No, we are not carnivores. But we’re no apes either.

I often read on vegan health groups that humans are not meant to eat meat because our guts are long like those of the apes (who are predominantly plant-eating) vs. the short guts of carnivores (meat-eating animals). In fact, I used to argue this way myself in my vegan days. ūüôā

However, once you understand a topic a bit better, the simplified and incorrect statements about it simply irritate you.

WHAT OUR GUTS SAY ABOUT US..

Human guts, when compared to those of existing apes, have similarities AND differences. Humans and apes show the same gut anatomy- simple acid stomach, a small intestine, etc.. However, humans stand apart from all apes: more than half of human gut volume is found in the small intestine while all apes have by far the greatest total gut volume in the colon; also the overall size of the human gut in relation to body size is small in comparison to that of apes.

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What this means is that humans have adapted to a “high quality” diet. Here high quality means a calorie and nutritionally DENSE diet, which includes animal foods and tubers. A high quality diet for humans means that¬†we need to eat a smaller volume of food to obtain the nutrients and energy we need.

The way our gut differs from apes says a lot. Most large primates have expanded colons, which is an adaptation to fibrous low-quality diets [“low-quality” here = highly fibrous foods such as leaves and bark]. The large colon allows fermentation of low-quality plant fibers (which allows extraction of additional energy in the form of volatile fatty acids). Our relatively enlarged small intestine (the principal site of nutrient digestion & absorption) and smaller colon¬†reflects an adaptation to an easily digested diet that is nutrient-rich.

There is a general consensus that current hominoids (apes and humans) come from a strongly plant-eating ancestry. Apes, however, evolved into larger bodies that allowed to sustain themselves on lower quality diets. By eating both animal matter [to satisfy requirements for essential nutrients] and plant sources [primarily for energy] humans were able to avoid the constraints imposed by body size increases in apes (such as lower mobility and sociality in apes). Simply speaking: the bulkier they get and the more time they spend eating, the less they move around and the less social they are, which is a disadvantage compared to humans.uuuu2

MMM… BRAINS

This dietary change in humans (adding animal and other dense foods), which departed from known plant-dominated diets of the apes, was eventually reflected in our brain size (much larger), overall form of our guts (shift in gut proportions, overall gut size) as well as dentition (smaller teeth, jaws). Concerning our particularly large brains: our brains are particularly energetically “expensive” as we expend a larger proportion of our daily energy on brain metabolism than other primates¬†(in comparison to other primates, our brains are 3 times the size). Paleontologists believe¬†that fast brain evolution happened about 1.8 mln. years ago and was associated with important changes in diet and foraging behavior (some argue it is specifically the addition of meat that allowed for such large brains to evolve). Apart from switching to high quality nutrition, humans show other adaptations to having a larger brain- compared to other primates we are “undermuscled” (less skeletal muscle) and fattier. Greater level of body fatness in human infants in fact helps grow a large brain by having stored energy and reducing energy requirements of the rest of the body (that has less muscle mass).

THUS…

The point is: no, we’re definitely not “meant” to be vegetarian. Also, the point is not to say that vegetarianism doesn’t make sense for many of us. There are plenty of great reasons to avoid animal foods (ethics, environment, etc.), plus it’s easy to have an adequate veg. diet for adults with availability of supplements (vegan diets are not recommended for small children, though, considering brain development; the several vegan PhDs I know did not raise their children vegan specifically because of this)¬†… but stating that we are not meant to thrive on both animal and plant sources is incorrect. Contrasting us with true carnivores [like cats] to show how very different we are (e.g. hey we don’t have claws and sharp teeth… um.. we however do have large brains to allow for sophisticated tool creation that replaces those) is also a terrible idea- we are not true carnivores either and have a dual dietary strategy [plants + animal sources].

