Will it give me man boobs? Asked so many guys...
Will it mess with my hormones? Asked so many ladies...
Let me dispel some of the soy myths with some solid nutrition evidence.
What is soy?
The word ‘soy’ refers to foods derived from soybeans, including tofu, tempeh, soymilk, edamame, miso, natto, tamari, soy sauce and soy nuts. Soybeans are similar to other legumes, like chickpeas, black beans and lentils, however contain their own unique nutritional properties.
Soy beans are...
high in protein
high in fibre
low in saturated fat
a source of antioxidants
high in phytoestrogens
There's one particular nutrient property that has given ‘soy’ its ambiguous health morality and has created a long history of bipolar soy confusion for consumers. This one factor has made the word ‘soy’ a connotation, leading people to believe that it's either “good" or "bad" or "maybe just not even worth the time"... but fortunately a boatload of scientific studies keep proving the benefits of soy.
Isoflavones... the suspect property
They call the particular soy suspect properties "phytonutrients", and the ones you find in soy foods are specifically labelled as ‘ISOFLAVONES’.
Isoflavones act as phytoestrogens due to their structural similarity to estradiol, the main oestrogen in men and women. This means they can mimic (to an extent) the activities of this hormone by binding to oestrogen receptors in the body. This affect is quite weak, but still as an affect. For example, they can block the binding of more potent oestrogens in the body, potentially playing a role in preventing hormone-related cancers like breast and prostate cancer.
Interestingly, the rates of breast and prostate cancers are lower among Asians, compared to people living in Western countries (like Australia), and this could be related to the significantly different consumption of Isoflavones in Asian diets, ~30my/day (15–47 mg/day), verse Western diets, less than 1mg/day (0.15–1.7 mg/day). One reason for this big difference is that Asian diets include more soy foods.
Isoflavone content of some soy foods (per 100g serve)...
Soy bean = 23 - 128mg
Soy milk = 15 - 30mg
Tempe = 87mg
Tofu = 8 -67mg
Miso = 25-89mg
Miso soup = 1.5mg
Edamame = 18mg
Soy protein = 91 - 200mg
More soy benefits...
Further to their anti-cancer potentials, Isoflavones possess antioxidant, antimicrobial, and anti-inflammatory affects. For example, Isfolavones are known to directly scavenge reactive oxygen species (ROS) in the body. ROS are destructive chemicals that are produced during normal oxygen metabolism; that is, they are produced when your body makes energy (ATP) out of the food you eat. ROS are also made during physiological processes that are stimulated by exogenous factors, such as when your immune system is fighting bad bugs (known as phagocytosis). A build up of ROS in your body is bad because they promote inflammation, as well as damage your cells and tissues.
In summary, Isoflavones deliver anti-inflammatory benefits and get rid of some bad chemicals (ROS) made in your body.
Even more soy benefits...
protection against heart disease
lower total and LDL cholesterol
lowered blood pressure
improvements to blood vessels (greater elasticity of artery walls)
reduced risk of osteoporosis
So is soy good or bad for you?...
Soy is good for you in the right amounts and forms.
How much soy should I eat/drink?
To get the above mentioned benefits, aim to consume about 30 to 50mg of Isoflavones each day. For example, one cup of soy milk or 100g serve of tempe or half a cup of cooked soy beans.