Non-fermented soy products (such as soy milk) are a terrible thing for long term health, even the unsweetened, non-GMO versions. Yes, Far Eastern cultures have been using soybeans for thousands of years and that's why traditionally they only consume fermented soy products.
So I came back to edit this because this morning I was rushing and didn't really justify my accusation.
Soy contains phytoestrogens, these are plant based chemicals that mimic the hormone estrogen in your body. We're talking whopping doses! An infant on soy based formula gets the approximate equivalent of 4 birth control pills every day. Little wonder girls as young as 6 and 7 are starting their periods.
Soy is considered goitrogenic. Goitrogenic mean thyroid suppressing, many foods are goitrogenic but soy is king of them all. The process by which this happens begins with blocking iodine getting into your thyroid. Most of us could be considered iodine deficient by many doctors. There is a long list of problems associated with hypothyroidism, trust me you don't want to encourage them!
Soy contains Phytates. Phytic acid is an enzyme inhibitor, it chemically binds with minerals in your food preventing absorption. All grains, seeds and nuts contain phytates, this is why traditionally these foods were soaked overnight to reduce the phytate content. Soy is so high is phytates that soaking will not make a huge difference. Fermenting does and that's why cultures traditionally consuming soy only eat fermented.
Soy is very high in trypsin inhibitors. Trypsin a digestive enzyme that breaks down protein, without sufficient amounts protein goes undigested potentially causing immediate stomach problems (discomfort, cramps, bloating, diarrhoea, bleeding). And in the long term possibly burning out your pancreas.
As for healthy populations consuming soy for thousands of years, I'll reiterate, Chinese and Japanese consume approximately 2 teaspoons of soy daily (approx. 10g) and only of the fermented variety. In contrast 100g of protein from unfermented soy product is often encouraged for unsuspecting westerners looking for healthy alternatives.
Also Japanese and Chinese populations tend to have a lot more iodine rich foods (mainly from the sea) than us westerners do. For perspective on iodine uptake disruption, Japanese iodine intake is estimated between 13.5mg to 45mg daily. The upper safe limit set by the NHS is 0.5mg and they say an adult needs 0.14mg. So the average Japanese gets between (27 and 90 times more than UK's safe upper limit and between 96 and 321 times more than the RDA. Not from supplements mind you!)