Nutritional Needs, Transfolk and Biological Sex

 The Credible Hulk, Hulks Out

So a few days ago I signed up for “MyFitnessPal” and began carefully tracking my eating via it, as my wife has done for over a year. (We use Fitocracy for exercise tracking though). It forced me to choose my gender as male or female. So I picked one, and wrote an email to the company, I hope politely, suggesting that they really ought to have another option, or at least allow people to leave gender unspecified. Facebook's decision to greatly expand the gender options available last Feb, was actually probably the final straw that led to me coming out publicly as trans. And now I can pick something other than male or female, or leave my gender unspecified, on literally every other social web site I participate in (Google+, Fitocracy, Pintrest, Blogger, Twitter, etc.). I even included a paragraph each trying to forestall two counter-arguments that I anticipated, that they need the gender information for marketing purposes, or to calculate nutritional advice responsibly.

I got a reply, after some politeness the gist was

“We will definitely look into the possibility of adding other gender display options. We definitely want to respect a persons right to define themselves as they see fit, however, their body's nutritional needs would still need to reflect it's original physiology. We will continue to look into it as a prospect for a future update to find a way that is both sensitive to the user's sense of identity and accurate for their body's composition.”

This infuriated me.

But like the Credible Hulk, I want to channel my rage into well reasoned arguments, and citation of details.

The idea of “biological sex,” “biological gender” or in this case “original physiology” is frequently used to write-off the concerns of transgender people. Such uses are almost always badly misunderstanding the biology (as in this case), and often are assimilating things to one of two dumb over-prevalent ideologies 1) external-genitals-are-the-beginning-and-end-of-all-discussion-of-the-biology-of-human-gender-and-who-should-take-which-gendered-social-role or 2) your-parents-best-guess-at-birth-is-the-only-biological-criterion-than-matters-and-all-further-destiny-is-determined-by-that-critical-moment. Both evaporate under examination, but like a persistent fog, keep coming back if you aren't careful.  Oh and since most transfolk will select their social gender when setting up their accounts anyway, if "original physiology" actually is important, then MyFitnessPal already has a problem regardless of whether they add more gender options or not.

So in this case, neither the shape of my genitals, nor the earnest best guess of my parents years ago is really the issue for my “body's nutritional needs.” And we'll look at that. But first I want to say a little about my “biological sex.” Biological sex is really made up of dozens of different criteria, which often line up pretty well for most cis binary people (although certainly not all), but which tend to go in many directions for intersex, trans, and non-binary folks. In my case, my skeletal structure is quite male, my hormone profile is quite female. My skin and hair are feminine (under the direction of my hormones), but my respiratory system is probably pretty masculine still. I have Wolffian structures and not Muellerian structures, and thus, for instance, a prostate but not a uterus. Like most people, my genetic sex has never actually been tested, and even if it were if I had Chimerism it might not show up. My gonadal tissue has never been biopsied, but is probably male, or mostly male, because I've sired two children in the past, although I probably infertile in both directions now. My BRAIN which is probably the most important biological bit, for gender issues, is a complex case. Current evidence is that even prior to hormone treatments, there are important ways in which trans-women's brains resemble physically cis-female brains more than cis-male brains, and trans-men's brains resemble cis-male brains more than cis-female brains. But once hormone therapy starts, the changes in brain structure become even more pronounced. Here's a good article on details. So my “biological sex” like most or all trans people, isn't a simple male or female, but a complex mix of male in this way, female in that way, and somewhere in between in that other way, with plenty of we-haven't-even-checked thrown in for good measure.

Gendered Nutritional Illusions

OK, but males need more calories that females right, and so they're entitled to eat more without feeling guilty right?  So which set of nutritional guidelines apply to trans people, or worse still to non-binary cases?  What are my bodies nutritional needs”? The USDA famously has long recommended different dietary guidelines for men and women. Which should I, or any other trans person use and why?

