In August 2022 a narrative review was published in the journal Progress in Cardiovascular Diseases titled "Debunking the vegan myth: The case for a plant-forward omnivorous whole-foods diet". This is a response to that paper.
The response to this paper is going to operate based on the follwing assumption, which any reasonable person should agree with:
For the statement "Diet X is unhealthy" to be true one of the following needs to be the case:
ALL possible iterations of Diet X fall under whatever definition is being used for "unhealthy" (or any other word used: "deficient", "inadequate", etc.)
-OR-
It is EXTREMELY difficult and unlikely for one to consume an iteration of Diet X that is "healthy".
Otherwise, there ARE practical versions of Diet X that are healthy, and therefore the statement is false. If both of these aren't true it is ridiculous to advocate or argue against adopting Diet X, because who cares that it CAN be unhealthy?
Claim
"However, epidemiology studies report that vegan or vegetarian diets are not associated with reduction in all-cause mortality rates"
Response
The most recently published of their citations, which they also base their big graph on, actually says the following:
When we excluded data for participants known to have changed diet group at least once during follow-up from the early mortality analysis, leaving data for 2155 deaths before age 75, vegetarians and vegans had significantly lower all-cause mortality than regular meat eaters, although there was no overall heterogeneity of risk between the diet groups: HRs for low meat eaters, fish eaters, and vegetarians and vegans compared with regular meat eaters were HR: 0.97 (95% CI: 0.86, 1.09); HR: 0.87 (95% CI: 0.74, 1.02); and HR: 0.86 (95% CI: 0.77, 0.97), respectively; P-heterogeneity = 0.068 (Supplemental Table 2). There was significant heterogeneity of risk between the diet groups for mortality from all malignant cancers combined, cancers of the lung and lymphatic/hematopoietic tissue, and other circulatory disease. In addition, vegetarians and vegans had significantly lower mortality than regular meat eaters for pancreatic cancer and digestive diseases, and fish eaters had significantly lower colorectal cancer mortality than regular meat eaters (Supplemental Table 2). Further adjustment for BMI left these associations largely unchanged.
In short, when the researchers conducted a separate analysis excluding those who changed their diet since the follow-up, the vegetarians DID have a significantly lower risk of all-cause mortality. Oh, and pancreactic cancer mortality, and digestive disease mortality.
Claim
"Moreover, vegetarians and vegans, compared to non-vegetarians, are generally more health-conscious, more physically active, have higher socioeconomic status, with lower rates of tobacco, alcohol, and drug use"
Response
Yeah. Good thing studies statistically adjust for those confounding factors. Researchers aren't that stupid.
Claim
"Plant-based diets centered around refined grains, sweetened beverages, candy, desserts, baked goods, fries, chips, etc. are particularly detrimental, and correlate with worse CVD outcomes compared to vegetarian diets emphasizing fresh produce, nuts, legumes, whole grains, tea, and coffee. The toxic features of the standard American that cause obesity, T2D, CVD and shortened life expectancy would not be averted by simply excluding all animal-based foods, but rather by reducing intake of the highly processed foods, refined carbohydrates, deep-fried foods, processed meats and sweetened beverages that are ubiquitous in our culture."
Response
In the words of Danny Ishay (formerly "Lifting Vegan Logic"):
This is a complete shock to us vegans. It turns out, that for a vegan diet to be healthy, it has to be comprised of healthy foods, and not junk food. I'm sure many of you are unaware of this information, "junk food isn't good for you". Crazy!
Claim
"Veganism has been linked with dysfunction of the neurological, psychological, musculoskeletal, hematological, and immunological systems."
Response
First of all, they cited the wrong source, but I quickly figured out they meant to cite this study instead. It was a systematic review on nutrients in a vegan diet which hypothesized that certain observed deficiencies in the vegans may lead to a higher risk of these dysfuntions in the vegans. This hasn't actually been demonstrated. The systematic review lumped studies assessing nutrient status vs nutrient intake together and didn't comprehensively discuss the contents of studies. Unlike this review, a newer and much more comprehensive systematic review with over 2 times as many studies found an overall adequate intake of most nutrients in vegans, with some nutrients of concerns in vegans, and also some in omnivores.(1) Also, I don't care, because they haven't even demonstrasted any deficiencies to be inherent, as outlined in the introduction.
Claim
"Dietary sources of vitamins B12, B2, niacin and D are almost exclusively animal-based foods. For vegans not on dietary supplementation, inadequate levels of these essential nutrients can result in neurocognitive impairment, anemia, and immune compromise."
Response
Their source for this claim is the previously discussed low-quality systematic review. In the newer one, vegans consumed enough niacin and Vitamin B2. And, obviously, vegans should supplement Vitamin B12 and usually Vitamin D as well. Non-supplementation is not inherent.
