Retailers selling food supplements are being urged by the Food Safety Commission to undergo a training course to better understand the products they sell.

The law lays down that "food supplements may only be dispensed by a pharmacist, doctor or a person with other suitable qualifications as may be laid down by the Food Safety Commission."

However, recent years have seen gyms, specialised shops and even supermarkets stocking up on such products without meeting these requirements.

A spokesman for the Environmental Health Department said there could be risks associated with these seemingly innocuous products. For instance, some supplements could have high levels of vitamin A, which could have negative effects on pregnant women.

Moreover, he pointed out that some of these products were actually classified as medicine and, therefore, could only be sold by pharmacies.

The department has already advertised short courses to train people involved in the sale of food supplements but a spokesman said turnout had been "very low".

Suzanne Piscopo, a nutrition education expert who lectures on the subject at the University, hailed this as a "step forward" and advised people to follow professional advice when it came to dietary supplements.

"If you are in general good health and eating a variety of foods from the different food groups, then you should have an adequate supply of the essential nutrients," Dr Piscopo said.

There would be times, however, where people might need more nutrients, such as during pregnancy or following surgery. "This needs to be done under professional guidance and for a limited period of time," the nutritionist said.

Nutritional supplements are very commonly found in gyms and specialised sports nutrition shops.

These also should be used with caution and under supervision, Dr Piscopo said, and "those with specific nutritional needs, such as those seeking to increase muscle mass during training, should seek guidance from trained personnel."

Education was also key, she said, adding "people need to know that taking too much of certain nutrients might have certain complications or it could be that certain nutrients might not work very well together."

She also warned that certain supplements might interact negatively with any medication being taken, thus affecting the efficacy of the medicine.

In other cases, money spent on supplements might be literally money down the drain as "there are certain vitamins the body stores, others which the body doesn't, so when you take excess water or fat soluble vitamins, such as vitamin B and C, these will be eliminated by the body, so you're basically paying for nothing," the nutritionist advised.