Recently I caught up with the Lachy and Raph @ Mind Muscle Project to record a second episode together on their show. We spoke primarily about planetary health and how we can use the evidence hierarchy in nutrition science to make sense of all of the studies available to us. Below is a summary of the major research that I mentioned during this conversation along with some other information that I believe you will find interesting – it’s a lot so just bookmark this page and look through it at your own time! If I missed anything please do send me a message on Instagram and I will add it in.
One of the major reasons for this round 2 episode was because I felt a few guests that came after my previous episode, namely Dr Paul Saladino (enthusiast of a Carnivore diet) and Leirre Keith (Author of the vegetarian myth) were making out as if their evidence was equivalent when it fact it is not – known as false equivalence. I have nothing against either of them personally, it’s their opinion that I am speaking to as I do not believe it is representative of the science.
As an FYI, here’s the evidence hierarchy
See where expert opinion is. That would be like me, or Dr Paul Saladino, giving you advice that’s not based on science. It’s VERY WEAK. And notice you cannot see anecdotes here? They are so weak they don’t even make the pyramid. This is someone who is unqualified just speaking from experience – e.g Karen on Facebook.
Rather than going through all of Paul and Lierre’s claims I just want to share a few things with you that I believe are enough for you to understand that these are probably not people we should be looking to if we want evidence based dietary advice.
Starting with the carnivore diet, there is literally not one clinical intervention that suggests eating only animal products is healthy. All of what Paul share’s is anecdotal or from mechanistic laboratory studies. At the same time we have a plethora of epidemiology that suggests the exact opposite – people eating more calories from animal products tend to have poorer outcomes.
One of Paul’s major arguments is that we do not need fibre. Yet in 2014 a short term clinical trial was done comparing the changes in microbiome composition when eating a 100% animal-based diet versus a 100% plant-based diet. This was published in the journal Nature – one of, if not the most prestigious journal in the world. Here’s what they found.
In just 5 days after eating the 100% animal-based or ‘carnivore’ diet there was:
While other studies, such as this 2018 Systematic Review, show us that consumption of dietary fibre decreases the risk of these diseases, type 2 diabetes, obesity and premature death – particularly consuming over 25g of fibre a day (note: carnivore diet provides 0g of fibre). Evidence supporting the benefits of fibre continue to come out each year. Most recently, a study looking at over 90,000 Japanese subjects found that compared to those eating low amounts of fibre, subjects easting high fibre diets had 18% (men) to 23% (women) lower risk of premature death. What’s the mechanism for this? There are many including the the cholesterol and blood pressure lowering properties of fibre. One of the other proposed mechanisms, thought to explain why it’s important to consume fibre, being the effect of soluble fibre on our microbiome. Soluble fibre passes through to our large intestine undigested and feeds our friendly gut bacteria which in turn produce short chain fatty acids. These molecules act as the energy source for our colon cells and help keep our gut wall healthy, preventing inflammatory compounds from passing into our blood. The best way to increase production of short chain fatty acids is by increasing the plant diversity in your diet – i.e the opposite of a carnivore diet. But why then are there anecdotal reports of people feeling better on a carnivore diet? Because it’s an elimination diet. There’s no debating that people have intolerances to certain plant foods. But most of the time this is a result of underlying dysbiosis (the bacteria in their colon is out of balance). When they remove plants (essentially the most radical elimination diet out there) they feel better – but this is a band-aid. Elimination diets are good for helping settle things down but they should only be conducted short term, before re-introducing foods to identify the trigger, improve diversity in the diet, and strengthen the gut. Think about what happens in just 5 days… eliminating plants from your diet is a fast way to create a microbiome that sets you up for developing disease.
I could go on and on about how crazy it is that people are adopting a meat only diet but I think that’s enough. There’s no science to support is. All signs point to it being incredibly dangerous. It may provide immediate relief for people with intolerances but that is speaking less to the healthfulness of meat and more to the fact they need to do work on building a stronger gut (just like building muscles in the gym takes work) to be able to regularly include the healthiest food groups in their diet.
Ok Lierre Kieth. Firstly her story is anecdotal. As mentioned in the episode with Mind Muscle Project, while interesting, this doesn’t even fall in the evidence hierarchy. It simply cannot be validated. All I can say on that is she is on record saying you cannot get all amino acids from plants and that she used to binge on eggs and dairy whenever chance she got. The former being scientifically incorrect and demonstrating a lack of understanding of human physiology and the latter suggesting some issues with eating behaviour. If that’s the case I do genuinely feel sorry for her and hope she’s been able to work through that with the right help.
However, my goal here is to not go into her personal story – as I said it’s really impossible for any of us to validate what she was actually doing. That’s why we have big studies with lots of data points. So with that said, I will simply address a few claims Lierre makes specifically about nutrition in general, not what did or did not happen to her. In fairness too Lierre before I went on the Mind Muscle podcast, and wrote this blog, I got a copy of her book to see how she supported her view. As I stated in the episode I was actually quite taken back – repeated references to Wikipedia and other authors (experts opinion is at the bottom of the evidence hierarchy) – and concerned by the fact that someone with such little evidence to support their opinion can get such air time. If you have solid evidence to support your point – you refer to a clinical study or a summary of studies. Not to Wikipedia or other author’s that share your same view. It’s actually quite dangerous that books like this exist and unfair to the reader’s who are not trained to evaluate the strength of scientific evidence.
