Soy Is Causing Fertility and Sexual Health Problems for Americans
How many times have you eaten soy today?
Even if you think the answer is zero, you’re likely wrong.
Soy has traditionally been used in many Asian cuisines, but these days it’s everywhere. It’s in your bread; it’s in your protein bars; and it’s in your chewing gum.
The only way to avoid soy is to cut out processed foods from your diet completely (if you’re doing this already, kudos to you). If you’re eating tofu and soya sauce, at least you’re aware that you’re consuming soy. However, when it’s used as a filler, it’s hard to quantify exactly how much you’re consuming.
Here’s a list of sources of soy you might not have known contain soy:
- Infant Formulas
- Protein Bars
- Vegetarian Meat Replacements
- Meal Replacement Shakes
- Baked Goods
- Chewing Gum
- Canned Fish
- Frozen Desserts
- Packaged Soup Mixes
- Processed Meats (hamburger patties, hotdogs, cold cut sandwich meats)
There might even be soy in your cosmetics and the food you give to your pets.
Why Is Soy in Nearly Everything?
If you only look at the macro and micronutrients in the soybean, it looks beneficial. Soy is one of the only plant-based protein sources that contains a full spectrum of amino acids. Soy is also low in fat, high in fiber and contains a broad range of vitamins and minerals.
From an agricultural viewpoint, soy seems positive at a glance too. Soy is cheap to grow and does well in a variety of climates. Being low maintenance makes soy one of the cheapest sources of flours and oils available on the market.
Soy is also used to make soy lecithin, an emulsifier that’s probably added to most of the processed foods in your cupboard.
Should you be concerned by how much soy you’re consuming? We’re going to break down the potential health complications for you; so keep reading to find out how this innocuous bean can wreak havoc on your health.
Here’s How Soy Came to the Western World
Soy has been a staple in the diets of people in Southern and Eastern Asia for hundreds of years. It’s thought that farmers started growing soybeans around 1100B.C.¹ British colonies brought the soybean to America in 1765.
In 1904, chemist George Washington Carver¹ (yeah, the peanut guy) discovered that soybeans are high in protein and can be made into an oil. He also realized that when farmers planted soy, they could preserve soil quality by rotating soy with other crops such as sweet potatoes and peanuts.
Soy played a minor role in American nutrition until after the Second World War. At this time, the demand for meat increased. And what was the cheapest source of food for livestock? Soy, of course.
In the 1970s many American people began taking an interest in soy as an alternative to animal protein2. Not surprisingly the increase in soy consumption occurred around the same time as the vegetarian movement.
Throughout the 1990s, the consumption of soy continued to rise as vegetarianism became more popular. Researchers began uncovering more evidence that a vegetable-based diet was linked to multiple health benefits. The American Diabetes Association3 officially endorsed vegetarianism in 1997.
Vegetarian diets based around fruits, roots and high-quality proteins like free-range eggs provide many health benefits such as a lowered risk of heart disease. However, vegetarian diets that are high in soy products may cause the overconsumption of chemicals that have negative health consequences.
Wait … Isoflavones in Soy Do What?
The presence of isoflavones in plants has been known for about a hundred years, but it wasn’t until Dr. Kenneth D. R. Setchell pioneered isoflavone research in the late 1980s that people began to realize that isoflavones might negatively affect humans.
Dr. Setchell found that the same isoflavones found in plants appeared in the urine of people who ate a lot of these plants. He went on to discover that soy and flax were the two most isoflavone-dense foods.
Interestingly, red clover is another plant that contains isoflavones similar to soy. In the early 1900s, farmers noticed their sheep that grazed on red clover developed fertility problems. In 1946, researchers confirmed4 that the high rate of fertility issues in sheep that ate red clover was due to the isoflavones.
Why would plants contain a compound that mimics estrogen in the body of mammals? Is it just a coincidence?
As it turns out, the isoflavone content in plants might actually be a defense mechanism to protect plants from getting eaten5.
Research shows that the levels of isoflavones may increase in soybeans during times of stress. In a study6 published in the Journal of Agricultural and Food Chemistry, researchers found that exposing soybean plants to high-temperatures increased the four genes that code for the plant to synthesize these chemicals.
