The thing is... your thirty second guide to everything: Dairy
What: Dairy: milk, cheese, butter, yoghurt. Full-fat, mind.
Why: Dairy has long been demonised on the basis that it contains saturated fat, which leads to Bad Things like strokes and heart disease. People self-diagnosed themselves with intolerances and switched to other sources of milk. First it was goat's milk, but that proved unpopular due to its general goat-iness, so then along came soy, which was going to save the world, except for the phytoestrogens. Early adopters then switched to various nut and plant milks - almond, hazelnut, oat, sesame, rice, barley - all very well, until you put them in coffee or tea and watch a greasy film develop. But now we can go back to good old cow's milk, safe in the knowledge that it does no harm. In fact, may very well be actively good, thanks to the bio-availability of its calcium and protein.
Why Now: A new study, a meta-analysis no less, of 29 other studies, shows no evidence that consuming dairy increases either serious heart problems or cardiovascular disease, and even suggests that fermented dairy products might lower the risk of heart attacks or stroke.
How: Easy. Switch back to full-fat cow's milk, butter, cheese and yoghurt. And oh, the cheapness of it! You can purchase a litre of milk for around €1, as opposed to double that for the fancier stuff.
Who: Presumably Elton John, Lindsay Lohan, David Beckham, Jessica Alba and the many more who starred in the 'Got Milk' advertising campaign. Athletes, body builders and anyone tapping into the high-protein, muscle-building trend.