Ashwagandha: What the Evidence Says, Side Effects and Who Should Avoid It

What ashwagandha is

Ashwagandha (Withania somnifera) is a shrub whose root has been used in Ayurveda for centuries, where it is classed as a rasayana — a rejuvenating tonic. Today it is sold worldwide as a supplement, most often for stress, anxiety and sleep.

What the research shows

According to the US National Center for Complementary and Integrative Health, research suggests some ashwagandha preparations may help with insomnia and stress, but the evidence on anxiety is unclear.

Many of the studies have been small, and they used different preparations and doses, so it is hard to say which product, at what dose, does what. There is not enough information on its long-term safety.

Side effects

Taken for up to about three months, ashwagandha appears to be safe for many people. Some people get drowsiness, stomach upset, diarrhoea or vomiting.

Rarely, ashwagandha supplements have been linked to liver injury. Stop taking it and see a doctor if you notice yellowing of the skin or eyes, dark urine, itching or pain in the upper right of your abdomen.

Who should avoid it

• Anyone who is pregnant or breastfeeding.
• People with thyroid disorders — it may affect thyroid hormone levels.
• People with autoimmune conditions.
• Anyone about to have surgery.
• People with liver disease, unless their doctor agrees.

Medicines it can interact with

Ashwagandha may interact with:

• Diabetes medicines and blood-pressure medicines, adding to their effect.
• Sedatives and sleeping pills, adding to drowsiness.
• Medicines that suppress the immune system.
• Anti-seizure medicines and thyroid hormone.

If you take any regular medicine, ask your doctor or pharmacist before starting ashwagandha, and tell an Ayurvedic doctor everything you take before they suggest it.