It looks like they asked (a large number of) participants what they eat, and checked a correlation between their health and how closely they follow their Planetary Health Diet[1].<p>First, I don't see any attempt to control for the fact that people who eat "healthy" diets (vegetarian, vegan, avoid sugars and red meat, etc) are often the same people who care about exercise, do routine health checks etc. So even if the diet itself was a placebo, this mere correlation would show results as if it's helpful.<p>Second, It's already a known fact that avoiding too much red meat and sugar is good for you, so it's not surprising that a mostly vegetarian/vegan diet has health benefits compared to the average. I guess this study shows that this diet, which was designed for planet health, is also good for human health? It's a noble goal, but most people - maybe selfishly - primarily care about their own health. It would be interesting to quantify how much <i>worse</i> for health this diet is compared to a diet optimised for human health[2].<p>I also don't get the 30% lower CO2 part. Is it about CO2 generated by growing food/raising livestock? One doesn't need a study to know that eating mostly plants generates less CO2.<p>Disclaimer: I don't have access to the full paper so I've only studied the available abstract.<p>[1] Mostly vegan with some animal protein: <a href="https://eatforum.org/eat-lancet-commission/the-planetary-health-diet-and-you/" rel="nofollow">https://eatforum.org/eat-lancet-commission/the-planetary-hea...</a><p>[2] Ideally it is (within an experimental error) as good as the "optimal" human diet, but it would be nice to hear that explicitly.
The diet:<p>> The food-based reference diet for generally healthy individuals aged ≥2 y emphasizes high consumption of high-quality plant-based foods (e.g., whole grains, vegetables, fruits, nuts and legumes, and unsaturated plant oils), low to moderate amounts of animal-sourced foods, and low intakes of saturated fats, refined grains, and sugar.
Almost any diet that contains mostly real food rather than artificial food-like substances will produce substantial improvements in health. Contents are hugely secondary to actually consuming real food.
>Methods<p>>We followed 66,692 females from the Nurses’ Health Study (1986–2019), 92,438 females from the Nurses’ Health Study II (1989–2019), and 47,274 males from the Health Professionals Follow-up Study (1986–2018) who were free of cancer, diabetes, and major cardiovascular diseases at baseline. The PHDI was calculated every 4 y using a semiquantitative food frequency questionnaire.<p>Into the roundfile it goes!