Now You See It and Now You Don't

I'm sure anybody following the news about nutrition research has noticed the now-you-see-it-and-now-you-don't nature of the evidence for the benefits of eating less meat. Epidemiological research seemed to indicate that people who ate less meat tended to have longer life expectancies. Then large numbers of people tried adopting the correlates of low-meat diets (e.g., low fat) and the advantages disappeared. That might mean the correlates of a low-meat diet in the ‘wild’ differ from the correlates of such a diet when deliberately adopted. One possible such correlate is that a low-meat diet in the wild tends to be a high-beans diet. In other words, it might be a high-protein, low-methionine diet. When low-meat or low-fat diets are deliberately adopted they tend to be high-grain. Grain protein is just as rich in methionine as meat protein so, if low-methionine diets are better, those diets would be ineffective. (Or maybe there's another explanation.)

Another case of now-you-see-it-and-now-you-don't evidence is that handing adolescents contraceptives lowers the abortion rate. There have been many studies that show that but areas that adopt the policy deliberately don't seem to have lower abortion rates. (The ‘blue’ states might have low adolescent birth rates but they don't have low abortion rates.) Maybe the studies are about what happens when an organization other than Planned Parenthood hands out the pills. When the policy is deliberately adopted, the people turn to Planned Parenthood and that fails. (Or maybe there's another explanation.)