First of all, thank you to everyone who read Part 1 of this series and for engaging in the discussion. i understand how close to the heart the decision to follow a vegan diet can rest. But I also feel that the emotion attached to a subject does not mean we shouldn’t dive into the important research that people are doing to help us make these important decisions. Indeed, it usually means it is doubly worth making sure we don’t spread bias based on feelings. Diet is not and should not be a faith based decision, we are talking about the health and lives of ourselves, our families, animals and the entire planet.
Much of what has clouded the discusiion is that the research has either been incomplete, the results have been muddied/taken out of context or that the experimental designs have been poorly constructed so that the results stated are not reliable or significant. This has happened from both sides but what we see in the movie Game Changers is another claim that a vegan diet will decrease illnesses like cancer and heart disease and increase lifespan.
Trying to decipher whether a specific food or group of foods is harmful or beneficial is very difficult. Defining and controling all of the outside factors that may also have an impact on the results , like exercise, smoking, alcohol intake, hereditary predispositions, other foods, etc., can make or break the reliability of the study. One common issue with the majority of research pointing at meat as a culprit for illness or increased mortaility is that it lumps all meat eaters into one category. Disregarding the quality of the animal product and the rest of the individuals’ lifestyle confounds any information you may be getting from them. And while you can definitley find vegans with unhealthy lifestyles, the people who tend to choose plant based nutrition are for the most part, a health conscious group.
We can take any number of incredibly healthy, active omnivores who eat clean, organic sources of animal products and then stand them next to an obese, sedentary omnivore who tends to eat burgers, bacon, sausages and pizza. Now ask anyone if they think there will be a difference in their blood work, hormone levels and projected lifespan. You will be hard pressed to find someone who would say that they should be lumped together in the same caetgory. Yet this is what has been done for almost all of the current literature.
One of the big headline grabbers in the last few years was The World Health Organization’s (WHO) report on the association between red meat consumption and cancer. This was an observational study, meaning that the researchers collect data, via questionnaires or interviews and then make inferences based on what they read or heard. In this study there was no, or very little controling of any other variables. You can not make statistically significant conclusions based on observational data. What you can do, is develop a hypothesis to study further using more technical, experimental methodolgy. The WHO reported an 18% increased risk of collorectal cancer for those who ate red meat, more specifically processed met. As far as observational studies go, an 18% increase of risk is so small that it can be chalked up to chance. We tend to look for massive correlations (100-3000%) of behavior and outcome to develop a working hypothesis towards causation. 18% doesn’t cut it. That said, it is perfectly fine to develop a hypothesis and then use double blind, variable controled experiments to further analyze. Instead this was printed worldwide and spread like wildfire as gospel. I read the results through a Harvard medical article and saw that same article posted by a number of friends and nutritionists that same week. No one goes back to look at the study and see if was properly formulated and statistically significant. The same will go for studies that are funded by the milk and dairy industry and so all of this muddied, contarary information gets harder and harder to wade through. So we just ingest the headlines and make snap decisions on what everyone seems to be agreeing upon. Whoever is more consistent or loudest wins.
It is no wonder that when you take someone off of a typical North American diet and give them more vegetables and fruits that the incidence of heart disease, cancer and diabetes drops. The research is pointing towards the obvious. But the healthy user bias is skewing where the focus should be – which is quality of food, and lifestyle rather than just animal products vs plants. We all know or presume to know the difference in quality from wild caught venison steak and factory farmed burgers or hormone injected chickens. We also know or should know the difference in quality between organic broccoli and processed veggie burgers. Unfortunately the clickbait headlines and representation of veganism in books and documentaries gloss over what is really happening in the science and tend to use vegan as an umbrella term for healthy. This is a disservice to the public who won’t take the time to investigate further. I spend days and days researching this stuff because i need to in order to best inform my clients but trying to find reliable sources of information and then unpacking it all is really tedious work. I don’t blame anyone for not doing it.
