This blog is about the intersection between evolutionary biology and food. But also about practical applications, sustainable agriculture, and general tasty things.
Melissa McEwen
Connect
Comments
science
09/21/2010 - 19:37
In autoimmune disorders the immune system attacks the body's own tissues. We recommend that these tissues be removed because clearly they are causing an immune reaction.
Um...what? It seems funny, but that seems to be the reaction of some scientists to Neu5Gc, a sugar that apes, but not humans, synthesize naturally. However, we do ingest it in food, particularly meat and dairy products.
Some humans have an inflammatory immune reaction to it. Does that mean it's bad to eat? Numerous papers on Neu5Gc that I've read seem to suggest so in their discussion sections.
I was reminded of that when reading this Atlantic article on chimp fertility studies:
Gagneux’s lab space was adjacent to that of his collaborator Ajit Varki, who had helped uncover the functioning of the sugars, known as sialic acids, on cell surfaces. The sialic acids on the surfaces of human and chimp sperm have become the focus of Gagneux’s work, too. Humans, as Varki discovered, have lost the ability to make one sialic acid, Neu5Gc, and Gagneux suspected that Neu5Gc played a role in fertilization. He hypothesized that Neu5Gc helped female chimpanzees, in a process called “cryptic female choice,” get the benefit of the most-compatible, highest-quality sperm. The sugar acted like the fuzzy part of Velcro and attached to barbs formed by sugar-binding proteins on the surface of the cells in the uterus or fallopian tubes. Neu5Gc, as Gagneux imagined it, might “sweet-talk” the female reproductive system.
Gagneux’s Neu5Gc ideas had a critical implication for human fertility. Although we have lost the ability to synthesize Neu5Gc, we ingest the sugar when we eat meat and dairy products, and it, in turn, can then be incorporated into our cells. Does Neu5Gc coat the surface of human sperm? Is it found more readily on the sperm of men who eat lots of animal products? Does the extremely foreign Neu5Gc then trigger in women an immune response that selects against the survival of the sperm? “It could be that men who eat loads of meat pass a threshold and become infertile,” suggested Gagneux. [emphasis mine]
This just cries out for better general education of scientists. Does her hypothesis make sense? Inuit and Nenet cultures eat almost all-meat. Shouldn't they have died out by then?
Maybe instead of pegging this sugar as the bad guy, we should wonder why we are reacting to it in the first place? Unfortunately all the populations that they have studied for a reaction have been western. Most people do seem to have a reaction to Neu5Gc, but this paper has a tantalizing graph:
See the humans clustered around the chimps? Who are they? Why the difference?
Dr. Ayers at Cooling Inflammation suggests the reaction might be due to too little dietary NeufGc:
If cow’s milk gangliosides are the source of Neu5Gc in breastmilk, then how do the infants develop antibodies to these relatively rare antigens? Babies receive all of their antibodies from their mother until their immune systems start to develop at about six months of age. The answer is hinted at by the observation of a mother whose exclusively breastfed infant developed sensitivity to breast milk after the mother ate dairy products. The mother reported that she shifted from a long term vegan diet to a meat diet to improve her nutrition during her pregnancy. It is also likely that she produced IgE antibodies to Neu5Gc, which were then transferred to her baby across the placenta during gestation.
I would also suspect that increased gut permeability due to the constant irritation from foods like gluten, poor gut microflora populations, and general inflammation play a role.
09/14/2010 - 16:31
Aunt Maude still sending you links on that study that purported to show how terrible meaty diets are? Here are some great links for a takedown:
Denise Minger on Brand-Spankin’ New Study: Are Low-Carb Meat Eaters in Trouble?
09/07/2010 - 13:53
If you read the media accounts you might think that this study is about Aktins or low-carb diets. But it's not. Because the people studied, as far as we know, weren't on such diets. Some of them just happened to eat lower carb and higher in meat, and the statisticians/idiots associated this with mortality. But were these people low carbers? For all we know they ate hot dogs from Safeway and their carb sources included twinkies and slurpies.
Here is a hint researchers: if you want to study a diet, have people actually do it. Don't try to evaluate a diet based on generalized data. Unfortunately these researchers are insulated by the fact that their data is behind a paywall.
Comment?: 2
09/06/2010 - 19:31
It's easy enough to stop eating crap and start eating a diet closer to what evolution intended. Other evolutionary disconnects are harder to remedy. As a young woman, I can say one of the hardest is childbearing. Most middle-class young women in developed countries cannot afford to have children during our prime childbearing years. Furthermore, having children often means relying on two incomes and leaving the childcare to someone else outside the family. American children start school young (Swedish children start school at 7, American at 4-5) and our schools generally do a terrible job at providing an evolutionarily-appropriate environment. Think about hunter-gatherer children: lots of play, mixed age groups, and spending time and learning from relatives.
What are the consequences of this evolutionary disconnect? I think we are just starting to see them. One alarming trend is that the age of puberty is falling. Some blame diet, others blame pollution, but it's probably all that and more. Here is an interesting study on how social factors might influence puberty. It suggests that poor mother-child bonds might lead to early puberty. The unfortunate thing about these studies is that it's often hard to tease out social issues like that fact that children whose mothers have to work long hours often live in environments that are poor in many other ways.
