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Is soy good for you?

Is soy good for you?

Team ErbologyErbology

Soy is one of the few complete plant-based proteins. During the 1990s soy was believed to be a miracle food. However, with research growing is this still believed to be the case?

September 07, 2022 8:49 pm

What is soy?

The soybean is a complete protein and a species of legume native to East Asia. What’s more, it contains all nine essential amino acids, making soy an important source of protein for many people, especially those who follow a plant-based diet.

Varieties of soybeans include:

  • Green soybeans: Often referred to as edamame, people steam and eat them out of the pod as an appetiser. They are also widely used in salads, stir-fries, and soups.
  • Yellow soybeans: Typically used to make soy milk, tofu, tempeh, and tamari. They can also be used to produce soy flour, which is functional in baking.
  • Black soybeans: Various Asian food cultures use fermented or simmer black soybeans in traditional dishes such as kuromame.

In general, the less processed a food is, the more vitamins, minerals, and beneficial compounds it may contain. Alternatively, the more processed a food is, the more salt, sugar, fat, and unnecessary additives it likely contains.

As a result, minimally processed soy foods, including, tofu, tempeh, edamame, and unsweetened soy milks, are considered healthier than soy-based protein powder, mock meat, energy bars, or sweetened soy milks.

vegan foods with vitamin b12

In addition, fermented soy foods, including soy sauce, tempeh and miso, are often considered healthier than non-fermented soy products. In short, fermentation helps reduce some of the anti nutrients naturally found in foods containing soy.(1) 

Soy-based foods are often at the heart of a plant-based diet, which more and more people are adopting for the benefit of their health and the environment. Subsequently, they are now widely accessible in almost every supermarket and are no longer just exclusive to quirky health-food stores. However, there is a lot of contradictory and confusing information regarding soy. Therefore, this article will review the latest scientific evidence to determine whether soy is good for you.

Nutritional content of soy

Soybeans are protein-rich and contain all of the essential amino acids that the human body needs. In addition, they are one of the few known plant foods (other than amaranth seed and to a lesser degree, quinoa) to contain all the essential amino acids, like those found in meat.

Moreover, soybeans are rich in fatty acids, fibre, vitamins and minerals. In addition to their vitamin and mineral content, soybeans are a natural source of polyphenols, an antioxidant that may help protect the body against cell damage and conditions such as heart disease.

Soy is especially rich in isoflavones, a polyphenol known as phytoestrogen due to its ability to attach to and activate estrogen receptors in the body. Soy isoflavones are one of the main reasons behind the many proposed health benefits of soy-based foods. Furthermore, depending on the variant, boiled soybeans can contain 90–134 mg of isoflavones per 100g.

100g of cooked soybeans contains:(2)

  • Kcal: 141 
  • Protein: 12g 
  • Fat: 6g  
  • Carbohydrate: 11g
  • Fibre: 4g 

However, the nutritional content of other soy products may vary based on how manufacturers have processed them and which ingredients they have added.

Cholesterol

Cholesterol is a fatty substance carried through your blood, attached to proteins. Your body needs cholesterol to build healthy cells. However, too much of it can cause serious health problems. Lipoproteins are a combination of proteins and cholesterol. In addition, there are different types of cholesterol, based on what the lipoprotein carries:

  • Low-density lipoprotein (LDL): “Bad” cholesterol, transports cholesterol particles throughout your body. LDL cholesterol builds up in the walls of your arteries, making them hard and narrow.
  • High-density lipoprotein (HDL): “Good” cholesterol, picks up excess cholesterol and takes it back to your liver.

Research suggests that soy may help lower LDL cholesterol levels and increase HDL cholesterol levels. An analysis of clinical trials indicates 14-50g of soy protein can significantly reduce LDL cholesterol levels in the arteries, while moderately increasing HDL (good) cholesterol levels. What’s more, whole soy products have a greater effect on improving cholesterol levels than processed soy products. This could be due to phytoestrogens or soy proteins working alone or together. Other factors include its high-fibre and low saturated-fat content. Interestingly, people with existing risk factors for heart disease, such as high cholesterol levels, had more significant decreases in LDL cholesterol than people with optimum cholesterol levels.(3) 

A study also found individuals who include at least 25g of soy protein daily in a diet low in saturated fat and cholesterol can reduce LDL cholesterol levels by about 3%. However, this could be because of a reduction in the amount of animal protein in the diet. Swapping out animal-based foods for plant foods like soy decreases saturated fat intake and increases fibre intake, which may indirectly improve our blood cholesterol levels. Although, more data needs to be available to form a definitive answer.(4) 

pumpkin seeds

Heart disease 

Heart disease is a broad term that covers many heart-related problems and conditions, from an abnormal heartbeat and birth defects to a buildup of plaque in the arteries. 

Research shows a link between soy intake and total cholesterol and LDL cholesterol levels, both known risk factors of heart disease. Diets rich in legumes, such as soybeans, have a biological plausibility to lower the risk of heart disease.(5) 

This could be due to isoflavones. They help reduce inflammation in blood vessels and improve their elasticity, two factors thought to protect heart health.(6) 

In addition, a recent review further links soy-rich diets to a 16% lower risk of stroke and heart disease.(7) However, despite biological plausibility, more research is needed to address confounding factors. 

Seek emergency medical care if you have the following symptoms of heart disease:

  • Chest pain
  • Shortness of breath
  • Fainting

Heart disease is easier to treat when detected early. Talk to your doctor if you have any concerns about your heart health. This is especially important if you have a family history of heart disease. If you think you suffer from symptoms of heart disease, make an appointment to see your doctor.

