Red meat, human vulnerability, and.. mammal pets?

12993520_545709718944195_6669954929821747069_nExciting day! Another diet-related talk at ASU’s Center for Evolution & Medicine. This was a nice break from the horror that is the last 2 weeks of the semester..

It’s taking me awhile to “digest” all the information (hehe), but I found the seminar fascinating and wanted to summarize some main points. Lots of open questions remain, but John Pepper of National Cancer Institute really shows how examination of any health problem needs to focus not only on proximate causes, but the ultimate or evolutionary causes.

So.. Pepper asks- why is mammal meat bad for humans, specifically?

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Meet Dr. Pepper!
In humans, red meat (he refers to it just as mammal meat) is linked to inflammatory diseases (cardiovascular, alzheimer’s, arthritis). What’s the mechanism behind this?
The inflammation from mammal meat has to do with our antibodies attacking something coming from other species.. When we eat mammal meat, we in fact incorporate something non-human from the diet- sialic acid.
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Both human and other mammals have sialic acid in their tissues, actually, but humans have a unique mutation that replaces the form found in other mammals (ancestral form- Neu5Gc) with a different one- uniquely human (Neu5Ac).
So.. if we eat meat we get the new aquired ancestral sialic acid, it becomes part of our cells, and the small structural differences in the two get recognized by the immune system.. which responds with a defense- inflammation!
Chimpanzees are humans’ closest evolutionary relatives, sharing a common ancestor 6–7 million years ago..
WHY does human sialic acid differ uniquely? The “Malaria hypothesis” (see Martin&Rayner, 2005) proposes that in Africa, early humans escaped from the ancestral pathogen they shared with chimpanzees. They managed to do so by replacing the pathogen’s binding target (ancestral sialic acid Neu5Gc) with novel Neu5Ac. With time, a population of that old evaded pathogen evolved to infect humans again by recognizing the new Neu5Ac..leading to the origin of malaria.
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The longer an animal has been domesticated, the more humans share parasites and diseases with them

If the Malaria Hypothesis explains why the initial change in humans happened.. why has it remained the same to this day? I mean, it’s been some several million years now- has this mutation been advantageous this whole time? It’s an important question because this sialic acid mutation poses a COST on our health: this trait causes chronic inflammation in people who eat mammal-derived foods + it also now causes vulnerability to malaria.

The hypothesis for why the human sialic acid modification is still around is that it
provides benefits- specifically, protection from parasites and pathogens via increased inflammation. This is relevant because of what humans have been doing for the last ~15,000 years. Animal domestication!
Humans are more vulnerable to shared pathogens from other mammals (than from non-mammals). So being around cattle, for example, carries a risk of catching pathogens from which that cattle suffers. Such animal pathogens impose a strong selective pressures on humans.. Pepper suggests that the uniquely human sialic acid (Neu5Ac) allows our diet to adapt us to the issue of animal pathogens by adjusting our inflammatory tone (how much inflammation we are experiencing): “those human populations that are exposed to domesticated food-mammals and their pathogens are also eating mammal-derived foods that are pro-inflammatory (both meat and dairy).”
Inflammation is a great example of a trade-off. It both has benefits (protection from parasites & infections) and costs (chronic disease, metabolic expense of mounting an immune response). The optimal balance for this trade-off would depend on how strong of a pathogen pressure you’re experiencing.
This increases inflammatory PROTECTION only where it’s most needed (like around animals). So this auto-immune inflammation from mammal foods in the diet not only increases likelihood of chronic disease, but protects against shared mammalian pathogens.
…..    ……    ……
It got me thinking about human culture and our ability to modify our environment in all sorts of ways- an example of “maladaptation” to modern times! Living in cities, not exposed to higher pathogen load from being around domesticated animals..yet having access to all the mammal meat we can buy = all put you in a situation where the good old sialic acid mutation might do more harm than good. Should people go vegan? Should they simply cut down on red meat? There was no discussion on the effect size of mammal meat eating and chronic disease, so I wouldn’t necessarily jump onto any lifestyle changes based on this talk. Yet the process of understanding this health concern through the lens of evolutionary medicine is quite fascinating!
 P.S. I’m not an expert on this topic. If you have something to correct or add, please comment 🙂
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Very cool use of evolutionary medicine principles in this case & a glimpse into why it’s important to use them if we want to understand disease.

 

No need for RAW (food) stress ;)

Most of my present acquaintances are unaware that I used to be a huge proponent of raw foodism. “Huge” meaning I spent hundreds (thousands, actually) of $$ traveling to get certified as a chef and an educator (centers in Chicago, Atlanta, and northern California), taught “cooking” classes at the local co-op, was a private chef for months, etc.

In fact, check out some of the raw vegan dishes I used to make!

