 While randomized controlled trials are highly reliable in assessing interventions like drugs, they're harder to do with diet. Dietary diseases can take decades to develop. It's not like you can give people placebo food, and it's hard to get people to stick to assigned diets, especially for the years it would take to observe effects on hard endpoints like heart disease or cancer. That's why we have to use observational studies of large numbers of people and their diets over time to see which foods appear to be linked to which diseases. And interestingly, if you compare data obtained from observational population studies versus randomized trials, on average there's little evidence for significant differences between the findings, not just in the same direction of effect, but of the same general magnitude of the effect and about 90% of the treatments they looked at. But wait, what about the hormone replacement therapy disparity I talked about in the last video? It turns out when you go back and look at the data, it was just a difference in timing in terms of when the premarin was started, and they actually showed the same results after all. But even if observational trials did provide lower quality evidence, maybe we don't need the same level of certainty when we're telling someone to eat more broccoli or drink less soda compared to whether or not you want to prescribe someone some drug. After all, prescription drugs are the third leading cause of death in the United States. It goes heart disease, cancer, then doctors. 100,000 Americans wiped out every year from the side effects of prescription drugs taken as directed. So given the massive risks, you better have rock solid evidence that there are benefits that outweigh the risks. You're playing with fire, so darn right I want to randomize double blind placebo-controlled trials for drugs. But when you're just telling people to cut down on donuts, you don't need the same level of proof. In the end, the industry-funded sugar paper concluding that the dietary guidelines telling people to cut down aren't trustworthy because they're based on such quote-unquote low-quality evidence is an example of the inappropriate use of the drug trial paradigm in nutrition research. You say, yeah, but what were the authors supposed to do? If grade is the way you judge guidelines and you can't blame them, but no, there are other tools like, for example, Nutragrade, a scoring system specifically designed to assess and judge the level of evidence in nutrition research. One of the things I like about Nutragrade is that it specifically takes funding bias into account. So industry-funded trials are downgraded. No wonder the industry-funded authors chose the inappropriate drug method instead. Helm is another one. Hierarchies of evidence applied to lifestyle medicine specifically designed because existing tools such as great or not viable options when it comes to questions that you can't fully address through randomized controlled trials. In a way, each research method has its own unique contribution. In a lab, you can explore the exact mechanisms. RCTs can prove cause and effect, and huge population studies can study hundreds of thousands of people at a time for decades. Take the trans fat story. For example, we had randomized controlled trials showing trans fats increased risk factors for heart disease. And we had population studies showing that the more trans fats people ate, the more heart disease they had. And so, taken together, these studies forged a strong case for the harmful effects of trans fat consumption on heart disease and, as a consequence, it was largely removed from the U.S. food supply, preventing as many as 200,000 heart attacks every year. Now, it's true. We never had randomized controlled trials looking at hard endpoints like heart attacks and death because that would take years of randomizing people to eat like canisters of Crisco every day. You can't let the perfect be the enemy of the good when there are tens of thousands of lives at stake. Public health officials have to work with the best available balance of evidence there is. It's like when we set tolerable upper limits for lead exposure or PCBs. It's not like we randomized kids to drink different levels of lead and saw who grew up to have tolerable brain damage. You can't run those kinds of experiments, so you have to just pull in evidence from as many sources as possible and make your best approximation. Even if RCTs, randomized controlled trials, are unavailable or impossible to conduct, there's plenty of evidence from observational studies on the nutritional causes of many cancers, such as on red meat increasing the risk of colorectal cancer. So if dietary guidelines aiming at cancer prevention were to be assessed with the drug-designed grade approach, they'd reach the same conclusion that the sugar paper did, low quality evidence. And so no surprise, a meat industry funded institution hired the same dude who helped conceive and design the sugar industry funded study and boom, lead author saying we could ignore the dietary guidelines to reduce red and processed meat consumption because they used grade methods to rate the certainty of evidence and though current dietary guidelines recommend limiting meat consumption, their results predictably demonstrated that the evidence was of low quality. Before I dive deep into the meat papers, one last irony about the sugar paper. The authors used the inconsistency of the exact recommendations across sugar guidelines over a 20-year period to raise concerns about the quality of the guidelines. Now obviously we would expect guidelines to evolve, but the most recent guidelines show remarkable consistency with one exception. The 2002 Institute of Medicine guideline that said a quarter of your diet could be straight sugar without running into deficiencies, but that outlier was partly funded by the Coke Pepsi Cookie Candy-Funded Institute that is now saying, see, since recommendations are all over the place, thanks in part to us, they can't be trusted.