Soy products are popular in many different diets, but Paleo excludes it entirely. Why is soy considered healthy from numerous viewpoints but not Paleo?
What Is Soy, Exactly?
Soy is a bean that belongs to the leguminous family of plants that produce one or several edible seeds in a pod. In addition to soybeans, other popular legumes include common beans, peanuts, peas, and lentils.
So, soy is a legume. Legumes are not Paleo. Why? Because they contain anti-nutrients such as phytates, saponins, and toxic lectins that can cause digestive distress and inflammation.
Soy further distinguishes itself with detrimental protease inhibitors and phytoestrogens. In other words, soy is loaded with potentially harmful substances.
That said, some folks tolerate legumes, including soy, better than other folks and fermenting soy diminishes the anti-nutrients and provides enrichment. Miso, tempeh, and natto contain probiotics and natto has the added health benefit of being a great food source of vitamin K2.
People in Asian countries still eat plenty of traditionally prepared soy foods, but westerners consume their soy most commonly as a plethora of modified foods and food additives. In the United States, almost the entire soy crop has been genetically modified to withstand heavy doses of Roundup herbicide.
It is very likely that the widespread use of soy products in the food supply is part of what adds to the poor state of our collective health both on personal and environmental levels. These things make soy a “leguma” non grata.
Soy isn’t always labeled as such, and can be referred to by many different names and preparations.
- Soybean oil
- Soy flour
- Soy meal
- Textured vegetable protein (TVP)
- Isolated soy protein
- Concentrated soy protein
- Soy lecithin
- Soy food alternatives such as milk, cheese, ice cream, yogurt, pasta, hamburgers, hotdogs, etc.
Many food preparations can contain soy and/or its derivatives. These are just a few examples:
- Baked goods
- Deli meats
- Infant formula
- Protein powders
- Peanut Butter
- Vegetarian meat substitutes
The History of Soy
In her expose, The Whole Soy Story, Kaayla T. Daniel chronicles the path of soy from its humble beginnings as a fertilizer in ancient China, to its transition to a food source throughout Asia, and onward to its current appropriation as a myriad of super-industrialized ingredients at the heart of the processed food juggernaut.
The ancient Chinese designated the soybean as one of the “Five Sacred Grains” along with rice, millet, barley, and wheat. However, unlike these grains, soy was not eaten. In fact, soy was considered inedible (likely due to the distress it caused the eater).
Although our ancestors didn’t understand the chemistry (soy “fixes” or enriches soil with nitrogen), they knew that soy was a great fertilizer. It wasn’t until Chinese cooks began fermenting soybeans around 2,500 years ago into a paste called chiang that it was incorporated into the diet.
Chiang was used as a medium to preserve animal foods such as fish and meat. Tofu and Japanese miso were developed shortly after and it wasn’t until much later, somewhere around 1000 AD, that natto was invented. Tempeh entered the Asian food scene even later in the 17th century. (Incidentally, tofu is not fermented as commonly believed. It is coagulated from soy milk and pressed into curds.)
Traditional forms of soy are still widely consumed in Asian countries, but less so than we might expect. Soy has always been eaten as more of a condiment to grains and protein and not as the center of the meal. It is very common to find tofu incorporated into soups and stews not as the main feature, but as a complementary ingredient.
There are significant regional differences today. Asians generally consume between 6-25 grams of soy protein a day. (1) To put that into perspective, a one-half cup of firm tofu contains 10 grams of soy protein.
In the United States, soy is now a staple in processed foods, including baby formula, and as a result, Americans are eating a lot of it. Soy consumption in the U.S. has increased astronomically from $300 million in 1992 to over 5 billion today. (2) Such astronomical growth is the result of relentless promotion by an increasingly powerful soy industry and the FDA health claim linking soy with heart disease reduction. The FDA health claim for soy recommends a total of at least 25 grams of soy protein each day to decrease risk of heart disease. (3)
The pro-soy campaign is working: (4)
- 31% of Americans consume soy foods or soy beverages once a week or more, compared to 24% back in 2010.
- 45% of consumers, up from 31% in 2010, seek out products specifically because they contain soy.
- Soy milk remains the most frequently consumed soy food, followed by edamame, energy bars, and tofu.
- More than 75% of consumers perceive soy products as healthy.
8 Major Problems with Soy
While many problems exist from such a high intake of soy, there are eight main reasons why soy is not a health food.
1. Soy is not heart healthy
An influential meta-analysis in 1995 of 38 controlled clinical trials showed that eating approximately 50 grams of soy protein a day in place of animal protein reduced LDL cholesterol by almost 13 percent. Let’s keep in mind that 50 grams of soy is equivalent to eight 8-oz glasses of soy milk a day or a lot of tofu! In 2000, the nutrition committee of the American Heart Association (AHA) published an update showing that 50 grams of soy a day lowers LDL only about three percent and has since retracted its health claim for soy. (5) Of course, all these studies obscure the real issue that cholesterol is not a reliable indicator of heart disease risk in the first place!
Like the thorns of a rose, phytoestrogens are produced by certain plants to protect themselves from predators. Plants use phytoestrogens as a weapon to attack insects and animals that eat them by sterilizing them to decrease their numbers and prevent further attacks.
