Slimming Herbs and Teas: The Hidden Drugs Inside Them

What is actually in a slimming tea or herbal capsule?

The honest answer is that you often do not know. A 2021 study published in Molecules analysed weight-loss supplements sold in Gulf pharmacies and online markets and found that a significant proportion contained pharmaceutical drugs that were not declared on the label. The most common adulterant was sibutramine, a prescription appetite suppressant that was withdrawn from the market in over 100 countries after clinical trials showed it caused heart attacks and strokes.

Sibutramine raises blood pressure and heart rate. Taken alone by a healthy adult in a controlled dose it was considered just about acceptable under strict medical supervision. Taken unknowingly by someone with undiagnosed high blood pressure or heart disease, as an ingredient in a tea bought from a market stall or a social media post, it can be fatal. A 2021 case report in Case Reports in Cardiology documented sudden cardiac death attributed to sibutramine found in an unlabelled slimming product.

Other drugs that have been detected in slimming products include thyroid hormones, diuretics, phenolphthalein (a laxative removed from over-the-counter products decades ago because of cancer concerns), and stimulant amphetamine-like compounds. The FDA's own database of adulterated supplements, reviewed in a 2022 paper in the Journal of Clinical Pharmacology, recorded thousands of tainted products over a 14-year period, with weight-loss products consistently the most contaminated category.

Why are these products sold if the ingredients are banned?

The gap between regulation and enforcement is wide, especially in markets where customs inspection of small parcels is limited and online retail crosses borders without scrutiny. A manufacturer can label a capsule as containing only herbal extracts such as green tea, garcinia cambogia, or bitter orange, and add pharmaceutical ingredients without declaring them. The product passes visual inspection easily.

The WHO identifies the Middle East and North Africa among regions with elevated rates of substandard and falsified products reaching consumers. Supply chains are often short and informal, a shop buys from a wholesaler who bought from a trader who imported from an unregulated factory. No one in that chain tests the contents.

This is not a fringe problem. A research team analysing products sold in UAE pharmacies found adulteration across multiple product lines. The pattern repeats across Egypt, Jordan, Lebanon, and countries where imports are inspected less rigorously. Buying a product from a licensed pharmacy in the same country it was manufactured and approved gives meaningfully better odds of knowing what you are taking, but it does not guarantee it.

What do laxative-based products actually do?

Many slimming teas that do not contain a banned drug still contain senna, cascara, or other plant-based laxatives at doses far higher than those used medically to treat constipation. These cause rapid emptying of the bowel, which shows on the scale as a weight drop of one to two kilograms within a day. That weight is water and bowel content, not fat. It returns the moment you drink and eat normally again.

Using senna or similar laxatives repeatedly over weeks or months depletes potassium, sodium, and magnesium. A low potassium level (hypokalaemia) causes muscle weakness, cramps, and, in severe cases, dangerous heart rhythm disturbances. People with underlying heart conditions, or who are also taking medications that affect potassium, face a greater risk. The tea that feels like it is working because the scale goes down is causing real physiological harm below the surface.

There is also a rebound effect. The bowel adapts to being stimulated repeatedly and eventually stops moving on its own. Some people who have used stimulant laxatives for months find they cannot have a normal bowel movement without them. This is a real and documented dependence that is very uncomfortable to reverse.

How to read a slimming product label without being misled

A label that says herbal, natural, plant-based, or traditional does not mean the product is safe or that the contents match what is printed. The following are additional warning signs that a product warrants particular suspicion. It promises rapid weight loss, often using numbers such as five kilograms in a week. It was bought through social media, a messaging app group, or a market stall rather than a licensed pharmacy. The packaging has no manufacturer address, batch number, or expiry date. It is imported without local regulatory approval markings.

Even products that carry a health ministry registration number in one country may not have been tested for pharmaceutical adulteration. Registration often involves checking label claims and manufacturing site documents, not chemical analysis of each batch. This is a known limitation of regulatory systems across the region, including in countries with relatively strong oversight.

If you want to check a specific product, the FDA's Tainted Products database is publicly searchable online at fda.gov. It lists specific brand names found to contain undeclared drugs. It is weighted towards products marketed in the United States but many of the same brands circulate in Arab markets.

Are there any herbal ingredients with real evidence for weight loss?

Green tea extract and caffeine have the most evidence among plant-derived products, and that evidence is modest. Studies show a small increase in energy expenditure and fat oxidation over a short period, producing an average weight loss of less than one kilogram more than a placebo over twelve weeks. This effect disappears entirely in people who already consume caffeine regularly, which is most of the region's adults given coffee and tea habits.

