Few foods have been as scrutinised and politicised in the West as the humble soybean. Not only are myths about soy’s effects on health widespread but soy is even used in political language. Who could ever forget the line “tofu-eating wokerati”’?
Despite this strange and controversial media presence, soy is a nutritious food, having been consumed for millennia, especially in its birthplace of east Asia. It is an important staple of many cultures’ diets and is becoming more and more popular in the Western world, especially as a plant-based protein source.
So let’s dig through the myths and facts about soy to learn more about its real nutritional value.
HOW NUTRITIOUS IS SOY?
Soy is considered by most dietitians to be a good source of protein, vitamins, and nutrients, and as suitable for all people in all stages of life (excluding the minority with a soy allergy).
Per 100g, boiled soybeans contain:
- Calories: 172
- Water: 63 percent
- Protein: 18.2g
- Carbs: 8.4g
- Sugar: 3g
- Fiber: 6g
- Fat: 9g
- Saturated: 1.3g
- Monounsaturated: 1.98g
- Polyunsaturated: 5.06g
WHAT ARE THE PROS OF EATING SOY?
MAY DECREASE YOUR RISK OF CERTAIN CANCERS
There are reasons to think that soy may help to reduce the risk of some cancers. In a series of observational studies, soy has been linked to lower instances of breast cancer in women and also prostate cancer in men. Several compounds in soy, like isoflavones and lunasin, are theorised to be cancer-preventative, although this research is currently correlational, not causational.
MAY HELP LOWER CHOLESTEROL LEVELS
The consumption of soy may be linked to lower cholesterol levels. In one analysis of 38 human experimental trials, participants who consumed an average of 47g of soy per day were found to have a decline in LDL cholesterol (“bad cholesterol”) without altering HDL cholesterol (“good cholesterol”). Another meta-analysis of 599 full-text articles also found a link between soy intake and lowered LDL cholesterol. According to more recent overviews of the research, the effect of soy on LDL cholesterol appears to be small and perhaps not clinically significant, although it is still likely an excellent alternative to animal protein for heart health thanks to its nutritional profile.
MAY PROTECT YOUR HEART
Soy’s effects on cholesterol may reduce stress on the cardiovascular system by a small amount. The American Heart Association Nutrition Committee has also stated that “many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat.”
Many of the vitamins and minerals in soy are beneficial for your heart and cardiovascular system at large. For example, soy is a great source of vitamin K, also called phylloquinone. A critical class of nutrients is known as isoflavones and is found rarely in most foods. People who consume more isoflavones through soy products are less likely to suffer coronary heart disease, according to a 2020 study that tracked the life outcomes of over 200,000 people. However, further research is required on these correlations to be sure of any causal effect that soy is having.
MAY IMPROVE BONE HEALTH
Soy has been linked to improved bone health, especially in one’s later years. To be specific, consumption of soy has been linked to lower rates of osteoporosis, higher rates of bone density, and lower rates of bone loss.
In one review of the scientific literature, it was shown that soy appeared to increase the bone formation rate in the human body and inhibit the rate of bone dissolution. This effect is most pronounced in Asian women, although all people felt some effect. This extra boost may be because Asian women are more likely to eat unprocessed soy, but scientists are still unsure of the exact mechanisms involved.
MAY HELP WITH MENOPAUSE AND HOT FLUSHES
Menopause is the period in women and some trans people’s lives when they cease menstruation. For many people, this period is accompanied by unpleasant side effects like hot flashes, cramps, mood swings, and more.
Soy can help alleviate these symptoms. A meta-analysis found that isoflavones in soy were demonstrated to reduce hot flushes in menopausal women. Not only that, but soy was found to reduce negative aspects of menopause like reduced bone density and increased body fat. Soy can be an important health food for women going through menopause.
MAY PROTECT GUT HEALTH
Due to soy’s high fiber content, it may be protective of your gut health. Your gut contains a microbiome, a collection of microscopic organisms like bacteria and fungi that live in our intestines. This is a good thing, even if the thought of it gives you the heebie-jeebies; the microbiome is essential for digestion and aids our immune system. Fiber is critical to maintaining a healthy digestive system because it helps feed our microbiome. And soy has plenty of fiber, far more than animal-based protein.
In both animal and human trials, this hypothesis is upheld: soy protects your gut health and even boosts your immune system. Nutrients in soy, like butyrate, have also been found to lower gut inflammation. Overall, soy products are good for your digestive health.
WHY HAS SOY BEEN CONSIDERED BAD FOR YOU?
Unfortunately, soy has a bit of a bad rep. Like many foods, soy is subject to frequent misinformation and sometimes even controversy. Let’s investigate some frequent criticisms of soy and see what the science says.
ANTINUTRIENTS
Antinutrients are naturally occuring chemicals that may block the absorption of other nutrients in the body. Antinutrients are found in many plant-based foods: for example, coffee contains tannins that block the absorption of iron.
For some individuals who are prone to deficiencies of certain vitamins or minerals, antinutrients are important to consider. For example, a person with a risk of osteoporosis should eat beets or nuts (which contain calcium-blocking oxalates) at separate times from calcium-rich foods like leafy green vegetables or tofu. Despite the scary name, antinutrients don’t damage the body itself, they just prevent some nutrients from being absorbed in large quantities.