Well, it turns out that the guidelines were always intended as estimates, and estimates for the “average” man or woman.  A bodies' caloric needs are shaped by your size and your daily activity level and probably fat to lean body mass ratio. Males are statistically larger than females in the US, so the “average” American male needs more calories per day, than the average American female.  But a male and female of the same size and same activity level, probably have close to the same caloric needs to keep their body weight stable. (Especially if their ages and BMI are similar).  Even here there is individual variation we don't understand well yet, but that isn't sex-linked.  Your caloric need to keep your body weight stable is roughly 13 calories per pound of body weight per day for a sedentary person, 16 per for a moderately active person, and 18 per pound for a vigorously active person. If, you'd like check out p. 14 of the USDA dietary guidelines, where they walk you through their process of estimating their recommendations based on differences in “reference height” and “reference weight” for the “average” healthy man or woman.  Whether you are male or female, or trans-female, or non-binary is not really the issue for determining your caloric needs, 

If you care about getting a good estimate of your own personal daily caloric intake for weight stability, figure it out based on your weight and activity level. If you want use a more detailed estimator, (we some times use this one), most use an updated version of the Harris-Benedict equations for estimating resting energy expenditure does include a gender component. But it's outdated in various ways, and evidence suggests, that gender is really functioning as a substitute for body-mass-index here. The equation is old, based on statistical regressions over small samples, and was updated in 1984, but folks who found “Resting energy expenditure is directly related to the size of the BCM (Body Cell Mass) and is independent of sex and age” and “there is no difference in resting oxygen consumption between the sexes when expressed as a function of BCM.” Now this is pretty steep Clinical Nutrition, for this humble ex-philosopher, but if I'm understanding correctly, basal metabolic rate (BMR) depends on your lean body mass, or your fat-free body mass, or your body mass other than adipose fat.  In older people and in women it is statistically normal for someone to have a higher percentage of adipose tissue. Consequently, a man and a woman of the same height and weight, will still have different BMR because more of the woman's body is statistically probably already fat rather than lean body mass (which burns more calories). But notice that lean body mass vs. adipose tissue, is NOT a matter of “original physiology” but is controlled mostly by hormone balance, so even on this theory, you should calculate based on your hormonal sex, if you can't find a good way to estimate adiposity directly, like you know the caliper estimator …  The Katch-McArdle formula for estimating BMR contains a Lean Body Mass component, but no gender component for instance.   Personally, I sometimes run the Harris-Benedict calculations with each gender and average them, to reflect my incomplete transition, trying to remember that they are all very rough estimates, and that your-mileage-may-vary.  I'll probably just use the female numbers once I think my BMI is in normal female ranges.  Oh, and even on this theory, there is significant individual variation from person to person that can't be explained by sex. Odds are high that, as with height or many other issues, statistical variation between the genders on caloric requirements are drowned out by variations within each gender.

A similar point holds true for marco-nutrient breakdowns. The optimal mix of carbohydrates, fats, and proteins varies wildly from person to person based on a number of factors, and there are certainly opposing ideologies at play here. But gender is not one of them. The USDA recommendations for carb/protein/fat balance don't depend on gender. I couldn't find anyone whose recommendations here did depend on gender. The closest to a gender difference I could find is that if you DO eat way too much protein, the medical problems it is likely to cause are slightly different depending on some gendered issues. Also there may be a slight difference in the type of fats one should consume. There is some evidence that ALA, one of the types of Omega-3 fatty acids, benefits some systems but may increase the risk of prostate cancer. Its unclear if maybe it is a net-boon even to people with prostates, but it does seem to be safer for people who lack prostates.  Similarly, the USDA recommends that men get more fiber than it recommends women get per day, but that is just scaled by their overall calorie recommendations. Men and women, and those of us in-between, should all have the same rough percentage of fiber in our diets. Oh, also there may be a difference in the "4th" macro - alcohol. Low amounts of alcohol consumption (as opposed to no alcohol consumption) do seem to have some health benefits for men, women, and folks in-between, but even minor alcohol use also increases breast cancer risks, which is a bigger problem for those of us with non-trivial amounts of breast tissue.

Genuine Gender Differences in Nutrition

For the most part men, women, and those of us otherwise gendered need the same things nutritionally regardless of our gender of identity, early life gender, "original physiology" or current biological gender details – although height and weight and activity level all matter, and body mass index probably matters. The calories you need and the macro nutrients you need, do not depend on your gender, although statistical illusions of various kinds, and estimates and recommendations that you haven't read the fine print on carefully enough can make it look like they do. But there are a few cases where there are real differences.

