Are there any dangers or contraindications to taking Ashwagandha?

Ashwagandha is generally well tolerated when taken at the recommended doses. However, like any dietary supplement, it may cause certain side effects, particularly when taken at high doses or over a prolonged period. The available clinical studies mainly report mild digestive problems and, more rarely, allergic reactions. By analysing around thirty clinical trials that assessed the effect of Ashwagandha on health, researchers were able to identify the most common side effects[1].

Digestive problems

Taking Ashwagandha, particularly at high doses, can cause abdominal discomfort, nausea, diarrhoea or vomiting. These effects are generally mild and temporary, and disappear once the supplement is stopped or the dose is reduced. To improve tolerability, it is recommended to take Ashwagandha with a meal and to avoid overdoses.

Causing allergies

In rare cases, Ashwagandha may trigger an allergic reaction, particularly in people who are sensitive to the Solanaceae family (such as tomatoes, aubergines or peppers). Possible symptoms include skin rashes, itching or mild breathing difficulties. If you experience any unusual reaction, you should stop taking the supplement and consult a healthcare professional.

Ashwagandha is considered safe at the doses usually recommended, and for people in good health. However, some serious side effects have been reported. Even if they are rare, it is important to be aware of them before taking an ashwagandha food supplement.

The dangers of ashwagandha for the liver

In recent years, several cases of liver damage have been reported in the scientific literature after taking ashwagandha in excessively high doses [2],[3]. Patients generally develop jaundice and symptoms, such as nausea, lethargy, itching and abdominal discomfort. Researchers believe that a compound present in ashwagandha extracts is responsible. The compound in question is a withanolide: withanone, which is present in significant quantities in ashwagandha, and to which many of its medicinal properties are attributed. But withanone has chemical groups in its structure - known as toxicophores - which, in medicines, are associated with undesirable effects and toxicity. Fortunately, we have a cellular detoxification system - gluthation - which neutralises these toxicophores, making the drugs containing them safe if used correctly. The same applies to ashwagandha. If taken in recommended doses, despite the presence of withanone toxicophores, our cellular detoxification system makes it safe. However, if taken in high doses, gluthation is no longer able to cope and detoxify the groups responsible for withanone toxicity, which can lead to liver damage[4]. In the majority of cases, liver damage regresses within a few months of stopping ashwagandha and with appropriate treatment.

Effects of ashwagandha on the thyroid gland

Several cases of hyperthyroidism (thyrotoxicosis) caused by high-dose ashwagandha supplementation have been reported in scientific studies, even in people who initially had no thyroid problems[6]. After two months of ashwagandha supplementation at a dose of 1950 mg per day (which is much higher than the recommended dosage), one woman experienced a worsening of her anxiety symptoms, as well as other symptoms, such as extreme fatigue, weight loss and an increased resting heart rate[7]. Hyperthyroidism was confirmed, and stopping ashwagandha allowed her to return to normal.

However, in the majority of cases, scientific studies report a beneficial effect of ashwagandha on hypothyroidism[8],[9]. As a reminder, hypothyroidism is characterised by insufficient production of the thyroid hormones T3 and T4. It appears that ashwagandha's stimulant properties may encourage the thyroid gland to produce these hormones. Ashwagandha could, therefore, help maintain normal thyroid function and offer support to people suffering from hypothyroidism.

However, few clinical studies have been carried out on this subject, which underlines the importance of caution:

• A clinical study was carried out by GANNON in 2014 on 60 patients and confirmed the pharmacological results in animals, particularly with regard to T4 secretion, suggesting therapeutic potential in hypothyroidism.

• A more recent study conducted by SHARMA in 2018 also revealed promising results. In this placebo-controlled clinical study, 55 subjects with hypothyroidism were given 600 mg of ashwagandha extract for 8 weeks. The results showed a significant decrease in TSH after 4 and 8 weeks of treatment, as well as a significant increase in T4 and T3 levels. These results suggest the potential of ashwagandha in normalising hormone levels in people with hypothyroidism.

However, it is important to stress that ashwagandha should not replace prescribed medication for hypothyroidism. Before starting any ashwagandha supplementation, it is advisable to consult a healthcare professional to assess the potential dangers and benefits, particularly for people with thyroid problems.

However, as a precautionary measure and due to a lack of scientific evidence on the subject, Ashwagandha is not recommended for people with thyroid disorders. Before starting any Ashwagandha supplementation, it is strongly recommended that you consult a healthcare professional to assess the potential risks and benefits, particularly for those with thyroid problems.

If you have no specific health problems, and provided you take it at the recommended dose (500 mg per day), Ashwagandha poses no health risk. However, there are several contraindications, notably certain medication regimens and certain medical conditions. Furthermore, Ashwagandha is intended for adults only and should not be given to young children. Do not take Ashwagandha as a dietary supplement without medical advice, especially if you are in any of the situations listed below.

1. If you have diabetes: Ashwagandha may improve insulin sensitivity and lower blood sugar levels[11] but may also interfere with diabetes medication. Your blood sugar levels could drop too low.

2. If you have an autoimmune disease: Ashwagandha may boost immune system activity, thereby exacerbating symptoms in people with autoimmune diseases. In particular, ashwagandha could worsen the progression of conditions such as multiple sclerosis, lupus and rheumatoid arthritis. Ashwagandha and immunosuppressant medicines must not be taken at the same time, as they have opposing effects.

3. If you have a stomach ulcer: As ashwagandha can irritate the gastrointestinal tract, it is best to avoid taking it if you have a stomach ulcer.

4. If you are due to undergo surgery: Given its effects on the body, ashwagandha may interfere with anaesthesia. It is recommended that you stop taking ashwagandha two weeks before any surgical procedure.

5. If you have thyroid problems: If you have hypothyroidism, do not take ashwagandha without medical supervision. In cases of hyperthyroidism, ashwagandha is not recommended.

6. If you are pregnant or breastfeeding: Ashwagandha should not be used during pregnancy or whilst breastfeeding. There is a lack of scientific studies and evidence to confirm that taking ashwagandha during these sensitive periods of life is safe.

Ashwagandha and drug interactions

There are several drug interactions with Ashwagandha which may, in some cases, enhance the effects of medicines and, in others, counteract their action. People taking medicines for diabetes, high blood pressure, immunosuppressants, sedatives or medicines for thyroid problems should not take Ashwagandha without medical advice. The same applies if you are taking anxiolytics such as benzodiazepines. Like benzodiazepines, Ashwagandha – which is known to aid stress management – acts on the receptors of the neurotransmitter GABA. There is therefore a risk that taking Ashwagandha at the same time may enhance the effects of anxiolytics.

Juliette Pouyat has been a scientific writer specialising in nutrition and health for 10 years. After studying chemistry, she wrote a thesis on the nutritional quality of infant milks and obtained a doctorate from the Institut National Agronomique Paris-Grignon. She is the author of numerous articles and several books on the links between food and health, food supplements and well-being. Juliette draws on recent scientific literature to write articles for the general public.