Phytonutrients

Phytonutrients, also called plant bioactives, are a diverse group of compounds produced by plants that are not considered essential nutrients for humans but may contribute to health. Unlike vitamins and minerals, phytonutrients are not required to prevent deficiency, yet many studies associate higher intakes with reduced risk of certain chronic diseases. They occur in fruits, vegetables, grains, legumes, nuts, seeds, herbs, and spices.

The term covers several chemical classes, including polyphenols (such as flavonoids, phenolic acids, and stilbenes), carotenoids (beta-carotene, lycopene, lutein), glucosinolates and isothiocyanates (in cruciferous vegetables), phenolic volatile compounds, and phytoestrogens (like isoflavones).

Potential mechanisms include antioxidant activity, anti-inflammatory effects, modulation of enzyme systems, influence on gut microbiota, and gene expression. Observational studies link higher dietary phytonutrient intake with lower risk of cardiovascular disease, certain cancers, and other conditions; randomized trials show smaller or inconsistent effects, with results dependent on dose, form, and population. Supplements are not universally beneficial and may be ineffective or harmful at high doses.

Bioavailability varies; cooking, processing, and the food matrix affect absorption. Some compounds become more available when cooked (for example, lycopene in tomatoes), while others degrade with heat or extraction. A varied diet rich in colorful fruits and vegetables is generally recommended to maximize phytonutrient intake.

In nutrition guidelines, phytonutrients are considered a component of a healthy dietary pattern rather than individual targets. Research continues to clarify effective doses, interactions, and which compounds are most beneficial for specific health outcomes.