| | Ed,
Thanks for your detailed reply. You make some good points, which are worth considering.
Nevertheless, I do have some reservations. I wrote, "Just because this diet was suitable for early man does not mean that it is suitable for modern man, even if, according to the abstract, our genes are still the same. Early humans had to endure periods in which food was relatively scarce. Therefore, those who stored calories more efficiently had a survival advantage, because they lived longer during times of famine. When food was not available, their metabolism slowed down, causing them to burn calories more slowly and be more likely to survive. And those who did survive under these circumstances were more likely to pass their genes on to the next generation.
However, in modern times, those genes may have the opposite effect. They may threaten your survival by causing you to gain too much weight and to develop diabetes, heart disease and cancer."
You replied, All true but irrelevant. In order for the above to be relevant to our discussion, it would have to differentiate between our diets. It doesn't. What the above says, indeed, all it says, is that we have a genetic preponderance for obesity and obesity-related disease. It doesn't say anything about the alternative macronutrient distributions -- or about the sources of calories -- between our diets. You say, "All true but irrelevant." Really? If it's all true, then doesn't that contradict your main premise, which is that the diet that was good early man is good for modern man? If the diet that was good for early man was relatively high in fat, it was probably on net low in calories, because of the periodic food shortages. That same diet if eaten on a daily basis without any periods of food deprivation would not be as beneficial. You can’t simply conclude that because early man ate a certain way whenever he could get food, we should eat that way.
I wrote, "The Pima Indians are a case in point. They develop Type 2 diabetes at 8 times the rate of white Americans, because the survival of their ancestors' was promoted by the capacity to store calories efficiently and to survive periods of food shortage." A "case in point" for what? For the fact that a diet that is good for people when food was relatively scarce is not necessarily good for them when food is relatively abundant and easily accessible. Pima Indians (1) eating more sugar, less fiber, less omega-3 fatty acids, and more omega-6 fatty acids ending up with obesity and Type 2 diabetes (2)? Well, that's not surprising (in spite of the high rate of disease development noted). I could have predicted that much. But what does it say about our current discussion? Well, not much. But it’s not just the diet; their metabolism is slower due to the presence of the so-called “thrifty gene,” which, by allowing them to survive periods of food shortage better than others, also makes them more susceptible to obesity and diabetes. Both of our diets have low sugar and high fiber, so this fact about the Pima Indians doesn't say anything there. Your diet has a higher omega-6:omega-3 ratio than mine -- making my diet more likely a useful solution to the Pima Indian 'diabesity' problem. I don't think that follows. You need to back that statement up with more evidence. The Pritikin/Ornish diet is so low in polyunsaturated, omega-6 fats that the ratio of omega-6 to omega-3 fats is probably quite good, is insignificant, because the extremely low-fat content of the diet makes one’s body more sensitive to insulin, which by itself works to prevent a rise in blood sugar. As I pointed out in a previous post, after a friend of mine who had Type 2 diabetes went on the Pritikin diet, she was able to go off her insulin entirely, much to the surprise of her doctor.
You mentioned that nuts were on the paleo diet. Nuts have a very poor ratio of omega-6 to omega-3 fats. For example, in almonds the ratio is a whopping 1800 to 1. In Brazil nuts, it's 1000 to 1, in pine nuts, 300 to 1; and in cashews, 117 to 1. If the ideal ratio of O6 to O3 is 2 to 1 or 1 to 1, nuts are a liability. There are no nuts on the Pritikin diet. (And please, no wise cracks!) On the other hand, there is fish; you can have fish every day, if you want. I eat sardines on a regular basis.
I wrote, “So, a diet relatively high in fat that enabled an early hunter-gatherer to survive periods of food shortage is not necessarily the best diet for modern man.” That's just begging the question regarding diets "relatively high in fat" and obesity and diabetes.
You didn't prove any connection of relatively high fat intake to obesity and diabetes, you just assumed it. Under your (false) assumption (that relatively high dietary fat makes you more fat and diabetic, and that less dietary fat means you'll have less body fat and diabetes), yeah, sure, your conclusion would follow. But you have to first prove your assumption -- against a mountain of evidence.
I could show you dozens of intervention studies where diets "relatively high in fat" caused more weight and/or fat loss than diets relatively low in fat (3). How do you explain that? How could you explain that? It runs diametrically opposite to your main assumption. I’m sorry. I was assuming high in calories as well, which I should have made clear. Of course, a diet that is high in fat but low in calories can cause more weight loss than a diet lower in fat but higher in calories. I could even show you studies where diets "relatively high in fat" led to less Type 2 diabetes, too. Think about it for a moment. The Mediterranean diet is relatively high in fat -- and it's so healthy!
