Lactaid fast act helps prevent the gas, bloating, or diarrhea that many people may experience after eating foods containing dairy. How does Lactaid fast act supplement work? Helps prevent symptoms by breaking down milk sugar (lactose) and making dairy foods easier to digest. Not a drug, but a dietary supplement containing the natural lactase enzyme. Works naturally and may be used by everyone ages 4 years and up. Why is Lactaid fast act better than ultra? Starts working quickly, so more milk sugar (lactose) can be broken down overall. Starts working more than two times faster than any ultra strength product available. Same convenient single pill dose.