To come up with his index, Drewnowski ranked foods based on their concentrations of nine essential nutrients (protein, fiber, calcium, iron, magnesium, potassium, vitamins A, C, E).

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Garlic also contains vitamin C, calcium, potassium, phosphorus, selenium and some key amino acids.

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"Grapes are very rich in sugar and contains tons of vitamin C, calcium and potassium, " she says.

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