Updated: Apr 10
Soy is one of the most polarizing nutrition topics. While one article may claim that soy is protective against certain types of cancer, another will claim that it causes cancer. The articles claiming that soy causes cancer base their conclusions on old, poorly designed research studies done on rats (something we don't support), and rats metabolize soy very differently than humans. Since then, many studies on humans have been conducted, showing positive outcomes of soy consumption.
Soy Has Isoflavones and Phytosterols
Contrary to popular belief, soy has lots of protective compounds that make it an extremely healthy and nutritious food. Not only is soy the richest source of isoflavones, but it also contains other health-promoting compounds such as phytosterols. Isoflavones are a class of phytoestrogens—plant-derived compounds with estrogen-like activity that may protect against age-related diseases and hormone-dependent cancers. Phytosterols are plant sterol compounds that block cholesterol from being absorbed and are a great addition to a heart-healthy diet. These are among many other healthful nutrients that soy contains. Below, you'll find four good reasons to add soy to your plate.
Soy May Reduce Cancer Risk
A 25-year study sponsored by the Japanese Ministry of Health, known as the Okinawa Centenarian Study, analyzed the high-soy diet of Okinawan elders compared to other elders around the world. What they found was that Okinawans are at a much lower risk of hormone-dependent cancers compared to people in other parts of the world. They found a significantly lower risk of breast, ovarian, and colon cancers compared to elders in North America. They attributed this to isoflavones' ability to inhibit the invasion of breast carcinoma and inhibit tumor growth. In regard to breast cancer recurrence, a large cohort study of over 5,000 female breast cancer survivors assessed the connection between soy food intake and breast cancer survival rate. They found that soy food intake was inversely associated with mortality and recurrence. This study concluded that soy food consumption was significantly associated with decreased risk of death and recurrence of breast cancer among women. Numerous studies have cited the same conclusion, solidifying the argument that soy may be a preventative means to hormone-dependent cancers.
Soy May Be Good for Heart Health
Research studies have identified that soy may be good for the heart. Both people with high cholesterol levels and people with normal cholesterol levels appear to benefit from the consumption of soy as it improves the ratio of HDL and LDL cholesterol. One study assessed the connection between soy consumption and risk of coronary heart disease in 64,915 Chinese women and found that there is an inverse relationship between soy food intake and risk of coronary heart disease, meaning that consuming soy foods may decrease the risk of coronary heart disease. If you’re wondering in what forms and how much soy they were eating — soy milk, tofu, and unprocessed soy products, like soybeans, were among the highest sources of soy that the women were consuming. The average intake of soy protein was 7.36 grams per day, which looks like a large handful of edamame or half a cup of firm tofu.
Soy Has Adequate Amounts of All Nine Essential Amino Acids
To be clear, all plant-based foods have all nine essential amino acids that we need to get through our diet. However, some plants may be low in specific amino acids. For example, legumes are high in the essential amino acid lysine, while grains have lower amounts of lysine. Therefore, eating a plant-based diet that includes legumes as well as grains would help ensure adequate lysine intake. As long as you're consuming a variety of plant-based foods, you can ensure you're getting plenty amino acids on a plant-based diet. Soy is one of several unique plant-based foods that contains adequate amounts of all nine essential amino acids necessary in the human diet. While animal protein is complete with essential amino acids, it has been shown to increase the risk of heart disease, cancer and diabetes, while soy protein has been show to reduce the risk of these lifestyle diseases. Studies show that replacing animal protein with soy protein may help reduce inflammation and the risk of heart disease.
Here are common soy foods and their protein content:
1/2 cup tofu: 10 grams of protein
1/2 cup tempeh: 15 grams of protein
1/2 cup black soybeans: 11 grams of protein
1/2 cup white soybeans: 13 grams of protein
1/2 cup edamame: 8.5 grams of protein
Soy is an Excellent Source of Vitamins and Minerals
Aside from the mentioned nutritious qualities of soy, it is also abundant in numerous other vitamins and minerals. Molybdenum is an essential trace element found in soy that breaks down harmful sulfites and prevents toxins from building up. Other abundant vitamins and minerals include vitamin K1, folate, copper, phosphorus, and thiamine. Vitamin K1 plays an important role in blood clotting, while folate is essential for making DNA and other genetic material. Copper ties perfectly into soy’s helpful aspects to heart health as a deficiency in copper can have adverse effects on the heart. Phosphorus is essential for bone health, while thiamine helps convert carbohydrates into glucose.
When considering bone health, soy is a rock star! One cup of roasted soybeans is an excellent source of both calcium and magnesium, two essential minerals for bone health. This same amount of soy is also an excellent source of vitamin B6, which is key for brain health, including mood and cognition. Finally, soy is an excellent source of iron, which is especially important for premenopausal women who menstruate.
Not only is soy a delicious source of plant-based protein that can enhance your culinary experience, but also a food that is abundant in nutrients that promote healthful benefits.
*Note that it is important to choose organic whole-food soy options like tofu, edamame, tempeh and miso, whenever possible, because most soy is genetically modified and loaded with pesticides including glyphosate.
Is soy new to you? Here are some recipes to get you started!
Hi! My name is Lina Abuhamdieh and I am a student at Georgia State University in the Coordinated Program for Dietetics. I have loved every minute of this program, and have especially enjoyed discovering new avenues in which I can work in once I graduate. My hope is to be a private practice dietitian and be able to provide clients with all things nutrition and fitness! I have also found a new passion in writing nutrition blogs, so I hope you enjoy!