Valerian

Is valerian safe?

Yes, for most adults using it for a few weeks. Valerian root is among the better-tolerated herbal sleep aids, and the European Medicines Agency accepts it as a medicine for mild nervous tension and sleep problems. Side effects at usual doses are mild: headache, stomach upset, a groggy feeling the next morning, sometimes vivid dreams.

There are two catches. It can rarely injure the liver, mostly when sold in blends with other herbs. And because it is a sedative, it adds to the effect of alcohol and sleeping pills. Whether it actually improves sleep is less certain than its safety.

How much valerian is normal?

The EU herbal monograph, which sets the dose for licensed products, gives 400 to 600 mg of dry extract per dose, up to three times a day, with no more than four doses a day. For sleep, the dose is taken half an hour to an hour before bed. NCCIH, the US government's complementary health centre, says 300 to 600 mg a day has been used with apparent safety for up to six weeks.

Valerian works slowly. The monograph says it is not suited to a single bad night and suggests two to four weeks of use, and a doctor or pharmacist if sleep is still poor after two weeks. Valerian teas and tinctures use the dried root at much larger weights, 0.3 to 3 g per dose, so compare products by extract, not by "root equivalent".

Overdose is not well documented, but it does not look severe. The monograph describes a case of about 20 g of root causing fatigue, cramps, chest tightness, tremor and dilated pupils, all gone within 24 hours.

Liver injury: rare, and usually in blends

LiverToxLiverToxA free US National Institutes of Health database that summarises what is known about liver injury caused by medicines, herbs and supplements.More in the glossary, the US National Institutes of Health database on drug-induced liver injuryDrug-induced liver injuryLiver damage caused by a medicine, herbal product or supplement. It is usually rare and unpredictable, but it can be serious.More in the glossary, gives valerian a likelihood score of C: a probable but rare cause of clinically apparent liver injury. Given how many people take it, published cases are few. Most involved products that also held skullcap or black cohosh, which makes it hard to know which herb was to blame. Injury typically began 3 to 12 weeks after starting and recovered within a few months of stopping. There are no convincing cases of liver failure from valerian alone.

That record is much cleaner than kava, the other well-known calming herb, which has repeated reports of severe liver damage and has been restricted in several countries. If you buy a sleep blend, check the label for skullcap and kava.

Drug interactions: mostly about drowsiness

Unlike St John's wort, valerian does not seem to change how the liver clears drugs. In a 2005 study, 12 healthy volunteers took valerian for 28 days, and their activity of four major drug-handling enzymes (CYP1A2CYP450 enzymesA family of liver enzymes that break down many medicines. When another drug or supplement speeds them up or slows them down, drug levels change.More in the glossary, CYP2D6, CYP2E1 and CYP3A4) did not change. Some test-tube studies found effects on CYP3A4, but they did not show up in people, and the EMA monograph lists no reported interactions.

The real interaction is additive sedation. Valerian on top of alcohol, a benzodiazepine such as alprazolam, a sleeping pill such as zolpidem, or sedating antihistamines can leave you drowsier than you expect, including the next morning. The EMA advises against driving or using machinery if you feel affected. Combining it with melatonin or CBD has not been well studied.

Does it work?

Less clearly than its popularity suggests. The EU accepted ethanol extracts of valerian for sleep problems because controlled studies showed shorter time to fall asleep and better sleep quality. But NCCIH says the evidence is inconsistent, and in 2017 the American Academy of Sleep Medicine recommended against valerian for chronic insomnia in adults. For long-term insomnia, cognitive behavioural therapy is the first-choice treatment in most guidelines.

What to check before buying

Product content varies. When researchers tested 14 valerian products sold in Canada, the levels of valerenic acids (compounds often used as quality markers) varied widely and often did not match the labels. In the UK and EU, a licensed product (in the UK, look for a THR number on the pack) is made to a set standard and dose. In the US, look for a USP VerifiedThird-party testingTesting of a supplement by an independent lab to check that it contains what the label says and is free of set contaminants.More in the glossary or NSF mark.

Who should be careful

• Pregnant or breastfeeding women: the EMA advises against use because safety has not been shown.
• Children under 12.
• Anyone taking sedatives, sleeping pills, opioids or drinking alcohol in the evening.
• People with liver disease, or who notice signs of liver trouble while taking it.
• Anyone having surgery: tell the anaesthetist you take it, and talk to your doctor or pharmacist about when to stop.

After months of nightly use, taper rather than stop abruptly. NCCIH notes withdrawal symptoms such as anxiety, insomnia and, rarely, heart rhythm disturbances.

How we scored it

Regulatory actions (85) and dose safety (80) are the strongest factors: no bans, an EU monograph and mild side effects. Organ toxicity (72) is held back by rare liver cases, and product quality (65) by inconsistent content. Valerian scores just above melatonin, which has fewer liver concerns but weaker product quality control in the US.