Herbal supplements are a booming business. Turmeric, ashwagandha, elderberry, echinacea, ginger, ginseng, mushroom blends and many more fill store shelves and online marketplaces. Sales have grown steadily for years. That growth brings more choice, but also more products of uneven quality, and herbal supplements are harder to get right than simple vitamins. Here is what is really going on, and how to buy with confidence.
Why herbs are harder than vitamins
Vitamin C is the same molecule whoever makes it. A plant is different. The amount of active compounds in an herb depends on the species, the part of the plant used, where and how it was grown, when it was harvested and how it was processed. Two bottles of the "same" herb can contain very different amounts of the compounds that matter.
Common quality problems
Independent testing over the years has found herbal products that:
- Contain less of the herb than claimed, or none at all.
- Contain a different plant, or filler such as rice powder.
- Are contaminated with heavy metals like lead, pesticides or microbes.
- Contain hidden drugs, particularly products sold for weight loss, sexual performance and muscle building. The FDA tracks these in its health fraud product database.
How to choose a better herbal product
1. Check the botanical name
A good label lists the Latin name, such as Withania somnifera for ashwagandha or Curcuma longa for turmeric, plus the plant part used, such as root or leaf.
2. Look for a standardized extract
Many herbs are sold as standardized extracts, meaning the product has been tested to contain a set amount of a key compound. For example, a turmeric extract might be standardized to 95% curcuminoids. Standardization helps you compare products and match them to research.
3. Match the dose to the research
Look up what dose was used in studies. Many products contain much less, especially in multi-herb blends. See proprietary blends explained.
4. Look for third-party testing
USP, NSF and other certifiers test for identity, potency and contaminants. Few herbal products carry these seals, which makes them more valuable when you find one. See what third-party tested means.
5. Ask for a certificate of analysis
Reputable brands can provide lab test results for each batch, including heavy metal testing.
6. Be cautious with imported traditional remedies
Some traditional medicine products bought online or abroad have been found to contain high levels of lead, mercury or arsenic.
Herbs with known safety concerns
Even good-quality herbs can cause problems for some people. A few to be careful with:
- St. John's wort: many drug interactions. See supplement and drug interactions.
- Kava: linked to serious liver damage.
- Comfrey (taken by mouth): can damage the liver.
- Ashwagandha: rare reports of liver injury, may affect thyroid levels, not for pregnancy.
- Green tea extract in high doses: linked to liver injury, especially on an empty stomach.
- Turmeric in high-dose extracts: rare liver injury reports. See turmeric and curcumin.
- Yohimbe: can cause high blood pressure and a racing heart.
- Ginkgo, garlic and high-dose ginger: may increase bleeding risk with blood thinners.
Who should be especially careful
- Pregnant and breastfeeding people.
- Children.
- People with liver or kidney disease.
- People taking prescription medicines.
- Anyone scheduled for surgery.
Where to find reliable information
The NIH's National Center for Complementary and Integrative Health maintains Herbs at a Glance, short fact sheets on dozens of common herbs covering what the science says and safety. It is an excellent free resource.
The bottom line
Herbal supplements can be useful, but quality and safety vary more than with vitamins. Look for the botanical name, a standardized extract, a dose that matches research, third-party testing and a reputable seller. Know the herbs with safety concerns, tell your doctor and pharmacist what you take, and be skeptical of big promises. Our herbal supplements category has more detail on individual herbs.