I have taken part recently in some interesting conversations on nutrition and I thought I would put down my current views on the topic. I will preface this with the fact that as an internal medicine physician my formal training in nutrition is minimal at best. The level of education on nutrition offered in even the most prestigious medical schools these days is embarrassing. We did not have even one course on nutrition and the whole topic was summed up in a few lectures over the course of my four years of medical school. In residency it was hardly ever mentioned. For something as important as what we put in our bodies multiple times a day and given that it in my opinion has the largest effect on health than any other behavior, this is appalling. So what I have learned about nutrition has been learned through my wife who is a naturopathic doctor and had extensive education on nutrition during her training, from self research and reading. There are two books that I have recently read that I highly recommend. Whole by T Colin Campbell (the researcher behind the famous China Study) which discusses not only nutrition and its role in our health but much of what is wrong with our current medical research and medical care delivery system. The second is In Defense of Food by Michael Pollan who also wrote The Omniovore’s Dilemma.
In my research I have found a few key facts. First, there has been very little research on food and nutrition. Again, I blame this mostly on the lack of profit incentive for the research to be done. No patented drug or medical device can come from the research hence no money. Therefore the investment simply is rarely made. Second, is that nutrition is far more complex than most of us think it to be, therefore studies that are done in test tubes or rats are often mistakenly and with disappointing results generalized to humans. Studies showed that foods high in vitamin C were good for you so supplementing vitamin C must be good for you. But experience has not shown this to be the case. Food high in beta carotene seemed to prevent cancer but supplementing it increased cancer. Same for vitamin E. So what is the problem? How come our research never seems to allow us to get to those isolated chemicals in food that make us so healthy? How come we are no closer to that pill that can make us healthy no matter what we eat now than we were 20 years ago?
The problem is complexity. With the micro-nutrients (minerals and vitamins) that we have isolated so far we have only scratched the surface of the over 10,000 phytochemicals in foods. Phytochemicals are plant made chemicals that have biologic functions in our body. So why can’t we simply isolate these and take them in pill form to achieve immortality and perpetual youth? Because we don’t even know what all of them are, or what they do to the body.
When you eat one piece of fruit you are likely taking in hundreds of phytochemicals. The quantity depends on the health of the soil that plant was grown in, how the growing season was that year, rainfall, sunshine, pests, symbiotic fungi and other organisms in the soil, how ripe the fruit was when it was picked, and even what time of day it was picked. Then when you eat that piece of fruit those chemicals will act on each other. Some blocking the absorption of others and others facilitating the absorption. Then as they act on your body some will deplete other nutrients in your body or increase them. And your body will change what it takes from the food based on its needs and current health. If the body needs more of a nutrient it will take in more and if it does not need it will not. Or absorption may be impaired by an infection or damaged gastrointestinal tract.
So when we see that a specific nutrient has antioxidant capabilities in a test tube, that does not mean that it will when combined in food form or in our bodies, or even that more antioxidant intake is what our body needs at that time. The only way to tell if an isolated nutrient of food is good or bad for us is to randomize a group of people to either receive the nutrient or food or not and compare the two groups. However, these studies are rarely done due to many issues I have discussed before. But these are really the only studies conclusions can be absolutely drawn from and that is why those studies are the final and necessary step before approving any pharmaceutical drug. But even pharmaceutical drugs prove the point as even though they are designed to have one desirable effect such as lower cholesterol or blood pressure they all have a long list of side effects because our knowledge of the complexity of the human body is still in its infancy.
So in the face of all this complexity what is one to do when deciding what to eat? Well in everything I have learned and come to believe I think it comes down to the basics of eating what evolved to eat as much as possible. Our diet has changed dramatically in the last 10,000 years since the spread of agriculture. And with industrialization our diet has changed even more in the last 100 years than in any other time in history. The problem is evolution does not act that fast and so our bodies are unable to adjust to such rapid change. And our changes in diet are based on taste preference and convenience, not on what is healthy for us. And the few health related food choices we make are based on very superficial and limited information.
