A human needs only around 50 chemical substances to stay alive in good health, which are composed of around 20 chemical elements.
These approximately 50 include a little more than 10 amino-acids for providing both the essential amino-acids and the additional bound ammonia that is needed, 2 or 3 amino-acid derivatives, vitamin C, around 7 or 8 essential fatty acids and liposoluble vitamins, 8 B-complex vitamins, water, salt and about a dozen minerals.
Besides these, there are a few additional chemical elements that might be needed, but if they are needed they are needed in quantities so small in comparison with their normal abundance as impurities in food that there have never been observed any cases where any harm could be attributed to their absence (e.g. silicon and bromine).
There are also various substances from plants that may be beneficial for health, but which are not known to be strictly necessary for anything.
