As many of you have already heard, I was a guest on Skeptically Speaking a few weeks ago, on the topic of why women menstruate. PZ Myers tackled the evolutionary perspective first, and then I got to answer audience questions and talk a little about my own research.
Because I think it’s important for listeners and readers to see where the evidence came from to support my claims, I am sharing references (and in several cases, past posts of mine that themselves contain references). That way you can look up these articles to learn more about each topic – using Google Scholar usually turns up whatever pdfs aren’t behind a paywall.
I want to thank Desirée Schell and K.O. Myers for their great work on the show. I had a great time and think that Skeptically Speaking is a truly fantastic way to share science. Schell was a wonderful host and I hope to be fortunate enough to be asked on again.
The history of the study of menstruation
Much of what I discussed in this section of the radio show can be found on my blog post “Menstruation is Just Blood and Tissue You Ended Up Not Using.”
I also think it’s important to point out that many hypotheses developed about menstruation often forget that the monthly cycle is a very modern occurrence. Not only are modern cycles in women in industrialized populations not necessarily 28 days in the first place (in fact, see my Guest Blog post about this from December 2010), but our ancestors very likely menstruated 50-100 times rather than the 400 or so that is our norm. The reason for this is first that they probably had neutral or negative energy balances (because they moved around so much more, and likely ate less), but also because they were pregnant and breastfeeding through most of their reproductive years. This also came up in the menstrual synchrony part of the conversation later.
Strassmann, B. (1997). The Biology of Menstruation in Homo Sapiens: Total Lifetime Menses, Fecundity, and Nonsynchrony in a Natural-Fertility Population Current Anthropology, 38 (1) DOI: 10.1086/204592
Birth control pills (hormonal contraception)
This topic is always very popular, and women understandably have a lot of questions about hormonal contraception. It is ubiquitous and almost expected for most reproductively aged women in many industrial, western cultures. Yet women are poorly educated on how they work and their broader effects. This leads to a lot of ambivalence about something that a huge proportion of women take every single day for decades. Two posts over at my old blog that I will eventually migrate here have some good information: “Summer of the Pill: Why Do We Menstruate?” and “Summer of the Pill: The latest fashion accessory to hit your uterus: the IUD!”
Additional reading on the history of the pill:
Gladwell, M (2000). John Rock’s error. The New Yorker. March 13: 52-63. http://www.gladwell.com/pdf/johnrock.pdf
Additional reading on the biology behind the pill:
Bentley, GR. (1996) "Evidence for interpopulation variation in normal ovarian function and consequences for hormonal contraception" in Variability in human fertility, eds L. a. M.-T. Rosetta, C.G.N. (Cambridge University Press, Cambridge, UK), pp 46-65.
Vitzthum VJ, Spielvogel H, Caceres E, & Miller A (2001). Vaginal bleeding patterns among rural highland Bolivian women: relationship to fecundity and fetal loss. Contraception, 64 (5), 319-25 PMID: 11777494
Vitzthum VJ, & Ringheim K (2005). Hormonal contraception and physiology: a research-based theory of discontinuation due to side effects. Studies in family planning, 36 (1), 13-32 PMID: 15828522
Additional reading on adolescents and hormonal contraception:
Deligeoroglou (2000). Dysmenorrhea. Annals of the New York Academy of Sciences 900(1): 237-244.
Vihko R, & Apter D (1984). Endocrine characteristics of adolescent menstrual cycles: impact of early menarche. Journal of steroid biochemistry, 20 (1), 231-6 PMID: 6231419
Additional reading on endometrial waves:
IJland M, Evers J, Dunselman G, van Katwijk C, Lo C, Hoogland H. 1996. Endometrial wavelike movements during the menstrual cycle. Fertil Steril 65(4):746-749.
IJland MM, Evers JLH, Dunselman GAJ, Volovics L, Hoogland HJ. 1997. Relation between endometrial wavelike activity and fecundability in spontaneous cycles. Fertility and Sterility 67(3):492-496.
Much of what I discussed on synchrony can be found on my blog post “Do Women in Groups Bleed Together? On Menstrual Synchrony.”
Effect of diet and activity on menstruation
Strangely enough, even though this is my own field of study, I don’t have any blog posts that discuss this!
Clancy KBH, Ellison PT, Jasienska G, Bribiescas RG. 2009. Endometrial thickness is not independent of luteal phase day in a rural Polish population. Anthro Sci.117(3): 157-163.
Ellison PT. 2001. On Fertile Ground. Cambridge, MA: Harvard University Press.
This material comes from some of my own research on iron-deficiency anemia. I discuss it in the blog post “Iron-deficiency is Not Something You Get Just for Being a Lady.”
Menstruation and… camping?
One audience member asked if it was true that menstruating women should avoid going camping because of the risk that the smell of their menstrual blood would attract bears. I found a pretty fun study in the Journal of Wildlife Management that suggests that black bears, at least, couldn’t care less if exposed to tampons, menses-soaked tampons, or women during menstruation. Scicurious was inspired enough to discuss this topic for her Friday Weird Science.
I also am planning a separate post on the idea that menstruation makes wild game run away. As it turns out, there is a very interesting anthropological history to this idea, so stay tuned!
Toxic Shock Syndrome
Davis JP, Chesney PJ, Wand PJ, LaVenture, M (1980). Toxic-Shock Syndrome. New England Journal of Medicine 303(25): 1429-1435. http://www.nejm.org/doi/full/10.1056/NEJM198012183032501
McCormick JK, Yarwood JM, Schlievert PM (2001). Toxic shock syndrome and bacterial superantigens: an update. Annual Reviews in Microbiology 55(1): 77-104.
Schlievert PM, Blomster DA, Kelly JA (1984). Toxic shock syndrome Staphylococcus aureus: effect of tampons on toxic shock syndrome toxin 1 production. Obstetrics and Gynecology 64(5): 666-671. http://ukpmc.ac.uk/abstract/MED/6436761
Shands KN, Schmid GP, Dan BB, Blum D, Guidotti RJ, Hargrett NT, Anderson RL, Hill DL, Broome CV, Band JD, Fraser DW (1980). Toxic-Shock Syndrome in Menstruating Women. New England Journal of Medicine 303(25): 1436-1442. http://www.nejm.org/doi/full/10.1056/NEJM198012183032502
Jasienska G, Thune I. 2001. Lifestyle, hormones, and risk of breast cancer. British Medical Journal 322:586-587.
Kahlenborn C, Modugno F, Potter DM, Severs WB. Oral contraceptive use as a risk factor for premenopausal breast cancer: a meta-analysis; 2006. Mayo Clinic. p 1290.
Strassmann BI. 1999. Menstrual cycling and breast cancer: an evolutionary perspective. Journal of women's health 8(2):193-202.
Detecting menses in the voice