Phytoestrogens can also impact humans who eat them and the hormonal effect is the subject of ongoing research and debate. The most common phytoestrogens in our diet are three soy isoflavones: genistein, daidzein, and glycitein.
Due to their estrogenic effects, soy isoflavones have been extensively studied in relation to fertility, growth, and the incidence of hormone sensitive cancers, especially breast cancer. In regards to breast cancer, there is still no clear consensus on whether soy isoflavones are helpful or harmful. Some studies show a benefit to soy isoflavone intake, some show no association, and other studies show that soy isoflavones may stimulate cancer growth. (6)
In addition to breast cancer, phytoestrogens are associated with:
- Infertility and reproductive problems, including cancers (in animals)
- Hypospadias, or genital irregularities, in boys whose mothers are vegetarians
- Reduced testosterone in men
- Excessive phytoestrogen levels in infants fed soy formula
The phytoestrogen load in infant formula is of particular concern as it may negatively affect infant health and have residual effects throughout the life cycle. Twenty five percent of infants, or 1 million each year, are now raised on soy formula. Adjusted for body weight, these infants are getting seven times the concentration of isoflavones recommended by the FDA or that are consumed by Asians following a traditional soy-based diet.
To put this in better perspective: infants on soy formula have circulating phytoestrogen concentrations approximately 13,000 to 22,000 times higher than their own endogenous estrogen levels or the equivalent of at least four birth control pills a day! (7)
What effects might all this extra estrogen have on babies? It has been observed that soy-formula fed infants are more likely to develop thyroid disease and use allergy medications in childhood, and girls are more likely to have longer bleeding and more discomfort during menstruation. (8) Clearly, infant soy formula should only be considered when no other feeding options exist.
Babies are just not meant to be fed processed soy formula. All we have to do is look at the differences in the ways Asians and westerners consume soy across the lifecycle and the wisdom of tradition reveals this. Asians eat relatively large amounts of soy across the lifespan, but they don’t feed it to their babies. Westerners who feed their infants soy formula provide a tremendous amount of soy in the first year of life compared to relatively little the rest of the lifecycle. (9)
Phytates are present in all parts of plants including leaves and stems, although they’re highly concentrated in the hull and bran of grains, and the outer layers of nuts, seeds, and legumes—including soy.
When eaten in moderation, there are beneficial aspects to phytates. However, when eaten in excess, phytates can decrease the bioavailability of minerals such as magnesium, zinc, iron, copper, and calcium by binding to them and preventing their absorption.
Excess dietary phytate may impede the function of pancreatic enzymes, interfere with digestion, and contribute to bacterial overgrowth and leaky gut. Fermentation diminishes the phytate content in soy.
Trypsin inhibitors in raw soy interfere with trypsin, the enzyme that breaks down protein during digestion. This can result in poor protein digestion, gastric distress, an overworked pancreas, and damage to the gut barrier. Both, the application of heat and the fermentation process deactivates trypsin inhibitors.
Over 90 percent of the soy crop has been genetically modified to be “Roundup Ready” to withstand Monsanto’s Roundup glyphosate herbicide. Roundup kills weeds that grow in soy fields but not the soy itself. However, over time, weeds developed resistance and now farmers have to use heavier applications of Roundup as well as additional herbicides.
Heavy herbicide use takes a tremendous environmental toll and there is a growing mountain of evidence that Monsanto’s agricultural practices for Roundup Ready soy is devastating not only the environment but also the lives of the people who work and live in those areas. The scope of the effects of genetically modified foods and glyphosate on the general population is still unknown and the subject of intense debate. (10)
Soy contains a class of toxic lectins known as agglutinins which are difficult to digest and can induce red blood cells to clump together. Soybean agglutinins can also increase gut permeability and stimulate the immune system. Soaking, heating, and fermenting reduces the amount of agglutinins in soy.
An Inferior Source of Protein
Soy is touted as being a complete source of plant protein, but it’s deficient in the essential amino acid methionine. Processing soy also destroys lysine, another amino acid.
Soy contains another type of anti-nutrient known as saponins. Saponins can be described as “soap-like” because they have properties that enable them to rearrange cell membranes so that they can slip through. Once leaked into your bloodstream, saponins are capable of initiating an immune response and systemic inflammation.
Bottom Line: Why Soy Is Not Paleo
Paleo is about choosing from a nutritional framework that places a premium on foods with the highest nutritional value and the lowest toxic loads; an approach that mimics the nutritional habits our hunter-gatherer ancestors evolved to thrive on during the 2.5 million years of the Paleolithic.
If you are going to eat soy, look to the past and apply the knowledge of what we know today: eat fermented varieties occasionally. If you have autoimmune disease, or are at risk for an estrogen-related cancer you may not want to consume soy at all.
Vegetarian women who are pregnant should be mindful of the amount of soy they consume since it can have a significant impact on the developing fetus.
P.S. Need help figuring out a soy-free diet? Try our meal plan, and get a free 14-day trial here.
Sign up for our Newsletter
Keep up to date with Paleo Plan news, recipes, and blog posts.