 A series of articles, published in the Annals of Internal Medicine, culminated in a recommendation suggesting people keep eating their red and processed meat. Nutrition researchers savaged these articles. The chair of nutrition at Harvard called it a very irresponsible public health recommendation, and the past Harvard nutrition chair was even less restrained. It's the most egregious abuse of data I've ever seen, said Walt Willett. They're just layers and layers of problems. Let us start to pick through these layers. First of several serious weaknesses was that the analyses and recommendations were largely based on the so-called grade criteria, which I talked about in my last video. The authors aired and applying the grade tools since that was designed for drug trials. Grade automatically scores observational studies as low or very low scores for certainty of evidence, which is exactly what you want when you're evaluating evidence from drug trials. You want a randomized double-blind placebo-controlled trial to prove the drug's risks and benefits. However, the infeasibility for conducting randomized clinical trials on most dietary, lifestyle, and environmental exposures makes the criteria inappropriate in these areas, since it would involve controlling people's daily diet and following them for decades. You can't do a double-blind placebo-controlled trial of red meat and other foods on heart attacks or cancer for dietary and lifestyle factors. It's impossible to use the same standards for drug trials. Like imagine telling one group of people to smoke a pack of cigarettes every day for the next 20 years to prove that cigarettes cause lung cancer. And how could you make it double-blind, like have the control group smoke placebo cigarettes? Yet in the meat papers, they were downgrading studies due to lack of blinding. Well, duh. I mean, in nutrition trials, how are you going to blind people to the fact of what they're eating? Great is just the wrong tool for diet studies. In fact, the authors admit that the reason their recommendations differ from all the others is that other guidelines have not used the great approach. And the reason is you can't randomize people to smoke, avoid physical exercise, breathe polluted air, or eat a lot of sugar or red meat, and then follow them for 40 years to see if they die. Now, that doesn't mean you have no evidence. It just means you have to look at the evidence in a more sophisticated way. And alternative approaches to great exist, like, for example, nutrient grade, which have specifically been developed to evaluate evidence from studies of nutritional and lifestyle factors. So are the authors appeals to standards of evidence motivated by a genuine interest in getting to the bottom of it, or just to advance the financial interests of industry? As the same lead author had done previously at the behest of soda and candy companies. The tool he employed in his meat and sugar studies could be misused to discredit all sorts of well-established public health warnings, like the link between second-hand smoke and heart disease, air pollution and health problems, physical inactivity and chronic disease, or trans fat. Industries could use it to sow doubt in any field where randomized controlled trials are not feasible, such as climate change. What are you going to have, some placebo planet? Strict adherence to grade guidelines could even be used to question the link between smoking and lung cancer. I know you can't randomize people to smoke, but can't you randomize people to quit a randomized control trial of the effect on aged men of advice to stop smoking? Of those randomized to quit, 13.7% died within the study window, whereas of those in the control group who got no special instruction, only 12.9% died. In other words, it didn't work. Disappointingly, the researchers concluded, we find no evidence at all of any reduction in total mortality. Wait, so is smoking not bad for you after all? Of course not. Anyone see the fatal flaw? They didn't randomize people to quit. They randomized people to advice to quit smoking. It's not like they could lock people in a room for a few years. At last follow-up, the stop smoking group was smoking 8 cigarettes a day compared to 12 cigarettes a day in the control group, so no surprise, there was no difference in mortality since there was hardly any difference in smoking, and the same thing with diet. There have been massive randomized dietary trials, the Women's Health Initiative, the Multiple Risk Factor Intervention Trial, that wasted hundreds of millions of dollars because people just flat out failed to follow the dietary advice, so the groups ended up eating similar diets in the end, so had similar disease outcomes, just like the randomized smoking quit trial. And it's not like the failure was a result of inexperienced investigators. These trials were conducted by some of the very best research teams who invested enormous efforts to achieve their goals. But it just shows you can't really run decade-long randomized trials that require changes in eating behavior. People just won't do it. Randomized controlled trials couldn't even show an effect on mortality of smoking, which is pretty remarkable considering that smoking is one of the most powerful known risk factors in the world. So basically the foregone conclusion, putting any kind of junk to the test in this matter, would echo the New Meat Report conclusion that people should eat whatever they want and do whatever they want. It's like a hijacking of evidence-based medicine. Of course we want the best evidence possible, but the whole process is now being manipulated and misused to support subverted or perverted agendas. It's very exciting and attention-grabbing to say there's no need to reduce meat intake. It's less exciting to say we reviewed studies to evaluate the validity using a system not meant to evaluate the validity of these studies than what we found is nothing. When asked whether physicians can advise persons whether a salad is healthier than a bowl full of sugar, one of the senior co-authors of the meat papers responded that physicians should tell persons that the quality of evidence is low, so it depends almost entirely on their preferences. When green criteria do not allow us to strongly recommend against smoking a cigarette with your bowl of sugar, we believe that alternative grading systems are preferable.