Anyway let’s go a few of these claims.
1 – “You cannot get Vitamin A on a vegan diet”. This is misleading. The precursor to Vitamin A is B-Carotene and if you’re eating a calorie sufficient plant-based diet you will be getting more than enough B-Carotene to meet the RDI recommendations for Vitamin A. For example, if you just ate a single medium sweet potato you would exceed the daily Vitamin A recommendations. Even people with a genetic mutation (BCMO1 gene), which reduces their conversion of B-Carotene to Vitamin A, are still able to maintain healthy Vitamin A levels. Furthermore, B-Carotene rich plants have been shown to be highly effective at improving Vitamin A status in individuals with deficiency. Yes, there are ‘nutrients of focus’ (as I call them), such as B12, Omega 3’s and Iodine that people on a vegan or plant-based diet need to pay attention to, but with a little bit of planning it’s very simple to achieve nutritional adequacy. And the bonus is, at the same time you are eating a diet that is low in saturated fat (increases ‘bad’ cholesterol as shown comprehensively here and here) and high in fibre, which time and time again have been shown to reduce one’s risk of chronic disease and premature death (see here and here). So while you do need to pay some attention to specific nutrients, Vitamin A is not one of them, and it’s a small investment of your time (maybe a week or so reading) in order to reap the health benefits of a diet associated with reduced incidence of disease and longevity for the rest of your life.
2- “Plant proteins are missing amino acids”. Simply not true. All essential amino acids start in plant form. Just like humans, animals rely on plants to get these. Yes, some plant foods have different ratios of essential amino acids to animal foods, but when you eat enough calories and a diet with even just moderate diversity, you will easily consume adequate levels of all 9 essential amino acids without any consideration. But don’t take my word for it. Track a single day of eating in the Cronometer app and it shows you the amino acid breakdown.
3 – “Carbohydrates are bad and they are all the same”. Firstly, carbohydrates is an umbrella term. Simply telling someone you eat carbohydrates does not give you an indicator as to how healthy their diet is. Just as there is healthy and less healthy fats, the same goes for carbohydrates! While we don’t want to be munching down on refined sugar and refined starches such as white bread, pizza, doughnuts, cakes and biscuits on a regular basis, we do want to be consuming unrefined carbohydrates found in fruits, vegetables, legumes and whole grains. Imagine trying to explain that these foods are unhealthy because they contain ‘carbohydrates’. Every single one of these foods is associated with improved health outcomes. Yes, even fruit! Here’s a few examples in the literature:
1- Whole grain consumption is associated with decreased risk premature death (Meta-Analysis including over 1 million participants)
2 – Whole grains, legumes, vegetables, fruit and fish all associated with decreased risk of premature death while red and processed meat was associated with increased risk of premature death (Meta-analysis of prospective studies)
3 – Fruit and dark leafy green consumption both associated with decreased risk of developing type 2 diabetes (Meta-analysis with Over 430,000 subjects). Similar findings in another meta-analysis here.
4 – Legumes the cornerstone of longevity diets and the most important predictor of survival.
I believe Lierre is getting confused here because she has been told that all carbohydrate molecules end up being broken down into the same molecule – glucose. While this is correct, the devil is in the detail. Firstly, refined carbohydrates are rapidly absorbed and result in large spikes in our blood glucose. Whereas, unrefined carbohydrates are more slowly absorbed, effecting our blood glucose in a completely different manner. In addition, unrefined carbohydrates are found next to fibre and important phytochemical that are removed in the refining process. So on one hand you get a huge amount of nutrition and a slow rise in blood glucose, and the other you get a rapid spike in glucose and minimal nutrition. It’s like saying a car is a car!
Anyway, back to my original point about false equivalence. It’s easy for someone to speak in a compelling manner about personal experience but often it becomes difficult for the listener to work out if what they are saying is actually in line with the literature. The last thing we want is anecdotal evidence to be guiding public health when we have decades of research that is far more valid and reliable. You would have to be a huge risk taker to change your diet based on anecdote alone, particularly when all of the science suggests that such changes are likely to be harmful – as in the case of the carnivore diet.
My goal is to bring people the science. I personally adopt a 100% plant-based diet and if I was being biased I would tell everyone to do the same. Because anecdotally I have had amazing results. But I don’t, because anecdotes are not how I create my recommendations. I believe the science very strongly shows us that diets made up of 85-100% of calories from plants are optimal but where that lands from person to person will be different. It’s the theme that matters most not the label (a healthy diet is rich in fibre, whole grains, sources of plant protein and polyunsaturated fat, while being low in saturated fat and refined carbohydrates) I would be lying if I said 100% plant-based is categorically healthier than 85%. The science does not tell us that – not now anyway. So I state a range and people can do with that what they want. One great way to eat this way if you don’t want to totally eliminate animal products is adopt a “Vegan before 6pm” style diet where your first two meals each day are plant based and then dinner includes some form of meat (preferably not red meat). I’ve outlined this flexitarian style diet here.
Yes, there are other factors such as planetary health and animal welfare that may also affect one’s dietary choices, but I’m a big believer that we shouldn’t let those pillars affect how we interpret the research on nutrition science.
Anyway, I hope this quick blog helps and you enjoyed the episode. And to Lachy & Raph – thanks for having me back on, let’s do it again soon.
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