It’s often assumed that the nutritional requirements of men and women are almost identical. Women lose iron through menstrual bleeding and therefore may require somewhat more iron than men. Some might also argue that women need more calcium and/or vitamin D, since they have a higher risk of developing osteoporosis. Finally, women may require more of certain nutrients during pregnancy. But other than that, not much attention is given to gender-related differences in nutritional needs. This may be an oversight, as there is some evidence to suggest that men and women have different requirements when it comes to the intake of several important nutrients, one of which is protein.
Five pieces of evidence support the hypothesis that men require more protein per kilogram of body weight than women
Before we begin, let’s point out the obvious so there’s no confusion: Women need to consume fewer grams of protein per day than men to stay in nitrogen balance, because they tend to have a lower body weight. This is not controversial, and not what this article is about. Rather, the hypothesis of this article is that women require less protein per kilogram of body weight than men. In other words, even if you have a man and a woman who weigh exactly the same and have similar physical activity habits, the woman will still require somewhat less protein.
Five different pieces of evidence support this theory…
1. The evolutionary evidence
Throughout the evolution of our genus, Homo, males probably ate more protein than females (on average). Hunter-gatherer societies are characterized by a division of labour: the men go out hunting and scavenging, while the women dig for tubers, collect berries, and take care of children. This is not to say that the men never participate in the latter activities, or that it’s unheard of for forager women to go out on a hunt; but in general, it’s safe to say that there is a marked gender-related difference in terms of the type of labour performed. This is likely how it’s been for millions of years, and it’s still the way things are done today. The Hadza, for example, are known to adhere to this practice.
The men of these types of forager communities will certainly bring back meat – acquired during a hunt – to the camp, where the women and children await; however, they also tend to consume some of it by themselves. And even if they bring it back to camp, they may end up eating more of it than the women, particularly if the women have been out gathering and eating tubers and other plant foods all day.
It’s obviously difficult to say anything with certainty regarding exactly what our primal ancestors ate. That said, there is a lot we do know. My belief, based on everything I’ve read and seen, is that Paleolithic men probably ate more meat, and hence more protein, than women. Perhaps needless to say, these are average values. There would have been variations between different hunter-gatherer bands, depending on location, climate, etc.
What this means is that the diets that conditioned the genome of the male members of our genus Homo likely contained somewhat more protein than the diets that conditioned the genetic make-up of the female members of our genus. Hence, men may have evolved to require somewhat more protein than women.
2. Differences in body composition between men and women
Women have (on average) less lean body mass than men, in proportion to total body weight, and therefore require less protein to maintain a stable level of muscle mass. This point is a continuation from the last section, in the sense that the male members of our genus developed more muscular bodies than the females, in part because they were more physically active, engaging in activities (e.g., running) that require muscular strength.
In a Paleolithic environment, being physically fit was a definite advantage in terms of survival and reproduction, particularly for the males, who were involved in strenuous activities such as hunting. Hence, natural selection would have favored individuals that were strong and physically fit.
3. Gender-related differences in protein metabolism during and after exercise
There are differences between the genders in the metabolic response to exercise. Both male and female athletes require more protein than sedentary people; however, the increase in protein requirement may not be identical between the two sexes. A 2000 paper indicates that the maximal increase (above the level needed by a sedentary person) is approximately 100% for elite male athletes and approximately 50-60% for elite female athletes (1).
Furthermore, females show a smaller increase in lean body mass following acute creatine loading as compared to males (1), and may catabolize less protein than men consequent to endurance exercise (2). Also, perhaps needless to say, men build muscle at a faster rate than women and therefore require more protein to recover optimally from resistance training.
4. Nitrogen balance studies
Nitrogen balance studies indicate that women might have a lower protein requirement than men (3, 4, 5). For example, a 2014 meta-analysis of nitrogen balance studies found that “there was significant difference in the natural logarithm of protein requirement when comparing data from males and females, with resulting values of 108.85 mg N/kg·d and 97.51 mg N/kg·d, respectively” (4).
It should be noted that nitrogen balance studies may underestimate human protein requirements (5). Nevertheless, nitrogen balance analyses do give us some insights into what constitutes the minimal level of protein intake needed to avoid a deficiency. Also, they can be useful for determining differences in protein turnover between men and women.
Since men tend to carry more muscle mass than females, in proportion to total body weight, and have a somewhat different metabolic machinery, it’s not really a surprise that nitrogen balance studies suggest that men require slightly more protein per kilogram of body weight than women to avoid a negative nitrogen balance. The 2014 paper quoted above indicates that the difference isn’t huge, but it’s definitely there.
5. Observations and anecdotal reports
My experience and observations suggest that men crave and need more meat and protein than women. I’m sure others have observed the same. Observational studies and anecdotal reports are not the strongest form of evidence, but they certainly shouldn’t be dismissed as insignificant. I don’t think it’s just a cultural thing that we look upon a steak of meat as “man food”, whereas salads and other plant-based dishes are often associated with the opposite sex.
One of the things I’ve noticed when living with women is that they don’t seem to have the same craving for meat as men do. Whereas some men, including myself, seem to deteriorate, both physically and mentally, on a low-protein diet, women seem to have fewer problems with eating a mostly plant-based diet. This is not to say that men need huge amounts of meat every day to function optimally, or that women barely need any protein at all. All I’m saying is that men in general seem to have a stronger craving for meat than women do.
What does this mean for you?
In my mind, there’s no doubt that the vast majority of people will benefit from eating more protein than what the dietary guidelines, which are based on nitrogen balance studies, recommend. This goes for both men and women. Protein can help you lose weight, build lean muscle, curb undesirable food cravings, and combat chronic disease.
For optimal results, include moderate amounts of high-quality protein in every meal and derive at least 20% of your total calories from this macronutrient. The exact intake level that is perfect for you depends on several factors, such as your gender and physical activity level and the inflammatory status of your body. If you’re a female, you may require somewhat less protein than if you are a male.
If you are healthy and know how to listen to the signals your body is sending you, the best tip may simply be to listen to your body, and let your appetite guide you towards an appropriate intake of protein.