For those without access to the full text, this is how the studied dietary patterns were defined in terms of food groups to be favoured/reduced (should bypass the paywall). Generally, these dietary patterns gave positive weightings for fruits, vegetables, nuts, legumes, and whole grains, and negative weightings for red and/or processed meat, sugar-sweetened beverages, and ultra-processed foods.

> AHEI-2010, Alternative Healthy Eating Index-2010;

> AMED, Alternate Mediterranean Diet score;

> DASH, Dietary Approaches to Stop Hypertension score;

> DRRD, Diabetes Risk Reduction Diet;

> hPDI, Healthful plant-based diet index;

> rEDIH, reversed Empirical dietary index for hyperinsulinemia;

> rEDIP, reversed Empirical dietary inflammation pattern;

> WCRF/AICR, World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) dietary score.

Results: https://www.nature.com/articles/s41591-023-02235-5/figures/2.

See other comment on this post dealing with the protein quality issue of plant-based proteins.

What are your thoughts on trials like this one that find when you look at the protein-related outcome we presumably care most about, muscle growth and strength, there are no significant differences between vegans and omnivores undergoing resistance training when matched for protein?

Some plant proteins do have a complete amino acid profile (soy, quinoa, buckwheat, hemp seeds, etc.), but for the ones that don't it's not that complicated getting sufficient quantities of all amino acids from plant foods. All plant foods contain all essential amino acids, but often in a lower proportion than one's dietary requirements (hence the 'incomplete' classification) - grains tend to have lysine as a limiting amino acid, while for beans it's methionine, so a grain + legume combination will get you a good amino acid profile.

Also copying a previous comment on bioavailability and quality of plant proteins:

> Plant protein sources do typically have lower PDCAAS and DIAAS scores, which is where the "low bioavailability" idea comes from, but this difference is almost entirely due to limiting amino acids rather than them not being digestible or absorbed. (Note that limiting amino acids does not mean the essential amino acid is not present, all plant foods contain all amino acids, it just means that the amino acid is present in a lower proportion than a person's dietary requirements.) If you're eating a variety of plant protein sources (literally just more than one really; something like rice and beans has a perfect or near-perfect PDCAAS score, for example) then this really shouldn't be an issue for you.

> In addition, when you look at the data on the outcome we're interested in (muscle mass gain) rather than getting bogged down in amino acid composition, postprandial muscle protein synthesis, measures of fecal/ileal digestibility, etc. plant proteins appear to be non-inferior to animal protein sources. This randomised controlled trial compared omnivores supplementing with whey protein to vegans supplementing with soy protein powder and found that when they were matched for protein (1.6 g/kg/day) and underwent resistance training, there was no difference in the improvements of muscle mass or strength.

> This review is really interesting and summarises the plant protein quality issue, and also covers the environmental aspects of different protein sources. Also this review covering the broader health and environmental issues of animal vs. plant proteins.

The leading driver of deforestation in both the Amazon and in general for tropical forests is beef, while 77% of soy is used as animal feed to the extent that, in the EU for example, it takes between 1 and 2 kilograms of soy protein to produce a kilogram of edible protein from beef, dairy, pork, or poultry. In other words, replacing all the meat people consume with soy products would reduce total soy consumption, and that's before you consider the other human-edible feed crops involved in livestock production and that other non-soy meat alternatives exist.

Soy consumed directly by humans is not the problem here; soy used as feed is.

This is the only study I can recall specifically comparing vegans and omnivores:

> Vegans had higher testosterone levels than vegetarians and meat-eaters, but this was offset by higher sex hormone binding globulin, and there were no differences between diet groups in free testosterone, androstanediol glucuronide or luteinizing hormone.

Plus, when you compare matched-protein vegan and omnivorous diets (with soy protein or whey protein supplementation respectively), the changes in muscle strength and mass following an exercise intervention are the same, at least in young men.

> A high-protein (~ 1.6 g kg−1 day−1), exclusively plant-based diet (plant-based whole foods + soy protein isolate supplementation) is not different than a protein-matched mixed diet (mixed whole foods + whey protein supplementation) in supporting muscle strength and mass accrual, suggesting that protein source does not affect resistance training-induced adaptations in untrained young men consuming adequate amounts of protein.

Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies

> Regardless of the statistical model, no significant effects of soy protein or isoflavone intake on any of the outcomes measured were found. Sub-analysis of the data according to isoflavone dose and study duration also showed no effect. This updated and expanded meta-analysis indicates that regardless of dose and study duration, neither soy protein nor isoflavone exposure affects TT [total testosterone], FT [free testosterone], E2 [estradiol], or E1 [estrone] levels in men.