Soy: High-quality protein and nutrition for kids

Good nutrition is critical during childhood and adolescence. During these formative life stages, consuming a balanced, nutrient-dense diet not only ensures optimal growth and development, but also helps establish dietary patterns that last into adulthood and affect long-term health. Serving nearly 5 billion lunch meals per year in the US (1), schools play an especially important role in shaping children’s dietary patterns. For that reason, nutritional requirements are key components of the school meals served through federal Child Nutrition Programs, like the National School Lunch Program (NSLP) and the School Breakfast Program (SBP).

Child Nutrition (CN) labels, which are voluntary food-crediting statements authorized by the USDA, make it easier for schools to determine how much that food fits into a healthy and balanced school meal. This month, the Impossible™ Burger received a CN Label, enabling schools to use this plant based product to help meet the daily nutritional requirements of kids in school. The product met the rigorous requirements in large part because of soy, the main protein source in our product and the only plant protein that rivals beef from cows in terms of protein quality. 

What is soy?

First domesticated for food in Asia, soybeans have been cultivated for centuries and are now widely consumed around the world in various forms. Common soy foods include whole soybeans (edamame), soy milk, tofu, and fermented soy products like soy sauce, miso, and tempeh. Soy-derived products include ingredients like soy oil, the most commonly consumed cooking oil in the US (2); soy lecithin, a fatty substance commonly used in food mixtures; and soy protein concentrate, a source of protein in a wide variety of foods, like nutrition bars and meat analogues. At Impossible Foods, we use soy protein because it is not only safe (see our blog on the safety of soy here) but also nutritious and health-promoting.

Nutritionally, soy stands out as a great source of protein. This is due not only to its total protein quantity, but also to the high quality of the protein it contains. The method most commonly used to define “protein quality” is Protein Digestibility Corrected Amino Acid Score (PDCAAS), which assesses a protein’s essential amino acid content and digestibility (3). Soy foods have PDCAAS values ranging from 0.91 to a “perfect” score of 1 (4-6). Soy protein concentrate has a published PDCAAS value of 0.99 (4). For reference, that of beef from cows is 0.92 (4). 

In addition, soy is rich in many other beneficial nutrients -- like fiber, polyunsaturated fatty acids, and essential minerals like calcium and iron -- that contribute to overall health. 

Over 15,000 peer-reviewed articles looking at health implications of soy intake have been written, and scientists widely recognize its health benefits. Clinical research since the 1960s has shown soy to have at least a modest lowering effect on cardiovascular disease risk factors, such as LDL-cholesterol levels and blood pressure (7-10). Other health benefits associated with soy include improved bone health (11-14) and reduced risk for breast (15-18) and prostate (19) cancers. 

The science is clear that soy foods are nutritious and health-promoting for individuals in the general population at all life stages. So, how does soy consumption benefit kids?

Soy and kids’ health:

Intake of soy among children and adolescents is not new; in fact, soy has served as a part of the traditional diet for kids in many Asian countries for centuries! Whether in the form of miso soup in Japan; doenjang guk in Korea; or mapo tofu in China, these and other soy foods make up a major part of typical school meals in many regions. In 2012, the USDA granted schools participating in the NSLP and SBP the option to offer commercially-prepared tofu and soy yogurt as meat alternates, citing the associated health benefits. Offering a variety of proteins that include plant-based options can help meet the needs of vegetarian and culturally diverse students and contribute to the overall health of all students (22). The Impossible™ Burger represents a logical next step for schools looking to incorporate more plant-based options that meet nutritional needs of school-aged children.

Soy, with its high protein quality and content of fiber and micronutrients, fits the bill as a nutritional powerhouse in a child’s diet.

Protein plays many important roles in the body, including serving as a building block for body tissues and providing energy -- functions that are especially important during the critical periods of growth and development experienced in childhood and adolescence. In the US, protein intake among children generally meets recommendations (23), but health experts continue to emphasize the importance of consuming high-quality, nutrient-dense sources. Soy is therefore a great option given its high protein quality and provision of many other important nutrients. 

Dietary fiber, a nutrient that is under-consumed in the US, is well-documented as improving gut, cardiovascular, and overall metabolic health (24). Increased fiber intake in children has been associated with decreased risk of digestive issues, like constipation, as well as lower risk of developing chronic health conditions, like heart disease and diabetes, later in life (25). Plant foods are the source of dietary fiber, and soy, being a plant, is no exception. Higher fiber intake is associated with overall higher diet quality in children (25), partly due to the lower fat and higher micronutrient content of plant foods which displace other, less nutrient-dense foods in the diet.

Calcium is an under-consumed micronutrient with important health implications for kids. It is essential for the accrual of bone mass that occurs in early life stages and affects bone mineral density and risk of fractures later in life. However, many kids do not consume adequate amounts (23). Soy can serve as a source of calcium in a child’s diet (26), whether in the form of whole soybeans (natural sources of calcium), fortified soy foods, or other soy-based foods that retain the naturally occurring calcium from their soy ingredients. For example, soy milk and tofu are often fortified with calcium, and studies have shown that the absorption of calcium from fortified soy foods is comparable to that from cow’s milk (27-29). Foods such as Impossible™ products also contain calcium, owing in part to the natural calcium content of soy.

Soy and isoflavones:

Soy is rich not only in nutrients but also in isoflavones, a type of phytoestrogen. Phytoestrogens are plant compounds that share structural similarity with 17-β-estradiol, the primary female sex hormone. A recent review of approximately 12 studies looked at short- and long-term health effects of soy isoflavone consumption in children and concluded that soy isoflavones do not cause adverse hormonal, pubertal, or other health effects (21). In fact, many studies have suggested that intake of soy isoflavones at young ages is associated with beneficial health effects, specifically protection against breast cancer, later in life (31-32, 35-37). Soy-based infant formulas (SBIFs) have been used for many decades, with extensive research to demonstrate their safety and ability to meet infant nutritional needs for normal growth and development as adequately as dairy milk-based formulas (30, 33, 34). While all current evidence suggests that soy isoflavones have neutral or health-positive effects, it should be noted that isoflavones are largely destroyed by the processing of soy into soy protein concentrate (SPC). Therefore, products that incorporate SPC, such as Impossible™ Burger, are not substantial sources of isoflavones. 

A note on soy allergies:

Over 160 foods have been associated with food allergies (38), which tend to be more common among children than adults. In the US, soy is one of “the Big 8” allergens, meaning that it is considered common enough to require labeling on a food package. However, the prevalence of soy allergy is much lower than that of other common food allergies. Self-reported data from 4 large surveys across the US and Canada show that soy allergy occurs in 0.2-0.5% of the child population in those countries; for comparison, the same surveys found that peanut allergy affects 1.16-2.2% of children (39). Typically, symptoms of soy allergy are mild, but in some cases can be severe (i.e. cause anaphylaxis), so children allergic to soy need to avoid consuming soy protein and may be advised by their allergist or pediatrician to also avoid foods made using other soy-based ingredients. Fortunately, children often outgrow soy allergies. Current research suggests that over 70% of children with a diagnosed soy allergy develop tolerance by the time they are 10 years old (40). For more information on food allergies as well as the allergenicity of Impossible Foods’ products, see our previous blog here.

In conclusion:

Soy serves as a nutritious food that can easily be incorporated into a school’s menu. Many nutrients essential for children’s health are currently under-consumed, and soy can help to address these concerns, as it is a source of high-quality protein, dietary fiber, and micronutrients. For these reasons, soy foods fit well into a healthy dietary pattern during childhood and adolescence and have a well-earned spot at the school lunch table.

References:

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