy deficiencies for a short period of time (more on that below).

The Facts About Going Vegan That Are Left Out

Here are the facts. Before going vegan, Lewis consistently dominated both sprinting and the long jump. After the heights reached in 1991, only 1 year after starting the vegan diet, Lewis started to lose his dominance in both the sprints and the long jump.

In 1992, he failed to qualify for the Olympic team in the 100 m or 200 m. Lewis did, however, qualify for the long jump and was eligible for the 4 x 100 m relay team. The vegan diet was starting to take its toll. Then in the 1992 Olympics, he ran a very fast 4 x 100 relay and won the long jump, but with a shorter jump than in previous years. He was unable to compete in his formerly strongest events – the 100m  and 200 m sprints.

Then in 1993, Lewis competed at the 4th World Championships in Stuttgart, but finished fourth in the 100 m sprint and did not even compete in the long jump. He did win a bronze medal in the 200 m sprint, which was his final Olympic or World Championship medal in a running event.

Starting in 1994, injuries kept Lewis largely sidelined for the next few years.

An impartial observer would say, “Here is a world class athlete who was performing very well across the board. Then he went vegan, had one great year, got progressively less consistent, and was ultimately sidelined by injuries.”

The Vegan Trap

Here’s the reason I believe this happened, courtesy of Steve Fowkes (click here to listen to the Bulletproof Radio episode with Steve Fowkes), a friend and one of the wisest biochemists I’ve ever known, and author of Smart Drugs & Nutrients II, one of the “bibles” of cognitive enhancement. Steve writes: (bolding is mine)

Unfortunately, the benefits to consuming a PUFA-containing product  do not counteract the rancid-oil exposure.  Furthermore, the non-rancid PUFAs deposit in the fatty tissues and cell membranes of the body where they become targets for oxygen free radicals.  This is the bad side.  The good side is that the PUFAs promote membrane fluidity and membrane permeability, which has a pro-metabolic effect that is in some ways similar to that generated by thyroid hormone, progesterone, exercise, vitamin D, vitamin A (not beta-carotene), magnesium and selenium (and other agents).  But because it mimics the effects of these other agents, there can be perceived benefits that are not truly biologically sustainable.  In other words, there is a perceived health change for the better, but I believe a vegan diet contributed to his rapid decline.

  • Higher protein intake has consistently shown to produce better training adaptations.(2)(3)(short term* vegan diets – but the long term effects hurt his performance, and then his body.  I noticed this with my own vegan and vegetarian experiments. The first 3 months, you’re on fire. Then things start to break, including your brain. I’ve heard this countless times from coaching clients and people who attend my meetings. The sad thing is that the most competitive, hardest working people who try vegan diets tend to stick with them the longest, for the simple reason that they remember how good the first 3 months felt. When their performance – and then health – decline, they convince themselves that it couldn’t be the vegan diet, because of how good it made them feel. So they suffer while they try to figure out all the other reasons their quality of life is gradually declining, but they do not make the connection.I call this the vegan trap – it’s a naturally occurring phenomena that takes advantage of the fact that behavior changes we stick to for 40 days (or 6 weeks) tend to become permanent, and the unfortunate fact that what is a fundamentally unhealthy diet makes you feel good for a time longer than 40 days. It’s the same psychological mechanism behind drug addiction.We don’t know with certainty exactly why Carl Lewis’ performance began to decline.  Maybe it was age, loss of enthusiasm, or simply better competition.  However, there is good reason to believe a vegan diet contributed to his rapid decline.
    • Higher protein intake has consistently shown to produce better training adaptations.(2)(3)(4)  A vegan diet isn’t zero protein, but it almost always ends up being deficient.(5)
    • Vegans and vegetarian are likely to be anemic and “have lower mean muscle creatine concentrations than do omnivores, and this may affect supramaximal exercise performance.”  Both of these things are going to impair athletic performance, and in the case of the latter, especially sprint performance.(6)
    • A vegetarian diet decreases muscle carnosine stores which are needed for optimal sprinting performance.(7)
    • 80% of long term vegans are deficient in vitamin B12, which is needed for proper mental function.(8)  B12 deficiency causes dementia, cognitive impairment, depression, and degenerative mental disorders.(9) None of these are going to improve your sports performance.

    So when it comes to the vegan diet, “Just Say No.” And remember that eating grass-fed meat kills far FEWER animals than a vegan grain-based diet, because there are no “tractor kills” in grass-fed agriculture. Behind every vegan hot dog are dozens of fuzzy mice, cute bunnies, turtles, snakes, and bugs that were mowed down by tractors and farm equipment. A diet high in healthy fats like the Bulletproof Diet only kills about 0.7 animals a year, including agriculture-related deaths, and it makes you healthier, stronger, smarter and happier and it will enable anyone to do more in the world.