Some experts see soy as a health food – a low calorie, complete source of protein that can even help to reduce cholesterol and heart disease risk.
Others argue that unfermented soy (as most of us eat it) is seriously bad for you – so who’s right?
What is soy?
The soybean is a legume native to East Asia. The plant is classed as an oilseed rather than a pulse by the UN Food and Agricultural Organisation.
In its natural state soy is full of potentially harmful anti-nutrients.
While countries with a long history of consuming soy have developed methods of fermentation to neutralise these toxins, most Westerners consume unfermented soy in the form of milk, tofu and infant formula.
You can also find unfermented soy in packaged or processed foods like protein bars, cereals, mayonnaise and meat substitutes, as it’s often used as a cheap source of protein.
Why might it be harmful?
Most of the controversy surrounding soy is down to the presence of isoflavones, a plant compound resembling oestrogen.
This phytoestrogen (as the mimickers are known) can potentially interfere with your endocrine system and hormone balance – which controls fertility, puberty, and the body’s response to certain kinds of cancer.
It’s thought that the isoflavones in soy are particularly powerful – for example, according to a study by the Dunn Clinical Nutrition Centre, drinking just two glasses of soy milk a day could provide enough isoflavenes to alter a women’s menstrual cycle.
Unfermented soy is also high in phytic acid, which can prevent the absorption of calcium, magnesium, copper, iron and zinc into our bodies.
Alternatives to unfermented soy
While you may want to avoid unfermented soy, fermented soy is a great source of vitamins and nutrients including vitamin k2 – which can specifically help prevent osteoporosis, cardiovascular disease and dementia.
Examples of fermented soy foods include tempeh, miso, natto and fermented soy sauce.
If you’re drinking soy milk as a dairy substitute, then almond, coconut and hempseed milk are all delicious alternatives.
Unfermented soy finds its way into so many foods lining our shelves that it can be hard to spot. As a general rule, I’d always advise you eat fresh, unprocessed foods and read your labels!