The evolutionary disconnect goes so much deeper than just eating inappropriate foods for our species like bread....it goes into how we work, move, and raise our children. The problem here is that the disconnect is so deep that it's hard to remedy it unless you want to run off and become Amish. And that the disconnect is psychological and social as well. How many 24-year-old women want to spend their days taking care of children anyway? How many of us have the extended family to help us?
Comment?: 10
07/12/2010 - 13:21
While I was gone, apparently The China Study received some belated smackdown. I've personally never paid much attention to that book. I took several advanced statistics classes for my degree and an epidemiology class. If I wanted to base my diet on that flawed methodology, I might be more interested. But you can hash and rehash data and it won't change the fact that epidemiology (like my own science, economics) has been responsible for crap conclusions that have not bared out in the real world. I don't think economics or epidemiology are bad and in fact I'm quite interested in them, but they are rough tools that I'm not going to use them to manage my life.
As Kurt Harris said:
This is all just epidemiology, and epidemiology is bogus. Now, I don't mean it has absolutely no value. It is good for hypothesis generation. It is almost worthless for finding the truth. It is especially worthless the way it is used by hacks like Campbell who are simply trying to sell people a book that tells them what they want to hear.
You can run all kind of analytics on that China data and maybe find some interesting hypotheses to test, but then you have to worry about the data itself. I'm not sure rural Chinese people from the 80s have much to tell us about what to eat in America now. As Denise pointed out, there are pathogens present in rural China that aren't exactly common in Brooklyn, NY.
While Denise's post is certainly very interesting, I'm alarmed that she is now working with a vegan epidemiologist, but who also is a fruit-based raw vegan. While there are several academics who have formulated scientific vegan nutrition, no conventional science supports the fruit-base raw vegan diet- it's pure quackery and lately its proponents have unfortunately been trolling paleo blogs.
Evolutionary fitness is not about epidemiology- it's applied evolutionary theory. I'll be reviewing some books in the next month about that science, but needless to say, I think it's a far better groundwork for living as a human.
Comment?: 8
02/22/2010 - 17:50
I've been reading the Continuum Concept lately and that, plus the comments I got, have led me to revise the graphic for the Faileo diet post
Mmm fatty fat flavored fatty fat
The earlier graphic was a pyramid, which many mistook for a dietary recommendation graph like the USDA's' idiotic food pyramid. I feel this graphic illustrates the philosophy behind my thoughts better. Plus it adds on a new concept, which is thinking about diet in terms of the human continuum. Just like the babies in The Continuum Concept biologically expect to be held, our bodies biologically expect certain food. When we consume things like soybean oil our bodies just don't function properly, just like babies that are never held as infants. Of course there is variance based on genetics, gut bacteria, etc, but overall animal fat is the nutrient that the human body seems to be evolved to eat.
Animal fat is the nutrient our bodies can handle most perfectly. We absorb it and utilize it in a way that fuels us without dragging us down. Contrast that with a dinner of just some chicken breast and some spinach. It's a meal that's "paleo", but unlike anything our ancient human would have encountered in a thriving environment. It takes energy to digest all that protein and fiber. Add a chicken thigh with a bunch of skin and things are looking a lot better in terms of actually fueling us.
Not on the human evolutionary continuum: too much omega-6, too much fructose, too many antinutrients, too few nutrients
Butter and ghee might get to jump the continuum...after all, they are very close to being like lard, tallow, and the other animal fats. But they have their detractors.
Another interesting thing about the analogy is that The Continuum Concept maintains that the consequences of not raising children the way humans evolved to be raised aren't just horrifying things like reactive attachment disorder, but annoying behaviors we very as normal in modern children. It's the same for not eating the way humans evolved to eat. Heart disease and diabetes are the tip of the iceberg. Health problems that probably aren't normal for humans include things we view as nuisances like acne, constipation, cold sores, and a whole host of other "small" things.
Comment?: 3
02/05/2010 - 21:50
From the comments:
Lets see how many diseases you could get from raw meat
Tapeworms Toxoplasmosis Salmonella Brucellosis Bottulism Trichinellosis
Just to name a few. Do you want to eat raw everything? Go ahead but read this first
http://en.wikipedia.org/wiki/Raw_meat#Raw_meat_diseases
Let's look at all the diseases you can get from vegetables:
Liver fluke, salmonella, pathogenic e coli, botulism, campylobacteriosis, listeria, staphylococcus aureus, brucellosis...the list goes on and on.
Actually, vegetables cause most food poisoning outbreaks. Cooked meat and fish also do plenty of damage. Definitely raw meat can be dangerous, but food poisoning is simply a danger of food. Most of the raw meat outbreaks occur when people make mistakes in the kitchen. Very few people want to eat chicken raw, but it's quite common for people to cut raw chicken and then use the same knife on vegetables for their salad. That's way different from intentionally eating raw meat.
Plenty of cultures from the Japanese to the Inuit consume raw meat without all keeling over and dying. For me, the benefits of eating raw meat outweighed the small risks. I only eat whole prime cuts from herbivorous animals, I don't just buy ground beef from the supermarket. Most contamination occurs during processing.
