Protein, menopause and health risks: facts versus fear-mongering

Someone asked me to comment on claims that a higher protein diet was problematic for post-menopausal women due to an increase in vasomotor symptoms (hot flushes), cardiovascular risk (plaque build-up on the arteries, and arterial stiffening) and risk of type 2 diabetes. It’s from this blog here, and I think this is a good illustration of different interpretations of the literature, and bias. I am (as you know) bias towards a higher protein diet. I'll say up front, that there is always individual variation - and I don't want to make broad-sweeping statements that might not suit all people. However, I'm hear to address the notion that (as a rule) women in the menopause transition need to avoid protein. Based on the blog, I've put a few of my thoughts below.

From a fat loss perspective, eating excess protein has been shown to be the least likely nutrient to increase overall fat gain, even when eating in excess calories. However, if your protein sources also deliver fat (think: pork belly) then yes you can gain weight. It is calories though, not the protein itself. Animal protein does contain saturated fat, however it has as much monounsaturated, if not more, than saturated fat, so I always find this an interesting argument against it, given that monounsaturated is protective in all realms of heart health, and you can always buy lean meat that has very little fat in it.

The idea that a higher protein diet stimulates more vasomotor symptoms is due to the thermogenic effect of eating more protein. Protein takes more energy to digest and absorb, in addition to the energy used in creating a muscle protein synthetic response. It is true that the thermic effect of protein is higher than that of carbohydrate and fat, and that this does increase body temperature, however the evidence would suggest that it is minimal and is more extreme if you are a rat, or a pig in an extreme environment. There is minimal evidence in humans, less in menopausal women, on this topic.

 There have been observational reports of women who follow a vegan diet having less vasomotor symptoms than those following an omnivore diet. That is interesting but isn’t the totality of the data. This observational study found macronutrient intake had no impact on vasomotor symptoms, and instead poor cardiovascular fitness and high fasting glucose that increases risk of night sweats and hot flashes. Let’s not forget, though, that nutrition epidemiology has several limitations and can’t be relied upon to determine cause and effect. Someone who follows a vegan diet is more likely to have other lifestyle factors that contribute to an overall healthier lifestyle. This study found that the most notable difference in the diet came from increased berries and vegetables that helped improve symptoms for the group in total (the fibre perhaps. In addition, those in the vegan diet did significantly more exercise than the omnivore group, as mentioned above this impacts on symptom severity.  Further, protein from dairy products may impact on vasomotor symptoms through an increase in inflammation from the A1 beta casein that can promote inflammatory processes if sensitive. A vegan diet is also likely to be higher in fibre. Fibre helps the removal of excess oestrogen that is responsible for vasomotor symptoms. These factors are hard to adjust away despite sophisticated statistical analysis.

 Blood pressure and cholesterol increases during the menopausal transition are often the result of dietary and hormone changes. Oestrogen is involved in cholesterol metabolism. When this drops, cholesterol tends to increase. Blood pressure increase can be the result of blood sugar elevations and increasing insulin, as oestrogen is an insulin sensitising hormone, once this drops, a diet higher in carbohydrate could impact on blood pressure. Most studies investigating the effect of protein on blood pressure would suggest that the opposite is true. For those who are overweight and have hypertension, a higher protein diet can improve blood pressure. The same was found in this study here. This meta-analysis of clinical trials concludes a favourable effect of higher protein on both blood pressure and cholesterol.

 While there are mechanistic trials that show an increase in macrophage activity that may promote atherogenesis, there are no human clinical trials to show this is the case. The research that is cited with this pathway found that first, leucine (an amino acid, the one that initiates muscle protein synthesis) is also responsible for mTor signalling and that protein in excess of 22% dietary energy in male mice accelerates atherosclerosis. In mice, this is a stronger signal and the effects of this occurs much more quickly due to the higher metabolic rate of mice. T-helper cells in mice and humans differ in their immune responses, with mice often showing a stronger Th1 (pro-inflammatory) response, while humans have a more balanced but complex interaction among Th1, Th2, and T-regulatory pathways. Further, the effect was in male mice and is used to justify lower protein intake in women. For these reasons, this is not a good reason to warn women off the macronutrient that is so important as we age.

There is no good evidence that a high protein diet impacts negatively on liver, the gut thyroid or kidney health. This is a myth that won’t die. Of course, I too remember lecturing on the negative impact of a high protein diet on the kidneys. I’d like to take this opportunity to apologise to all my students for my role in spreading this misinformation. There’s not a ton of human clinical data looking at protein’s effects on the liver, this study suggests a higher protein diet reduces liver fat and markers of inflammation. The evidence for protein negatively impacting the thyroid is weak, and most would agree that studies such as this are reflecting the impact of a low calorie diet, not the impact of a high protein diet. If anything, a low protein diet could negatively impact thyroid function, not a high protein one. When it comes to the gut, certainly some people struggle to digest protein-based foods. I notice this especially when people are increasing their protein intake, and it could be that their gut is not used to the additional protein and needs more digestive support using something to stimulate the stomach acid or added digestive enzymes. The body does adjust though.

 What we are certain of, though, is that an increased body fat level, and increased insulin resistance because of lower oestrogen increases risk of cardiovascular disease. And, when it comes to diet, carbohydrate intake is something to be mindful of with both health concerns, not protein. Protein stabilises blood sugar levels (it doesn’t drive blood sugar up) and regulates appetite – both of which helps protect against excess body fat and the development of insulin resistance. It is always opportunity cost when it comes to diet. If someone is recommending a lower protein diet, then they are also advocating for a higher carbohydrate diet, as we must get our calories from somewhere. It makes it more difficult to adhere to an appropriate calorie load without the satiation effect of protein, thus increases the risk of gaining body fat. This fat gain is more likely to be around our midsection due to the lower oestrogen level, and this increases our risk of inflammation and insulin resistance.

 I’m also going to point out the obvious here too: there are many many smart people who firmly believe that women need to be eating more than 1.5g per kilogram of bodyweight in protein. These are scientists who truly understand protein metabolism and the effects of ageing. This most recent review of literature suggests protein is protective against the development of type 2 diabetes (not responsible for it).

What we do know is that protein is important for bones, muscles, appetite regulation and hormone production. And our brains need MORE protein in one meal as we age to stimulate muscle protein synthesis. This isn’t dangerous for cardiovascular disease risk and in fact the research would suggest the obvious. The thing that IS dangerous is that women are at greater risk of cardiovascular disease as we age because of lower oestrogen. We are also at greater risk of early death if we have a fall that results in a fracture. We need the substrates that protect muscle and bone – that is, protein (and, of course, activity). To suggest we need to worry about too much protein for most women in the menopause transition does not line up with what most of the literature says.