Not a Gamechanger: A scientific and personal view.

The Gamechanger Movie. Cited as proof that plant based diets are superior for athletic performance and health. Before I get into the science, my personal view: what had the potential to be a very informative look at an important area of diet and athletic performance turned out to be flawed in fact, with spurious conclusions far removed from the underlying data, emotive and – at times – utterly ridiculous. It will (has) create further separation and tribalism in dietary views in the general population, rather than a helpful and informative debate.

To be clear from the outset, vegan diets can be awesome for health and performance.

They can also be atrocious. Omnivorous diets can be awesome for health and performance. They can also be atrocious. It depends on what you include, and to what degree what you include meets your needs. This is most definitely not an anti-plant based or vegan diet

Now let’s look at some of the key content of Gamechanger. This focuses on athletic performance and health. Ethical, moral and / or environmental debates are not addressed.

What is a plant based diet?

Gamechanger does not distinguish between plant based, vegetarian and vegan diets. These are 3 different ways of eating, each of which presents different dietary challenges that followers must be aware of and focus on. Plant based diets can include dairy, meat and fish. It simply means a diet where the majority of the food volume comes from plants. A vegetarian diet incorporates some animal based products (the specifics depend on the individual and type of vegetarianism they follow). A vegan diet contains no animal derived products. As Gamechanger unfolds the main focus is on vegan diets, and so – by default – this will be the focus for the remainder of this blog.

More plants!

Scientific research performed to date supports that a diet rich in fruit, vegetable, wholegrains, legumes, and some nuts and seeds is beneficial for the health of most individuals. This is primarily due to the fibre, vitamins and minerals they can provide. And that a large proportion of the western population do not hit recommended targets for these and thus would be assumed to benefit from increasing their intake of such plant based products. To be clear, we are talking here about whole, unprocessed plant products. Not something highly processed with artificial non-nutritive sweeteners, emulsifiers and other added ingredients. In this, Gamechangers is well supported in promoting high intakes of plant based foods.


Now, protein. Research indicates individuals who train, and are not in a calorie deficit require 1.2-2.0g protein per kg bodyweight (American College Sports Medicine, ACSM, and the International Society of Sports Nutrition, ISSN). If in a calorie deficit this can rise as high as 3.0g/kg bodyweight (ISSN). In addition, where protein is obtained from plants it is estimated that requirements are 10-25% higher as protein is typically not as high quality (more on the definition of this later) as animal protein. As per Gamechanger, the average plant based diet is more than sufficient to meet recommended requirements. However, if the maths they cite is followed it transpires that per their references the average vegan takes in 70g protein per day. As per evidence backed research this comes in under the lower end of the recommended ranges by the ACSM and ISSN.

Gamechanger also suggests that most meat eaters obtain at least half of their protein from plants. They have no data to back this up. From my own experience, most of my omnivorous clients obtain most of their protein from animal sources with some coming from nuts and wholegrains, and a little from legumes. Ask around and see what conclusion you draw.

Gamechanger also claims that the same amount of protein can be obtained from a peanut butter and wholegrain bread sandwich as from 3 ounces of beef. And therefore it is not challenging to have a high protein intake on a vegan diet. It is absolutely true that you can get the same amount of protein from the beef and the sandwich, but it should be put it in context. Three ounces of beef contains approximately 20g protein, 4-8g fat and 120-150kcal. The same amount of protein can be obtained 60g wholegrain bread and 50g peanut butter, which contains 23-26g fat and 450-480kcal. This is a higher proportion of daily calorie intake and therefore potentially limits the total protein (and carbohydrate) intake for the day – depending how many calories an individual needs to target for their body composition and performance goals. It is a fact that obtaining the recommended protein intake is typically more challenging on a vegan diet. Absolutely achievable, but it will typically require more planning and attention.

The final point on protein: protein quality. The current most advanced scientific definition of protein quality considers both the specific amino acids the protein contains (does it contain all the essential amino acids in ideal proportions for what the body needs), and how easily the protein is absorbed in the body (i.e. how much of what you eat can actually be accessed and used by the body). All proteins are given a score of their protein quality. The protein digestibility-corrected adjusted amino acid score (PDCAAS). The only whole proteins that hit the maximum score of 1.0 are animal proteins. This doesn’t mean other proteins are not useful or ‘poor’ quality. But Gamechanger’s claim that plant proteins are of inherently higher quality is simply unfounded.