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Is this amazing or what? I’m still quite proud of my raw culinary past. The recipes used soaked nuts, dried fruits, sprouted items (like buckwheat) and of course lots of vegetables and fruits. While fun & unique, it was also very time-consuming, rather expensive, and not necessarily healthier. It did fit well with people who have allergies (since raw recipes don’t use soy, wheat, peanuts or many other problematic foods).

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I almost spend all day writing down why exactly I have concluded raw veganism is unnecessary and based on false beliefs… But that would be a true waste of time (and rather dull to me) so I’d rather redirect you to already well-written articles!

False belief 1: We are meant to be plant-based because our physiology shows we’re herbivores! 

  • NO. (my previous blog post). And it’s a good reminder not to attempt to compare our diet to that of other animals and insects (insects! people make the point that insects and animals don’t cook food! insects & animals also can’t perform surgery or produce toilet paper)
  • Another thing worth mentioning is the incorrect assumption that vegetarian/vegan folks are healthier than others because they avoid meat. Majority of big studies I went through in my nutritional epidemiology class compared meat-avoiders with people on a standard american diet…and didn’t do a good job controlling for the fact that they compared health-conscious vegetarians with generally regular unhealthy folks. Luckily i don’t have to write more, because THIS ARTICLE did it for me AND gave citations (woohoo!). Pay attention that health benefits of meat-eaters is more correctly attributed to other healthy behaviors (avoiding refined sugar and grains, oils and trans fats, avoiding smoking and so on).

False belief 2: Cooking is unnatural.

  • First of all, let me point out that some types of cooking of some foods produce potentially carcinogenic compounds. HERE is my post on acrylamides. Like with other valuable claims from raw foodists- this is not supposed to mean you should never eat baked potatoes. It means having antioxidants in your diet from other plants is very important. The new genetically modified potato, by the way is designed to decrease acrylamide content. Unfortunately, generalized anti-GMO sentiments might win over that benefit. 
  • How Cooking Made Us Human Read this wonderful New York times article on the Catching Fire book and how cooking was instrumental in our evolution! I remember I was aghast when i heard of this book- you mean turning food into murderous evil toxic stuff that kills cute kittens made us human?? I’m clearly joking here, but not actually over-exaggerating too much. Many of us in the raw community would absolutely avoid the healthiest of soups, since cooked was equivalent to “toxic” and “addictive” in our heads.
  • Humans are adapted to controlling fire & using it to cook.  See part of the  “Human adaptation to the control of fire” paper here (click on pics to enlarge). For full paper, here is the citation but it might not be free unless you have university affiliation- Wrangham, R., & Carmody, R. (2010). Human adaptation to the control of fire.Evolutionary Anthropology: Issues, News, and Reviews, 19(5), 187-199. TRY HERE.

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  • Here is a fun piece of “fake information” online. I have to address this…Screen Shot 2015-01-30 at 6.36.44 PM

    Author states:
    “Fire was only discovered a relatively short time ago”

  • No- fire was controlled prior to emergence of homo sapiens. In fact, the earliest convincing evidence of fire use for cooking appears the 780,000-400,000 years ago.
  • Animals show that anatomy can adapt very quickly to a change in diet. With human populations that have a history of dairying (like northern Europe), ability to digest lactose into adulthood has evolved at least twice in the last 7000 years. For people with a recent history of eating starch-rich foods, they exhibit higher copy numbers of the gene encoding for a certain enzyme.

    Author states:
    “Out of the millions of species of animals and insects on the Earth, only people intentionally eat cooked food”
  • *cricket sounds*……….. What is this supposed to argue? There is no way to discredit a completely illogical statement.

    Real point here: humans are adapted to cooked diets. Reductions in masticatory and gastrointestinal anatomy show that. See Wrangham article cited earlier. 

 


 

3. False belief 3: We need to eat an all-alkaline diet (or high raw plant diet)Alkaline

First of all, just to clarify: your body can’t actually get “acidic”  (see photo & citation*) though dietary acidosis is a thing. Acidosis is a proces s or trend toward acidaemia ( blood pH of less than 7.35) but without necessarily reaching a pH of less than 7·35″. **  Increasing fruit and vegetable intake, reducing processed junk and not making your diet heavy on meat is a great recommendation to avoid the trend towards acidaemia, though it’s unclear it actually benefits bone and kidney health:

“Both dietary interventions (lowering protein and increasing fruit and vegetable consumption) and nutritional supplementation (with K and Mg salts) have been shown to normalise acidosis, but with discordant results on whether this is then associated with clinical improvement in bone, muscle or other physiological or pathophysiological conditions. A positive NEAP [net acid load] diet results in increased urine Ca, N and bone marker excretion, and predisposes to kidney stones. Whether or not, over the longer term, this translates to lower bone density, increased bone and muscle loss with ageing is unclear and requires further investigation.”**

This does not necessitate eating a raw vegan diet though– it necessitates being reasonable and, like recommended by parents, governments, and nutritionists, make sure to eat your fruits & vegetables and minimize high-caloric processed foods. This also doesn’t mean eliminating animal foods at all. Here is a great article*** that estimates the “acid load” of diets of hunter-gatherers (HG) and modern diets. They find the HG diets were neutral (e.g. not “too acidic”, if you prefer) and contribute elevated diet acidity of modern diets to processed cereal grains. Great idea to minimize on processed products anyway!

