You may lack vitamin D if you avoid milk but you can get that from fish and eggs, or exposure to sufficient amounts of sunlight. Again, this was not a problem for our ancestors, but it may be difficult for northern Europeans and people who spend too much time indoors.

And drinking too much milk can actually be bad for your bones. One 10-year study in the US involving thousands of women surprisingly found that women who drank two or more glasses of milk had a 45 per cent increased risk of hip fracture. This may have been because eating too much protein, found in meat and milk, actually decreases the health of the bones. The underlying reason is that protein is made from amino acids and when the bloodstream is too acidic the body releases calcium from bone to neutralise it. So you need to strike a balance between your protein intake and calcium intake.