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"In addition to their vitamin and mineral content, soybeans are a natural source of polyphenols, an antioxidant that may help protect the body against cell damage and conditions such as heart disease."

Bone health 

Sufficient calcium helps to keep bones healthy. Moreover, poor bone health can cause conditions such as rickets and osteoporosis, and increase the risk of breaking a bone from a fall later in life. The low estrogen levels experienced during menopause may cause calcium to leach from the bones. As a result, bone loss may cause postmenopausal women to develop weak and brittle bones. 

Isoflavones may also be an effective alternative to hormone replacement therapy (HRT) for women with osteoporosis. Furthermore, HRT can cause severe side effects and increase the risk of stroke, breast cancer, and coronary heart disease. Several studies in this review suggested that isoflavones were as effective as HRT for restoring bone density. An intake of 40–110mg of soy isoflavones per day may reduce bone loss and improve markers of bone health in menopausal women.(8,9) 

Practically put, 40–110mg of soy isoflavones per would be the equivalent of eating around 140–440g of tofu or 35–100g of cooked soybeans each day.(10) However, further research is needed before soy’s benefits towards bone health are conclusively known.

Vegan watermelon tomato salad ingredients

Menopause 

Soybeans are the most common source of isoflavones in food. Furthermore, the amount of isoflavones varies depending on the type of soy food, preparation method and brand. Some of the richest sources of isoflavones include soy flour and soy nuts.

Due to similar structures, soy isoflavones may mimic the hormone estrogen. However, research suggests that soy isoflavones differ from estrogen in many ways, especially as each have different unique effects on the human body. 

Moreover, isoflavones are a class of compounds also referred to as phytoestrogens, or plant estrogens, due to their ability to bind to estrogen receptors in the body. During menopause, woman’s estrogen levels decrease, which leads to symptoms, such as fatigue, vaginal dryness, and hot flashes. Phytoestrogens may alleviate these symptoms by binding to estrogen receptors in the body.(11)

Therefore, due to its phytoestrogens content, soy may reduce menopausal symptoms. They appear to act like a mild form of HRT. However, compared with traditional HRT, it would take almost a year of regular soy consumption to have similar health benefits.

More research is needed. However soybeans may help women to manage menopausal symptoms such as flushes, fatigue, joint pain, depression, irritability, anxiety, and vaginal dryness, even if only modestly.(12) 

Poke Bowl Ingredients

Soy allergy

Allergies occur when a person reacts to substances in the environment that are harmless to most people. A soy allergy can occur in some people due to a reaction to soy protein causing the immune system to have an abnormal reaction.

Symptoms of allergies include:

  • Itching
  • Tingling sensation of the mouth and lips
  • Flushed skin
  • Nausea
  • Diarrhoea
  • Wheezing and shortness of breath
  • Hives
  • Dizziness and confusion

Interestingly not all products containing soy will cause a reaction. Actually, many people with an allergy to soy can safely eat soy lecithin, soya bean oil and some fermented soy foods as they are less allergenic than those containing raw soybeans.

The symptoms and signs of allergies are common to other medical conditions, so always see your doctor for professional diagnosis and treatment. If diagnosed, make sure to always read food labels. 

Thyroid 

The thyroid is a small gland in the neck, just in front of the windpipe (trachea). It produces hormones that regulate the body’s heart rate, muscle and digestive function, brain development and bone maintenance. Furthermore, having too much or too little of these hormones can cause health complications that may need treatment.

Scientists have investigated whether soy intake interferes with thyroid function. In one study participants ate soy foods as part of a vegetarian diet. Researchers found that women with a higher soy intake had a higher chance of having elevated levels of thyroid stimulating hormone (TSH). A high TSH level may signify an under-active thyroid (hypothyroidism). Interestingly, researchers did not find the same results in men. However, the researchers explain that soy is likely to be safe. Although, consuming excessive amounts may create health risks in some people, such as those with undiagnosed hypothyroidism.(13) 

Furthermore, a review of 14 studies found that soy foods don’t affect thyroid function in people with healthy thyroids. However, if you suffer from hypothyroidism, you might want to monitor how much soy you eat. Soy foods may interfere with the body’s absorption of thyroid medication, but only if you overdo it. The evidence is still far from conclusive. However experts advise to wait at least four hours after consuming soy to take your thyroid medicine.(14) 

The only accurate way of finding out if you have a thyroid problem is to have a thyroid function test (blood test for hormone levels). If you’re unsure, or you have an underlying health condition such as hypothyroidism, bring it up with your doctor the next time you discuss your diet.

soy fields

Environment 

The global trade and production of soy doesn’t just impact biodiversity, it also affects the climate, due to the generation of greenhouse gas. However, an alarming 77% of the world’s soybean crop is fed to livestock, especially for beef and chicken production.(15) 

To get the same amount of protein from beef as you would from soy requires 32 times more land. Therefore, if everyone were to swap meat for soy, agricultural deforestation would reduce by an estimated 94%.(16) 

As a result, when soy farming focuses purely on human consumption, its environmental impact is a non-issue. Hence, to minimise our environmental impact, it’s evident that reducing meat intake is one of the leading solutions. 

Is soy good for you?

Soy is a nutrient-dense source of protein that can be safely consumed several times a week, and probably more. In addition, it’s likely to provide health benefits, especially when eaten as an alternative to red and processed meat. What’s more, the greenhouse gas emissions of soy are 24.5 times lower than beef. Therefore, not only is it healthier for you, it is also healthier for the planet. 

Very few concerns about soy are supported by strong scientific evidence, and more research is needed to confirm the remaining. Additionally, speak to your doctor, If you suffer from thyroid problems, or think you have an allergy. 

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