I just finished listening to the book, T
he Story of the Human Body: Evolution, Health and Disease by
Daniel Lieberman, a professor of Biological Sciences at Harvard. It was interesting, especially the first part where he described how we branched from apes and chimps and became bipeds roaming the grasslands and eating more tubers and grasses and meat; and how we evolved to walk and run long distances, and how we would just wear down the faster animals, and how we can handle heat more than most animals. It makes me realize I wasn't being kind to my dog by taking him on long jogs in the heat of the day in Louisiana summers! Later in the book he talked about diseases of mismatch caused by living in our current environment that is so different from that in which we evolved. I didn't agree with some of his views on what's wrong with the modern diet, but I was interested to learn about how myopia and impacted wisdom teeth are results of our modern behavior (reading and being indoors a lot; and eating soft food).
Some of my curiosity about the book has to do with what diet did we evolve to eat? That might not be the correct question really since we evolved to be adaptable to a variety of diets. But there is a diet that we ate more of during the tens of thousands of years that we became "human" and that was the hunter-gatherer diet. Now I think there is some disagreement about what that was, and there was a lot of variation in time and place for the humans and humanoids. But my understanding from Dr. Lieberman is that our ancestors at tubers, fruit, grasses, meat, fish, and nuts and seeds. The tubers were barely digestible and we used tools to smash them until edible and at some point started cooking them. I wonder what the grasses were, things like wild oats and wheat? Those too were smashed. I wonder what the nuts and seeds were like. Isn't quiona a seed? and that's more like a grain than a sunflower seed as far as it's nutritional content goes. I'm kind of surprised that nuts and seeds were that abundant, but it doesn't appear to be in question that they made up a significant portion of the diet. There's a lot of variation in estimates about how much meat they ate, and there was probably a similar variation in different populations. Of course, all of these foods were different from today's versions. Our ancestors developed very strong and large jaws from chewing food--which allowed plenty of room for their wisdom teeth!
An interesting thing I learned was that life for hunter gatherers was generally more pleasant than the back-breaking work of the agriculture eras. Wow, I guess progress is not necessarily a good thing for us. And the agriculture era was when diseases of mismatch began, which I didn't know.
Relating this to my diet, it makes me question some of what I learned from my favorite plant-based diet gurus, while also questioning Dr. Lieberman. Before getting to that I will say that even if my ancestors ate meat, it doesn't mean I have to. I have the choice not to and I think it's the correct and moral choice. But it's worth looking at what nutrients I could be missing from not eating meat, and making up for that in my vegan diet. So here are some thoughts I have after reading the book:
1) First an issue with Dr. Lieberman's assertion that mismatch diseases began in the agricultural era, including heart disease and cancer. He blames carbs and sugars for a lot of our ills--that's a popular thing to do these days. But the China study showed that rural Chinese eating a mostly vegan diet had essentially no heart disease or cancer. And they eat a lot of rice. So chalk one up for agriculture and carbs. However, none of these groups were perfectly vegan so they had more than the minimal amount of fats in their diets, which is related to my next point.
2) One thing that makes me concerned about the McDougall/Esselstyn low-fat vegan camp is that our ancestors did eat meat and nuts and seeds, and that provided more fat than we might get from the low-fat vegan diet. When I follow McDougall/Esselstyn, my fat percentage is only 5-7%. Dr. McDougall says this is enough. But there have never been humans who ate this low amount of fat since there have never been fully vegan populations as far as I know. This is where Furhman makes more sense to me. He points out that nuts and seeds have a similar nutritional profile as meat. And our ancestors ate them (though again, how similar to today's versions I don't know). Just 1 ounce of nuts and seeds raises my fat percentage to 15% which seems closer to what our ancestors ate (I've seen estimates ranging from 15-50%). And eating some flax, chia or hemp seeds adds the ALA compounds that can be converted to omega-3s by our body. Of course, 1 oz of nuts and seeds doesn't conflict with any of the doctors, but they sure do get in a lot of arguments about them. Dr. Fuhrman cites lots of studies about the health benefits of nuts, and Jeff Novick and Jeff Nelson point out all the flaws in the studies. A lot of people conclude, as I did, that you don't need any. Now my thinking is, I agree the studies are flawed, but maybe there's still good reason to include them if you are vegan (and don't eat oil) in order to increase your fat percentage. Also I get skin rashes when I don't eat any nuts or seeds at all and my nails get brittle.
3) Then there is the glycemic issue. Some call it the carb or starch issue, but to me it's a blood sugar issue, that is, how quickly does a food get converted to sugar and get into your blood stream? Dr. McDougall asserts that we are starchivores and that glycemic index is a non-issue. For me, it's an issue I can feel. I don't test my blood sugar, but I know how I feel after eating pancakes with maple syrup. And unfortunately, I don't feel so hot if I eat nothing but Japanese sweet potatoes--not surprising since they taste like candy after I over-bake and refrigerate them (soooo good though). I think this is a situation of modern agriculture turning whole foods into, well, candy. There is an argument about white potatoes between the Fuhrman and the other guys too. I find white potatoes don't bother me as much as Japanese sweet potatoes. I haven't tried eating only potatoes so don't know how much is too much for me but 1 serving a day seems fine for me. I think beans are a good starch to eat because they haven't been bred (yet) to be super digestible. I find that I am sensitive to high glycemic foods such as whole grain flours, dried fruit, and lots of potatoes and sweet potatoes; and feel better if they don't make up the majority of my calories.
So my conclusion today is that I prefer to eat a vegan, low-glycemic diet that includes some nuts and/or seeds. Before modern agriculture, probably all whole foods were low-glycemic but I'm not sure that's the case with modern starches. Beans (legumes), on the other hand, are still a good low-glycemic starch. I would prefer to limit potatoes, squash, corn and intact whole grains to a few servings per day. And the same goes for a lot of fruits: I'll try to eat more berries along with my bananas. So my idea of an optimal vegan diet in today's world is one that includes raw and cooked vegetables (more non-starchy than starchy), beans, nuts and seeds, and some fruit. It's a lot like the Fuhrman diet, but without the smoothies and veggie juices.