Claim
"Veganism increases the risk for bone fractures, sarcopenia and, depression/anxiety."
Response
They cite a sytematic review on vegetarian & vegan diets and bone health. At one point this review states:
some factors associated with BMD and fracture risk, such as the time that vegetarians and vegans had been following the diet, daily energy intake, number of hours engaged in physical activity, BMI, use of hormone replacement therapy, sunlight exposure, consumption of alcohol, and smoking behavior, could not be evaluated because this information was not reported for most of the studies.
BMI is a crucial factor for bone health and no adjustment for that is a problem. Additonally there were no adjustments for Vitamin D, which is also crucial. Also, we see in large high-quality prospective cohort studies that vegans who ensure a reliable source of Vitamin D and calcium aren't at an increased risk of bone fractures.(4)
I'm just going to quote straight from their study about depression:
Limitations include the cross-sectional nature of the data which restricts the possibility of drawing causality especially because it is impossible to tell if the diet type preceded or succeeded the depressive symptoms. Further limitations include the absence of some dietary data and in particular the impossibility to calculate energy intake which is an important factor for investigating nutritional issues. We also cannot draw out the possibility of residual confounding: for instance, we lacked an assessment of eating disorders, which could be associated with both depression and food restrictions. Likewise, personality was not assessed though it may affect both variables of interest. For example, vegetarianism may be associated to perfectionism, which by itself may possibly reflect vulnerability for depressive symptoms.
Instead of citing a single low-quality cross-sectional study the authors might want to turn their attention to a 2022 systematic review that found the overall evidence on the topic of vegetarianism & depression to be extremely low quality.(2) Yet, 56% of the studies still found no increased risk. And the few studies included in the review that were graded as good-quality found a lower risk of depression among vegetarians. So, if anything, the evidence points in the opposite direction.
Vegans may on average consume less protein which could possibly lead to sarcopenia. Using the core principal outlined in the beginning, this has not been demonstrated to be inherent. Vegans can consume enough protein, and protein-matched vegan vs. omnivorous diets can support similar muscle and strength gains.(3)(4)
Claim
"Some of these benefits might have been from contemporaneous reductions in salt and smoking. Even so, the nutrients provided by red meat and dairy when consumed in excess contribute to atherosclerosis, but in moderation may balance the diet and improve overall health and longevity"
Response
Excuse me, did you just cite a fucking The Atlantic article?
Claim
"Infants fed a vegan diet suffer from growth retardation/failure to thrive, and are at increased risk for psychomotor regression, bone fractures, severe vitamin B12 deficiency, marked hypocalcemia with seizures, anemia, respiratory distress with metabolic alkalosis, and death"
Response
They cite a narrative review to support their claims. Here is a quote from the narrative review:
The present review included nine studies: five recommendations/position papers, one case report, one brief report, one review, and one editorial. Neither randomized controlled trials nor observational studies were found.
What an absolute joke. So, zero actual studies were included. Actual studies on infants fed vegan diets find that they do just fine.(5)(6)(7)(8)
A vegan infant should be supplemented with B12 to prevent deficiency. The claim regarding psychomotor aggresion & bone fractures stems from a case report of a single infant with Vitamin D deficiency. Solution: Supplement Vitamin D. Crazy, right?
The claims about hypocalcemia, seizures, anemia, respiratory distress, metabolic alkalosis, and death stem from a report about children fed plant milks instead of breastmilk or infant formula. So, hear me out on this one, BREASTMILK IS VEGAN. And there is also vegan infant formula.
Claim
"Low vitamin B12 intake is a significant problem in vegan diets due to avoidance of vitamin B12-rich foods, such as meat, poultry, and eggs. A lack of vitamin B12 has been linked to neurological and hematologic problems. Moreover, Vitamin B12 may possess anticancer properties; conversely, inadequate B12 consumption may contribute to carcinogenesis. Consequently, if B12 is not adequately replaced, a vegan diet may inadvertently increase risk of some types of malignancy, including cancers of the breast, cervix, GI tract, and liver."
Response
Google "supplement".
Claim
"Epidemiological studies report the vegans who do not supplement with omega-3 fatty acids will be at high risk for deficiency of both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found predominantly in fish, seafood, game meats and pastureraised eggs. Recent studies report that low omega-3 levels in the cell membranes and blood are associated with reduced life expectancy, and higher risk of major adverse CVD events (myocardial infarction, stroke, and CVD death). Furthermore, omega-3 deficiency is associated with depression, anxiety, systemic inflammation, autoimmune disorders, autism, macular degeneration, asthma, and periodontal disease. Alpha linolenic acid (ALA) is a plant-based omega-3 that can be hepatically converted to the beneficial long-chain fatty acids, but the liver converts <5% of ALA to EPA, and virtually none (<1%) to DHA."