Back to the correlation of meat and cancer – A meta analysis released just after thw WHO report calculated a 10% risk of colorectal cancer with the intake of processed meat. This is just about half of what the previous observational study reported. But the main problem is that there was a no dose response, meaning that across all studies, it didn’t matter how much meat was eaten by the groups who had the highets intake, the response was the same. So one study could have a much higher average intake for their specific high meat consumption group than another and it didn’t change the rate of colorectal cancer. What this suggests is that another variable was responsible for the correlation.
Two more large observational studies comparing an omnivore diet with a vegan diet showed no difference in incidence of cancer when controlled for vegetable intake, smoking, alcohol intake, activity level and socio-economic status. The authors suggested that you can eat as much meat as you like as long as you increase fruit and vegetable intake. Once you do this, or elimintae other variables, the correlation to developing cancer disappears (Appleby et al., Mirshahi et al.).
But other studies show that vegans and vegeatraian live longer than Omnivores, so what about those?
The biggest and most recent of such studies are the 2 Seventh Day Adventist Studies taking place in the US taking data from over 100,000 Adventists to compare to the typical American, omnivore diet. The results were impressive, reporting as much as a 9.5 year longer life expectnacy for vegan adventists. It found fewer deaths from ischemic heart disease, cardiovascular disease and all cause of mortality. The vegans weighed 30 lbs less on average, rated lower on the body mass index scale and had less incidence of insulin resistance (SDA Health Study 2).
Seventh Day Adventists are an intereting cohort because part of their belief system incorporates a healthy lifestyle that includes exercise and excludes tabacco smoking, alcohol, most or all animal products and sometimes even coffee, tea and sodas that include caffeine. They represent a fairly large population that has been vegetarian or vegan for many years and it has allowed for interesting insight into the benefits of a healthy lifestyle. But the unfortunate reality is that the kind of bias I mentioned above of comparing healthy, active vegans to the the general population of meat eaters is present in this study as well. We know right off the bat that these particular vegans are more likely to not smoke or drink alcohol or sugary sodas and we know that they are generally quite active. We can not say the same for the meat eater group of this study and so the difference found in overall lifespan, and deaths from cardiovascular and heart disease could be coming from any number of other variables. It is important to mention that The SDA health study 2 did more to control for variables such as smoking and BMI, but still did not cover all possible oustide vactors and so the authors themselves cautioned as to what generalizations could be made for the public. Yet this is not the message you will find from souces such as Harvard Health, Healthline, Huffington Post and many more.
Fortunately, there are a number of other studies that have compared the lifespans of vegans and/or vegetarians vs omnivores with healthier lifestyles. The results from all of the these studies show an equally improved lifespan for both vegans/vegetarians and omnivores compared to the general population and no difference in lifespan between the two groups themselves. One of the studies chose the omnivore group from those who shopped at health food stores or read healthy lifestyle magazines would in general be more health conscious meat eaters. The other studies used similar tactics, by finding vegetarians who subscribed to health magazines and then asking them to invite family members who at meat. This is making a pretty big assunption that the meat eaters do indeed lead healthy lifestyles and yet all of these studies had similar results to the one mentioned above. One even showed a 10% inrease in mortaility for the vegan/vegetarian group but the authors suggestted that the outcome was related more to other lifestyle habits such as activity level, smoking and alcohol intake (Chang-Claude et al.). Without controling for all of these factors it will not be enough to make any significant conclusions but at least things are moving in the right direction.
There is no question that including more fruits and vegetables to your diet is a healthy choice (though some carnivore dieters would disagree). What I think we should question is whether it is healthier to exclude animal products from our diet. As per the science on protein quality and quantitiy from Part ! and from the review of the studies we have comparing vegan and omnivore lifespan, so far, I believe it is pointing towards no, especially for those of us who want to thrive rather than merely meet the recommended daily allowance of nutrients.
Part 3 will review the research on saturated fats and the very odd claims from the Game Changers film that cloudy blood from a meat burrito equals unhealthy blood.