However, the same foods that contain antinutrients — leafy green vegetables, legumes, peanuts, broccoli, nuts, whole grains — also contain far more quantities of vitamins and minerals. If you don’t have a specific health concern it is unwise to avoid foods because of antinutrients.
Soy contains a few antinutrients – lectins, phytates, and oxalates – but experts say any negative effects are minimal. Dietitian Taylor Wolfram argues that the benefits of a well-rounded diet outweigh the minimal effects of antinutrients. Empirical reviews of the effects of many antinutrients confirm this: the beneficial effects of eating plant-based foods far outweigh antinutrients.
AMINO ACIDS
Some people claim that soy is not a “complete” protein source containing all the amino acids the human body needs from its diet, but this is untrue and concern over sources of “complete” protein is largely misplaced.
There are 20 amino acids that humans need: 11 of them we can produce ourselves and 9 of them are obtained through food. Meat products always contain high levels of all the essential amino acids. Some forms of plant-based protein have lower levels of one or two of them. However, soy does contain high levels of all the essential amino acids, and is high in protein, containing 18.2g per 100g serving. Soy, when consumed in a diverse diet, is an excellent source of protein. And because our bodies are able to maintain reserves of amino acids and recycle them, there’s no need to worry about finding “complete” protein sources.
DANGER TO BABIES
There is some evidence that excess soy milk consumption for babies born underweight may be harmful due to its aluminum content. However, the health claim that soy is harmful for all babies is not supported by rigorous empirical research.
Research from multiple studies has also shown that soy-based formula does not harm a baby’s immune system, brain functioning, thyroid function, or sexual development when compared with formula made from cow’s milk. Babies with special health conditions, like babies born premature or with severe allergies, may need to avoid soy, but parents should consult a doctor to determine the best options first.
DIGESTIVE ISSUES
There is limited evidence that soy may cause digestive issues. In fact, the biggest reason participants give for dropping out of studies of soy intake is because of gastrointestinal distress (although this is still rare overall).
This is likely for two reasons. Firstly, soy is a FODMAP food, a category of food that can cause digestive distress to certain people. Secondly, increasing fiber intake quickly may be distressing to the body. The digestive system, when used to certain types of food, may need time to adjust to a new quantity of plant-based fiber.
People interested in increasing their soy intake should gradually introduce it to their diet to avoid the possibility of these unpleasant effects. Heat can also make soy more digestible, so make sure to cook your tofu well!
DOES SOY RAISE ESTROGEN LEVELS?
No, soy does not raise estrogen levels, regardless of the gender of the person eating it. Soy does contain isoflavones, a category of phytoestrogen. These isoflavones are responsible for many of the health benefits of soy, like their theorised cancer-preventive properties.
However, phytoestrogens are not the same as estrogen. The effects of phytoestrogen on estrogen in the human body can be varied and are not fully understood. However, they include inhibiting estrogen as well as sometimes stimulating weak estrogenic activity.
FEMINISING EFFECTS IN MEN
The phytoestrogen within soy has triggered critics to use pejorative terms like “man boobs” or “soy boy” to criticise men who are plant-based, vegan, Asian, or who eat less meat than is considered “masculine”. However, these claims are based on nonsense.
Advocates of debunked claims about feminisation may point to a 2008 study that found soy consumption linked to a slightly lower sperm count in men. However, this study has been heavily criticised by experts, who argue that the number of men who eat soy regularly (only 20 men), was far too low to draw any robust conclusions.
When tested on larger populations, soy had zero effect on estrogen, testosterone, or any sexual hormone in men. Further, a meta-analysis of 32 studies found zero link between soy intake and any feminine attributes in men; the authors concluded that “men can feel confident that making soy a part of their diet will not compromise their virility or reproductive health.” Even men’s fitness magazines like Muscle and Fitness endorse soy as a form of protein suitable for growing muscle and appearing masculine.
HOW MUCH SOY SHOULD YOU EAT?
Scientists are in agreement that a varied and well-planned plant-based diet is beneficial for human health and soy can play a large part in this diet. An adult can reap the benefits of soy with anywhere from 1 to 4 servings of soy a day, although this varies from person to person.
Your ideal consumption of soy depends on your age, ideal caloric intake, fitness goals, and other factors. Consult a dietitian or doctor to talk about what’s best for your body.
ARE SOME SOY PRODUCTS HEALTHIER THAN OTHERS?
In general, unprocessed foods are healthier than processed foods. Less-processed forms of soy include raw soybeans, tempeh, and tofu. Highly processed forms of soy include soy protein powder, sweetened soy milks, and soy protein isolate.
However, it is important to note that not all processing is the same. Even highly processed forms of soy like meat alternatives are healthier than less-processed meat products. For example, a processed soy-based burger is considered as healthy or healthier than an unprocessed meat burger.
CONCLUSION
Despite occasional media hysteria, soy is a nutritious food with many advantages, including possible boosts to your immune system, cardiovascular system, and gut health.
