Wednesday, December 14, 2016

British Study: Vegan Mortality Rates Similar to Meat-Eaters

Appleby et al report that in their study of more than 60,000 people including more than 20,000 vegetarians and more than 2000 vegans all-cause mortality did not statistically differ between vegans, vegetarians, pesco-vegetarians, and low-meat eater groups compared to regular meat-eaters.

In this population, they report "Separating the vegetarians and vegans for the 6 most common causes of death did not reveal any statistically significant differences in mortality between vegans and regular meat eaters."

This result is different from the AHS-2 study which suggested that vegetarians of all types (including occasional meat eaters and persons who ate fish but not meat) had a 12% lower all-cause mortality rate than regular meat-eaters.  Appleby et al. suggest that this difference might result from a difference in animal protein intake between British vegetarians and Adventist vegetarians.  The regular meat eaters in this British study consumed only 2.1 times more animal protein than the British vegetarians+vegans, whereas in the Adventist study the regular meat eaters consumed 2.6 times more animal protein than the vegetarian groups. 

 Another possibility not accounted for is the meal timing practices of Adventists.  As I discussed in my book Intermittent Fasting, the Adventist church doctrine recommends consuming only two meals daily in the morning and at noon.  Perhaps Adventist vegetarians (which includes semi-, pesco-, lacto-ovo, and vegan vegetarians) are more likely to use time-restricted feeding schedules than British vegetarians, and this accounts for their small advantage over Adventist regular meat eaters in overall mortality.

However, it is important to note that in the Adventist study the lowest overall mortality in both men and women was found in pesco-vegetarians not vegans or lacto-ovo vegetarians, and among the Adventist women pesco-vegetarians, semi-vegetarians, and lacto-ovo vegetarians all had lower overall mortality rate than vegans (Table 4).

Source:  JAMA Internal Medicine
Another "surprise" was the finding of no significant difference in ischemic heart disease death between groups.  The authors give one possible explanation:  "Incident, nonfatal IHD may also lead to the effective medical management of established risk factors for IHD (e.g., drugs to treat non-HDL cholesterol and high blood pressure), lowering subsequent IHD mortality and partially nullifying the differences between vegetarians and meat eaters found for IHD incidence."  Perhaps the regular meat eaters had a heart disease death rate similar to vegetarians because they used drugs to manage heart disease risk factors.

In this study, risk of death from cancer for vegetarians was only ~10% lower than for regular meat eaters.  The AHS-2 study found no reduced risk of cancer mortality for vegetarians.

Vegetarians including vegans had the highest risk of death from mental and behavioral disorders and cerebrovascular disease (Table 2).

Per Table 1, regular meat eater men in this study consumed 11% of energy as animal protein and 16.5% of energy as total protein (animal+plant).  Regular meat eater women consumed ~12% of energy as animal protein and ~18% as total protein.  Put otherwise, these meat eaters obtained 88-89% of their calories from non-animal protein sources.  Their total meat intake for men was 115 g per day (just about 4 ounces) and for women 106 g per day (just under 4 ounces per day).  For both genders, total and saturated fat intakes were similar for all groups.

Vegetarian (vegans+vegetarian) women consumed on average only 36 g more fruit and 45 g more vegetables than regular meat eater women; vegetarian (vegans+vegetarian) men consumed on average only 56 g more fruit and 55 g more vegetables than regular meat eater men.

In Essential Macrobiotics I discussed how it has been established that ever married individuals have lower disease risks and greater longevity than never married individuals.  I found it interesting that in this study, there was an apparent relationship between meat-eating and marriage.  From Table 1, the percentage of married or cohabiting men was:  regular meat eaters, 76%; low meat eaters, 69%; fish eaters, 66%; vegetarians, 61%; overall, 68%.

For women, the percentage married or cohabiting was:  regular meat eaters, 76%; low meat eaters, 63%; fish eaters, 63%; vegetarians, 58%; overall, 65%.

Thus, there appears to be a positive relationship between meat-eating and marriage, i.e. meat eaters were apparently significantly more likely to be married than non-meat eaters.   Thus, a higher proportion of the regular meat-eaters enjoyed the health benefits of marriage.  I have to wonder if the much elevated risk of death from mental and behavioral disorders among vegetarians and vegans may be linked to their lower rate of participation in marriage.   This concept is discussed thoroughly in the book A Cry Unheard: The Medical Consequences of Loneliness by James Lynch.

