- Soy products are becoming increasingly popular as more consumers seek alternatives to meat, but their acceptance has led to increased scrutiny
- We examine three areas: the effects of plant oestrogen, growing herbicide use and the nutritional value of ‘future foods’
The humble soybean has been consumed by humans for thousands of years, with evidence of soybean domestication dating as far back as prehistoric China.
Because they are high in protein, soy products have become a staple in the diet of vegans, vegetarians and communities that typically lack diverse protein sources. They are also high in nutrients including fibre, iron, magnesium, potassium, protein and zinc, and according to some scientists, may help lower the risk of heart disease.
In the West, large-scale consumption of soy did not begin until the 20th century and most consumers have had little exposure to the food. Now, the emergence of a variety of new foodstuffs, such as Impossible Foods' soy-based burgers, has led to increased scrutiny regarding the possible effects of soy on humans. We examine some of the questions being asked.
Plant oestrogen effects
"The health effects of soy and its individual constituents are among the most controversial issues in clinical nutrition," says Tej BG, a naturopath and clinical nutritionist at the Integrated Medicine Institute in Hong Kong.
Concerns, he says, are mostly based on the presence of isoflavones " a type of plant oestrogen " in soy products, in particular the effect that plant oestrogen may have on people with hormone-sensitive cancers.
A compilation of studies by Harvard University's T.H. Chan School of Public Health, however, states that soy consumption could be potentially beneficial for breast cancer sufferers, as plant oestrogens may block the action of oestrogen " which encourages cancer cell growth " in some tissues and in some people.
"If soy's oestrogen-blocking action occurs in the breast, then eating soy could, in theory, reduce the risk of breast cancer because oestrogen stimulates the growth and multiplication of breast and breast cancer cells," the report states. "Studies so far have not provided a clear answer. Some have shown a benefit with soy consumption and breast cancer while others show no association."
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The Harvard University research also found that the effects of soy consumption varied depending on a range of factors, from ethnicity to hormone levels and the type of soy consumed.
BG says a multitude of contradicting studies and analyses of soy consumption has led to conflicting reports in the media, and has contributed to uncertainty in the public perception of soy products. He believes further research needs to be carried out to arrive at more definitive conclusions.
According to a 2016 study in the journal Nutrients, concerns on the possible negative effects of isoflavones toward some individuals come from primarily animal studies. Human studies tend to support the safety and benefits of soy foods.
Mingfu Wang, a professor at the University of Hong Kong's school of biological sciences, says that until a consensus is reached, people might choose to avoid soy products that contain high levels of isoflavonoids.
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"Nowadays, if you have this kind of concern, you can take purified soy protein products," Wang says. "These have much lower amounts of isoflavonoids than normal soybean products " but you do have a certain group of people that are looking for isoflavonoids for their health benefits."
Growing herbicide usage
Concerns about the use of pesticides and herbicides in the production of soy have risen in turn with demand, as have concerns about the use of genetically modified soy.
Herbicide use has continued to rise rapidly in conventional soybean production in the US, says Charles Benbrook, a visiting professor at the University of Newcastle in Britain, who has investigated the effects of genetically engineered crops on pesticide use in the US and wrote other studies on herbicides.
Benbrook says three herbicides " glyphosate, 2,4-D and dicamba " account for most of the rise. Glyphosate is a probable human carcinogen, and the other two are possible human carcinogens, he says.
The emergence and spread of weeds resistant to glyphosate is driving up herbicide use by corn, soybean and cotton farms in the US, Benbrook explains. This reliance on herbicide use is increasing and is likely to accelerate in many areas.
"Nonetheless, most people are at low risk of exposure to those herbicides from their diets," Benbrook says.
Glyphosate is the key ingredient in the commercial weed-killing product Roundup, which was originally produced by the US agrochemical company Monsanto and is now produced by German chemical giant Bayer, which bought Monsanto last year.
While the US Environmental Protection Agency (EPA) has labelled glyphosate as "not likely to be carcinogenic to humans", other groups disagree. In 2015, the World Health Organisation's International Agency for Research on Cancer claimed that it is "probably carcinogenic to humans". The announcement followed two recent prominent court cases that awarded cancer patients tens of millions of dollars after claiming that Roundup caused non-Hodgkin's lymphoma.
It would be better to have whole soy products rather than just concentrated soy protein productsTej BG, naturopath and clinical nutritionist, Integrated Medicine Institute in Hong Kong
Following the EPA's announcement, US Secretary of Agriculture Sonny Perdue said that "if we are going to feed 10 billion people by 2050, we are going to need all the tools at our disposal, which includes the use of glyphosate."
Benbrook says that everyone should be concerned given the collateral damage that arises from excessive reliance on glyphosate-based herbicides. He adds, though, that the risks are modest for the people who do not work with herbicides, nor live or work in areas where they are sprayed.
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"However, many mysteries remain over how they impact human health, and more surprises are likely," he says.
Future foods
While traditional soy products such as tofu and soy milk are increasing in popularity, recent years have seen new soy products resembling meat and dairy foods appearing on store shelves and in restaurants.
The global market for soy food products was US$37 billion in 2017, according to US firm Hexa Research, and is estimated to rise to US$57 billion by 2025.
Companies such as US firm Impossible Foods, famous for its meatless burgers, are further diversifying by experimenting with making foods such as fishless seafood products. BG, however, sounds one note of caution.
"Highly refined manufacturing processes may reduce some nutrients, or they could have other ingredients added to them," he says. "However, they could be used as a treat by vegans and vegetarians, or for those wanting to reduce animal food sources."
The nutritionist says the healthiest soy products are those that have been minimally processed so they retain their nutrients.
"It would be better to have whole soy products rather than just concentrated soy protein products," he says.
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As consumers increasingly seek alternatives to meat amid sustainability issues and animal welfare concerns, more soy-based food products are expected to reach the market. Despite the heavily processed nature of some of these new products, the trend is seen as a positive sign by some experts.
"I'm very happy with the growth of soybean products," Wang says. "Soy is one of the best foods we can find in nature because it has a balance of nutrients, lipids, proteins and fibre, and also contains extra phytochemicals with health benefits.
"I think it is good news that people recognise that we have the technology to use soy protein to replace wheat, and enhance the flavour and texture. In the future you will see more and more plant-based products coming to the market, not only from soy."
Nick Halla, senior vice-president of international for Impossible Foods, says his company's objective is to transform the global food system.
"Our goal is to replace animals as a food-production technology by 2035, and provide consumers with meat, fish and dairy foods that are good for both people and the planet," he says.
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Commenting on concerns over the manufacturing of the company's products, Halla contends that the term "processed" has a negative connotation because it has long been associated with unhealthy junk food.
"Some food manufacturers compound the breach of their consumers' trust by trying to conceal their poor choices with respect to health and nutrition from consumers," Halla says. "The problem isn't processed food " it's food manufacturers who put profit above their responsibility for their customers' well-being and right to make informed choices."
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