Response
Based on the fact that vegans have similar cognitive function to omnivores,(9) reduced rates of cardiovascular disease and death,(10) no consistent higher risk of depression or anxiety (as demonstrated earlier), and there is no evidence that vegans have a higher risk of systemic inflammation, autism, autoimmune disorders, macular degeneration, asthma, or periodontal disease, it seems that maybe omega-3s aren't that much of a problem for vegans. The authors of this review obviously completely fail to cite any study actually demonstrating low omega-3 intakes in vegans leads to these or any negative health outcomes. Vegans do have some level of long-chain fatty acids in their blood, and since there are no widely accpeted reference ranges for omega-3 status, we have no reason to assume these are insufficient. Especially considering that, as I've already said, vegans don't suffer any impairments associated with low omega-3s.
Claim
"Fig. 4. Risk of bone fracture among various dietary groups."
Response
This graph is based on the 2020 EPIC-Oxford study on bone fracture. In this study, BMI and dietary calcium were adjusted for, but only via categorisation, which is known to bias results when examining continuous variables with non-linear responses.(11) Additionally, the study did not adjust for or even consider Vitamin D status or intake. Not to mention, when the researchers only looked at those with a BMI over 22.5, the increased risk of bone fractures in the vegans completely disappeared. As previously highlighted, vegans who ensure a source of Vitamin D & calcium are not at risk for bone fractures.
Claim
"Vegan and vegetarian diets frequently result in mineral deficiencies. Phytates are anti-nutrients found in grains and legumes. These compounds interfere with the absorption of essential minerals including calcium, zinc, iron, iodine, and magnesium"
Response
Vegans on average have a much higher intake of magnesium than omnivores which would likely overcome any inhibitory effects. These phytates are clearly very bad at being anti-nutrients seeing as vegans tend to have adequate zinc and iron status.(12) Regarding calcium, I'll just quote the very position paper they cite:
Dietary fibre seems not to impair calcium absorption, since in one study more calcium was absorbed from kale than cow milk [112]. Regardless of solubility, the calcium from calcium salts used to fortify foods is absorbed with similar efficiency to the calcium in cow milk [113] except that the absorption from calcium citrate malate is slightly higher [111]. The tricalcium phosphate used to fortify soy milk is absorbed with only about 75% of the efficiency of cow milk calcium [114]. The calcium from the calcium chloride and calcium sulphate used to produce tofu has similar bioavailability to the calcium from milk [115]. The bioavailability of calcium from mineral water is similar to or better than that from milk [116].
Clearly, vegans can absorb enough calcium, even if phytates do impair absorption (although tofu is high in phytates so that claim is questionable).
Claim
Because vegan and vegetarian diets generally include copious amounts of grains and legumes, they are unavoidably high in phytates, which reduce the absorption of non‑sodium minerals.
Response
While short term studies on single meals tend to find inhibitory effects of phytates on iron absorption, long-term studies involving regular phytate consumption find no inhibitory effects.(13)(14) Additionally, some research suggests no inhibitory effects of phytates on zinc absorption.(15) And once again, vegans clearly have adequate status of these minerals. If a vegan is actually concerned about this for some reason they can, hear me out, not consume "copious amounts" of grains and legumes.
Claim
"Vegans and vegetarians are at increased risk for iron-deficiency despite the presence of substantial amounts of iron in many plant-based foods. Plants contain the non-heme form iron, which is and less bio-available than heme‑iron from animal sources. Accordingly, levels of ferritin and hemoglobin are significantly lower in vegans/vegetarians. Iron deficiency increases a pregnant woman's risk of having preterm delivery, low-birth-weight infant, and impaired brain development in their infant."
Response
Cool story, it's still not an inherent aspect of a vegan diet. Plus, Vitamin C-rich food can significantly increase the absorption of non-heme iron.(16) Also, can they stop citing a systematic review that included half as many studies and is not nearly as detailed as another systematic review that was fully published at the time of this paper?
Claim
"Vegans also are at increased risk for zinc deficiency. While meat, fish, shellfish, dairy, and eggs are rich sources of bioavailable zinc, some zinc-rich plant foods (nuts, seeds, and whole grains) have poor bioavailability, again owing to the presence of phytates, which inhibit zinc absorption in the gut. Inadequate zinc consumption is associated with depression, dermatitis, diarrhea, and alopecia, all of which are more common among vegans."
Response
All already addresed. Wait a second, "all of which are more common among vegans"? Excuse me? That's a bold claim, for which they provided no citation. All they cited was a systematic review on nutrients in hair loss (not on vegans). They made the direct and bold claim that dermatitis, diarrhea, and alopecia are more common among vegans. They didn't say they "probably are" due to associated deficiencies. They say "ARE more common". I guess we're just lying for fun now? Obviously a paper on hair loss didn't mention diarreah but, uhm, "vegoon eat lot of fiber" or something.