Most of the raw foods I eat aren't exactly shocking. Millions of people eat sushi and raw oysters every day. Be careful, but life is too short for scare mongering. Thanks for the warning :) I do know about food poisoning. I had food poisoning, serious chronic salmonella that sent me to the E.R. I was a vegetarian then.
Comment?: 1
01/28/2010 - 23:16
I would hate for people to think that the paleo diet is about recovering some "paradise lost." Just because peasant agriculture was miserable for most people doesn't mean foraging was a walk in the part. Almost every foraging culture studied has a wide range of remedies for illness and medicine men are revered. Hunter-gatherers suffered from malaria, tuberculosis, parasites, wounds from wild animal bites, and all sorts of horrendous infections.
The preferred medicine against diarrhea was clay, kaolin-like powders or pulverized bone ash while bee larva, certain tree barks and the fruits of two trees were eaten to relieve constipation.
But many detractors of the paleo diet point to studies of more modern hunter-gatherer cultures to draw out evidence they were ill. We have to remember that what is left on that lifestyle is people who were able to survive on the worst lands not coveted by farmers. The Inuit or the San diet might be healthier than most American diets, but neither is really similar to the diet of paleolithic people.
In Innu mythology, Matshishkapeu (literally the "Fart Man") is the most powerful spirit—even more powerful than the Caribou Master, Kanipinikassikueu. He proved himself when the Kanipinikassikueu refused to give the Innu any caribou to eat. Matshishkapeu was so angry that he cursed the Caribou Master with a painful case of constipation.
It's even possible we could do better. For example, both the high and low fiber diets of hunter-gatherers are touted as solutions to digestive problems, but digestive ailments clearly still plagued cultures eating both diets. Personally, I try to eat the vegetables that work for me and I don't worry about counting fiber. I'm pretty such that if I ate the bazillion grams of fiber the San eat, I would feel pretty sick. Maybe that's what anecdotes like this convey: there is lots of learn from hunter-gatherer and ancestral diets, but imitating their fiber consumption with BRAN4LIFE bread is on the same level as imitating snake bite wounds by keeping your own pet PALEOvipers.
Despite all that hunter-gatherers suffered, the paleo diet is about avoiding diseases of civilization, and it seems they did that well. We should eat like them, but still with an eye to the fact that they ate what they could to survive.
Postscript: I think many of the stomach problems attributed to hunter-gatherers were probably post-infectious or in the case of the Inuit, because of a lean time...literally...Vilhjalmur Stefansson found that without ample amount of fat, stomach issues ensued.
01/24/2010 - 18:53
This paper explores the diets of gorillas and uses it to recommend a diet for humans low in fat and high in dietary fiber. This is a common mistake. Dozens of vegetarian groups say that because the great apes are vegetarians (which they aren't...but animal food intake is fairly low) that humans are also naturally vegetarians. The most extreme groups say we should eat only fruit because, as primates, we thrive on sugar.
But read the paper carefully. The gorilla diet is very very high in fiber, but that fiber is getting converted into free fatty acids. This conversion is vital for gorillas, providing them with 57% of their calories. That leaves 15.8% of calories from carbohydrate, making the gorilla a defacto low carber! Humans claiming to emulate ape diets by eating lots of fruit aren't able to get the same nutrition. Fruits that are palatable to humans are much higher in sugar and lower in fiber than what the great apes eat. Furthermore, the human colon is tiny in comparison to great ape colons, so even if we did eat high-fiber fruit we wouldn't be able to process very much of it into free fatty acids.
Here is why a fruity "ape" diet is bird-brained:
- There is some fermentation of fiber into FFAs in humans, but much less since our colon is only 17% of gut volume. In apes it is typically around 50% of gut volume.
- Since apes are basically converting most of their food into FFAS, they are basically low-carbers. Humans gorging on melons are eating an amount of sugar that no ape in the history of the world has ever eaten.
- Humans are a fairly unusual species. Contrary to popular misconception, gorillas and chimps are our relatives, not our ancestors. Re the latest fossil evidence "indeed, the new evidence suggests that the study of chimpanzee anatomy and behavior—long used to infer the nature of the earliest human ancestors—is largely irrelevant to understanding our beginnings." It also means that comparing our digestive system to lions and cows is pretty pointless since we are a unique clade.
- Humans are the longest lived primates. A diet high in sugar cannot support this longevity. Without modern dental-care, humans eating high sugar diets would not live very long because they would lose all their teeth. Our "natural" diet would not be the one that makes our teeth fall out. Apes experience tooth decay in the wild, but it matters less since they don't live as long.
- Our brains require nutrients like iodine and DHA that simply can't be found on a diet of forest foods. Furthermore, our brains are big and hungry for calories. While modern fruit eaters can survive because of the wealth of sugar-rich fruit at the grocery store, there is no evidence that a homo sapien could survive by foraging for only wild fruit. In fact, there is strong evidence that homo sapiens could not survive in a forest environment at all without access to cultivated foods.
Comment?: 1
Recent Comments