Well, I had to cringe when I saw how long it's been since I've posted. I will provide the usual excuses for work, internet issues, family issues, etc getting in the way. My passion for educating people on nutrition and skepticism hasn't gone away though, and I was prompted to post again after being alerted to some comments made on a blog produced that is produced here in my local area.
If you haven't already found Dogma Debate, it's time to add it to your watch list, particularly if you are interested in seeking out the truth by using science. My comments reference show #78, which was co-hosted by Rachel and Aron (the main host, Dave, was absent). At about the one hour mark a listener called in with a question regarding evolution and our diet, specifically whether or not we should be eating meat or not. The caller did state that he was a passionate vegan, and Rachel did mention that she was not an expert in that area (she does have expertise in evolutionary biology, however). As an RD/CDE, my credentials indicate this is my area of expertise, so let me chime in as though I was on the show.
First of all, evolutionary reasoning may explain why things are the way they are today, but they do not explain how things "ought" to be; the latter falls under modern science. In other words, we can look at our evolutionary past, say, "the evidence indicates that we evolved as omnivores" but it doesn't say "we should continue to eat a certain way based on how things were for x number of years." Which brings me to another misunderstanding of evolution when it comes to the way we eat, we weren't "naturally selected" to eat anything. Hominids have evolved eating whatever they could get their hands on, so to speak, and that shaped how we evolved, not the other way around, particularly since what we could get our hands on was not always the most nutrient dense product. We can look at evolution and say "yes, our ancestors ate animal flesh at it shaped them a certain way" and "what was it about the animal flesh that humans needed and we modern humans might need now" but not "should we keep getting these nutrients from the same source when their are other sources available?"
Second of all, I think I need to point out that people in my profession talk about eating for good "health," we are talking about how to eat in such a way that you can have the strength do to your daily tasks well (aka. physical fitness) and that you are relatively disease free (or that you have brought your chronic conditions under control). When an evolutionary biologist talks about fitness, however, he/she is looking at how many offspring a species can leave behind. I have been guilty of mixing up the terms as well, and have been very glad when other scientists have called me out on it. In other words, you could actually be able to reproduce on a diet of fried white flour with a vaguely chocolate coating, but would you actually be disease free and able to climb stairs without getting short of breath? The answer to that last question (which I am not giving anyone permission to try) needs to be tested by principles of modern science, not merely looking at our hominid ancestors and stating "they didn't eat such as such."
So, it looks like we will get answers about "what" we ate from our past, but not "should" we eat it to suit our modern idea of health. Can we still use any of the information about the "what" to make decisions about our modern way of eating, however, when it comes to eating meat? Maybe. If at the very least we can look at what we do know about what our ancestors ate, figure out how they benefit/do not benefit the human body, and find modern equivalents that still give us the same benefit, we might be able to start figuring out how much and how often we should eat certain foods. We also know, as Aron pointed out, that there is a documentated correlation between when meat entered the diet and cranial size increase, and that it can become more difficult to maintain the appropriate level of macro and micronutrient intake if we seek out other sources that have not been part of our history. I didn't say it was impossible, but it does require more work, and people need to understand what they are undertaking.
I do slightly disagree with Aron and the callers statement that the decision is merely an ethical one as oppossed to merely looking at the chemical composition. I think we need to look at both the health implications of the people involved and the ethics of eating animals. I will disclose, as I have on other parts of this blog, that my specialty is diabetes, I work with an elderly population, my significant other has Type 1 diabetes, and I myself have celiac disease. When it comes to diabetes, the macronutrient composition, particularly carbohydrate, has a large influence on how well one can maintain those good readings on the blood sugar meter, how much pharmaceutical help a person might need, and what kind of complications can be prevented later. For example, let's say you know that you need to keep your carb intake about 30 grams a meal (I know, some of you are lower), and about 20-30 grams of protein. If I eat a 3oz chicken breast, I get about 21 grams of protein and no carbs, I get my protein and I might even add in some sweet potato fries and green vegetables to get some carb and micronutrients/fiber. If I eat beans and rice to get a complete protein--I would need to eat about 1.5 cups of beans and 1/3 of a cup of rice. I would now be at about 45 net carbs (or more, depending on the beans), and probably see a significant increase in my blood glucose. I will probably make the decision to not rely on legumes for my health (someone else might do a better job of finangling the numbers, but not everyone can or will). I also know that because of my condition, most grains (including the gluten free kind), legumes, dairy, nuts, and soy cause me unbearable pain, so if I want protein, animal products is the way to go. Now, those of us that find our quality of life and overall health is better because we eat animal products can still make decisions about eating humanely raised meat, find other ways to minimize our impact on the environment, and even find some alternate ways of cooking/processing certain foods (like legumes, for me) that allow nutrients to be absorbed more efficiently.
And we also need to remember that the way a person labels their diet doesn't always indicate how healthy or how sustainable he/she eats. I've know people who eat vegan who subsist mostly on sugar-added peanut butter on white bread, and I've known vegans that carefully prepare nutrient dense meals of locally grown produce and soaked/sprouted beans with quinoa. I've know low carb people that eat grass-fed beef with (again) locally grown produce and other low carb people who subsist on processed foods like atkin's bars, etc. When you change your diet, know what you are in for, don't just follow someone else's advice.
Hmmm....I wonder if I might be too long winded for a podcast?
For a bit more info: David Despain provides a great summary of the symposium "The Evolution of Human Nutrition" here. Read what he says in the comments too!