This blog is about the intersection between evolutionary biology and food. But also about practical applications, sustainable agriculture, and general tasty things.
Since a diet a raw vegan of only raw fruits, vegetables, and nuts is not an appropriate diet for our species, many people suffer from health problems on such diets. When I get comments from healthy long-term raw vegans here, I take it with a grain of salt since I know that people are so attached to the "purity" of raw vegan that they will engage in denialism before they admit they have a problem.
A questionnaire study of raw vegan diets found that many women on them suffer from amnorrhea, which means they stop having their monthly periods. They concluded that "Since many raw food dieters exhibited underweight and amenorrhea, a very strict raw food diet cannot be recommended on a long-term basis." (note the study did not include raw foodists who include animal products in their diets).
Unfortunately, instead of admitting their diet was deficient, many have written articles about how periods are bad anyway, because it's not something wild animals or our primate relatives have and it's a sign that we have "toxins" on our bodies. Here is one from Debbie Took (who later confessed on Letthemeatmeat that she was considering adding raw dairy into her diet and has since stopped posting on her blog, though I hear she is fruitarian now):
To many feminists, the idea of the menstrual blood as being 'impure' is heresy, but...'The toxicity of menstrual blood has been well substantiated. Mach and Lubin (Journal of Pharmacology and Experimental Therapy 22:413 (1924)) showed that the blood plasma, milk, sweat and saliva of menstruating women contains a substance that is highly toxic to protoplasm of living plants. This toxic substance is not present during the intermenstrual periods.' Even the sweat and saliva! And these toxins are not present when not menstruating. It's as if the body is 'gathering together' toxins in the period preceding menstruation, prior to expulsion at menstruation, to get the body all nice and clean again for possible impregnation the following month. But, sure, the study's old, and if anyone knows whether any subsequent studies have refuted it, let me know.
I thought of this post because Dr. Kate Clancy, a physical anthropologist, just posted about it in her blog:
Dr. Bela Schick, a doctor in the 1920s, was a very popular doctor and received flowers from his patients all the time. One day he received one of his usual bouquets from a patient. The way the story goes, he asked one of his nurses to put the bouquet in some water. The nurse politely declined. Dr. Schick asked the nurse again, and again she refused to handle the flowers. When Dr. Schick questioned his nurse why she would not put the flowers in water, she explained that she had her period. When he asked why that mattered, she confessed that when she menstruated, she made flowers wilt at her touch...Dr. Schick decided there was something nasty in the sweat of menstruating women. Others took up the cause. Soon, people were injecting menstrual blood into rodents, and those rodents were dying (Pickles 1979). Others were growing plants in venous blood from menstruating women to determine phytotoxicity; the sooner the plants died, the higher the quantity of menotoxin assumed in the sample.
It reminds me of elementary school science fairs and of the people who claim vegetables are toxic because of some study that put something ridiculous like purifiedcapsaicin on a cell culture and...no surprise the cells died! As if that is like eating peppers. These experiements were badly done and produced invalid results, the modern scientific understanding of periods is that they don't have to do with toxins:
Thankfully, the most accepted idea is that menstruation did not evolve at all, but is a byproduct of the evolution of terminal differentiation of endometrial cells (Finn 1996; Finn 1998). That is, endometrial cells must proliferate and then differentiate, and once they differentiate, they have an expiration date. Ovulation and endometrial receptivity are fairly tightly timed, to the point that the vast majority of implantations occur within a three-day window (Wilcox et al. 1999). So it’s not that menstruation expels dangerous menotoxins, but rather that menstruation happens because the endometrium needs to start over, and humans in particular have thick enough endometria that we can’t just resorb all that blood and tissue.
Guess what? Plants didn't evolve to grow in menstrual blood, just like we didn't evolved to eat uncooked animal-free food. The essential factors of cooking or eating animal fat is that they are appropriately calorically dense for our small digestive systems and giant hungry brains. Physical anthropologist Dr. Richard Wrangham discusses his book Catching Fire here:
I think we can probably digest them—this is guesswork because we don't really know—but the point is they're very full of indigestible fiber. So the average human diet has, even in the more fibrous hunter-gatherer types, 5 to 10 percent, say, indigestible fiber. With our chimp studies, they eat 32 percent indigestible fiber. So that is something that the human body is not designed to handle. And the reason we can say that is that we have small colons and small stomachs which are adapted to food that has high caloric density. And food the chimps eat has low caloric density.
Anthroologists will continue to argue about which is more important- animal foods or cooking, but either way, a raw vegan diet doesn't fit our anatomy.
