Kelp is especially high in iodine, which must be present for proper glandular function and metabolism. It also contains iron, sodium, phosphorus and calcium, as well as magnesium and potassium. Kelp is a source of vitamins A, B1, B2, C, D and E, plus amino acids. Kelp also makes a popular salt substitute. Because the plant’s nutrients come in a natural form, they are easily assimilated by the body.