I remember a discussion in an endocrinology course about modern women having three times number of
periods compared to hunter gatherers and that may be contributing to some gynecological problems including cancers. They attributed more periods to less pregnancies and childbirth but I wondered if diet plays a role. Some researchers believe it does. Though they link the cancer to increased fat intake. However, years ago the nation of islam had a pamphlet on women's health that claimed monthly menstruation is not typical or natural, though other non-human primates also have heavy cyclic menstrual bleeding. Though I take their stuff with a grain of salt. There have also been some controversy between the evolutionary biologists and endocrinologists regarding menstrual cycles that confuses things to me.
In the personal sphere, with the exception of this month, since last march my periods have been much heavier and longer than usual. At times it would last for more than two weeks. After checking for hormone levels, abnormal cells, pre cancer etc. everything was ok except my iron levels. I also have fibroids. When my iron levels normalized with diet and the periods were still frequent and long and heavy, it was even suggested that heavy bleeding can occur pre-menopause, and so I may be in early menopause. At 41 that's pretty early. As I've increased the my meat and fish oil intake since late august, the real difference was observed this month. My period was only seven days, moderately heavy and without pain. I suppose the ketogenic diet was the reason for the improvement. So, I was also wondering if it it's not about early menopause and just that a sustained ketogenic diet would reduce the frequency and extent of bleeding in general. Which gets back to the question: not counting pregnancy and breast feeding how frequent were periods for a normal hunter-gatherer woman?
I also found
this article . It is interesting though they fall for the anti-fat dogma. From what I understand however, it is increased fat intake in young female lab animals not in adults that is correlated with rather than cause increased cancer.
Some tidbits from the article:
In evolutionary terms, menstruation is a relatively recent
development (Finn 1994). Multiple hypotheses have surfaced as to why a
few mammal species menstruate while the vast majority does not. The opinion
of many scientists is that since natural selection has not eliminated it,
menstruation must have some benefit (Travis 1997). However, since menstruation
only occurs when pregnancy does not take place, natural selection may not
have had an opportunity to select against any negative effects of menstruation.
Until recently, most females became pregnant within a few years of first
menses, and would therefore pass on their genes before the deleterious
effects of menstruation occurred (Finn 1996)
While the reasons behind why women menstruate remain unclear,
research shows that the number of menstrual cycles modern women experience
differs greatly from the number experienced by pre-agricultural women.
It is impossible to know with certainty the reproductive patterns that
prevailed 10,000 years ago. However, it is likely that the reproductive
patterns of Stone Age women are more closely related to those of current
hunter-gatherer societies than to those of western women (Eaton and Eaton
III 1999). The best opportunity to study the natural pattern of human reproduction
occurs with women in current foraging societies. American women currently
experience three times as many menstrual periods as women who have continued
living in the ways of earlier ancestors. Foraging women are 16 years old
at menarche, 19.5 year old at first birth, nurse for three to four years,
have a completed family size of 5.9 live births, and an average age at
menopause of 47 years. They experience a total of 160 ovulations in their
lifetime. Contemporary American women are 12.5 years old at menarche, 24
years old at age of first birth, nurse for 3 months (if at all), have a
completed family size of 1.8, and are 50.5 years old at menopause. American
women experience approximately 450 ovulations within their lifetime (Eaton
et al 1994). A study done with the Dogon women of Mali shows a similar
relationship. The Dogon are a foraging society that practices natural fertility
by not using modern contraceptive methods. The Dogon have a fertility rate
of 8.6 ± 0.3 live births per woman. Median number of lifetime menses
experienced by the Dogon was 109, with a U-shaped relationship between
menstruation and age showing that, from menarche to menopause, women in
primary child-bearing years (20 —34 years old) rarely menstruated (Strassman
1999). Overall, this data indicates that monthly menstruation for decades
on end is not the historical norm. Today, women have earlier menarche,
later first birth, and fewer pregnancies. There is also a decreased suppression
of menstruation through lactation as _ of children are never breast-fed
and the rest only breast-feed for 3 months. Early menarche is an especially
recent development. In the 19th century, the age of first menarche
was the same as in the hunter-gatherer women observed today. The earlier
age of first menarche can be linked to an increase in caloric intake, while
at the same time occupational, educational, and social forces have led
to a later first birth (Eaton and Eaton III 1999). The consequences for
these changes in menstrual cycling may be seen in cancer rates among women
in industrialized nations.
The increased number of menstrual cycles experienced by
western women may increase the risks of developing cancer in the reproductive
organs. Breast cancer afflicts one out of eight women (Strassman 1999).
Unfortunately, it is impossible to determine the breast cancer rates in
ancestral hunter-gatherer societies. However, medical anthropologists estimate
that it was rare. One model suggests a 100-fold increase in breast cancer
rates from those in ancestral women (Eaton and Eaton III 1999). Less than
2% of current breast cancer cases are caused by heritable mutations. The
other 98% of breast cancer cases are probably due to the longer time span
between menses and first live birth, along with increased menstruation
rates (Strassman 1999). The chances of developing breast cancer decrease
with later menarche, earlier first birth, high parity, and earlier menopause.
This is because the susceptibility of the breast to carcinogens is directly
related to its epithelial cell proliferation rate and inversely related
to its degree of tissue differentiation. After menarche, but before the
first
birth, epithelial cells in the intralobular terminal ducts are especially
susceptible to carcinogens. Pregnancy and lactation induce differentiation
of these cells into well-developed secretory lobules that have a slower
proliferation rate and are more resistant to carcinogens. Increased exposure
to estrogen from an increased number of menstrual cycles also elevates
the risk of breast cancer as estrogen accelerates breast epithelial cell
proliferation (Eaton et al 1994).
I am going to check out one of the books listed in the citation: Coutinho, E.M., Segal, S.J., 1999. Is Menstruation Obsolete?
New York: Oxford University Press. A blurb on
Is menstruation obsolete?. . Note that one of the authors promote depo-provera birth control for stopping menstruation. I don't agree with that at all but the book seems interesting and I will add it to my very long reading list
Another interesting book I want to check out is Fibroids, Menstruation, Childbirth, and Evolution: The Fascinating Story of Uterine Blood Vessels.
Given the bits and pieces remembered form my course, and what I've come across my guess is that childbirth and breast feeding has a lot to do with total number of cycles, particularly amongst hunter-gatherers but diet also regulates the age at which menarch and menopause occurs. Furthermore, diet is certainly a strong influence on the health associated issues with menstrual cycles. Thus both diet and number of pregnancy contributes. What is the "normal" average age for menarche and menopause is the question. Is it the estimated 16 years for pre-agriculuralist compared to 12 for westerners?
