A question I get a lot from visitors to my homemade yogurt website is: "Can I make homemade yogurt from lactose-free milk?". Strictly speaking, the answer is no… but yes.
Let me explain. Lactose is the sugar in all milk from mammals. Coconut, soy, almond and rice milk are not really milk, do not contain lactose, and will be the subject of a future blog post. So individuals who are lactose-intolerant typically cannot enjoy milk, and the reason is that they lack the enzyme lactase. Lactase breaks the lactose down into two simple sugars: glucose and galactose, which can easily be consumed by anyone who can ingest sugar.
It is worth noting that most of the world's population (as much as 70% by some estimates) lacks this enzyme after about the age of three or four. This is nature's way of weaning us off of our mother's milk. But variety is the spice of life, and some humans never lost the ability produce lactase. Primarily of Middle Eastern and European decent, these people went on to domesticate mammals and drink their milk. Other groups of people, like Native Americans, are almost exclusively lactose-intolerant, and therefore never domesticated mammals for their milk. So as a "disorder" it would be more accurate to say that a minority of people are "lactose-tolerant", since intolerance is the usual condition. But I digress…
So brands of milk like Lactaid have come on the market, specifically to address this issue of lactose-intolerance. If you look at the ingredient labels of regular cow milk, and a lactose-free brand, you will see that the sugar content is the same. Why would this be if the lactose was removed? Well, it is because Lactaid has lactose in it when it goes into the container. But it also has lactaid, the enzyme needed to break the lactose down into glucose and galactose. So it is true that the milk no longer has lactose when it gets to you which is why they can market it that way but it accomplishes this by converting it to two other sugars. The bacteria cultures in yogurt would do this anyway, so it actually saves them a step. This is why you can indeed make homemade yogurt from lactose-free milk, but not because there is no lactose in it. Rather, because lactase has been added for you.
It is worth noting that there is not much lactose left in yogurt even when you use regular old milk. As a result, many lactose-intolerant individuals can enjoy it. You might want to try a small amount of good quality plain yogurt, and if all goes well, start making your own. If that fails, use Lactaid or other lactose-free brand.