I’ve been wanting to take a look at vegan diets for some time, and since we’re all trapped home, I figured this’d be the time to do so. I will be looking at veganism in different lenses in an attempt to draw a clearer image for myself, and hopefully the reader.
We’ll look at vegan diet’s effects on health, sports performance & physique, then bash The Game Changers for representing everything absolutely wrong in the nutrition industry. I must caution; this'll be another series...And this be part 1.
Vegan Diets & Health
About 3 years ago; a meta-analysis was conducted on 100+ observational cohort studies examining the effects of veganism on various health parameters such as BMI, lipids, Cardiovascular risk and Cancer risk . In the above-mentioned analysis, 80 of which were cross-sectional with the remainder being Prospective studies. The latter is of more relevance as they are higher on the hierarchy of evidence.
Results from the meta-analysis found a reduction in incidence of ischemic heart disease by 25%, but not of total cardiovascular & cerebrovascular mortality, as there was decreased Cancer incidence by 8% but not of cancer mortality . These results are of course in comparison to omnivorous diets, and they aren't particularly surprising, although I question their validity for reasons I will explain briefly.
Vegan diets in general tend to have less saturated fats, as well as foods that lower LDL-cholesterol such as Legumes, soybeans & vegetable oils. What's more, they're normally hypocaloric due to their satiating (filling) effect as they’re low in nutrient density and high in fiber. As a result, vegans will tend to have lower blood lipids and lower BMI when compared to the omnivores, thus having lower risk & Incidence of cardiovascular disease and metabolic syndrome. This result, partly derived from having lower BMI in general, and not the vegan diet itself.
That said, I want to address the weaknesses of these studies, because they are important in interpreting the overall results gathered.
First and foremost, the selection criteria for omnivore subjects was haphazardous and was defined as 'anyone consuming all types of foods'. That really puts a large question mark on the entire study, because that selection criteria allows for consumption of all variant foods without restrictions of sorts; essentially eating whatever & whenever without regard to what is being consumed. It is not a diet; it is just unstructured eating. That contrasted to a severely restricted diet that comprises high amounts of fiber and antioxidants, will surely produce better outcomes.
A vegan approach, by definition, is a diet whereas omnivores are thereof lacking. To illustrate further, in (Rouse et al., 1983) subjects on the omnivore diets were instructed to eat more saturated fats and limit their fiber intake to 20 grams, and at the same time the vegan group was instructed to increase their fiber intake, eat more fruits and remove all sources of meats . This setup holds no ground in the real world, because, as you add restrictions to omnivores and structure their diets as opposed to instructing them to eat junk, results will differ immensely.
Unfortunately, there are no controlled trials comparing vegan diets to a structured omnivore diet, although I reckon things will go in favor of the structured omnivore diet for a reasons I will discuss shortly. Entertain this thought for a minute. If you’re eating a balanced amount of dairy, protein, fruits and vegetables, what would the outcome be like?
Another drawback present is of study bias, where moderate-to-high bias prevailed across the 80+ cross-sectional studies rendering their evaluation difficult . For example, confounding factors such as smoking, hypertension, family history, high BMI were not included in the studies, but weigh heavily on Cardiovascular disease & Cancer. That said, the studies are not worthless, but we ought to be careful when interpreting their effect, and we should require some clinical trials to evaluate them, should they be replicated. Forget not, that cross-sectional studies cannot infer cause and effect, rather be used to generate hypotheses for further evaluation.
Finally, the risk ratio was derived from the 20+ prospective studies to which I previously alluded to, is affected by the selection criteria. It is worth mentioning the results again; a reduction a 25% in incidence of cardiovascular disease and an 8% reduction in Cancer incidence . Nevertheless, the comparison between a limited, high anti-oxidant diet and unstructured eating is redundant. It only shows that eating more fruits and veggies is better than little, and certainly better than zero, but it does not imply that the consumption of meat is harmful, nor risk-elevating of disease.
When one designs a study, in which people are instructed to eat junk or purposefully reduce fruit and vegetable intake, then compare that sample with a high anti-oxidant diet. The results...well, the results are above.
On that note, I do want to draw your attention to something a extreme importance; vegan diets are not without harm as they predispose to B12, zinc, calcium, essential fatty acids, iron, and possibly vitamin D deficiencies   . Yes, it's one long list of things one should not possess on a diet, as they are capable of causing critical harm. That is not to say, one cannot supplement their diet with vitamins & minerals, but I would argue, a diet in need of that much fortification is neither ideal nor healthy.
If we were to compare a structured omnivorous diet against a vegan diet, both devoid of supplements; I'd put my money on the omnivorous diet as its self-sustaining without need of fortification. And lest not forget, vegan diets are severely lacking in protein quantity and digestibility  . I have the intention of touching on that in part 2 of this series. And you can read about protein digestibility in Part 1 of the All Protein Things series.
I hope that I addressed this aspect of vegan diets sufficiently, and although more evidence is required to draw further conclusions, this'll need to do for the time being as this marks the end of Part 1.
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