Lactose-free describes foods whose content of milk sugar, known as lactose, is below a defined, very low limit. For people who tolerate lactose poorly, this labelling can offer guidance, and individual tolerance should be clarified with a doctor if in doubt.
In practice, heavily filtered forms such as whey isolate usually contain less lactose than simple whey concentrate, but they do not automatically carry the lactose-free label unless the limit has been expressly tested. Plant protein sources such as pea, rice or soy protein are naturally free of lactose because they contain no animal milk.
The entry Whey isolate explains more about more heavily filtered whey, and the guide Lactose-free protein offers an overview of dairy-free alternatives.
