It is easier than ever to add soyfoods to your diet. Plant-based burgers, including those made from soy, are now served at more and more fast-food establishments and soymilk, along with almond milk and oat milk, are found everywhere from mom-and-pop grocery stores to coffee shops owned by international corporations. But there has been some pushback against these products of late because they are classified as ultraprocessed foods. So, what are ultraprocessed foods and why does evidence indicate eating soy burgers and drinking soymilk can contribute to meeting nutrient needs regardless of how they are classified?
Traditionally, the merits of a given food are based entirely on nutrient content. However, in 2009, Brazilian researchers developed a food classification system based entirely on processing.[1] This food classification system has caught on big time as evidenced by the number of scientific papers evaluating this new system. Understand that most foods are processed to some degree in their journey from the farm to the plate, including staples like rice, wheat, meat products and dairy products. Even soybeans must be processed to make traditional soyfoods such as tofu, which has been consumed for centuries by Chinese and Japanese populations.
Many staples in the diet, such as bread, cheese, and wine, bear little or no resemblance to their starting commodities and are highly processed and prepared but are often not regarded as “processed” by consumers. Nutritionists recognize the important role that processed foods can play in meeting nutrient needs.[2]
However, the consumption of ultraprocessed foods has been linked with all sorts of adverse health outcomes.[3] In short, ultraprocessed foods are defined as formulations of ingredients, mostly of exclusive industrial use, that result from a series of industrial processes (hence ‘ultra-processed’) with the fractioning of whole foods into substances that include sugars, oils and fats, proteins, starches, and fiber. Many of the foods classified as ultraprocessed are what are commonly referred to as junk foods, a term that has been around for many decades. Junk foods typically provide lots of calories but not a lot of nutrition. They are certainly not the type of food one would want to build their diet around.
Soy burgers and soymilk are also classified ultraprocessed foods, but in contrast to junk foods, these foods provide several nutrients. Furthermore, in contrast to soy burgers and soymilk, beef and cow’s milk are classified as unprocessed or minimally processed foods, even though the soy products and their animal product counterparts share many of the same nutritional attributes. For example, the amount, and the quality of protein, provided by a soy patty and a beef patty are similar.[4] And the amount of protein[4] and the amount of bioavailable calcium[5],[6] provided by cow’s milk and calcium-fortified soymilk are similar.
The similarity between cow’s milk and soymilk accounts for why in the just–released 2020-2025 US Dietary Guidelines, it states “For individuals who choose dairy alternatives, fortified soy beverages (commonly known as ‘soy milk’) and soy yogurt—which are fortified with calcium, vitamin A and vitamin D—are included as part of the dairy group because they are similar to milk and yogurt based on nutrient composition and in their use in meals.” The other plant-based milks are not recommended as replacements for cow’s milk.
While it is true that some soymilks contain added sugar, cow’s milk is naturally rich in milk sugar, which some people are unable to digest and can result in gastrointestinal disturbances.[7] And while beef protein and soy protein are both high quality proteins, soy protein lowers blood cholesterol.[8] Also, in comparison to many other sources of protein, soy protein is very efficiently produced,[9] resulting in reduced greenhouse gas emissions.[10]
Finally, new research from the University of Illinois helps to address concerns about processed soy.[11] This study is especially notable because of its duration – 2 years— and its size, with more than 150 participants. The men in this study consumed daily either about 20 grams of soy protein or 20 grams of milk protein (casein). There was no effect of soy protein on testosterone levels. Over the years concerns had been raised that soy could lower testosterone levels and as a result, feminize men. However, this study, along with a statistical analysis of more than 40 human studies published early this year, shows this is not the case.[12]
This 2-year study also found soy had no effect on a hormone thought to increase risk of some cancers.[11] Again, concerns had been raised that soy raised levels of this hormone.[13] But this study shows this is not case.
In conclusion, both the traditional soyfoods, such as tofu and tempeh, which are classified as minimally processed foods, and more processed soyfoods, such as soymilk and soy burgers, can help meet nutrient needs.
References
[1] Monteiro CA. Nutrition and health. The issue is not food, nor nutrients, so much as processing.PublicHealth Nutrition. 2009;12:729-31.
[2] Weaver CM, Dwyer J, Fulgoni VL, 3rd, et al.Processed foods: contributions to nutrition.Am J Clin Nutr. 2014;99:1525-42.
[3] Costa de Miranda R, Rauber F, Levy RB. Impact of ultra-processed food consumption on metabolic health.Curr Opin Lipidol. 2021;32:24-37.
[4] Hughes GJ, Ryan DJ, Mukherjea R, et al.Protein digestibility-corrected amino acid scores (PDCAAS) for soy protein isolates and concentrate: Criteria for evaluation.J Agric Food Chemistry. 2011;59:12707-12.
[5] Zhao Y, Martin BR, Weaver CM. Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow’s milk in young women.J Nutr. 2005;135:2379-82.
[6] Tang AL, Walker KZ, Wilcox G, et al.Calcium absorption in Australian osteopenic post-menopausal women: an acute comparative study of fortified soymilk to cows’ milk.Asia Pacific J Clinical Nutrition. 2010;19:243-9.
[7] Usai-Satta P, Scarpa M, Oppia F, et al.Lactose malabsorption and intolerance: What should be the best clinical management?World J Gastrointest Pharmacol Ther. 2012;3:29-33.
[8] Blanco Mejia S, Messina M, Li SS, 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.
[9] González AD, Frostell B, Carlsson-Kanyama A. Protein efficiency per unit energy and per unit greenhouse gas emissions: Potential contribution of diet choices to climate change mitigation.Food Policy. 2011;36:562-70.
[10] Seves SM, Verkaik-Kloosterman J, Biesbroek S, et al.Are more environmentally sustainable diets with less meat and dairy nutritionally adequate?Public Health Nutrition. 2017:1-13.
[11] Bosland MC, Huang J, Schlicht MJ, et al.Impact of 18-month soy protein supplementation on steroid hormones and serum biomarkers of angiogenesis, apoptosis, and the growth hormone/IGF-1 axis: Results of a randomized, placebo-controlled trial in males following prostatectomy.Nutr Cancer. 2021:1-12.
[12] Reed KE, Camargo J, Hamilton-Reeves J, et al.Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies.Reprod Toxicol. 2021;100:60-7.
[13] Messina M, Magee P. Does soy protein affect circulating levels of unbound IGF-1?Eur J Nutr. 2018;57:423-32.