If you are pregnant or nursing, you are going to need a lot more calories. I've encountered pregnant and nursing trans-men, so gender isn't exactly the issue here, but the details of your biological sex are. Similarly, if there is even a small chance that you might become pregnant, it probably makes sense to make sure your Folic acid levels are good. Insufficient Folic acid can be devastating to embryonic neural development. Since my wife was once pregnant for months without realizing it, while she believed herself to be infertile, I like to encourage Folic acid pretty broadly, even to people who think they are very unlikely to become pregnant.

Similarly, there is very little doubt that menstruating people need significantly more iron than non-menstruating people. Again, it's not exactly gender linked, because pre and post menstrual women are in the same boat as non-menstruating men, and menstruating trans-men or non-binary types are in the same boat as menstruating women. 18mg a day for menstruators and 8mg a day for non, is the current USDA recommendation (and too much iron does have some health risks).

Finally calcium is the tricky case. For a long time, high calcium intake was thought to be a protection against osteoporosis, which is a much more prevalent problem for women than men, and seems to be linked to hormonal balance. But as it happens, the human calcium metabolism is pretty complex, and much effects how well it is absorbed in the intestines, and how much the kidneys choose to excrete. So it looks like when the body is having calcium issues in the US, that insufficient intake is not necessarily the issue. Contrariwise, even moderately high levels of calcium intake (2000 mg a day, twice the USDA recommendation for folks 19-50), seems to up the risks of prostate cancer significantly. So avoiding excessive calcium intake is probably a good idea, especially for older people with prostates, and having slightly over 1000mg of calcium a day, may or may not be helpful for people worried about osteoporosis.

So if you are an entirely "average" and "healthy" man or woman, the USDA recommendations are probably pretty close, but if you are a little taller, shorter, thinner, heavier or say genderqueer, you may need to modify them a little to better fit your own needs.  But "original physiology" is NOT the issue.  Sigh.  Take care of your bodies folks.  I know I personally love mine more than I used to, and am trying to draw on this motivation to be ever slowly better about my diet and exercise.

Oh, and one more thing.  Social gender, and gender of self-identity has many complex interactions with food choice, body-image, pressure to exercise, cooking skill and dozens of other things.  The CULTURE of nutrition is gendered in many, many complex and important ways, deserving many posts of their own, even if the physiology of nutritional needs cares far more about height, weight, and BMI, in most cases.  When we are approaching actual dietary advice, or figuring out actual strategies for ourselves - motivations, and habits, and all those social and cultural issues become critically important again ...

Sources

"The Transgender Brain." (2013?) Transas City. http://transascity.org/the-transgender-brain/

USDA Dietary Guidelines for Americans 2010 - http://www.cnpp.usda.gov/sites/default/files/dietary_guidelines_for_americans/PolicyDoc.pdf

The Harvard Medical School Family Health Guide “Good Nutrition: Should Guidelines Differ For Men and Women - http://www.health.harvard.edu/fhg/updates/update0906b.shtml

Roza, A. M & Shizgal, H. M. (1984) “The Harris-Benedict equation re-evaluated: resting energy requirements and body cell mass.” The American Journal of Clinical Nutrition.

Johnstone, Alexandra M; Murison, Sandra D; Duncan, Jackie S; Rance, Kellie A; Speakman, John R; Koh, YO (2005). "Factors influencing variation in basal metabolic rate include fat-free mass, fat mass, age, and circulating thyroxine but not sex, circulating leptin, or triiodothyronine". American Journal of Clinical Nutrition 82 (5): 941–948. PMID 16280423.

Muth, Natalie Digate. (2012) "Do men and women have different nutritional needs?" http://www.acefitness.org/acefit/healthy-living-article/60/2461/do-men-and-women-have-different-nutritional/

Tsang, Gloria. (2007) "Men vs. Women: Differences in Nutritional Requirements"   http://www.healthcastle.com/nutrition_men_women.shtml