Soy is one of the most researched foods on Earth. From sustainable growing practices to its effects on lowering blood cholesterol and weight loss, hundreds of studies are conducted on this unique bean each year. The Soyfoods Association of North America has scoured the data for you, and determined what is sound science based on study design, outcome, sample size and more.
Here's what you need to know from the best of 2015 research:
#1: It Was a Good Year for Older Women
No more hot flashes, mood changes or problems sleeping: post-menopausal women can celebrate with a tall soy latte! The European Food Safety Authority (EFSA) said that soy isoflavones, or phytoestrogens, are safe with no negative effects on mammary glands, uterus or thyroid, adding to a growing body of evidence that shows women can benefit from phytoestrogens and relieve menopause symptoms, such as hot flashes.
A study by Purdue University found an additional benefit of isoflavones for post-menopausal women – bone calcium retention. At 105 mg of isoflavones daily, or about four servings of traditional soyfoods, over a 50-day period, the women increased bone calcium retention by 7.6 percent, showing that soy is an effective bone-preserving agent. The study found benefit even when lower amounts of soyfoods were consumed.
#2: Healthy Moms, Healthy Babies
Soy doesn't just benefit older women; it benefits women of all ages – including those who are pregnant or trying to get pregnant.
About 10 percent of women in the U.S. develop gestational diabetes, or high blood sugar, during pregnancy. If uncontrolled, gestational diabetes can lead to high blood pressure and a difficult delivery or C-section of a large baby that is at risk for obesity and type 2 diabetes later in life. A clinical trial found a diet with increased soy protein for six weeks of pregnancy significantly lowers fasting blood sugar, insulin levels, and fat circulating in the blood..
#3: Soy Found to Improve Fertility
Many women struggle with infertility, and for these prospective parents, they can face difficult medical regimens and stressful waiting. Good news for these couples: A large-scale study at a Boston fertility center showed female consumption of soy improved birth rates for couples undergoing fertility treatment.
For men, soy intake had no negative impact on fertility. A continuation of the study by Jorge Chavarro and team at Harvard University found male soyfood intake unrelated to clinical outcomes.
#4: Keeping Men Healthy
Men were definitely not left out of the soy research benefits this year. A Chinese study analyzing isoflavone levels in the blood discovered that those who consumed soy had the lowest likelihood of developing prostate cancer, and, even more, soy greatly reduced the risk of the cancer metastasizing, or spreading throughout the body.
Researchers at The Ohio State University found that soy decreases multiple inflammatory markers that can impact prostate cancer and progression, including reducing infections. Early stage prostate cancer patients had 68 mg soy isoflavones daily for eight weeks via soy flour bread. Soy intake led to an improved immune system response, reduced inflammation related to early development of cancer cells, and encouraged an active immune system throughout cancer progression.
#5: Gaining Muscle Strength
Soy is a lean, green, protein machine – the only plant protein equivalent to animal protein with all nine essential amino acids in ratios needed for muscle growth and recovery. And, after exercise, the intake of complete protein is key to muscle building and repair. Soy provides a more sustained release of protein's building blocks than whey, so when these proteins are combined, the latest research shows it creates an ideal, prolonged release of protein for long-term increase in lean muscle mass.
#6: Retaining Muscle Strength
For those of us whose gym membership card has been collecting dust – only 21 percent of adults in the U.S. meet the recommendations for physical activity – researchers in Japan found that soy protein prevented the weakening of skeletal muscle caused by immobilization or sedentary lifestyles.
#7: Reducing Cancer Risk for All Ages
University of Washington doctors determined that high soy consumption has no effect on women getting breast cancer for the first time, and, even more, discovered that women who eat a lot of soyfoods have reduced risk of breast cancer recurrence.
A study that looked at biomarkers found that in young girls, high levels of soy isoflavone genistein along with low exposure to BPA showed long-term decreased risk of breast, gynecological, esophageal, lung and urological cancers, cardiovascular disease and Alzheimer's disease.
#8: Non-Fermented Soyfoods Protect the Stomach
Researchers in Japan evaluated more than 30,000 men and women, over a period of 15 years, and found people that consumed the most soyfoods had a significantly decreased relative risk of stomach cancer, the leading cause of cancer-related deaths. Specifically, higher intakes of non-fermented soyfoods such as tofu, soymilk and edamame were significantly associated with a lower risk of stomach cancer and were found to actually have a protective effect against developing the cancer.
#9: Kids – Growing Up Healthy
A new book, "The New Puberty," looks at the percentage of girls who are going through early puberty and the environmental, biological and socioeconomic factors that could cause this. In an interview, one of the authors, Dr. Louise Greenspan, a clinical pediatric endocrinologist, addressed the impact of soy on breast cancer, noting "soy is actually protective and that higher soy intake may lead to later puberty" because estrogen mimicking effects of soy may "down-regulate the estrogen receptor, so that later in life, your body doesn't perceive or see estrogen in quite the same way."
Speaking of early soy consumption, in year 12 of the long-term Beginnings Study at Arkansas Children's Nutrition Center, researchers are finding neurodevelopment patterns of soy-formula-fed infants tracked closely with those of breast-fed infants.
#10: Cholesterol-Lowering Capabilities
We have known for some time that soy protein helps lower cholesterol. But a 2015 meta-analysis showed soy significantly lowered LDL-cholesterol by 4.8 percent and lowered triglycerides by 4.9 percent, with even great impact for people who were diabetic or hypertensive – reducing LDL-cholesterol by 7.5 percent. We also found out why soy helps lower cholesterol; soy protein particles activated the pathway that increased the uptake of LDL-cholesterol.
#11: High Blood Pressure Is Nuts
One study showed that eating mixed nuts, including soy nuts, tree nuts and peanuts, had a significant effect in lowering diastolic blood pressure, a measure of pressure in the arteries when the heart is resting. Just be sure to choose unsalted varieties!
#12: Soy Helps Curb Appetite
Teens can eat you out of house and home, but new research shows choosing a high-protein, soy-based snack vs. no snacking helped curb hunger longer, reduced confusion-bewilderment and increased cognitive flexibility.
#13: New Soybean Could Reduce Allergy Concerns
A new soybean, the "Triple Null," has been developed that greatly reduces allergenic responses and the requirement for heat-treating. We'll keep you updated if these beans make it to mainstream farming!
#14: Pumping Iron for Vegetarians
There is often concern over vegans and vegetarians not getting enough iron in their diets, however; nearly all studies show that vegetarian iron status is within the healthy "normal" range. New research may explain why these vegetarians and vegans are still getting plenty of iron – your body adapts to regular consumption of a high-phytate diet and counteracts the nutrient-absorption inhibiting effects.
#15: Mice Are Not Men
For years we've seen conflicting research on soy – first a rodent study shows some negative effect, but in human clinical studies we do not see similar results. Why is this? A new study out of the Netherlands show us that rats' breast tissue activates soy isoflavones at a rate 30 times more than humans, leading to an extreme and distorted hormonal effect, that is not seen in humans. This raises the question: Why are we still using rodents for soy research?