Lastly, all this material should not support the notion that we ought to eat¬†bacon 10 times a day.. meat clearly¬†has a place in our diet, but this shouldn’t be used to justify a purposeful meat overload (I’m not sure what the benefit¬†is for advocating heavily animal-based diets, considering modern animals are fattier and less packed with phytochemicals than the wild ones + there’s the whole issue of antibiotic and hormone use at the minimum. Unless, of course, you go on the “carbs are evil” side, but I am not in favor of that view… or you imagine our ancestors ate predominantly meat, which does not look to be the case since the diets varied dramatically depending on environmental circumstances).¬†

(Note: I’m not pretending to actually be an expert on any of these topics; I simply read peer-reviewed articles and hang out with evolutionary anthropologists ūüôā ).

References: 

Milton, K. (2003). The critical role played by animal source foods in human (Homo) evolution. The Journal of nutrition, 133(11), 3886S-3892S.

Leonard, W. R., Snodgrass, J. J., & Robertson, M. L. (2007). Effects of brain evolution on human nutrition and metabolism. Annu. Rev. Nutr., 27, 311-327.

P.S. The bottom line is: these t-shirt designs are both incredibly dumb (disclaimer- i laughed a bit..but immediately felt guilty :D)

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Healthy Eating- Real or Imaginable??

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The lobby of one of the conference hotels during non-busy time. The hallways were overflowing with anthropologists all over the world just hours later ūüėÄ

This December I presented on my research at the American Anthropological Association in D.C. (woohoo!) What a blast! The conference was bursting with anthropologists all over the globe; the 5-day event was so packed with presentations that the program which included just names of talks & authors ran about 500 pages.

Anyway, one of the interesting moments from the trip was a scholar¬†(I believe she did some work in Latin America but I don’t know what kind of anthropologist she was), who was seemingly¬†bothered¬†by our session on food and nutrition. Our talks focused on¬†“healthy eating” as a social construct [a social phenomenon¬†created and developed by¬†society; a perception or idea¬†that is ‘constructed’¬†through cultural or social practice]. My talk was on how perceptions of what healthy eating means differs among and within cultures (Ukrainians & Americans in my study), while other presenters talked about¬†how food is discussed in the Canadian Arctic and among those following a traditional “paleo” diet plan.¬†

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Presenting on my Ukrainian study!

The question this lady asked was why we spoke of healthy eating as something created and perceived by humans as if there is no objective healthy diet supported by science.

It’s a bit funny¬†to hear someone being surprised that concepts are¬†discussed as a social creation vs. an objective reality at an anthropology meeting.. but that shows how food and healthy eating can be quite emotional when one is health conscious! I would bet this scholar was¬†someone who personally cares about eating well for her own health. Understandable. Food is a very emotional topic- it is not only good/bad for health and looks, it also represents our identity, our culture, our experiences, etc.

Part of my answer to her was that science might not be able to give her what she is looking for- the objective healthy diet. Not because science sucks, but because nutrition studies are lengthy, complicated, and costly (see my post on why nutrition science doesn’t suck HERE). My favorite example of why nutrition science is hard to rely on is SUGAR. Look at this World Health Organization 2003 report (see full report).

The common sense¬†might tell you that¬†added sugar can’t be good- it adds calories, maybe it makes you hungrier or disrupts bodily processes, maybe it’s just unnatural. People I interview often mention that sugar is one of the main causes of weight gain. Common sense, right? Well, look at the WHO report and check out Free Sugars (=¬†all monosaccharides and disaccharides added to foods by the¬†manufacturer, cook or consumer, plus sugars naturally present in honey, syrups and fruit juices).¬†The only convincing evidence from scientific studies is that free sugars increase the risk of dental caries. Not weight gain, not diabetes, not heart disease. Does this mean sugar is only bad for teeth? No, it means there isn’t evidence that it causes other disease with the studies that we have. So if you want to state with complete confidence that added sugars lead to chronic disease and obesity, you might have a hard time backing it up.

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Thinking that there is no such thing as a healthy diet is unsettling. We want clarity. :S Saying that “healthy eating” is an idea constructed socially, however, doesn’t mean that there is no such thing as healthy eating. It does mean that there are multiple ways one can eat well to avoid disease- it can be vegetarian, vegan, paleo, regular calorie restricted¬†diet, Mediterranean diet, etc. etc. etc.

Historical perspective on what good/healthy eating is.