Isoflavones bind to estrogen receptors in mammals; however, they don’t bond as strongly as estradiol (the active form of estrogen produced by the human body).
Imagine a field of red clover with a herd of sheep trampling through and buffeting on the sprouts. A tiny little soybean can’t fight back against a sheep, but it can exact its revenge by lowering the sheep’s fertility. If the sheep have fewer babies, less clover will be eaten. Genetically, sheep and humans aren’t as different as we like to think we are (we share about 50-60 percent of the genome of a banana). If isoflavones can impede the reproduction of sheep, there’s a reason to believe it might have a similar effect on humans.
What Does Estrogen Do in Humans?
Estrogen is the primary sex hormone in females that give them secondary sex characteristics like breast tissue and menstruation cycles. The ovaries are the primary site of estrogen production. However, fat cells and the adrenal glands also contribute to overall estrogen levels.
When estrogen production is disrupted, negative effects like poor bone health and infertility can occur (sometimes purposely in the case of birth control).
The primary sex hormone in men is called testosterone. However, men also need a small amount of estrogen for bone and sperm health. Too much estrogen is a more common problem for men than too little estrogen. If estrogen levels are too high, men can develop impotence, excess abdominal fat and low sex drive6.
The enzyme aromatase can convert testosterone to estrogen. Generally, high testosterone is linked to low estrogen, and low testosterone is linked to high estrogen.
Are Phytoestrogens the Same as Estrogen?
Phytoestrogens are chemicals that naturally occur in plants that replicate estrogen in mammals8. There are several different types of phytoestrogens.
The most common types include isoflavones, prenylflavonoids, coumestans and lignans. Isoflavones are the most commonly studied phytoestrogens.
Different forms of soy have vastly different isoflavone content. Here is the isoflavone content of various soy products as reported by Harvard School of Public Health10:
- 1 cup Soy Milk: 6 mg
- 3 oz Tofu: 20 mg
- ½ cup Boiled Soybeans: 55 mg
- 1oz Dry Roasted Soybeans: 40 mg
- ½ cup Edamame
- 1 Soy Burger OPatty: 5 mg
- 3 oz Miso: 37 mg
- 1 tbsp Soy Sauce: 0.02 mg
Genistein and Daidzein
Two of the most common types of isoflavones in soy are genistein and daidzein. They make up more than 65 percent of soy’s total isoflavone content8.
It’s thought that more than 60 percent of processed foods contain these isoflavones7. They’ve been proven to have endocrine-disrupting effects and harmful reproductive consequences in humans.
Research shows that low levels of genistein and daidzein11 consumption can stimulate breast cancer growth in people who already have breast cancer12.
Ethnic Differences in Soy Consumption
Some researchers think that different ethnic groups may metabolize soy differently. In Asian countries where people regularly eat fermented soy products, the daily isoflavone intake for these people may reach 15-50mg per day13.
In Western countries like the United States, daily intake is generally less than 2mg per day. Not only do Asian people consume more soy, but they may also have a genetic advantage.
Dr. Setchell found that only about 25 percent of Western people have the intestinal bacteria needed to convert the soy isoflavone daidzein into the bioavailable form of isoflavone called equol. Lifestyle factors and diet play a role in the amount of these bacteria present.
Fifty to 60 percent of Eastern Asian people seem to be able to metabolize daidzein to equol14.
Soy Interferes with Puberty
Since Soy products may disrupt natural estrogen levels, consuming soy products may be harmful to children who haven’t yet gone through puberty.
Several animal studies show that exposure to the isoflavone genistein may affect sexual development. Studies8 on rats have found that genistein impairs the development of ovaries in rats.
Fetuses exposed to high levels of phytoestrogens may also face altered development.
One of the first studies15 looking at the effect of soy came from Puerto Rico in the 1980s. Between the years 1978 and 1981, the rate of premature breast development in young girls increased by 300 percent. The researchers found a positive correlation between premature breast growth and the consumption of soy-based formulas in infancy.
In a 2008 study16, researchers compared urinary isoflavone levels with the pubertal development of girls in New York City. The researchers found that girls with higher levels of isoflavones in their urine had delayed pubertal development.
A German study17 came to a similar conclusion that isoflavone consumption was linked to delayed puberty in girls. However, the study found that isoflavone consumption didn’t affect the onset of puberty in boys.
