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Nutrition and daily life

Herbal supplements: strong effects, hidden risks

Herbal capsules, extracts and powders seem "natural" and harmless. But they can interact with medicines, harm the liver and increase bleeding. This section covers the main risks.

Last updated: ~1 min read
Capsules and dried herbs in shadow.
Figure 1.Herbal supplements aside.

01Short answer

During treatment take herbal supplements only with your team's approval. St John's wort lowers levels of many medicines, including some chemotherapy drugs and immunosuppressants. Extracts of turmeric (curcumin), garlic, ginger and ginkgo can increase bleeding. Green tea extract does not mix with drugs such as bortezomib. Echinacea stimulates the immune system and is unwanted after transplant. Normal amounts of spices in food are usually fine.

02Simple explanation

Only with approval.

St John's wort weakens medicines.

Extracts can cause bleeding.

Spices in food: fine.

03Scientific explanation

MSK About Herbs: many herbs act on CYP450 enzymes and change levels of chemotherapy and other medicines.

NCCIH: "natural" does not mean "safe"; the contents and quality of supplements are not checked as strictly as medicines.

04What happens in the body?

Quality

Heavy metals and undeclared substances have been found in herbal products.

Yellow flowers in golden light.
Figure 2.St John's wort — Herbal supplements: strong effects, hidden risks

Procedures

Before surgery or a biopsy, report all herbal products.

Root and golden powder.
Figure 3.Turmeric — Herbal supplements: strong effects, hidden risks

Interactions

Supplements can change medicine levels in the blood through liver enzymes such as CYP3A4.

Food first

A varied diet usually provides the vitamins you need; supplements only when there is a need.

05Supplements: four steps

List them, show your team, check the evidence, take only with agreement.

List — Write everything down.1ListWrite everything down.
Show — Doctor and pharmacist.2ShowDoctor and pharmacist.
Check — Evidence and risk.3CheckEvidence and risk.
Agree — Only with approval.4AgreeOnly with approval.
OpennessTell everything.
FoodPlate first.
SafetyInteractions.

06Key points at a glance

TopicIn brief
QualityHeavy metals and undeclared substances have been found in herbal products.
ProceduresBefore surgery or a biopsy, report all herbal products.
InteractionsSupplements can change medicine levels in the blood through liver enzymes such as CYP3A4.
Food firstA varied diet usually provides the vitamins you need; supplements only when there is a need.

07Key terms

Extract
A concentrated substance from a plant.
Immunosuppressant
A medicine that dampens the immune system.
Dietary supplement
A product of vitamins, minerals, herbs or other substances.
Interaction
One substance changing the effect of another.

08Key points

  • Only with approval.
  • Know the bleeding risk.
  • A spice is not an extract.
  • A supplement is not a treatment.
  • Report every one.

09Frequently asked questions

Is herbal tea OK?

Some are; see the herbal teas section, “Chamomile: evening calm in a cup”.

What about folk remedies?

Talk openly with your doctor and do not hide them.

Is a "natural" supplement harmless?

No. Natural substances can also act strongly and interact.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Is herbal tea OK?

  2. What about folk remedies?

  3. Is a "natural" supplement harmless?

My questions

12Sources

  1. NIH Office of Dietary Supplements. Dietary Supplement Fact Sheets
  2. NCCIH. Using Dietary Supplements Wisely
  3. National Cancer Institute. Complementary and Alternative Medicine
  4. Memorial Sloan Kettering. About Herbs, Botanicals and Other Products
  5. U.S. Food and Drug Administration (FDA). Safe Food Handling
  6. Food Standards Agency (UK). Cooking your food
  7. NHS inform. Preparing and cooking food safely
  8. World Health Organization (WHO). Salmonella (non-typhoidal) — fact sheet
  9. U.S. Food and Drug Administration (FDA). Selecting and Serving Fresh and Frozen Seafood Safely
  10. NHS. Fish and shellfish
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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