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Respectably high in nutrients, it is also loaded with both fiber, which keeps it on health experts’ recommended foods lists.

Sewage also poses significant environmental risks – it increases nutrients in the water leading to algal blooms which then eventually denies other wildlife – like fish - oxygen.

Vitamin A - a nutrient found in cod liver oil - is sometimes offered as a part of a treatment for measles, especially if someone is deficient, Dr Cook said.

"We're having too many high flows, too many low flows, we've got too many nutrients, pesticides and soil in the river," he said.

For all its plant and animal life aboveground, the Amazon rainforest’s soils are surprisingly poor in nutrients necessary for growing food.