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 *Deng, G., & Cassileth, B. (2013). Complementary or alternative medicine in cancer care [mdash] myths and realities. Nature Reviews Clinical Oncology,10(11), 656-664.

** Pizzorno, J., Frassetto, L. A., & Katzinger, J. (2010). Diet-induced acidosis: is it real and clinically relevant?. British journal of nutrition, 103(08), 1185-1194.

*** Sebastian, A., Frassetto, L. A., Sellmeyer, D. E., Merriam, R. L., & Morris, R. C. (2002). Estimation of the net acid load of the diet of ancestral preagricultural Homo sapiens and their hominid ancestors. The American journal of clinical nutrition, 76(6), 1308-1316.


 

4. False belief 4: Raw Food is superior because it has all the enzymes intact

  • There’s no scientific support for this, and that’s about it. **** In fact, this was my turning point in adhering to this lifestyle: I realized this very foundational claim has no basis.
    The evidence raw proponents cite is a 1985 book called Enzyme Nutrition. That’s 30 years ago… good science is self-replicating so I would expect there to be more studies on such a potentially fascinating subject if there is something to it.. I don’t see any.

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**** Hobbs, S. H. (2005). Attitudes, practices, and beliefs of individuals consuming a raw foods diet. Explore: The Journal of Science and Healing, 1(4), 272-277.

CONCLUSION!

None of this is supposed to go against the fact that eating a lot of fresh fruits and vegetables is very important and very healthy! HERE is a nice Scientific American article giving examples when some vegetables are better and worse when cooked.

But this is supposed to discourage you from forming a belief system that humans aren’t “supposed” to eat cooked and animal-based food***** or that there is a need to stick to eating raw plants only. It is also supposed to prevent damaging thinking- e.g. a hot chicken soup is toxic; cooked food is addictive; non-organic food is dangerous. Humans have a tendency towards monotonic thinking- it’s hard for us to be OK with the fact that something we consider “bad” is only bad at high doses and is actually  essential and beneficial at lower doses (e.g. fat, salt in the diet for some people). Considering this lifestyle takes a lot of time and effort, does not necessarily results in weight-loss (and when it does- it’s just because you eat less calories, not because raw food is magical.. if you go heavy on the nuts & oils you will gain wait), and there is absolutely no reason to consider this eating natural or superior I believe this dietary approach is unnecessary and attempting to stick to a highly raw food diet results in a lot of stress for no reason.

 


 


EXTRAS

Note:I  am intrigued by the possibility that this approach might have therapeutic benefits. It’s not based on any present science, folks, but I would be excited to see studies of this eating plan as a medicinal diet for improvement of certain conditions!!

You are welcome to comment on the blog and ask questions or challenge some of the statements! I’m not anti-raw as much as I am pro-science and evidence. I’d love to research very specific topics so please comment with a specific concern 🙂
***** As a good friend of mine noted- it’s important to remember that vegetarianism/veganism is not only a choice to be healthy..but it’s also a choice due to environmental and ethical concerns. I’m unqualified to cover those in detail, but it is obviously an important reason some people avoid animal products and I’m not arguing against it!
p.s. Links to all sorts of websites debunking some raw food ideas or talking about its shortcomings, etc. Just stuff that came up after 2 minutes of Googling 😉
http://www.veganhealth.org/articles/cooking
http://www.takepart.com/article/2013/05/08/jane-says-raw-foodism-raw-deal
http://www.mindbodygreen.com/0-13454/3-reasons-no-one-should-be-on-a-raw-foods-diet.html
http://www.hellawella.com/top-10-annoyingly-stubborn-nutrition-myths-debunked/9645
http://www.fredericpatenaude.com/blog/?p=2036
http://www.sciencebasedmedicine.org/simply-raw-making-overcooked-claims-about-raw-food-diets/
http://news.sciencemag.org/evolution/2012/10/raw-food-not-enough-feed-big-brains
http://www.huffingtonpost.com/david-katz-md/raw-food-diet_b_2015598.html
http://renegadehealth.com/blog/deathofraw
http://www.beyondveg.com/tu-j-l/raw-cooked/raw-cooked-1b.shtml