As vegan dieting is becoming more and more popular, The Game Changers documentary on plant based diets is going viral. In it, an impressive production team with lots of celebrities but few nutritionists endorses the central message that “the best source of protein is plants.” In this review, I’m not going into any of the anecdotes about single sports events or how my grandmother ate no meat/meat every day and lived to be a 100 years. I’ll stick with the science to answer the question of whether plant protein is indeed best for our health, physique and physical performance. As I’ll focus on objective data, I won’t go into ethics.
Let’s start with our health.
1. Is meat going to kill me?
The Game Changers documentary claims meat causes cancer, inflammation and cardiovascular disease. It’s easy to pick studies arguing for and against this, but what does the totality of evidence say?
Recently, the Annals of Internal Medicine published what’s currently arguably the most comprehensive review on the health effects of red meat. After weighing the evidence of 5 new systematic reviews of the literature, they concluded there’s insufficient evidence to reduce red meat intake.
Shortly after, another umbrella review of systematic reviews and meta-analyses by Händel et al. (2019) concluded that past associations between meat – processed red meat even – and negative health effects are biased and of poor methodological quality: “the better the study design, the lower the probability of an association. Moreover, the overall certainty in the evidence was very low across all individual outcomes, due to serious risk of bias and imprecision.”
Overall, the average person with a Western diet these days is generally better off consuming more veggies than more meat, but eating meat in the context of an overall healthy diet should be fine for your health.
2. Is a vegan diet the healthiest diet?
Vegetarians have an excellent health record in the literature, particularly the epidemiological literature. However, vegetarians almost by definition tend to be more health conscious than the average meat eater. Someone on a vegetarian diet is on a diet and a very restrictive one at that, so they’re evidently more health conscious and invested in their diet than the average person. In many studies the vegetarian group has a lower body fat percentage, a higher fiber intake, a higher vitamin intake and a higher intake of anti-oxidants than the meat-eating group.
Despite these advantages, vegetarians and vegans don’t consistently have better overall health than omnivores. Studies comparing all-cause mortality rates between vegetarians and omnivores have produced mixed results.
- In one prospective cohort study, vegetarians in the UK had similar all-cause mortality as comparable meat-eaters.
- In another pooled analysis of 2 large prospective studies in the UK, vegetarians had a lower risk of cancer than meat eaters, but fish eaters had just as little risk of developing cancer as vegetarians.
- One author’s mini-review found lower all-cause mortality in vegetarians than omnivores, mostly due to improved cardiovascular health, but this came with increased risk of non-communicable disease, particularly blood disorders.
- An older review of prospective studies found similar all-cause mortality rates in vegetarians and meat eaters.
- A review of vegetarianism in Austria found that “a vegetarian diet is associated with poorer health (higher incidences of cancer, allergies, and mental health disorders), a higher need for health care, and poorer quality of life” in spite of vegetarians overall being leaner and consuming less alcohol than meat eaters.
- A subsequent cohort analysis of the elderly found similar all-cause mortality rates in vegetarians and non-vegetarians despite the vegetarians living an overall significantly healthier lifestyle.
The mixed results make perfect sense if we evaluate the health effects of each food group individually. While plants offer certain health benefits and nutrients, animal foods do too. While plants shine in terms of vitamins, anti-oxidants and phytochemicals, animal foods have a higher protein quality and are typically richer in bioavailable minerals, especially iron, beneficial fatty acids like omega-3s (EPA and DHA specifically) and B-vitamins.
It makes sense then that multiple studies have found health benefits from adding animal foods to a vegan diet and vegetarian diets increase the risk of nutrient deficiencies. In other words, ‘flexitarian diets’ tend to be healthier than vegan diets.
3. What happens if you increase your protein intake with meat?
Several studies have been conducted on this with similar results. For example, Daly et al. (2014) studied what happens when elderly strength training women add 160 g cooked meat to their diet 6 days a week. That’s a whole lotta’ meat for ol’ Bessy, but it didn’t kill her. In fact, compared to the control group, the meat eating women gained more muscle and more strength with a greater reduction in measured inflammation and no adverse effects on blood lipids or blood pressure.
Overall, the literature is quite clear that meat is an excellent protein source for muscle growth and strength development that generally doesn’t pose health risks in the context of a good diet, even in large amounts in elderly individuals.
4. Is plant protein superior to animal protein?
Campbell et al. (1999) compared strength training men that consumed either a lacto-ovo vegetarian diet or an omnivorous diet where 50% of protein intake came from meat. The meat eaters gained significantly more muscle. Protein intakes did not significantly differ per group but were a bit higher in absolute terms in the meat eating group, so it’s possible the higher protein intake and not the protein quality per se caused the difference in muscle growth.
Haub et al. (2002) found that strength training men gained just as much strength and muscle on 0.6 g/kg protein from beef as from textured vegetable (soy) protein. However, the absolute increase in muscle cross-sectional area was nearly 50% larger in the beef group: 6.0% vs. 4.2%.
Hartman et al. (2007) found milk was better for muscle growth than the same macros from soy protein.
Several more studies have compared equal amounts of soy protein to other animal protein supplements, like whey protein powder, to see which is better for measures of muscle growth and strength development. Some suggest soy and animal proteins are equally effective for our gains , but the majority found animal proteins are better [2, 3, 4, 5]. None found plant proteins are superior.
Overall, it’s clear that animal protein sources are either superior or at worst equally effective as plant protein sources. This is exactly what you’d expect based on their protein quality indices. Plant proteins typically have suboptimal amino acid profiles for the human body with relatively poor digestibility compared to animal proteins.
Plant protein sources are not as high quality as animal protein sources and vegan diets are not optimal for our health. So if you’re not a vegetarian for ethical reasons, there’s absolutely no incentive to turn vegetarian for your health or physique.
If you’re an ethical vegetarian, you’ll have to put in a bit more work than omnivores to get the same results from your efforts in the gym. It’s a sacrifice you’ll have to make to stand up for your beliefs. Lacto-ovo vegetarian diets and pescatarians have it much easier. However, with meticulous attention to the diet and strategic supplementation, you can likely achieve equivalent results as meat eaters. To end with some fitspiration for vegans, the before-after photo below shows the 4.5 month results of one of my vegan online coaching clients.