New Research Challenges Old Beliefs About Protein and Iron in Plant-Based Diets
For decades, plant-based diets have carried a subtle—but persistent—stigma: that they’re somehow nutritionally inferior to diets that include meat. Critics have long argued that key nutrients like protein and iron are harder to come by in a vegan lifestyle. Plant proteins, they claim, are incomplete or harder to digest, while iron from plant foods is less absorbable than the kind found in meat. But a growing body of new research is turning those assumptions on their head.
A recent editorial in The Journal of Nutrition explores whether plant-based diets can adequately support muscle health in older adults—particularly in preventing sarcopenia, the age-related loss of muscle mass and strength. While conventional wisdom suggests that only animal protein can provide the quality needed to maintain muscle, emerging evidence tells a different story: when properly planned, vegan diets can deliver muscle-building results on par with omnivorous ones (1).
Backing that up, a randomized controlled trial found that active older adults who followed a balanced vegan diet maintained daily muscle protein synthesis rates that were statistically identical to those eating a meat-inclusive diet. Even more compelling, the vegan group experienced lower cholesterol levels—with no negative effects on blood sugar, blood pressure, or other health markers—indicating that plant-based eating can fully support muscle health while offering additional cardiovascular benefits (2).
Another common belief is that meat is more filling than plant-based options. But a recent study comparing breakfast meals made with beef versus black beans and kidney beans found no significant difference in satiety. Participants felt just as full after eating the bean-based meals, despite the lower protein content—likely due to the fiber naturally found in legumes, which promotes lasting fullness. This challenges the assumption that animal protein is uniquely satisfying, especially for older adults (3).
Then there’s the issue of iron. While it’s true that the non-heme iron found in plant foods like soy is less readily absorbed than heme iron from meat, a comprehensive review shows that soy-based foods—especially when paired with vitamin C-rich ingredients and processed to reduce phytic acid—can make a meaningful contribution to daily iron requirements. Importantly, replacing some meat with soy does not significantly impair iron absorption, reinforcing the idea that soy is a strong nutritional ally in plant-forward diets (4).
Additionally, new research suggests that high intakes of heme iron—the form found in red meat—may actually increase the risk of chronic disease. A 2024 study integrating biomarker and epidemiological data found a significant link between heme iron consumption and higher type 2 diabetes risk, adding further reason to approach animal-based iron sources with caution (5).
Taken together, these studies reflect a major shift in the conversation around plant-based nutrition. Far from being nutritionally lacking, vegan diets—when thoughtfully constructed—can rival traditional eating patterns in supporting satiety, strength, and health. The old doubts around plant protein and iron are losing their grip. A new era of plant-powered nutrition is gaining ground—and it’s backed by science.
References
- Barnes TM, Burd NA. The Muscle Building Potential of Vegan Eating for Older Folks. Journal of Nutrition. 2025 Apr;155(4):1009-1011. E-pub 2025 Feb 3. doi:10.1016/j.tjnut.2025.01.029 https://pubmed.ncbi.nlm.nih.gov/39909192/
- Domić J, Pinckaers PJM, Grootswagers P, Siebelink E, Gerdessen JC, van Loon LJC, de Groot LCPGM. A Well-Balanced Vegan Diet Does Not Compromise Daily Mixed Muscle Protein Synthesis Rates when Compared with an Omnivorous Diet in Active Older Adults: A Randomized Controlled Cross-Over Trial. Journal of Nutrition. 2025 Apr;155(4):1141-1150. E-pub 2024 Dec 26. doi:10.1016/j.tjnut.2024.12.019 https://pubmed.ncbi.nlm.nih.gov/39732437/
- Fluit MJ, Adams BF, Ribau ZJ, Duncan AM. Beans Improve Satiety to an Effect that Is Not Significantly Different from Beef in Older Adults: A Randomized, Crossover Trial. Journal of Nutrition. 2025;155(3):1193-1201. doi:10.1016/j.tjnut.2025.02.008 https://jn.nutrition.org/article/S0022-3166(25)00089-6/pdf
- Hackl LS, Moretti D, Sabatier M. Absorption of Iron Naturally Present in Soy. Advances in Nutrition. 2025 Apr;16(4):100396. E-pub 2025 Feb 26. doi:10.1016/j.advnut.2025.100396
https://pubmed.ncbi.nlm.nih.gov/40020920/ - Wang F, Glenn AJ, Tessier AJ, et al. Integration of epidemiological and blood biomarker analysis links haem iron intake to increased type 2 diabetes risk. Nature Metabolism. 2024 Sep;6(9):1807-1818. doi:10.1038/s42255-024-01109-5 https://www.nature.com/articles/s42255-024-01109-5
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