Soy Nutrition Institute

Soyfoods Highlighted in Position Paper By Academy of Nutrition and Dietetics

By Mark Messina, PhD, Executive Director, Soy Nutrition Institute

According to the Academy of Nutrition and Dietetics, including soyfoods in vegetarian diets is one easy way to make this eating pattern more healthful. 1 

In the most recent update to their position on vegetarian diets by Melina et al.,1 the Academy, which is the national professional organization for dietitians, cited the regular use of legumes and soy products as a good way to ensure adequate protein intake and for providing other nutrients as well. Other vegetarian nutrition experts have emphasized the importance of consuming three servings per day of legumes in order to ensure adequate intake of the essential amino acid lysine (http://veganhealth.org/articles/protein#lys).  

Although vegans and vegetarians typically have higher intakes of legumes than the average American, their bean intake is still quite modest. For example, in the Adventist Health Study-2, even vegans consumed on average only about 84 grams of non-soy legumes per day, or the equivalent of just one serving.2 In contrast, vegans consumed about 202 grams of soyfoods and soy-based meats,2 which equates to about 1½ to 2 servings of soyfoods per day.3 The versatility and convenience of soyfoods makes them an easy option for meeting lysine requirements. 

Soyfoods also make it easier to meet protein needs on plant-based diets. Vegetarians who eat mostly whole grains and beans may have higher protein needs since the protein in these foods is less digestible compared to animal protein.4 This isn’t true of soy protein, though, which is comparable to the protein found in animal foods.5

Soyfoods can also be an important source of calcium for people on plant-based diets. Although the Academy’s position paper suggests that calcium is absorbed from plant milks at about the same rate as from cow’s milk, this has actually only been shown for soymilk.6 Data on the absorption of calcium from other plant milks like those made from almonds or rice haven’t been published.  Since many factors in foods affect absorption, calcium bioavailability may vary among different plant milks.

Melina et al.1 also noted that “although foods such as soybeans, cruciferous vegetables, and sweet potatoes contain natural goitrogens, these foods have not been associated with thyroid insufficiency in healthy people, provided that iodine intake is adequate.” 

In the case of soybeans the “goitrogens” are isoflavones. Because isoflavones have the potential to be iodinated instead of tyrosine (tyrosine iodination is a critical step in the synthesis of thyroid hormone) concern has been expressed that soyfood-consumers whose iodine intake is marginal would synthesize insufficient amounts of thyroid hormone. However, a 2012 clinical study found that only very negligible amounts of isoflavones are iodinated.7 So this concern appears to be without foundation.

Soyfood consumption may contribute to the lower total and LDL-cholesterol levels seen in vegetarians and vegans as noted by the position paper. Certainly, much of this benefit can be attributed to the lower saturated fat and higher fiber content of plant-based diets, but soy protein may also be a factor as it directly lowers cholesterol levels.8 

While the position paper addressed the needs of vegetarians, soyfoods can provide similar benefits for nonvegetarians, too, providing more varied options for meeting protein and calcium needs. The Dietary Guidelines suggest that all Americans should increase their bean consumption. Adding soyfoods to menus is an easy way to adhere to that recommendation. And as Americans seek alternatives to cow’s milk, soymilk is the best option for providing high-quality protein and well-absorbed calcium.


References

  1. Melina V, Craig W, Levin S. Position of the Academy of Nutrition and Dietetics: Vegetarian Diets. J Acad Nutr Diet. 2016;116:1970-80.
  2. Orlich MJ, Jaceldo-Siegl K, Sabate J, Fan J, Singh PN, Fraser GE. Patterns of food consumption among vegetarians and non-vegetarians. Br J Nutr. 2014;112:1644-53.
  3. Rizzo NS, Jaceldo-Siegl K, Sabate J, Fraser GE. Nutrient profiles of vegetarian and nonvegetarian dietary patterns. J Acad Nutr Diet. 2013;113:1610-9.
  4. Kniskern MA, Johnston CS. Protein dietary reference intakes may be inadequate for vegetarians if low amounts of animal protein are consumed. Nutrition. 2011;27:727-30.
  5. 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 Chem. 2011;59:12707-12.
  6. 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.
  7. Sosvorova L, Miksatkova P, Bicikova M, Kanova N, Lapcik O. The presence of monoiodinated derivates of daidzein and genistein in human urine and its effect on thyroid gland function. Food Chem Toxicol. 2012;50:2774-9.
  8. Jenkins DJ, Mirrahimi A, Srichaikul K, et al. Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms. J Nutr. 2010;140:2302S-11S

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