The official stance on a healthy diet is not purely unbiased either- the political and historical context shapes what is officially recognized. ¬†I heard a very interesting talk on the differences in nutrition perceptions between Denmark and Germany during 1940-1945 by Dr. Jensen (University of Copenhagen). She talked how in the early 20th century macronutrients, salts, water and ash were believed to be the sole constituents of food. ¬†Then vitamins were discovered resulting in growing scientific interest in identifying new “micronutrients”, a development that altered (diminished) the perceived importance of the macronutrients (protein, fat, carbs). ¬†So as in Denmark micronutrients became the focus, good nutrition became about vegetables- the source of many micronutrients. In Germany, however, a country experiencing hunger during WWII, macronutrients remained as most important considerations in nutrition textbooks (with protein considered the primary element of food- for the satiety and strength it provides, especially for a country at war!). The point is- the scientific (and thus public) perceptions of what good eating means is shaped by societal circumstances.

It all just depends…

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Baklava- a middle-eastern dessert I am absolutely insane about. My friends sometimes wonder how I can study health yet eat something so “unhealthy” as a high sugared dessert. IS it unhealthy? Turkish people love their sweets, yet traveling around Turkey will show you that the population is not plagued by obesity and chronic disease.

Back to whether an objective healthy diet exists or not. If we ignore for a second that people disagree on the details of what one should eat to stay healthy (is carb or fat evil? is animal protein toxic? should you go vegan? avoid gluten like the plague?), most folks at the minimum agree that eating “real” or whole foods is important (or in other words- avoiding or limiting modern processed foods and focusing on the less modified foods). I suppose we could say that this definition of a healthy diet is generally accepted. If we move on from processed vs. whole, though, here are a couple of examples of when something generally healthy might not be good¬†for you or vice versa:

Cabbage! A wonderful plant full of micronutrients (vitamin K! Vitamin C!) that protect one from various diseases; the plant is often stated to have anti-inflammatory and anti-cancerous properties. Awesome. Unless you have hypothyroidism since cabbage is one of the foods that interfere with the thyroid function.

Dairy! Gets a lot of bad rep from the paleo community and others. While recently¬†thought as very important for bone health and what not, there is a lot of talk that we have not evolved to tolerate it quite well and it is thus an unhealthy substance to consume. Our genes are still adapted to the pre-agricultural diet (before ~10,000 yrs ago), as many paleo proponents will argue. Yet there is evidence to challenge the assumption that humans are essentially unchanged since the Paleolithic era. E.g. “recent” evolution of lactase persistence and variation in the number of genes that code for amylase production tied to starch consumption. In other words, mutations have occured that allow many folks to digest and thrive on dairy and grains just fine.

–¬†Phytates.¬†Plants have a lot of great ingredients that generally affect us positively¬†(e.g. vitamins protecting from disease), but it depends.. For example, phytates in grains and nuts are usually viewed as bad for us because they can bind to certain dietary minerals leading to deficiencies (iron, zinc, etc.).. In West Africa, many Hausa plants contain substantial amounts of these phytates (especially in cereals and legumes) but these botanical chelators have a potential malaria-suppressive effect (awesome!!). However, this anti-malarial effect may be antagonized by antioxidants in other foods (e.g. such free radical traps as Vitamins C, E, beta carotene, selenium). Antioxidants is something many of us try to increase in the diet..yet if you are living in malaria-prone regions of the African continent, you might want to concentrate on the opposite dietary strategy- phytate-rich and antioxidant-poor foods.

989898So is there an objectively healthy diet? Generally- all eating is healthy since it is required for survival.. undereating and overeating is not good.. lacking a variety nutrients is not good.. and that’s mostly¬†it. Of course, different things work for people- someone might not tolerate dairy, others might feel miserable on a vegan diet; some thrive on salads others can’t digest raw plants well. If only we could all grasp the wonderful concept of moderation and apply it in our lives without struggle. In fact, it is because self-control is so hard to maintain that we want simplified solutions-¬†a diet plan, a list of “bad” foods to simply avoid, etc.

Happy Holidays– don’t overeat on most days, yet don’t let yourself stress so much about what you’re eating that you are unable to enjoy life! ūüėČ *grabs a big fat piece of dark chocolate and kicks back*.