3-MCPD

We easily go for less healthier choices, not knowing what is in the products that we buy. Soy sauce is one of those choices, as when we shop in our supermarket, we rather buy soy sauce there than in our health food store.
The "commercial" soy sauce has nothing to do with the "traditional" soy sauce from our health food store.
Most commercial soy sauces contain sugars and also 3-MCPD. 3-MCPD or (3-monochloropropane-1,2-diol or 3-chloro-1,2-propanediol) is an chemical compound which is carcinogenic and  has male anti-fertility effects. 

It is  created in foods by protein hydrolysis by adding hydrochloric acid to speed up the reaction of the (soy) protein with lipids at high temperatures.
It has been found far exceeding health standards by in some cases thousand of times in many Chinese and Southeast Asian sauces such as Oyster sauce, Hoisin sauce and Soy sauce, but Korean or Japanese sauces do not utilize hydrochloric acid in production and therefore do not produce 3-MCPD.

This does not means that Korean and Japanese sauces are healthier, it means only that they do not contain 3-MCPD.

I once had the honour to speak with the 85 years old cook of Hirohito, the former emperor of Japan, and he told me that at the imperial court, they only used Kikoman soy sauce, but not the commercial one, which is made in only one day, but a brew only made for the emperor, fermented for more than one year.

Using hydrochloric acid is a far cheaper and faster method but inevitably creates carcinogens, which is why artificial soy sauce can sell for far cheaper than traditionally fermented soy sauce. One good soy sauce available in Thailand is the Sun Chaw Wong  soy sauce, made from GMO free ingredients, rich in amino acids, fermented for up to one year. This brand has 3 different soy sauce , one is without sugar.