Foods rich in the vitamin include salmon, swordfish and eggs, as well as fortified milk, yogurt and orange juice.

The abundance of greenery to eat at this time of year gives cows and goats the potential to produce rich, fortified milk.

To test the strategy, it has been applied to the fortified milk (adding a BLA product known as an antimicrobial destroyer).

Consumption of fortified milk increased dietary vitamin D intake and raised serum 25(OH)D concentrations, but not to the level thought to reduce fracture risk.