Let's start with the A2 versus A1 milk debate. A1 and A2 refer to different proteins that can occur in milk depending on the breed of cow - some cows produce mostly A1 milk, others mostly A2. Milk produced in Australia is usually a mix of the two. Some evidence suggests the A1 protein could be a risk factor for Type 1 diabetes and heart disease - but the jury is still out and, according to Food Standards Australia New Zealand, there's insufficient evidence to make any recommendations.

''Another theory suggests that A1 releases an opioid peptide that may affect movement in the gut which can affect digestive health,'' dietitian Elena Oswald says. ''The research is still ongoing but with A2 milk I've seen improvements in patients with gastrointestinal pain and discomfort as well as constipation and diarrhoea.''

Lactose-free milk is a simpler story. Lactose is the sugar that occurs naturally in milk but some people are lactose intolerant, meaning they don't have enough of the enzyme lactase to digest lactose. This can cause symptoms such as bloating and diarrhoea (but is different to having a milk allergy, which demands avoiding milk altogether).

What about cholesterol-lowering milks? These are enriched with plant sterols to help lower levels of ''bad'' LDL cholesterol. According to the Heart Foundation, plant sterol-enriched foods can be useful if you have high cholesterol or diabetes (and therefore a higher risk of heart disease, too). But if you do opt for sterol-enriched products, have at least one daily serve of orange vegetables or fruit, such as sweet potato, carrots or rockmelon, because plant sterols can lower levels of antioxidants called carotenoids, and that may increase the risk of heart disease, the Heart Foundation says.

As for organic milk, research from Britain suggests it has higher levels of healthy omega-3 fats - but we can't assume this applies to organic milk produced in Australia. The main difference with organic milk is that cattle feed on pasture grown in organic soil enriched with compost, not synthetic fertiliser, says Greg Paynter, a soil consultant to organic farming industry association Australian Organic Organic milk also comes from cattle that graze on pasture - this may not be true of all cattle in the conventional dairy industry, some of which spend time in feedlots eating grain or other supplements.

If you want calcium for bones, it's worth comparing labels because some brands have added calcium that delivers as much as 200 milligrams per 100 millilitres, compared with about 120 milligrams for most other milks - worth considering if you don't consume much dairy food, dietitian Kate Marsh says.

''Some people assume that low-fat milk has less calcium, but reduced fat milk has the same or sometimes more calcium compared with full-fat milk,'' she says.

If you opt for dairy-free milk, her advice is to compare calcium content. ''Most soy, rice, oat and almond milks have added calcium but amounts can vary, so always check,'' she says.

''Nutritionally, soy's advantage over other plant milks is that it's closer to dairy milk in its protein content and composition of nutrients. Some soy milks also have B12 added, which is important for vegans,'' Marsh says.

Price varies a lot, too - almond and oat milks in supermarkets can be less than half the price of products at health food stores.

As for avoiding added hormones or antibiotics in milk, any milk will do. According to Dairy Australia, no growth hormones are fed to dairy cattle and antibiotics are used only if an animal needs treatment for disease - in which case the milk isn't sold for human consumption.

Paula Goodyer blogs at smh.com.au/chewonthis