Claim
"A meta-analysis concluded that vegans consume significantly less protein and fewer essential amino acids compared to other diet groups. Moreover, plant protein is less digestible than animal proteins."
Response
Does less mean not enough? German vegans get around 1.2 g/kg of bodyweight per day of plant protein with sufficient intakes and blood concentrations of all amino acids.(17)
The citation for digestibility is their favorite outdated systematic review on nutrient intake in vegans which itself states:
"there are substantial differences in the level of digestibility among plant proteins, with soy protein or gluten reaching 95% that of animal protein sources and whole cereals and purses reaching levels between 80 and 90%. The level of digestibility of plant proteins can be even lower (50–70%), or adversely influenced by food processing mechanisms, such as heating. Furthermore, using the Protein Digestibility–Corrected Amino Acid Score (PDCAAS) which was adopted by WHO plant protein is not rated as highly as animal and milk protein
Over 95%, or 80-90%, sounds pretty good for more. The PDCAAS is based on rodent models. Humans, in fact, tend not to be rodents. The only thing that actually matters is actual outcomes. Protein-matched vegan vs. omnivorous diets can support similar muscle and strength gains.(3)(4)
Claim
"Taurine is an amino acid that helps to support endogenous antioxidant levels, and may be important for optimal function of the brain, heart, eyes, and immune system. Because plants contain little to no taurine, many vegans and vegetarians are deficient in this important amino acid, which can predispose them to a myriad of health issues. Animal foods such as seafood, fish, poultry, and beef are rich in taurine"
Response
Their citation for the benefits of taurine is a study using doses of supplemental taurine several dozen times higher than what anyone could reasonably obtain from diet alone, vegan or not. How exactly can you be deficient in a non-essential nutrient with no established dietary needs or reference ranges for blood levels?
Claim
"A longitudinal cohort study of 4181 German citizens, ages 18 to 65 years found that 1.3% were “strict vegetarians,” and 4.5% were “semi-vegetarians.” After controlling for other relevant variables, the vegetarians had significantly higher rates of depression, anxiety, and eating disorder"
Response
They based an entire figure on this study but it simply speaks for itself:
On the whole, our results strongly corroborate the past findings in smaller samples of adolescents and young adults, which have demonstrated that in contrast to physical health, a vegetarian diet is not associated with better mental health. Whether compared with a control group of non-vegetarians matched for important socio-demographic characteristics, or with non-vegetarians in general, vegetarians show elevated prevalence rates of diverse mental disorders. Importantly, we found no evidence for a causal role of vegetarian diet in the etiology of mental disorders. Rather, our results are more consistent with the view that the experience of a mental disorder increases the probability of choosing a vegetarian diet, or that psychological factors influence both the probability of choosing a vegetarian diet and the probability of developing a mental disorder.
This wasn't hard to miss, it was the conclusion of the paper. The conclusion was a result of the findings discussed earlier in the same paper:
"For depressive and anxiety disorders, as well as somatoform disorders and syndromes, the results of the t-tests indicate that on average the start of a vegetarian diet follows the onset of mental disorder."
Claim
"Observational studies routinely find that vegan and vegetarian diets increase the risk for iodine deficiency and hypothyroidism. A European study reported that 80% of vegans and 25% of lactovegetarians had iodine deficiency. Plant-based foods, except for seaweed, are inadequate dietary sources of iodine compared to animal products, such as fish, meat, and eggs. Iodine is a particularly vital nutrient for pregnant women and young children. Iodine deficiency during pregnancy increases risk of impaired mental development during childhood."
Response
Google "iodized salt", "supplement", and as you mentioned, "seaweed". These are concerns that vegans should be aware of. They are not, however, inherent.
Final brain-damage-indicative claim
"Maintaining ideal health while adhering to vegan diets requires a sophisticated understanding of potential pitfalls, and close attention to detail regarding supplementation and medical testing. A more logical and evolutionarily congruent approach is to simply include modest amounts of nutritious animal-sourced foods."
Response
"Sophisticated understanding" and it's just eating enough food and a balanced diet, and paying attention to 2-3 nutrients. Yes, that's more logical. It's logical to pay for animal abuse & murder when we clearly don't have to. It's logical to eat foods that are worse for the environment in literally every metric. It's logical to spend your time "debunking" a diet because you're too lazy to understand how anyone could eat a diet that may be slightly harder to maintain, but doesn't involve the systemic exploitation, mutilitation, abuse, and murder of billions of sentient land animals and trillions of sentient marine animals.
How can you, O'keefe, claim to have debunked a diet if none of it's supposed pitfalls are inherent to it? 41% of Americans are Vitamin D deficient.(18) I DID IT! I DEBUNKED AN OMNIVOROUS DIET!