How supplements can pose risks

Many of us regularly take nutritional supplements, often believing them to be safe as these are marketed as ‘natural’, including various vitamin, mineral or multivitamin supplements. Over the years, these products have grown increasingly popular as people look for various ‘natural’ or safe ways to improve their health. At the same time, given the increase of lifestyle-related diseases, a large number of people take prescription medications for various health conditions or over-the-counter medicines for minor ailments like fever or headache.

The assumption that supplements are always harmless can be misleading. Combining these with medications without proper medical guidance may lead to interactions that either enhance or reduce the effects of many medicines. This can cause adverse effects, reduce the effectiveness of treatment, or, in rare cases, lead to serious health risks. It is important to understand these risks and consult a healthcare provider before taking supplements alongside medications.

Dangerous interactions

Supplements contain active compounds that can influence how the body processes medications — effects of pharmacokinetics and pharmacodynamics in scientific parlance. Pharmacokinetics refers to how a drug is absorbed, distributed, metabolised and eliminated by the body. Supplements can alter these processes. For example, some supplements may speed up drug metabolism by inducing liver enzymes, reducing the medication’s effect. Others may slow down metabolism by inhibiting these enzymes, potentially leading to toxicity.

Pharmacodynamics relates to the effects of a drug on the body. Some supplements can enhance or counteract a drug’s action, leading to unintended outcomes, as we will explore in the following examples.

Risk of bleeding: Glucosamine, often used for joint health, can increase the risk of bleeding when taken with blood thinners like warfarin or aspirin. Ginkgo biloba, a popular supplement for memory enhancement, can significantly impact blood clotting, particularly when taken alongside anticoagulants, increasing the risk of complications during surgery or injuries. Fish oil, rich in omega-3 fatty acids, may thin the blood and heighten bleeding risk, particularly when taken in high doses, if combined with drugs like aspirin.

Risk of clotting: Ginseng may reduce the efficacy of anticoagulants, increasing clot-formation risks, and can also elevate blood pressure when taken with antihypertensives. Vitamin K, vital for blood clotting, can counteract warfarin’s effects if consumed in excessive amounts in supplements.

Risk of sedation: Ashwagandha seems to have sedative effects, and there is some evidence that it may increase the effects of some sedatives and anti-anxiety drugs.

Risk of electrolyte imbalance: Magnesium supplements can interact with diuretics like furosemide, causing electrolyte imbalances that may lead to irregular heart rhythms or muscle weakness.

Multiple interactions: Grapefruit juice inhibits liver enzymes, increasing the levels of drugs like statins and many others, which can lead to side-effects.

Decreased effects of medications: St John’s Wort, popular in the West and increasingly sold in India (over 50 different products are available, priced from Rs 200 to Rs 5,000), accelerates drug metabolism, reducing the efficacy of antidepressants, contraceptives, immunosuppressants, and certain heart, cancer, HIV and allergy drugs. Calcium supplements can bind with antibiotics like tetracyclines and quinolones (ciprofloxacin), reducing their absorption. These should be taken at least two hours apart.

Iron supplements can decrease the absorption of thyroid medications like levothyroxine. Best is to take these several hours apart. Goldenseal, used for infections and sold by several companies in India, reduces metformin levels, impairing glucose control in diabetics.

Herbal tea ill-effects

Even seemingly mild preparations, such as herbal teas, can affect medication efficacy. For example, high doses of green tea may reduce levels of the heart medication nadolol, while peppermint tea can interfere with drug absorption. Additionally, chamomile has a mild anticoagulant effect, which could heighten bleeding risks when combined with anticoagulant medications.

Serious drug interactions

Narrow therapeutic range drugs: Medications like warfarin, cyclosporine, digoxin, and antiepileptics (phenytoin, carbamazepine) require precise dosing to maintain their levels within a tightly controlled range. Interactions with supplements can significantly disrupt these levels, leading to serious health risks, including toxicity or treatment failure.

Before surgery

Before undergoing surgery, it is essential to let your anaesthetist and surgeon know about any supplements you are taking. Certain supplements can interfere with how your body responds to anaesthesia, increase the risk of bleeding, or impact your heart rate and blood pressure. Herbal supplements may need to be stopped weeks before planned surgeries. Even in emergencies, sharing details about the supplements you use is critical. This information helps your doctors anticipate potential issues and manage them effectively.

Liver metabolism: Many drugs and supplements are metabolised in the liver. Products like milk thistle, often used to support liver function, can alter liver enzyme activity, impacting drugs like statins or cyclosporine.

Chronic conditions: Patients with kidney, liver or heart diseases should exercise caution, as supplements can exacerbate these conditions or interfere with medications.

While supplements can offer health benefits, they also carry risks when combined with medications. Staying informed and discussing your supplement use with a healthcare professional can help you avoid problems and make the most of your treatment.

It is best to check with a qualified healthcare professional before trying new supplements or making changes to your medications.

— The writer is professor and head, Department of Pharmacology, PGIMER, Chandigarh

Minimising the harm

• Consult your doctor: Always inform doctors about any supplements or herbal products you are taking as they can identify potential interactions and adjust medication regimens accordingly.
• Time it right: Space out the intake of medications and supplements to minimise risks.
• In correct doses: Avoid high supplement doses unless advised.
• Choose sources wisely: Purchase from reliable suppliers to reduce contamination or mislabelling risks.
• Stay informed: Seek evidence-based information and avoid self-prescribing supplements without understanding the potential interactions.
• Read labels carefully: Check ingredient lists and warnings. In India, supplements are regulated by the FSSAI, and labels must include details like recommended doses and disclaimers. For instance, the label should mention “NOT FOR MEDICINAL USE” and there should be a disclaimer that the product is not intended to diagnose, treat, cure or prevent diseases. Additionally, in some countries, independent third-party organisations exist to ensure the product contains the listed ingredients, meets high-quality standards, and is free from contamination or adulteration.
• Monitor health: Regular check-ups and monitoring of drug levels, blood tests for kidney and liver functions and other parameters, can help detect adverse effects early.