Vitamin D keeps our bones and muscles strong, and now there's some evidence it could help protect us from Covid-19. With many of us deficient in the 'sunshine vitamin' could food fortification be the best way to ensure we're getting enough?

Emily Thomas hears how enriched milk and margarines have helped to almost completely eliminate vitamin D deficiencies in Finland, and how plans to fortify flour could prevent devastating bone diseases like rickets in Mongolia.

As more countries are urged to act, we ask whose responsibility fortification should be - governments' or the food industry's? Plus, why is it so hard to get enough vitamin D from sunlight or our regular diets, and is it possible to get too much?

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Producers: Simon Tulett and Sarah Stolarz

Contributors:

Kevin Cashman, professor of food and health at University College Cork, Republic of Ireland;

(Picture: An optical illusion of a boy 'eating' the sun. Credit: Getty Images/BBC)