Women who ate meat regularly were more likely to have children than those who restricted or avoided meat eating.  Seventy-seven percent of women who were regular meat eaters had children, 65% of low meat eaters, 52% of fish eaters, and 42% of vegetarians.   Women who restricted meat intake were more likely to have used oral contraceptives than regular meat eaters.  Thus, a higher proportion of the women who regularly ate meat enjoyed the health and longevity benefits of having children, which I also discussed in Essential Macrobiotics

A perusal of Table 1 shows also that meat eaters were on average heavier (by BMI), less physically active, and more likely to be on long-term medical treatment than people who restricted meat intake.  Women who were regular meat eaters were also more likely to have ever used hormone therapy.

It makes me wonder whether marriage and childbearing are more important to health and longevity than restricting animal products.  From an evolutionary perspective, if marriage and childbearing made some men and women weak and sick, they would stay away from it, and people of this lineage would die out.  If marriage and childbearing confer health benefits, people will stay married and bear children, and this lineage will thrive.  And it would make sense for biology to favor health in parents, as healthier parents will provide more support to children than unhealthy parents, and hence have more successful offspring; whereas people who got sick from marriage, childbearing and child-care would abandon all three, leaving few or no descendants.   Thus it is no stretch of the imagination to suppose that Nature would confer substantial health benefits to people who love raising children.

As I have previously noted, in The Intelligence Paradox: why the intelligent choice isn't always the smart one, evolutionary psychologist Satoshi Kanazawa noted that for 1.8 million years, our ancestors did not have the problem of deciding what diet was best for health and longevity.  They simply ate what Nature provided and they could access.  That meant anything edible they could get their hands on, and it is certain that none deliberately chose vegetarian diets:

Hence, it would seem highly unlikely that natural selection would favor strict meat-avoider lineages with greater health than lineages that had a deep love for bearing and caring for children.  In the Darwinian fitness games, any one who avoids eating animals and having children is going to be replaced by those who get married, have children, and invest their time and energy in making those children into economically and reproductively successful adults. 

Even if avoiding animal products prolonged your own life by 10 years, if you don't have children, you don't live as long as some one who dies 10 years younger, but has several children who also have children.  Every child is the irreversible biological marriage of mother and father and if the parents are of the same ethnic stock each child is a virtual reincarnation of the parents.

If you still have time, you might want to avoid your lineage going the way of the Dodo bird.


Martin in the Maldives said...

Hi Don.
Interesting article and analysis, thanks.
Being vegan/vegetarian is by no means healthy. Out of my 3 vegetarian friends, only 1 is following a healthful whole-foods/plant-based diet as part of a healthy lifestyle. The other 2 are more concerned about animal welfare and factory farming, eating plenty pasta and white bread, soda+chips, beer+fries, and regularly miss meals.
I would say I am a "meat avoiding" omnivore, eating very little meat/fish/dairy for health reasons, along with plenty whole grains and fruits/veg at every meal.
So I think the simple classifications of vegan/vegetarian/omnivore are insufficient to capture the real benefits of a healthy diet.

Don Matesz said...


Yes I agree with your observation. The fact that many vegetarians do not follow healthful diets probably contributes considerably to the inconsistent findings of health benefits for vegan/vegetarian diets in population studies. It seems to me there is a tendency of advocates of meat-free diets to attribute large benefits to avoiding meat/fish/dairy alone, which studies like the one discussed here seem to be providing evidence against. Adventists tend to eat more whole foods regardless of vegetarian or not, and if they adopt vegatarian ways, it is for health reasons, not animal welfare, which may make studies of Adventist vegetarians more revealing on this issue than this British study (which was the authors of the British study acknowledged as a possible reason that they didn't find the reduced mortality rate for "vegetarians" found in AHS-2). It is for this reason that I find it interesting that in the Adventist studies, the strict meat & dairy avoiders don't appear to be enjoying lower all-cause mortality rates compared to those who include some small amounts of animal products whether lacto-ovo, fish, or semi-vegetarian. As I discussed in Essential Macrobiotics, all well-documented free-living groups known for their exceptional longevity and resistance to disease (e.g. Okinawans, Abkhasians) eat 'some' animal products as small parts of otherwise predominantly plant-based diets.

Tan said...

Thanks Don, for all your thorough analyses throughout the years.

Don Matesz said...

Thanks Tan, I appreciate your appreciation!