Phytochemicals

Phytochemicals are biologically active compounds produced by plants. They are not considered essential nutrients for humans, unlike vitamins and minerals, but they may influence health outcomes. Most phytochemicals are secondary metabolites that help plants defend against pests, attract pollinators, or cope with environmental stresses.

Common categories include polyphenols (such as flavonoids and phenolic acids), carotenoids (e.g., beta-carotene, lycopene), alkaloids, terpenoids, organosulfur compounds (for example allicin and isothiocyanates), and glucosinolates. Other groups include lignans, stilbenes, and betalains. Because of this diversity, phytochemicals encompass thousands of distinct structures.

Sources and intake: They are abundant in fruits, vegetables, whole grains, legumes, nuts, seeds, herbs and spices, tea, coffee, and some fungi. Diets rich in plant foods generally provide a broad mix of phytochemicals. Cooking, processing, and preparation can increase or reduce their content and bioavailability.

Health effects and evidence: Laboratory studies show various mechanisms—antioxidant, anti-inflammatory, and modulation of enzymes and receptors—by some phytochemicals. However, evidence from human trials is inconsistent, and effects are often small or dependent on context, dose, and matrix. Bioavailability varies; metabolism by gut microbiota can influence activity.

Terminology and research: Phytochemical research aims to understand their mechanisms, stability, and how they are absorbed and transformed in the body. The term phytochemicals is an umbrella label; phytonutrients is sometimes used to imply health benefits, although the distinction is not strict.