字幕表 動画を再生する 英語字幕をプリント “Food as Medicine: Preventing & Treating the Most Dreaded Diseases with Diet” Good evening. For those of you unfamiliar with my work, every year I read through every issue of every English-language nutrition journal in the world so you don't have to. [Laughter, applause.] Every year my talks are brand new because every year the science is brand new. I then compile the most interesting, the most groundbreaking, the most practical findings to new videos and articles I upload every day, to my nonprofit site, NutritionFacts.org. [Applause.] Everything on the website is free. There's no ads, no corporate sponsorship. It's strictly noncommercial, not selling anything. I just put it up as a public service, as a labor of love. New videos and articles every day on the latest in evidence-based nutrition. In my 2012 review, I explored the role diet may play in preventing, treating, and reversing our deadliest diseases. In 2013, I covered our most common conditions. And in 2014, I went through our leading causes of disability. This year I'd like to address some of our most dreaded diseases, and cancer tops the list in the latest Gallup poll. The #1 cancer killer in the United States of both men and women is lung cancer. But if you look at the rates of lung cancer around the world, they vary by a factor of ten. If there was nothing we could do to prevent lung cancer, you'd assume the rates would be about the same everywhere, I mean if it just happened kind of randomly. But since there's a huge variation in rates, you assume there's some contributing cause. And indeed we now know that smoking is responsible for 90% of lung cancer cases. So, if you don't want to die of the #1 cancer killer by just not smoking, we can take 90% of your risk and throw it out the window. Colorectal cancer is our second leading cause of cancer death, and for that there's an even bigger spread around the world. So it appears colon cancer doesn't just happen, something makes it happen. Well, if our lungs can get filled with carcinogens from smoke, maybe our colons are getting filled with carcinogens from food. Why do African Americans get more colon cancer than native Africans? Why that population? Because colon cancer is extremely rare in native African populations, like more than 50 times lower rates than Americans, white or black. We used to think it was all the fiber that they were eating, However, the modern African diet is highly processed, low in fiber, yet there's been no dramatic increase in colon cancer rates. And we're not just talking low fiber intake. We're talking United States of America low fiber intake, down around half the recommended daily allowance. Yet colon disease still remains rare in Africa, still 50 times less colon cancer. Maybe it's because they're thinner and exercise more? No, they're not, and no they don't. If anything, their physical activity levels may actually be lower than ours. So if they're sedentary like us, eating mostly refined carbs, few plant foods, little fiber — like us, why do they have 50 times less colon cancer? Well, there is one big difference. The diets of both African Americans and Caucasian Americans is rich in meat, whereas the native Africans' diet is so low in meat and saturated fat they have cholesterol levels averaging 139, compared to over 200 in the US So yes, they don't eat a lot of fiber anymore, but they continue to minimize meat and animal fat intake, supporting evidence that perhaps the most powerful determinants of colon cancer risk are the levels of meat and animal fat intake. So why do Americans get more colon cancer than Africans? Maybe the rarity of colon cancer in Africans is associated with their low animal product consumption. But why? Did you ever see that takeoff of the industry slogan, "Beef: It's What's For Dinner." "Beef: It's What's Rotting in Your Colon." I remember seeing that on a shirt with some friends and I was such the party pooper —no pun intended— explaining that, no, meat is completely digested in the small intestine, and never makes it down into the colon. No fun hanging out with biology geeks. But it turns out I was wrong! It turns out up to 12 grams a day of protein can escape digestion, and when it does, it reaches the colon, it can be turned into toxic substances like ammonia. This degradation of undigested protein in the colon is called putrefaction, so a little meat can actually end up putrefying in our colon. The problem is some of the by-products of this putrefication process can be toxic. The same thing happens with other animal proteins. If you eat egg whites, for example, some of that can putrefy too. So you say, wait a second. There's protein in plants, too. Ah! The difference is that animal proteins tend to contain more sulfur-containing amino acids like methionine, which is found concentrated in fish and chicken, and then eggs. Less in beef and dairy, but much less in plant foods, which can be turned into hydrogen sulfide in the colon, the rotten egg gas that, beyond it doesn't just smell bad, but it can produce changes in the colon that increase cancer risk. Now there is a divergence of opinion as to whether it's the animal fat, cholesterol, or animal protein that's most responsible for the increased cancer risk, but as all three have been shown to have carcinogenic properties, but, I mean, does it really matter since a diet high in one is high in the others. But the protein does more than just putrefy, though. Animal protein consumption causes an increase in blood levels of a cancer-promoting growth hormone called IGF-1. But remove meat, egg whites, and dairy proteins from our diet, and our bloodstream can suppress cancer cell growth about eight times better. An effect so powerful that Dr. Ornish and colleagues appeared able to reverse the progression of prostate cancer without chemo, without surgery, without radiation — just a plant-based diet and other healthy lifestyle changes. The link between animal protein and IGF-1 may help explain why those eating low carb diets tend to die sooner, but not just any low carb diets— specifically those based on animal sources, whereas actually vegetable-based low carb diets were associated with a lower risk of death. But meat-based low carb diets are high in animal fat as well. So how do we know it wasn't the saturated fat and cholesterol that was killing people off and had nothing to do with the animal protein? What we would need is a study that, you know, follows a few thousand people and their protein intakes out for 20 years or so and just see what happens: who gets cancer, who doesn't; who lives longer? But there's never been a study like that... ...until now. [Laughter.] 