Deficit in the diet leads to damage connective tissue, bleeding gums, poor healing capacity, etc. collectively known as scurvey. Citrus fruits are a good source. It has been hypothesized that geographical patterns of skin pigmentation arise from these considerations. Iodine must be present to activate the hormone thyroxine, produced by the thyroid gland. Living organisms must obtain nutrients for the purpose of growth and maintenance which, requires energy and key building blocks.
Energy is required to drive the chemical reactions in the cells of any organism.
This takes place in the mitochondria of eukaryotic cells. The principle organs involved in digestion are the stomach, small intestine, and large intestine. The pancreas lies between the stomach and small intestine and secretes additional digestive enzymes and buffers to neutralize conditions. The liver secretes bile which breaks up fats for digestion. The large intestine is where water and minerals are absorbed.