Vegetable stand at a market with many different vegetables on display

Bare essentials

Some necessary molecules we can only get from our diet

Many key molecules are produced by chemical modification of what we eat, a process catalysed by enzymes.

Some molecules – known as ‘essential’ – can’t be made in this way and have to come directly from our food. They were probably in good supply in our evolutionary past and so we lost the ability to make them. Of the 20 amino acids in human proteins, ten are essential. Diets including meat, dairy products and soy contain proteins with a similar average amino acid composition to ours. Vegans do not eat animal-derived protein, so they have to mix grains (eg wheat, rice and oats) and legumes (eg peas, beans and lentils) to make sure they get a complete and balanced supply of amino acids. Eating beans on toast is one way to do this.

Other components we must get from our diet include a few essential fatty acids found in a range of seeds and vegetable oils and in fish. We also need vitamins, which can be made by plants or animals, and minerals, which are found in soil or water. Water-soluble vitamins, such as several B vitamins and vitamin C, cannot be stored in our tissues and must be replenished regularly.

Most vitamins and minerals are needed only in minute amounts and are plentiful in common foods. Health agencies publish minimum requirements worked out by nutritionists. Averages are a rough guide, but individual values need to be adjusted for age and sex, height and weight, and how active you are. Too much of certain vitamins can harm your health (see our article on whether you need to take vitamins).

Lead image:

muammerokumus/Flickr CC BY


Further reading

About this resource

This resource was first published in ‘Food and Diet’ in June 2011 and reviewed and updated in August 2016.

Microbiology, Health, infection and disease
Food and Diet
Education levels:
16–19, Continuing professional development