This lovely little piece of woo makes the claim that healthy humans eating a "natural" diet don't have periods.
The majority of women in modern cultures however, experience instead a copious disabling monthly bleeding - that neither their wild primate cousins nor humans living close to nature do (2:30; 15:232). Insightful doctors have long been aware that nature did not intend the ovulation cycle to be accompanied by cramping, nervous tension, or any of the long list of symptoms we've come to associate with "having a period" - let alone by the days of bloody flow we now accept as "normal", but which they rightly call a hemorrhage:
That's also nonsense. It's not discussed often enough in ethnographies, but it's clearly there. The biography of Nisa, a !Kung woman, discusses it. And I doubt that if it were unnoticeable and rare that some Melanesian societies would have taboos about it.
That said, if your period is disabling, that might have to do with a modern diet. I've definitely had shorter, lighter, and less painful periods since I started eating whole unprocessed real foods, but I would be very alarmed if I didn't have a period. If you aren't getting one, you do need to see a doctor, and if you are paleo you need ton consider whether or not you are eating enough calorie-dense foods.
If you do not want to eat animal-based foods, consider following Wranghams example and eating some cooked food. I think a lot of vegans initially benefit from raw veganism because so many vegan foods are so horribly processed (and it is an excellent weight-loss diet). Some of them succeed because they are able to eat massive amounts of fruit or tons of calorically dense nut concoctions, though many eventually succumb to nutrient rather than calorie issues (or they are post-menopausal and telling young women that not having a period is normal, which just boggles my mind). When I think of what unhealthy veganism means, I not only think of raw veganism, I think of Foodswings in Williamsburg, which serves up such unhealthy delicacies as breaded fried processed soy-meat. There are plenty of alternatives to both diets, such as steamed root vegetables, soaked or sprouted lentils, or fermented buckwheat.
I said I'd go to bed, but then I read something interesting. Lately there has been some discussion in the comments here about what level of body fat is healthy for women. Is it healthy for women to be as lean as men should be (below 18% body fat)? Some authors say yes. After all, don't women in third world refugee camps have babies all the time?
Turns out it's more complex than that. Ancient Bodies, Modern Lives is my go-to reference on this sort of thing and lo and behold it had some answers on this matter.
To a great extent, reproductive hormone levels are set during development and reflect resource availability while a girl is growing.As we will see with regard to fetal development, a maturing system (the reproductive system in this case) reads cues about the environment to assess future conditions and adjusts levels of hormones and other components of the system to match the expected conditions. If a girl develops in a health-rich environment, her system "expects" that environment to be stable, but if she experiences short-term deprivation fo food, for example, her reproductive system may down regulate to wait for the expected better times.
Wenda mentions some rare examples of famines in first world countries, like the Dutch famine in WWII, where fertility levels completely crashed. So it's theorized that each woman has a "set point" established while growing up that determines her body's response to food intake.
Ammenorhea is a complex condition. Lots of long-distance runners suffer from it(which makes me doubt that women participating in persistence hunts was ever part of our evolutionary history)...but others don't. It sounds like a cliche, but everyone is different. For exercise-induced ammenorhea, it's not just body fat that's a factor, but cortisol and probably quite a few other hormones.
I would note that many advocates of low body fat for women are men. My own opinion is that this is foolish and will lead women to disordered eating. The only body fat that you want to avoid is visceral fat. I guess if you don't want to have children and care mostly about being super lean you can do that...but don't pretend it's healthy or natural.
Lassek and Gaulin also argue that hip and buttocks fat are the primary sources of fatty acids that are passed from the mother to the fetus during gestation and the infant during lactation. These long-chain polyunsaturated fatty acids play a major role in brain development. Thus, they argue, hip and buttocks body fat does not just signal overall energy availability for pregnancy, but also signals that the essential fatty acids for brain development are in sufficient supply. Does hip and buttock fat correlate with cognitive abilities? IN an examination of the third NHANES study database, Lassak and Gaulin found that high amounts of hip and buttocks fat relative to waist size (a low waist-hip ratio) was predictive of women's own and their offspring's cognitive performance. They refer to this fat as "a privileged store of neurodevelopmental resources.
I think other people refer to it as "my humps"
Edit: some commenters got the idea that this is about being "fat", which is it not. I mention that visceral fat is a highly unhealthy possession, and it is. Ideally a woman should have a relatively flat belly (unless she is pregnant), but not worry about ample hips, buttocks, or breasts.