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However, regulatory steps relating to biofortification by genetic engineering will have to be taken before these plants could be cultivated.

By identifying the minute changes in the genetic code that have caused these high-iron phenotypes, the research has unlocked new opportunities for biofortification -- enhancing the nutritional value of food.

There could also be legislation passed to allow food producers to put more vitamin D in foods that don't naturally contain it, in a process known as fortification, as well as growing produce and breeding meat to be more vitamin D-rich through biofortification.

Researchers are also exploring biofortification - for example, rearing animals to produce vitamin-D rich beef, pork, chicken and eggs.

The key is biofortification, or cross-­breeding locally grown sweet potatoes with versions rich in vitamin A, so that over time the crops naturally get better at addressing the deficiency.