People often report feeling better when adopting restrictive diets, largely due to short-term improvements (e.g., weight loss or improved energy). Popular examples include very low-carbohydrate or ketogenic diets, which emphasize protein and can reduce appetite while driving rapid initial weight loss, and detox or juice cleanses, which rely on caloric restriction and high fluid intake to produce weight loss along with a perceived psychological “reset.” However, these approaches are often difficult to sustain and may introduce unintended trade-offs, including nutrient deficiencies that can negatively impact long-term health.
Despite that, the popularity of these and other elimination diets persists due to the perceived potential to benefit specific health targets. To put it bluntly, many elimination diets get credit they haven’t fully earned. Their popularity persists because people feel better, but that improvement is often driven less by the diet itself and more by the broader behavior shift that comes with it: increased exercise, greater intention, and tighter control over what is being consumed. At the same time, these approaches tend to strip out a large share of ultra-processed, energy-dense, nutrient-poor foods—those low in fiber and high in saturated fat—so it’s no surprise outcomes improve. The question isn’t whether people feel better; it’s whether the restriction is doing the work or simply acting as a blunt tool to clean up the diet. By one definition, Americans get approximately 50% of their calories from these types of foods.1 It’s not hard to see that dramatically restricting their intake would result in a more healthful diet overall, pretty much regardless of the composition of the other 50 percent.
Foods that are not nutritionally optimal can also contain soy ingredients—such as soybean oil and concentrated soy protein—because of their wide availability and versatility. As a result, removing these ingredients from the diet can coincidentally reduce intake of less healthful foods. But that doesn’t make the strategy sound. It mirrors the same flawed logic seen in poorly executed restrictive diets—like ketogenic or juice cleanses—where perceived benefits often stem from broadly cutting out categories of foods rather than making intentional, nutritionally informed choices. In both cases, the improvement is driven by what is removed, not by what is thoughtfully retained, risking the loss of valuable nutrients and undermining long-term dietary quality.
Soy protein is a high-quality,2 hypocholesterolemic protein,3,4 and soybean oil has a fatty acid profile that promotes cardiometabolic health5 independent of the food containing these soy ingredients.6 Both soy protein and soybean oil carry FDA health claims for coronary artery disease prevention.5,7 Using soy protein and soybean oil as guides to avoiding certain foods means losing out on the health advantages they provide.
However, if soy protein is present in a product in tiny amounts because it is being used for functional purposes (emulsifier, stabilizer, texture modifier), rather than for its nutritional attributes, that product is not going to contribute significantly to meeting protein needs or to cholesterol reduction. Even if soy protein is present in larger amounts, the food containing it may not favorably affect the quality of the diet, and therefore, overall health, despite helping to meet protein needs. That depends upon the overall composition of the product (e.g., is it soy protein-rich, but high in sodium, saturated fat, and sugar, and low in fiber?).
Soybean oil may provide an even better example of a healthy ingredient often finding its way into products of varying, and often, poor nutritional quality. Soybean oil accounts for over 7% of U.S. caloric intake and over 40% of our intake of both essential fatty acids, the omega-6 fatty acid, linoleic acid, and the omega-3 fatty acid, alpha-linolenic acid.8 It plays a huge role in the U.S. (and global) food supply.9
When thinking about foods containing soybean oil and/or concentrated sources of soy protein, one key question is whether a given product would be healthier if the soy ingredient were replaced. It almost certainly would not, and, in all likelihood, might make it less so. For example, replacing soybean oil with beef tallow drives up the saturated fat content of a product. Similarly, replacing soy protein with pea protein results in a food with lower protein quality and no demonstrated cholesterol-lowering effect.10
This isn’t just theoretical. Clinical research has found that in hypercholesterolemic men (>5.7 mmol/L, ~220 mg/dl), consuming muffins containing 25 g/d soy protein lowers blood cholesterol in comparison to the consumption of muffins containing a similar amount of casein.11 Similarly, when study participants consumed several different foods, including bread rolls, muffins, cookies, brownies, a spread, and smoothies that contained soybean oil, liver fat accumulation was reduced in comparison to the consumption of those foods containing palm oil.12 And the consumption of an experimentally-created mayonnaise containing soybean oil lowered cholesterol in comparison to the consumption of a mayonnaise containing palm-olein oil.13
Avoiding foods containing concentrated sources of soy protein or soybean oil may be one way to steer clear of poor-nutrient-dense foods, but that approach will also eliminate foods that provide health advantages. As always, focus should be on the overall nutrient content of a food, not any single ingredient.
References
1. Dunford EK, Popkin B, Ng SW. Junk food intake among adults in the United States, J Nutr. 2022;152:492-500.
2. Hughes GJ, Ryan DJ, Mukherjea R, Schasteen CS. Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation, J Agric Food Chemistry. 2011;59:12707-12.
3. Blanco Mejia S, Messina M, Li SS, Viguiliouk E, Chiavaroli L, Khan TA, et al., A meta-analysis of 46 studies identified by the FDA demonstrates that soy protein decreases circulating LDL and total cholesterol concentrations in adults, J Nutr. 2019;149:968-81.
4. Jenkins DJA, Blanco Mejia S, Chiavaroli L, Viguiliouk E, Li SS, Kendall CWC, et al., Cumulative meta-analysis of the soy effect over time, Journal of the American Heart Association. 2019;8:e012458.
5. Messina M, Shearer G, Petersen K. Soybean oil lowers circulating cholesterol levels and coronary heart disease risk, and has no effect on markers of inflammation and oxidation, Nutrition. 2021;89:111343.
6. Jenkins, David J A et al. “Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms.” The Journal of nutrition 140 12 (2010): 2302S-2311S .
7. Food and Drug Administration. Food labeling, health claims, soy protein, and coronary heart disease, Fed Reg. 1999;57:699-733.
8. Blasbalg TL, Hibbeln JR, Ramsden CE, Majchrzak SF, Rawlings RR. Changes in consumption of omega-3 and omega-6 fatty acids in the United States during the 20th century, Am J Clin Nutr. 2011;93:950-62.
9. Messina M. Perspective: Soybeans can help address the caloric and protein needs of a growing global population, Frontiers in nutrition. 2022;9:909464.
10. Phillips SM. Current concepts and unresolved questions in dietary protein requirements and supplements in adults, Frontiers in nutrition. 2017;4:13.
11. Bakhit RM, Klein BP, Essex-Sorlie D, Ham JO, Erdman JW, Jr., Potter SM. Intake of 25 g of soybean protein with or without soybean fiber alters plasma lipids in men with elevated cholesterol concentrations, J Nutr. 1994;124:213-22.
12. Cole RM, Zarich S, Fairchild K, Thompson K, Najappa M, Kolipaka A, et al., The effects of linoleic acid-rich soybean oil on ectopic liver fat in adults nonalcoholic fatty liver disease: a randomized controlled double-masked trial, Current Developments Nutr. 2025;9:234.
13. Karupaiah T, Chuah KA, Chinna K, Matsuoka R, Masuda Y, Sundram K, et al., Comparing effects of soybean oil- and palm olein-based mayonnaise consumption on the plasma lipid and lipoprotein profiles in human subjects: a double-blind randomized controlled trial with cross-over design, Lipids Health Dis. 2016;15:131.
This blog is supported by SNI Global and U.S. Soy.
