Milks ain't milk.

I have a choice of several supermarkets for my grocery shopping. All sell full cream and "light" milk with 4% and 2% fat respectively for $1 per litre, and most also have racks of other milks at higher prices. For example, you can buy unhomogenised milk for a premium of 50% over the normal price. The only difference between this and regular full cream milk is that the fat is not dispersed throughout the volume of the container and can rise to the top and form a nice lump of cream. People who buy this are paying extra for something which costs less to make but which has no nutritional or chemical difference to cheaper milk. For very good reasons none of the supermarket chains sell unpasteurised milk. There are people who advocate the use of raw milk, claiming that pasteurisation somehow affects nutritional value, and I assume they will pay more when they buy it from unscrupulous farmers who are prepared to bypass health regulations.

The supermarkets also sell "A2™" branded milk. A2 beta-casein is a protein found naturally in milk (another protein called A1 is also there) and this form of milk is supposed to contain more than usual. Many health claims are made for A2 milk to justify a price premium of sometimes more than 100%, and recent research has apparently supported these claims. The research was published in the European Journal of Clinical Nutrition and was funded by the company owning the brand name "A2". The findings seem to show that A2 milk is more easily digestible and causes less reaction in dairy-sensitive consumers. Unfortunately, a closer examination of the published paper shows some flaws which should be obvious to anybody halfway through a first-year university course on statistics and experimental design. There were 36 subjects in all, eight of whom said that they suffered some form of reaction to drinking ordinary cow's milk. Of those eight, 61% said that they experience less bloating drinking A2 milk rather than A1. 61% of eight is near enough to 5, so the results were based on the subjective reports of five people. This is hardly the sort of research that should encourage consumers to change a significant portion of their diet to something much more expensive. It is interesting to note that another milk manufacturer is now labelling its milk as naturally containing A2, a statement which is absolutely true.

Another recent labelling fad in the marketing of milk was to use the words "permeate free". There is no such chemical as permeate – "filtrate" is what passes through a filter, and "permeate" is the word used to describe what passes through the kind of filter known as a semipermeable membrane. There is a legitimate use for membrane filtration in the processing of milk, as it is used to adjust the concentration of components in the finished product. For example full cream milk is required have a fat content of 4% (or to be 96% fat free!). Membrane filtration is used to adjust the fat content by allowing the levels of essentially insignificant components to be adjusted. The word "permeate" was being used in labelling to suggest a difference when there is no difference at all. Technical and scientific language used in advertising is almost always there to confuse people who are scientifically illiterate. The next time there is an extended drought in Sydney we will be drinking permeate from the desalination plant at Kurnell, but we will probably call it "water" and nobody will be concerned at all.

I live in the Blue Mountains West of Sydney and sometimes think it's the food fad capital of the world. My local pub has gluten-free steak on the menu, and there is a sign (under the peanut dispenser!) on the self-serve nut bar at Coles advising that the products may contain peanuts, gluten, soy, and milk products. Gluten is a protein found in wheat and other cereals and there are people who have a sensitivity to it, having a condition called coeliac disease which is serious as consumption of quite small amounts of gluten can cause inflammation of the gut. However, the vast majority of people demanding gluten-free food have no diagnosis and are just following a form of fashion, as are those self-diagnosed with "lactose intolerance". I have diabetes, a medically-diagnosed intolerance to a food component, and I have to be very aware of food labelling standards but I'm often told that I don't understand the problem.

The one good thing you can say about these fads is that they are relatively harmless. Drinking milk with more A2 or less permeate or choosing gluten-free pizzas can damage the wallet but for the vast majority of people will make no difference to their health. This doesn't mean that nonsensical claims should not be challenged.

This article was published as the Naked Skeptic column in the November 2014 edition of Australasian Science