A month or so ago, a contact (okay, it was my mum) emailed me a story from The Canberra Times.
"Celebrities love 'The Greenprint'. But What Exactly is it?".
It turns out that Queen Bey recently advocated a diet book called "The Greenprint".
To quote the article, "The Greenprint" is the title of a new book by the superstar couple's personal trainer, Marco Borges, a plant-based guru who has also worked with Jennifer Lopez, Shakira, Pharrell, Diddy and Ryan Seacrest."
The title refers to the impact on the planet that one can make by going plant-based.
Interesting concept for sure.
In the next section, Borges goes on to say;
"I decided to practice wellness through exercise and nutrition. As I immersed myself in all the science, the data and the clinical trials, I realised that if you were looking for optimum wellness, improved performance and your best chance of survival, you had to move toward a plant-based diet."
And here's where things start to get a little bit sketchy.
Now if you've read much of my work before, you know that I am agnostic when it comes to nutrition methods. Or at least I try to be as much as possible.
I don't mind how people choose to go about reaching their nutritional goals. As long as it meets the critical dietary principles and isn't dangerous. I work with vegans and vegetarians and while it requires a little more leg work to build a healthy diet that covers all bases, it's definitely possible.
If someone chooses to go vegan based on ethical issues, then that's fine. You can't argue with someones personal ethics. That's their choice.
What I disagree with is that "all the science, the data and clinical trials indicate that a plant-based diet is optimal for health, performance and best chances of survival".
I'm going to give Borges the benefit of the doubt and assume that the newspaper wasn't interested in the particular studies he's referring to.
I mean, what other reason could he have for making those claims?
It's not like he's selling a.... oh wait.
Even so, let's have a look at what the science says when it comes to health, performance and survival.
Is a plant-based diet going to make you healthier or allow you to live longer?
When we're looking at all-cause mortality, we're talking epidemiological studies. Which means we're looking for associations between particular variables rather than determining causation.
Some studies have associated plant-based diets with a lower rate of all-cause mortality. [1,2,3] With the strongest effect seen in a study based in Germany which found a 55% reduced risk.
Impressive right?
Don't push your tear-soaked bacon aside yet though.
In contrast, multiple studies have found no difference in all-cause mortality between those who eat meat and those that don't.[4,5,6,7]
A 2017 systematic review and meta-analysis analysed 96 studies and found there to be no significant difference in all-cause mortality.
What gives?
Why do some studies show a benefit while others don't?
It all depends on what they're actually comparing.
One of the problems with observational studies is that it's hard to account for all the potential confounding variables.
For example, the average vegetarian tends to be more health-conscious than the average meat eater. Choosing to be vegetarian or vegan usually indicates that an individual cares more about their health than the general population.
Plant-based eaters tend to have lower BMI, smoke less, drink less and be more active. All of these aspects play significant roles in all-cause mortality.
For example, the German study that showed such a significant impact collected study participants via questionnaires in "several vegetarian magazines".
This is what we call a"healthy user bias", whereby individuals who apply for studies are more likely to be "health conscious". So they compared individuals who likely prioritise their health, versus individuals who don't.
To know whether removing meat and animal products our diet increases health and our lifespan, we'd have to study equal groups. To compare vegetarians/vegans against health-conscious omnivores. Preferably, omnivores that consumed near equal amounts of fruit, vegetables, fibre, and were of a healthy weight.
To my knowledge, no studies have done this in a well-controlled way.
Yet, the studies that showed no difference in mortality did do a better job at taking these problems into account.
The Health Food Shoppers Study recruited participants for both vegetarians and omnivores from questionnaires in health food stores, clinics and health food magazines. The idea being that omnivores who shop at health food stores are more likely to be health conscious than the general population.
What did the researchers find?
Participants in the health food store group lived longer than people in the general population. Not surprising given their higher level of health consciousness. But there was no difference between vegetarians or omnivores.
The EPIC-OXFORD study in the UK recruited vegetarians first through the Vegetarian Society of the United Kingdom. The vegetarians were then asked to invite friends and relatives who consumed animal products, with the assumption that their friends of vegetarians are likely to be healthier than the general population of omnivores.
While a bit of a stretch, both vegetarians and health-conscious omnivores had a lower risk of early death than the general population. But there was no difference in lifespan between the vegetarians and meat eaters.
It appears that the studies that did a better job of considering all the confounding factors saw no difference.
So what about performance?
This was a particularly bold claim.
To my knowledge, there is no data to suggest that plant-based diets are better for performance.
A systematic review in 2016 by Craddock and colleagues concluded:
"Currently, the evidence for consuming a predominately vegetarian-based diet and improved athletic performance is lacking. In the eight studies which were identified in this review, however, the vegetarian-based diet did not improve performance, nor did it hinder it."
So as we can see, it's not quite so clear. We don't have the evidence to support the claims Borges made.
What I find most frustrating is that most people are going to read his claim, and take his reference of science as proof enough.
And I guess that's the hidden message of this article.
Just because someone talks about science, don't take their advice as gospel.
At this point, I don't think we can definitely say that a meat-free diet is better for health.
It also depends on what we consider a plant-based diet. Is it meat-free? Or is it the majority coming from plants?
If I eat a cauldron full of fruit and veg but also consume a decent whack of animal protein, is that plant-based?
I prefer an inclusive, rather than exclusive mindset with food. For health, I'd focus first on eating more fruits and vegetables, rather than cutting out animal products (or any foods for that matter).
In general, cutting out foods or food groups makes it harder to get all the necessary vitamins and minerals we need. A poorly planned diet is going to cause issues, regardless of whether you're an omnivore or a vegetarian/vegan.
The clear takeaway is that people who pay attention to their diet, eat more whole foods, and are a healthy body weight tend to be healthier and live longer.
So whichever dietary method allows you to do that consistently is fine.