Pros: More cost effective than Lactaid style milk
Cons: May need 24 hours for reaction to complete
For the executive summary, read only the bolded items.
If a user likes milk but gets gassy to diarrhea from it, the culprit is often the lactose in milk. The solution is lactase enzyme, which digests lactose, a simple sugar, into simpler sugars glucose and galactose. Lactase occurs naturally in most people, but the concentration of enzyme could drop as one ages. If you are lactose intolerant but like milk, adding more lactase is your answer.
Pharmax is liquid lactase that you can add to milk or drink directly. It comes with a measured dropper. Lactase enzyme doesn't expire and is destroyed by heat, typically 40C or more.
A bottle of lactase enzyme, per labeled instructions, uses 5 drops per pint then let stand refrigerated for 24 hours. The entire bottle of enzyme, has 300 drops or treats just over 7 gallons. 1 gallon of regular milk cost ~ $4. Total cost of Pharmax treated milk, 7 gallons x $4 each, $28, + $13 for Pharmax lactase = $41/7 gallons or $5.86/gal. Lactaid is 3L for $6, or $7.60 gallon. Clearly, a more cost effective solution.
Is it the same as Lactaid, a popular lactase reduced milk sold in the USA? Yes, but Pharmax treated milk is sweeter and some regular milk has slightly different tastes depending on the type of farm it comes from.
But there's more.
Technically, one may not need 5 drops of enzyme per pint, and thus increase the cost effectiveness of the product even more. Lactose intolerance varies from person to person, some cannot digest any lactose at all, while some can tolerate more than others. Thus, milk can be anywhere from lactose free to lactose reduced.
Enzymes are not destroyed, but each 'unit' of enzyme converts roughly at a fixed rate, so putting more drops accelerates conversion until the enyzme is feedback inhibited. It doesn't mean you need more enzyme to work on a gallon versus a pint. The enyzme is also optimal at a higher temperature and acidic pH. If you store milk to allow more time for the enyzme to work, this also gives the existing enzyme more time to work so you can use far less drops per gallon. Just how much this mean to each person has to be worked out by trial and error as the concentration of enzymes varies in different products, the enzyme's effectiveness can vary depending on its source, and the way 'feedback' inhibition works on a particular enzyme. A user at Amazon.com suggested 10 drop per gallon and this worked for me after standing for 3 days. and later I managed to reduce the enzyme to only 5 drops per gallon, rather than per pint.
One could simply follow the Pharmax recommendations and gradually reduce the dosage until one get's gassy, then move back up to the last dose that was trouble free.
When partially treated lacatase milk is drank, the acidic pH of your stomach and the higher body temperature can reactivate portions of enzyme deactivated but still in the milk, further catalyzing a reaction inside your body that was no longer active in the milk bottle in the cold fridge.
Lactaid milk also contains a lot of residual lactase used to digest the lactose. You can mix Lactaid with regular milk in another container, again depending on your tolerance for some lactose, allow the lactase in there to digest the lactose in regular milk and letting it stand for some days in your fridge. Experimenting, I found I can tolerate a 1:4 mix of Lactaid to regular milk drank directly without letting it stand, sometimes more.
Note, the above tricks only work for milk. Some cheeses and foods have much lactose that it could overwhelm an enzyme given the time to reduce lactose, e.g., young cheeses or creams. For mozzarella, it would be better to drink the enzyme directly or take a lactaid pill, a separate product.