The nutraceutical market continues to grow rapidly in Europe, and Italy remains one of the leading countries in both production and consumption. Today, millions of people use supplements, herbal complexes, plant extracts, and bioactive substances to support their well-being, prevention, and quality of life.

This widespread use, however, requires greater clinical attention. Nutraceuticals are not “neutral” substances: they can interact with medications, alter their absorption, change their metabolism, or increase their side effects. In some cases, the risk involves life-saving therapies, cardiovascular drugs, anticoagulants, antiepileptic drugs, or cancer treatments.

For this reason, the doctor’s role becomes central in managing a truly integrated and safe therapy.

Nutraceuticals and medications: why interactions are important

Many patients take dietary supplements without informing their doctor, believing that “natural” automatically means harmless. In reality, numerous bioactive compounds use the same enzymatic systems as medications and can alter their behavior in the body.

Interactions between nutraceuticals and medications can:

• reduce therapeutic efficacy;
• increase medication toxicity;
• alter the bioavailability of active ingredients;
• cause even severe adverse reactions;
• interfere with chronic polypharmacy.

The risk is especially high in elderly patients, frail individuals, and those taking multiple medications simultaneously.

Pharmacokinetics and pharmacodynamics: how interactions occur

To understand the risks, it is essential to know two key concepts:

Pharmacokinetics

It studies what the body does to the medication:

• absorption;
• distribution;
• metabolism;
• excretion.

Many nutraceuticals can affect hepatic cytochrome P450 enzymes or P-glycoprotein, altering the plasma concentrations of medications.

Pharmacodynamics

This analyzes the biological effects of the medication on the body. Some supplements can enhance or antagonize the therapeutic effects of medications.

Medications most at risk of interaction with supplements

Particular attention must be paid to medications with a narrow therapeutic index, where even small changes in concentration can cause toxicity or loss of efficacy.

The main ones include:

• anticoagulants such as warfarin;
• digoxin;
• lithium;
• phenytoin;
• antiplatelet drugs;
• immunosuppressants;
• chemotherapeutic agents;
• cardiovascular medications.

In these cases, the uncontrolled introduction of a nutraceutical can compromise the therapeutic balance.

Interactions in oncology: a risk that is often underestimated

One of the most delicate areas concerns cancer therapies. Many patients use plant extracts or antioxidants on their own to reduce the side effects of chemotherapy.

However, substances such as:

• green tea;
• turmeric;
• St. John's wort;
• high doses of antioxidants;
• concentrated flavonoids,

can interfere with:

• tyrosine kinase inhibitors;
• taxanes;
• immunotherapies;
• medications metabolized by hepatic cytochromes.

Some nutraceuticals actually act on the same cellular transporters and enzymatic systems as anticancer drugs, increasing the risk of:

• toxicity;
• therapeutic failure;
• disease progression.

For this reason, any supplement taken during cancer treatment should always be evaluated by the doctor.

St. John's wort, valerian and herbal remedies: when “natural” alters drug metabolism

Many products used for sleep, anxiety, or mood can significantly alter hepatic metabolism.

St. John's wort (Hypericum perforatum), for example, is one of the most powerful natural enzyme inducers and can reduce the efficacy of:

• oral contraceptives;
• antidepressants;
• anticoagulants;
• immunosuppressants;
• cancer medications.

Valerian, ginkgo biloba, garlic, high doses of omega-3, and turmeric also require attention when taken alongside pharmacological therapies.

The intestinal microbiota influences drug interactions

Today we know that the intestinal microbiota plays a key role in the metabolism of nutraceuticals.

Polyphenols, flavonoids, and herbal complexes are transformed by intestinal bacteria before absorption. Alterations in bacterial flora due to:

• antibiotics;
• unbalanced diet;
• intestinal inflammation,

can alter the bioavailability of bioactive compounds and their ability to interact with medications.

This makes the clinical response highly individual.

Caution with fiber, minerals, and activated charcoal

Some interactions are physicochemical and occur directly in the gastrointestinal tract.

Substances such as:

• psyllium husk;
• psyllium;
• calcium;
• magnesium;
• iron;
• aluminum;
• activated charcoal,

can reduce the absorption of:

• antibiotics;
• thyroid hormones;
• tetracyclines;
• quinolones.

To reduce the risk, it is advisable to separate their intake by at least three hours.

When to take nutraceuticals: the role of chronobiology

The time of day can also affect efficacy and safety.

Some examples:

• fermented red rice is generally taken in the evening to synchronize with nighttime cholesterol synthesis;
• vitamin D and curcumin are better absorbed in the presence of fats;
• amino acids and diuretics are often more effective on an empty stomach.

Correct timing of intake can improve bioavailability and reduce drug interactions.

Nutraceuticals and surgery: when to discontinue them

Before surgery or dental procedures, it is essential to discontinue certain supplements with anticoagulant or antiplatelet activity.

The main ones include:

• ginkgo biloba;
• garlic;
• high doses of omega-3;
• vitamin E;
• turmeric.

Discontinuing them in advance reduces the risk of intraoperative and postoperative bleeding.

The doctor's role in integrated therapy

Today, the doctor must manage not only prescribed medications but also the entire range of bioactive substances taken by the patient.

A proper medical history should always include:

• supplements;
• herbal teas;
• phytotherapeutics;
• nutraceuticals;
• herbal products;
• vitamins and minerals.

Many patients do not spontaneously report these products because they do not consider them part of their therapy.

Personalized medicine and pharmacogenetics

Genetic variants of hepatic cytochromes can profoundly alter individual responses.

Polymorphisms of the systems:

• CYP2D6;
• CYP2C19;
• CYP3A4,

which affect the ability to metabolize drugs and nutraceuticals.

This explains why some people develop serious adverse effects even with low doses, while others show reduced responses or therapeutic failure.

Technology, databases and artificial intelligence

The increasing complexity of the sector makes the support of:

• updated databases;
• digital tools;
• pharmacovigilance systems;
• applications dedicated to interactions.

Information should always be verified through authoritative sources such as:

• Italian Medicines Agency;
• Italian National Institute of Health;
• Italian Society of Pharmacology;
• Italian Society of Nutraceuticals.

Artificial intelligence can also be a valuable support, but it cannot replace clinical judgment. Algorithms can, in fact, generate inaccurate information or incorrect scientific references, especially in a highly dynamic sector such as pharmacological interactions.

Nutraceuticals represent an important resource for prevention and metabolic support, but they must be managed with the same scientific rigor reserved for medications.

Pharmacological interactions can be clinically relevant and require:

• pharmacological knowledge;
• monitoring;
• therapeutic personalization;
• patient education.

Only through conscious collaboration between the doctor and the patient will it be possible to integrate nutraceuticals and medications effectively and safely, transforming integrated medicine into a real tool for health and prevention.