Human history has shown us that humans can survive on a wide variety of foods. From Eskimos to Bedouins the climates we can survive in and the diets associated with the climates are amazingly diverse. But surviving on a diet and thriving on it are two very different things. Animals can adapt to survive on new food sources quickly as those that cannot survive on it die off and only those that can survive to reproduce. But the selective pressure between those that thrive on the diet and look healthier and have more energy get more mating opportunities separating them from those that merely survive but do not thrive on the diet can take hundreds of thousands if not millions of years. To put the time scale of evolution in perspective if you took all the time since the beginning of dinosaurs to now and compressed it into one day the dinosaurs would have existed for the equivalent of 18 hours. Humans would have been on earth now for the equivalent of 10 minutes. So the selective pressures on humans from evolution have been minimal at best. Most of our evolution happened before humans walked the earth.
With this in mind I find the best reference for what we should eat to be Chimpanzees and Bonobos. We share a common ancestor with these primates in the not too distant past and genetically they are the most similar to us than any other living thing on the planet. We share over 98% of our DNA with Chimpanzees. However, while our diet has changed dramatically in the last 10,000 years and even more so in the last 100, chimpanzees and Bonobos eat very similar diets to what our common ancestor would have eaten.
So what is this diet? It is the exact same diet that most of the research done on diet is showing us is healthy. A mostly plant-based diet with as wide a variety of plants as possible and very little lean meat. Chimpanzees eat about 60% fruit, 38% vegetables, nuts, seeds, leaves, and 2% meat (usually in the form of monkeys). There are usually well over 100 different types of plants in a Chimpanzee’s diet. And there are no refined grains in this diet such as wheat, corn or rice.
Given this I do not find it surprising that study after study shows that plant-based food decrease the risk for cancer and heart disease. That vegetarians and vegans have lower risk for diabetes and hypertension. That eating meat increases the risk for heart disease and cancer. In fact one study I have highlighted before showed that a vegan diet was better for diabetics by every health measure they looked at than the American Diabetes Association Diet.
Chimpanzees and their ancestors have had time to adapt so that they not only survive but thrive on this diet. Over millions of years mammals have been eating adaptations to this diet and with each generation those that are healthier, more robust appearing, stronger, and had more energy had more chance to mate and increase their numbers. This subtle pressure takes a long time, much longer than the 10,000 years that agriculture has been prevalent.
Only after the widespread use of agriculture did refined grains such as rice, wheat, and corn enter our diet in large amounts. And only after farming came about did we start to eat meat that was from domesticated animals such as cows and pigs that is much fattier and has much more omega 6 fatty acids which are inflammatory than omega 3 fatty acids which are anti inflammatory. The animals we ate prior to this we monkeys, deer, rabbit, squirrel and a myriad of other lean, wild and much healthier animals. Our ancestors used to eat about 50% omega 6 fatty acids and 50% omega 3. Today that ratio is about 15 to1 in the average Western diet. And only after farming did meat become such a large proportion of our calories.
There is no doubt we have evolved to the point where we can survive on this diet but given the increasing spread of heart disease, diabetes, cancer, and obesity it is clear we have not evolved to thrive on it.
I feel much more research on a microscopic scale will need to be done before we even have what we could consider a beginning to understanding the effect food has on our body. And I would love to see far more studies that randomize people to certain diets so we can actually draw some conclusions from them. Lets do a study randomizing people to a diet with naturally occurring foods with no refined grains or processed food and very little meat (preferably lean meat high in omega 3) and compare that to the American Heart Association diets, or ADA, or TLC, or Atkins diets. Diet is the most important health recommendation we make to a patient so it should be evidence based.
Until that happens I think we are best suited to staying on the diet we have evolved to thrive on. Clearly eating what we can survive on is not working.