Four years ago, I began taking the much-promoted glucosamine supplement after hurting my knee in a skiing accident. Glucosamine is made from shellfish and is widely believed to promote joint health — the theory is that it speeds up the production of the protein needed to grow and maintain healthy cartilage. My doctor said it might help rebuild the damaged cartilage and improve my joint strength.
I didn't hesitate, and immediately started taking the recommended dose, 1,500 mg a day. Not long after, I had Irritable Bowel Syndrome (IBS). My doctor prescribed medicines to relax the bowel muscles but they didn't help.
Then, early last year, I ran out of glucosamine and didn't restock. My knee was better and I was taking fish oils, which were being promoted as the new miracle supplement for joints.
Within a few days, my bowels returned to normal and remained so until, after another ski accident damaging the same knee recently, I began taking glucosamine again.
Within a week my IBS had returned and I made the link. I researched glucosamine and found that side-effects include diarrhoea and loose stools. I stopped again and, hey presto, everything is back to normal.
Sales of health supplements have soared in recent years. It is such a huge market that manufacturers spend around £40 million (Dh228 million) a year, just telling us about their products.
As supplements are either made from natural substances or mimic substances produced by our bodies, many assume they cannot do any harm.
But we are wrong, say health professionals. They say the health-supplement industry is unregulated, which means manufacturers are not required to list potential side-effects.
"Health supplements can produce ill effects," warns Anna Raymond, from the British Dietetic Association. "People take supplements randomly but they can be toxic if taken with some medicines or in high quantities."
"Most people don't know that glucosamine and other supplements are only licensed as a food but are sold as a medicine," says Dr Dillon.
"We can get everything from a healthy diet. But people feel fluey and start taking supplements they don't need. They could end up with hypervitaminosis, caused by excessive amounts of supplements." This can lead to vomiting, lethargy and even renal failure.
So, what can you do to ensure your safety? Raymond advises anyone who starts taking supplements should tell their doctor. Here's how to identify some of the supplements with potentially negative effects you won't find listed on the packet.
Glucosamine
What it is: The supplement, which is made from crab and lobster shells is often taken to ease the symptoms of arthritis. It should be avoided if you have a seafood allergy.
Potential side-effects: According to the Arthritis Research Campaign, UK, these can include stomach upset, constipation, diarrhoea, headache and rash. Glucosamine can also react with anti-diabetic treatments by increasing blood sugar levels.
The UK Commission on Human Medicines has noted that glucosamine has a negative interaction with the blood-thinning drug warfarin and warns against taking these substances simultaneously. The supplement might also cause water retention, as it attracts water.
Kelp
What it is: This supplement is made from a seaweed, which is the fastest-growing marine algae in the world — it can grow two feet in a day and is most abundant off the north California coast. Kelp is a rich source of minerals and trace elements, including iodine — deficiency of which can lead to an underactive thyroid. It is marketed as a treatment for thyroid imbalance, caused by the thyroid gland producing either too much, or too little of the hormone.
Potential side-effects: Studies have linked kelp to an increased risk of thyroid dysfunction. It is also a blood thinner and shouldn't be taken with aspirin or any medicine to lower blood pressure.
In 2007, research at the University of California found high levels of arsenic in eight out of nine kelp supplements. Arsenic is linked to hair loss, headaches, confusion and drowsiness.
Potassium
What it is: Maintaining an adequate potassium level is important for bone health and the proper functioning of the body. Potassium supplements are often taken to help combat insulin resistance, arthritis and menopausal symptoms such as fatigue and mood swings.
Potential side-effects: Taken in high doses as a supplement, potassium can have side-effects including arrhythmia (faulty heartbeat) — and can even be fatal.
Research at Oregon State University has also linked it to muscle weakness, confusion, stomach pain and numbness or tingling in the hands, feet or mouth.
Potassium supplements react badly with some medicines and shouldn't be taken by anyone suffering from kidney or heart disease, severe dehydration or high blood pressure.
Older people who often have too much potassium in their bodies should avoid these supplements — kidneys are less efficient at eliminating potassium as we age.
Melatonin
What it is: Natural melatonin is a hormone made by the pineal gland and regulates sleep. Supplements can control our sleep/wake cycles and are used to treat sleep disorders.
Potential side-effects: These include raised blood pressure, headache, lower body temperature, fatigue and depression. A daily intake of 1-3 mg of melatonin increases its levels by 20 times the normal amount.
The British Pharmaceutical Society says that studies on its effectiveness to treat jet lag have been conflicting.
Calcium
What it is: Calcium is essential for the growth and maintenance of healthy bones and teeth, and for blood clotting, muscle contraction, healthy nerves and good hormone function. It is usually taken by women to boost bone health.
Potential side-effects: Recent research by Auckland and Aberdeen universities reflected other studies in finding a 30 per cent increased risk of heart attack among women taking calcium supplements — most of them are post-menopausal and concerned about osteoporosis.
This increase is due to the risk of calcium supplements accelerating the hardening of blood vessels.
