Although the Linus Pauling Institute has a long-standing, deep relationship with vitamin and mineral research, we also study other compounds for their role in human health and disease. If you ever read nutrition research or see it discussed in the news, you may come across the unusual word ‘phytochemicals’.

Want to know what they are?

Put simply, the word ‘phytochemical’ means ‘chemicals found in plants’ (phyto means plant or plant-derived). However, that is a very poor definition for the compounds that LPI is interested in, since it could apply to virtually anything from a plant. Starches, oils, and sugars, for example, could all be considered phytochemicals by this vague definition.

Micronutrients could also be considered phytochemicals if they come from a plants, but scientists tend to use the word in a specific fashion. Put simply, phytochemicals are compounds that are only found in plants but are not nutrients that are needed by the body – in other words, they are not considered nutritionally essential.

For example, a blueberry is a fruit that is full of a variety of compounds in both the flesh and skin. The skin of a blueberry in particular contains a class of compounds called anthocyanidins that give the blueberry its distinctive color.

When you eat a blueberry, your body absorbs the sugars, vitamins, and minerals that provide you energy or make up the building blocks of your body, but you also consume these anthocyanidins. They don’t provide your body with energy or make up your body’s structure, so they can’t be called nutrients.  You can think of them as simply being ‘along for the ride,’ but that would understate their potential.

Although the body does not need them to survive, phytochemicals can have health effects. Depending on the specific compound, the dose, and how the body reacts to the compound, some of them can have positive effects on health, while others may have negative or no apparent effects at all.

Many people consider phytochemicals as an ‘extra benefit’ of eating plants. Since plants rely on a wide variety of chemical pathways that do not occur in animals, they can come in all different forms. Although many classifications exist, the list of these compounds is large and ever expanding. Some estimates have the list of currently known phytochemicals as high as 10,000.

High-quality studies are available for only a small fraction of these compounds. Although the research is continually growing and becoming more complex every day, there is much that we don’t understand about many different types of phytochemicals. Many of these compounds travel through the digestive tract without ever being absorbed by the body, except in very small quantities. This may mean that many phytochemicals can have an impact on gut health but limited effects inside the body.

Additionally, many phytochemicals that are absorbed into the bloodstream are rapidly chemically modified by enzymes, affecting their biological activity in complicated ways. We have included many phytochemicals in the Micronutrient Information Center  if you wish to know more about them and how they work in the body.

As a last word, we must add a cautionary note about phytochemical supplements. Currently there is little evidence to recommend any specific phytochemical supplement. Plant-based foods are prominent features of a healthy dietary pattern, but purified phytochemicals provide levels much higher than usual levels that would normally be found in the diet. Many of these compounds may not be accepted as completely safe, so a dose of caution – as always – is warranted.