6,000 men and women over age 50, across the US, were followed for 18 years and those under age 65 with high protein intakes had a 75% increase in overall mortality, a 4-fold increase in dying from cancer. But not all proteins. Specifically animal protein. Which makes sense given the higher IGF-1 levels in those eating excess protein. Eating animal protein increases IGF-1 levels, which increases cancer risk. The sponsoring university sent out a press release with a memorable opening line: "That chicken wing you're eating could be as deadly as a cigarette—” [Applause.] —explaining that eating a diet rich in animal proteins during middle age makes you four times more likely to die of cancer — a mortality risk factor comparable to smoking. Look, almost everyone's going to have a cancer cell or pre-cancerous cell. And at some point the question is: does it progress? And that may depend on what we eat. See, most malignant tumors are covered in IGF-1 receptors, but if we have less IGF-1, the tumor may not progress. And it wasn't just the more deaths from cancer. Middle-aged people who eat lots of proteins from animal sources were found to be more susceptible to early death in general. Crucially, the same did not apply to plant proteins like beans, and it wasn't the fat; it was the animal protein that appeared to be the culprit. So what was the response to this revelation that diets high in meat, eggs and dairy could be as harmful to health as smoking? One nutrition scientist replied that it was wrong and potentially dangerous. Not the discovery animal protein might be killing people, but the way they were telling people about it. It could damage the effectiveness of important public health messages. A smoker might think "why bother quitting smoking if my cheese and ham sandwich is just as bad for me?" [Laughter.] You know, that reminds me of a famous Phillip Morris cigarette ad that tried to downplay the risks by saying "you think second-hand smoke is bad, increasing the risk of lung cancer 19%, drinking one to two glasses of milk every day may be three times as bad— 62% increased lung cancer risk. Or doubling the risk frequently cooking with oil, or tripling your risk of heart disease eating nonvegetarian, or multiplying your risk six-fold eating lots of meat and dairy." So, they conclude, let's keep some perspective. [Laughter.] The risk of lung cancer, the risk of second-hand smoke may be well below the risk reported for other everyday activities. So breathe deep, basically. That's like saying, "Oh, don't worry about getting stabbed because getting shot is much worse." How about neither? Two risks don't make a right. [Applause.] Though you'll note, when Phillip Morris bought Kraft, they stopped throwing dairy under the bus. [Brief laughter.] The heme in the ham may also play a role. Heme iron is the form of iron found in blood and muscle, and may promote cancer by catalyzing the formation of carcinogenic compounds. Cancer has been described as a ferrotoxic disease: a disease, in part, of iron toxicity. Iron is a double-edged sword. Iron deficiency causes anemia, but excessive iron may increase cancer risk, by acting as a pro-oxidant, generating free radicals that may play a role in a number of dreaded diseases like stroke. But look, only the heme iron, the blood and muscle iron, not the nonheme iron that predominates in plants. Same with heart disease – only the heme iron. Same with diabetes – only the heme iron. And same with cancer. In fact, you can actually tell how much meat someone is eating by looking at their tumors. To characterize the mechanisms underlying meat-related lung cancer development, they asked lung cancer patients how much meat they were eating, and examined the gene expression patterns in their tumors, and identified a signature pattern of heme-related gene expression. Though they just looked at lung cancer, they expect these meat-related gene expression changes to occur in other cancers as well. The safest form of iron then is non-heme iron, found naturally in abundance in whole grains, beans, split peas, chickpeas, and lentils, dried fruits, nuts, and seeds. How much money can be made on beans, though? So the food industry came up with blood-based crisp bread made out of rye and cattle and pig blood, one of the most concentrated sources of heme iron, about two thirds more than chicken blood. Though if blood-based crackers don't sound appetizing, they do have cow blood cookies or blood filled biscuits. The filling does end up "a dark-colored, chocolate-flavored paste with a very pleasant taste." Dark-colored because spray-dried pigs blood can have a darkening effect on the food product's color. But the worry is not the color or the taste. It's the heme iron, which because of the potential cancer risk is not considered safe to add to foods for the general population. This reminds me of nitrosamines, a class of potent carcinogens found in cigarette smoke. They are considered so toxic that carcinogens of this strength in any other consumer product destined for human consumption would be banned immediately. And if that were the case they would have to ban meat. One hot dog has as many nitrosamines and nitrosamides as five cigarettes. And these carcinogens are also found in fresh, unprocessed meat as well: beef, chicken, pork. But practice Meatless Mondays and you could wake up Tuesday morning with nearly all of these carcinogens washed out of your system. So toxic, nitrosamines should be banned immediately, but are still allowed for sale in cigarettes and meat because the carcinogens are found there naturally. It would be illegal to add them, but hey, if they're found... Right? Just like the heme iron, not safe enough to expose the general population to, but allowed for sale at the deli counter. The irony is that the iron and the protein are what the industry boasts about. Those are supposed to be the redeeming qualities of meat: protein and iron, but sourced from animal foods may do more harm than good. And that's not to mention all the other stuff, like the saturated fat, industrial pollutants, and hormones, that may play a role in our third leading cancer killer, breast cancer. Steroid hormones are unavoidable in food of animal origin, but cow milk may be of particular concern. The hormones naturally found in even organic cow's milk may have played a role in the studies that found that a relationship between milk and dairy products with human illnesses, not just like teenagers' acne; but prostate, breast, ovarian and uterine cancers; many chronic diseases plaguing the Western world; as well as male reproductive disorders. From an increased risk of early puberty all the way to endometrial cancer in older women. But hormonal levels in food could be particularly dangerous in the case of vulnerable populations, such as young children and pregnant women in which even a small hormonal intake could mean a large change in metabolism. Look, dairy milk evolved to put a few hundred pounds onto a calf, but the consequences of a lifetime of human exposure to the growth factors in milk have not been well studied. We know milk consumption increases IGF-1, which is linked to cancer, and we're milking cows while they'