Soy and Sperm Quality
If you’re trying to have a baby or if you’re worried about your future fertility, you may want to avoid soy products.
In a study published in Human Reproduction, researchers examined the effects of soy on sperm quality. They assessed the sperm quality of 99 men and adjusted the data for age, BMI, caffeine consumption, time since last sexual activity, smoking habits and alcohol consumption.
They found that there was an inverse relationship between soy consumption and sperm volume. The consumption of soy didn’t seem to affect sperm mobility or total ejaculated volume14. In one study17 published in Endocrinology, researchers found that neonatal exposure to phytoestrogens delayed the onset of sperm production in adolescent rats.
Soy and Female Fertility
A study published in the International Journal of Women’s Health examined the effect of soy on the health of 11,688 North American women between the ages of 30-50. Fifty-four percent of the women were vegetarians15.
The women had a mean isoflavone intake of 17.9mg per day, which is high compared to most North American people. Six percent of the women had no isoflavone consumption. The study found that women who consumed an above average amount of isoflavones had an increased risk of fertility problems.
Other research shows that in utero exposure to estrogenic agents can cause functional changes to female reproductive organs. Children exposed to isoflavones through breast milk may have fertility problems later in life16
How potent is soy’s effects?
Research20 shows that feeding children a soy infant formula had almost the same effect as directly injecting the phytoestrogen genistein. One rodent study21 found that rats exposed to genistein had irregular menstruation cycles. The rats also had impaired ovary function and problems with fertility.
Soy Protein Isolate
Soy protein consumption may negatively affect your testosterone levels.
Testosterone is an essential hormone for both men and women, but it plays a particularly important role in male health. Higher levels of testosterone are associated with improved mental health, muscle mass and delayed symptoms of aging. Unfortunately, testosterone levels naturally decline with age by about one percent per year17.
In a study22 published in Cancer Epidemiology Biomarkers & Prevention, researchers examined the effect of a soy protein supplement on young, healthy males. The twelve subjects in the study consumed 56 grams of soy protein per day. After a month of consuming soy protein, the men had 9 percent lower levels of testosterone than at the beginning of the study.
The caveat is that the results didn’t reach statistically significant. Hopefully, more research comes out in the next few years that can further examine the effects.
Soy protein is one of the worst soy products you could be buying. Normally people consume protein powder to increase muscle mass, but stimulating estrogen has the exact opposite effect.
Besides the negative effects caused directly by consuming soy, consuming soy protein might also rob you of more valuable protein sources. In a study published in Nutrition and Metabolism, researchers looked at the bioavailability of soy protein for elderly individuals18.
The researchers found that soy protein consumption led to much worse protein synthesis than whey protein consumption.
The results don’t seem to be isolated to seniors. In another study, researchers compared the bioavailability of these two proteins for young, healthy individuals19. The researchers concluded that whey was significantly more effective for building muscle tissue.
How to Avoid Soy and Improve Your Overall Health
At a glance, soy may seem like a nutritious protein source. However, it can have endocrine disrupting effects. Unless you want to impair your fertility and make building muscle more difficult, it’s best to avoid soy products in your diet.
If you want to avoid soy, you can start by avoiding products such as tofu, roasted soybeans, miso soup, or any other food that’s directly made from soybeans. However, it’s also a good idea to read the fine print of the processed products that you’re buying. Check the ingredients to see if soy lecithin is listed.
If you’re eating a healthy diet filled with organic fruits, roots and meats you shouldn’t be eating many processed foods anyway. Foods that come in a can or package may contain traces of soy in places it doesn’t belong.
There’s no reason to eat soy when there are so many other lean protein sources available. If you’ve previously had breast cancer or if you’re at high risk of developing prostate cancer, you should be particularly careful with your soy consumption.
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From the toxic chemicals in plastics to the endocrine disrupting additives in your meat, the Western lifestyle is slowly stealing your health. You may not immediately notice the health implications of drinking from BPA-laden containers or eating a turkey that has been injected with antibiotics, but the cumulative effects over time will leave you hormonally imbalanced and suffering from micronutrient deficiencies that can lead to disease and poor health.
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Citations and Sources
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