Glucomannan, a fibre derived from konjac root, has reasonable evidence for reducing appetite and improving cholesterol slightly, and it is generally safe as a food additive. It works by expanding in the stomach and slowing gastric emptying, which extends the feeling of fullness. It has no cardiac or blood pressure risk and is not a stimulant. It is not exciting and will not produce dramatic weight loss, which is why it is not heavily marketed.

Bitter orange, often listed on products as Citrus aurantium or synephrine, was introduced as a replacement for ephedrine when that was banned. The evidence for weight loss is weak and the cardiovascular risk profile is similar enough to ephedrine that most pharmacologists advise against it. If you see it on a label, treat the product with the same caution you would apply to a stimulant drug.

What does sustained weight loss actually require?

Fat loss requires a sustained energy deficit: taking in fewer calories over time than the body uses. This is not exciting, it does not sell teas, and it is not fast. But it is the only mechanism by which body fat is reduced. Every method that produces lasting results, whether dietary change, increased physical activity, structured behaviour change, or medication prescribed by a doctor, works through this mechanism. Everything else is either water weight, bowel content, or fraud.

The prescription medications available for weight management today, including GLP-1 receptor agonists such as semaglutide, work by changing appetite signalling and have a meaningful evidence base from large clinical trials. They are available in some countries in the region and must be prescribed by a doctor who has assessed cardiovascular risk and other factors. These are not the same as slimming supplements sold online.

A registered dietitian or a doctor trained in obesity medicine can assess your starting point honestly, rule out underlying conditions that affect weight such as hypothyroidism, and set a realistic plan. That visit will cost less in money and risk than a prolonged course of adulterated supplements.

Which groups face the highest risk from slimming supplements?

People with any cardiovascular condition, including high blood pressure, a previous heart attack, or an arrhythmia, face the greatest danger from products containing sibutramine or stimulant adulterants. Sibutramine was studied in people known to have cardiovascular disease and the trial was stopped early because the harm was clear. The same drug taken unknowingly carries identical risk.

People with diabetes who are also taking medications to lower blood sugar face a compounded risk from products containing diuretics, which raise blood glucose and cause dehydration, and from stimulants, which blunt the effect of insulin. People on warfarin or other blood thinners should be particularly careful because several herbal extracts, including green tea at high doses, affect drug metabolism through the liver.

Adolescents are a growing market for slimming products and represent a group at particular risk, both because their cardiovascular systems are still developing and because they are more likely to buy products through social media channels where regulatory oversight is minimal. If you are a parent and your child is interested in slimming products, a conversation with a paediatrician or family doctor is the right starting point, not a supplement.

What to do if you have been taking a slimming supplement

If you have been taking a herbal slimming product and have no symptoms, the most important step is to stop it and not replace it with another similar product. Do not assume a different brand is safer. Many products circulate under dozens of brand names with identical contents.

If you have developed symptoms while taking a product, particularly heart palpitations, a fast pulse, severe headache, chest discomfort, muscle weakness, or cramps, stop the product and seek medical attention. Bring the packaging or a photograph of it so the doctor can look up the brand. If a sibutramine-containing product was taken for weeks or months, a blood pressure check and basic cardiac evaluation are reasonable.

If you experienced symptoms but they resolved when you stopped, tell your regular doctor at your next visit. There is no requirement to report to a regulator in most countries, but in countries with a pharmacovigilance centre, such as Saudi Arabia's National Pharmacovigilance Centre or Egypt's Egyptian Pharmacovigilance Center, reporting helps flag products that may harm others.

Sources

• Jairoun AA, Al-Hemyari SS, Shahwan M et al: Adulteration of Weight Loss Supplements by the Illegal Addition of Synthetic Pharmaceuticals, Molecules (Basel, Switzerland), 2021
• Carles M, Pietri T, Micallef J et al: Presence of sibutramine and sildenafil in weight loss dietary supplements: a case series with analytical and clinical investigation, Clinical toxicology (Philadelphia, Pa.), 2025
• Rodriguez-Guerra M, Yadav M, Bhandari M et al: Sibutramine as a Cause of Sudden Cardiac Death, Case reports in cardiology, 2021
• White CM: Continued Risk of Dietary Supplements Adulterated With Approved and Unapproved Drugs: Assessment of the US Food and Drug Administration's Tainted Supplements Database 2007 Through 2021, Journal of clinical pharmacology, 2022
• Cebi N, Yilmaz MT, Sagdic O et al: A rapid ATR-FTIR spectroscopic method for detection of sibutramine adulteration in tea and coffee based on hierarchical cluster and principal component analyses, Food chemistry, 2017
• World Health Organization: Substandard and falsified medical products fact sheet