The Answer to the Pritikin Puzzle

 matchalover: Great questions.

I am not an expert and can not answer all of your questions.  However, I thought you might be interested to know that the Portland VegFest conference this last weekend featured speaker, Mark Messina, PhD.  “Dr. Messina has devoted his time primarily to the study of the health effects of soy foods and soybean isoflavones.”

After looking at all the science around soy, his bottom line was that people *should* be eating soy foods.  There were some limitations.  For example, Dr. Messina did point out the same case study that Dr. Greger points out where a man drinking huge amounts (12 cups?) of soy milk every day ran into problems.  But he felt that all the research points to an over all health benefit from a certain number of servings of traditional soy foods (like tofu and tempeh) each day.

I only caught the last part of the speech.  So, I don’t know if he addressed IFG-1 specfically, but I did catch his bottom line and I do know that he *did* address cancer.

That said, I do know that Dr. Greger has videos coming up with titles such as:   “Too much soy may neutralize benefits” and “How much soy is too much?”  So stay tuned.  Based on all of the videos from Dr. Greger and based on the talk by Dr. Messina, it is my guess that like many things (such as protein, vitamin A, etc.), there is an optimal range for soy food intake.  You don’t want too little or too much.

 Apparently, eating less food includes eating less of the bad food that increases IGF-1 in our bodies. I don’t think it’s a matter of a vegan vs. an omnivore diet, but a matter of the specific nutrients in a food, vegan or animal. Seems to me that we’re better off eating most plant foods since this is what nature suggests. Our ancestors weren’t fast enough to run down animals, didn’t have claws and fangs, so they naturally ate plants. But when their ideal foods were in short supply or they were less in tune to their instincts, they became scavengers and ate whatever was available. It’s possible however that not all plant foods were part of our original diet or are healthy for us- especially processed, concentrated soy, as Dr. McDougall gives evidence for in  http://www.youtube.com/watch?v=mHYFOJBU434 so it’s probably best to avoid it as a staple. Legumes, along with grains and some other plant foods have anti-nutrients and poisons in them, although some of them can be removed by cooking. But not all of them. And I don’t know whether the first humans cooked or not. So it’s possible that not all of grains or legumes are totally healthy even after this processing or part of our native diet. All I can conclude is that just because it comes from a plant, that doesn’t mean that we should eat it. I would guess that most traditional vegetables and fruits are safe though- although I wonder about the nightshade family of vegetables for example, are safe at least some people who seem to be sensitive. And there is evidence that cultures have thrived on white rice for example, the bran containing some toxins.

 Hi,

I also watched that BBC documenatry, and I would love to know the answer to that as well. The documentary is: BBC Horizon 2012: Eat, Fast and Live Longer.

Liz: While you can find studies to show anything you want, the way to get your answers is to look at the body of scientific evidence. That body of evidence is pretty clear, with studies favoring plant based diets FAR outweighing studies saying anything else.

Concerning your specific questions: “Haven’t studies comparing vegetarians vs. non-vegetarians always concluded pretty much same all cause mortality” No. I’ve seen studies where vegetarians and vegans live longer. The latest study I saw put vegetarians at 7 years longer life. Based on what we know about nutritional science, I would expect whole-food vegans with b12 supplement to live even longer – precisely because we get less cancer, heart disease, etc.

“The vegetarians died of cancer.. just like the meat eaters, and had higher probability of getting certain cancers?”
No. Not just like. One thing to remember is that there can be a huge difference between vegetarian and vegan. Vegetarians can end up getting as much animal protein as meat-eaters. Dr. Greger recommends eliminating animal products, not just meat. So, it probably isn’t hard to find studies that show small effects on vegetarians. However, vegans have been shown to have signficantly less cancer, especially breast, prostate, colorectal and I believe others. I highly recommend that you read The China Study if you want to educate yourself on the link between diet and cancer. You might also watch Dr. Greger’s video Uprooting the Leading Causes of Death – available on this site.

re: “The vegetarians died of cancer…”
One thing I like to remind people is that lowering probability of something happening is not the same thing as guaranteeing that it won’t happen. If I find out that I lower my risk of getting cancer by say (I’m just throwing out a number to make a point) 50%, I consider that a significant reduction and worth my effort. Put another way: If two people in your family would get cancer by doing nothing, but one person could be saved by doing something, wouldn’t it be worth it to do something?

So, what is the actual probability/lessening of risk? That depends on types of cancers, environmental factors, which studies you look at, etc. But one think is almost always clear: The lessening of risk is significant. So, to answer your question: “Am I restricting what I eat unnecessarily?” That’s for you to answer. But if you want the best chance of avoiding the most common diseases afflicting Americans and other Western cultures, then the answer is very clear: NO. You are doing exactly what you need to do to help yourself.

Best of luck to you.