Now this has me curious. This isn't my first or even second time telling you about this. This isn't our first debate on the subject. So why haven't you integrated this information yet? To be sure, a diet relatively high in fat, if it were very low in carbs, could lead to less Type 2 diabetes. I don’t deny that. But that doesn’t mean that it’s a healthier diet in other respects.
The Mediterranean diet, which you say is “so healthy,” was featured in the Lyon Diet Heart Study involving 300 patients in an experimental group and 300 control patients, all of whom had a recent heart attack. One group received the American Heart Association Step 1 Diet; the other, the Mediterranean Diet. The patients on the Step 1 Diet, which is similar to a traditional Western diet, did worse than those on the Mediterranean diet. Nevertheless, after four years on the Mediterranean Diet, 25 percent of the patients either died or had another major cardiac event. The Mediterranean diet did nothing to arrest or reverse heart disease;.it simply slowed its progression. An extremely low-fat diet, by contrast, can arrest and even reverse it.
I wrote, “Also, while our genes may be the same as those of our ancestors, their expression can be favorably altered through changes in diet and lifestyle.” Like above with the Pima Indians, this finding also supports my diet over yours. While your diet has a gene-expression-modulating phyto-chemical content similar to mine, my diet is higher in the key, gene-expression-modulating B vitamins and the omega-3 fatty acids). Here is an illustrative quote from the FAQ section over at www.thepaleodiet.com:
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Q: What do you think about epigenetics? Many scientists (in Germany) believe that the concept of the Paleo Diet is no longer tenable.
A: Epigenetics is defined as the science studying changes in phenotype or gene expression by mechanisms other than changes in DNA nucleotide sequence1. The phenotype is someone's appearance which it's determined by the genotype (stable and heritable) and the environment (nutrition and other lifestyle factors) which give place to the epigenotype (heritable, labile and rapid)1. Epigenetic changes are controlled, among other mechanisms, by methylation and histone modification. Altered methylation pattern and histone modification may lead to increased susceptibility to disease. E.G. cancer is associated to generalized hypomethylation and localized promoters hypermethylation1. Histone manipulation may also increase or decrease disease susceptibility2.
Both, methylation and histone manipulation are under the control of dietary substances. For example, methylation depends on SAMe availability, which in turn is influenced by vitamin B6, vitamin B12 and folate intake3, and long chain polyunsaturated fatty acids such as DHA4. On the other hand, certain substances such as garlic, horseradish, fiber, blueberries, apple, onion, nuts, berries, red grapes, broccoli, etc. are known nutrients involved in histone modification2.
The Paleo Diet is rich is all of these nutrients ... So is the Pritikin diet, with the exception of nuts, which as I indicated have an unfavorable ratio of omega-6 to omega-3 fats.
I wrote, “A study done at the School of Medicine, University of California, San Francisco found that over 500 genes were beneficially affected in this way. Disease preventing genes were up-regulated, and genes that promote heart disease, breast cancer, prostate cancer, inflammation, oxidative stress and other illnesses were down-regulated. The diet that accomplished this was a low-fat, plant based diet, not a paleolithic one.” It's a false assumption to say that the low-fat, plant based diet "accomplished" this (insinuating some kind of dietary superiority). This Ornish study, like his others, used many interventions simultaneously. And, like his others, the diet is, in turn, given the credit. It's almost like he's a charlatan out to sell diet books or something (or to just prove a pet theory). Not true. A study done in Finland, which was restricted to diet got similar results. [Kallio, P., M. Kolehmainen, D. Laaksonen, et al. 2007. Dietary carbohydrate modification induces alterations in gene expression in abdominal subcutaneous adipose tissue in persons with the metabolic syndrome: The FUNGENUT Study. Am J Clin Nutr 85(5):1417-27] If Ornish comes out and says that his diet deserves all the credit then I will know he is a fraud. One of the dietary supplements he was giving -- fish oil -- only provides evidence that the paleo diet (higher in fish than your diet) might have worked even better. Is it necessarily higher in fish than my diet, which allows fish to be eaten every day? Is fish required on the paleo diet, or just permitted? And if it’s required, how much are you supposed to eat? Just curious, how much fish do you eat, Ed? You had previously said that you ate a pound of meat a day. How much fish do you eat in addition to that? And do you also take fish-oil supplements?
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