The lower PDCAAS of plant proteins is usually in large part due to the fact that the plant proteins is not a ‘complete’ protein, i.e. do not contain all the essential amino acids in sufficient quantities to optimise protein synthesis in the body. Legumes are typically limiting in methionine, grains are typically limiting in lysine and threonine, and nuts and seeds are typically limiting in lysine. By combining complementary plant proteins, i.e. those limiting in different amino acids, a complete protein can be made and therefore the protein quality of the meal can be enhanced … potentially near to 1. This is something to focus on if you are following a vegan diet.

Correlation, not cause

Two correlations that Gamechanger focuses on are saturated fat intake and heart disease, and meat intake and cancer. To note, correlations. I believe heart disease also correlates with people who play the lottery. This does not mean that playing the lottery causes heart disease. Based on the research performed to date, the biggest causal risk factors (from a lifestyle perspective) for both heart disease and the cancers referred to are smoking, alcohol, low vitamin and mineral intake and a sedentary lifestyle. It so happens that vegans tend to be more focused on health based behaviours and therefore less likely to smoke and drink excessively, and more likely to eat lots of vitamin and mineral rich plants. Therefore, people who suffer heart disease and these cancers are more likely to be meat eaters than vegans – hence the correlation. This does not mean meat intake causes heart disease or cancer! A side note – nitrates found in some processed meats have been found to increase the risk of certain cancers … but not meat itself.

Carbs, carbs, carbs!

So far we have focussed on protein and meat. Gamechanger also highlights that carbohydrates are essential to athletic performance. Yes, they are. Any sport that requires above low to moderate intensity activity is primarily dependent on carbohydrates. But carbohydrate intake is not necessarily higher or lower on a vegan or animal product containing diet! Not sure why Gamechanger assumes carbohydrate intake is necessarily impaired when animal products are included in the diet. We are absolutely not talking about going ketogenic!


It is a fact that vegan athletes (recreational or professional) typically have to be more focussed on obtaining certain micronutrients, as they are not as easily available from plants. This is not a good or bad thing. It is simply how things are. Some of the most key for athletes are iron, calcium, vitamin B12 and omega 3. Let’s look at these now.

To tackle iron first. Again, Gamechanger sadly cites evidence that does not exist. Fibre and other plant compounds kind of trap the iron found in plants and so you don’t absorb it as well in the gut. In addition, the form of iron found in plants is non-haem, which is inherently not very absorbable in the gut. Gamechanger gets this wrong. The best sources of iron are dark green leafy veg, legumes, and wholegrains, as well as fortified food products. Although you may not take in much of these, it is not recommended that you supplement unless you are under the guidance of a doctor to do so. This is because excess intake is also toxic. If you are worried you may be deficient, see your GP and ask them to test you – then if you are, they will give you supplements and continue to test you regularly to make sure you are not ending up with toxic levels in your system.

With calcium, again fibre and other plant compounds trap that found in plants and so make it harder to absorb. As with iron, the best sources of iron are dark green leafy veg, legumes, and wholegrains, as well as fortified food products.

Vitamin B12 is central to nerve, energy and red blood cell function and it is not present in active form in plants. So if you are vegan, you need to look out for marmite, nutritional yeast, fortified foods or consider a supplement (taking supplements with food to aid absorption).

Omega 3 and omega 6 are both essential fatty acids. By this I mean that they are fats we cannot make in the body and therefore must gain from our food. We never need to worry about getting Omega 6 really as we have sooo much in the standard western diet … in fact, typically too much. In terms of Omega 3, the best plant sources are linseed flaxseed, avocado, walnuts, pumpkin seeds, hemp seeds and brazil nuts. I would be conscious of not having too much flax, hemp and pumpkin versus the other things in this list, as flax seed is also high in omega 6 and we want to ideally consume a higher amount of omega 3 than omega 6 (omega 3 and omega 6 antagonise each other within the body to a degree, and omega 3 is the one we want to dominate overall!).

And for a laugh …

And just an amusing point on athletic performance to round this blog out.

Gamechanger claims Conor McGregor lost his fight against Nate Diaz because his athletic performance was inferior because he eats meat, namely steak. Nate Diaz is vegan. What a leap! No mention that research evidence supports meat intake as an effective way to obtain the protein and fat soluble vitamins required to support athletic performance (plants can be too). Or that McGregor was fighting 2 weightclasses above his weight, against a fighter effective at getting his opponent to the ground and choking them out. Or that maybe Diaz had a more effective training regime for the fight. Nope, it was the steak!

In summary

So, to reiterate, vegan diets can be awesome for health and performance. They can also be atrocious. Omnivorous diets can be awesome for health and performance. They can also be atrocious. It depends on what you include, and to what degree what you include meets your needs.


© 2020 by Sinead Roberts
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