Weight loss supplement not light on promise

DOES IT WORK?African mangoes and weight loss

NEW YEAR’S resolutions to lose a few pounds are upon us again. With obesity on the rise, weight loss has become a serious business. Various food supplements claim to provide natural help in shedding extra pounds. One supplement rapidly growing in popularity comes from a tree with the scientific name, Irvingia gabonensis.

The tree grows in many parts of Africa and is commonly known as “African mango” or “bush mango”. African mango differs completely from the mango fruit that has become more popular in recent years. The mango fruit tree is native to India, although it is now cultivated around the world because the fruit is a rich source of vitamins, minerals and antioxidants.

The African mango also produces an edible fruit and many parts of the tree are used for various purposes. Medicinally, the bark and leaves have traditionally been used to treat infections and wounds. Recent interest has focused on the tree’s seeds, which are called dika nuts. These contain 50 per cent fat and are rich in dietary fibre. However, researchers in Cameroon, western Africa, have been testing an extract of Irvingia seeds as a weight-loss supplement. The early positive results have led to Irvingia becoming the latest plant included in many natural weight-loss products.

In Cameroon, Irvingia is added to many traditional dishes.

A group of researchers examined whether it influenced dietary fat intake and might contribute to weight reduction. This group has published a series of studies examining the effect of Irvingia seed extract on obese people.

The first was published in 2005 and involved 40 obese subjects. They were randomly assigned to take a placebo or the extract at a dose of just over 1g three times daily. After 30 days, those taking the extract had lost an average of 5.6kgs compared with 2.2kgs in the placebo group. Those taking the extract also had significantly lower blood pressure, total cholesterol levels and blood glucose levels.

In 2008, another study found similar results although the participants received a combination of Irvingia and Cissus quadrangularis, a west African vine. The two herbs together produced more weight loss than placebo or the vine alone. A third study was published in 2009 in which a much lower dose of extract was used: 150mg before lunch and dinner. This randomised, double-blind study involved 120 overweight or obese volunteers. After 10 weeks, those taking the extract had lost an average of 12.8kgs, compared with a loss of 0.7kgs in the placebo group. Total cholesterol, blood glucose and other relevant parameters were also lowered.

Other research has shown that Irvingia extract contains soluble fibre which is known to slow stomach emptying and give people a sense of being full. Some evidence also exists that Irvingia may contain ingredients that directly suppress the appetite.

The three clinical trials reported few problems with the supplement. A very small number of people reported flatulence, headaches or problems sleeping.

The results from research conducted on Irvingia so far are promising. However, more work is needed to replicate the findings from these three small trials, one of which used a combination product.

Independent research is also needed because the same research group has conducted all the studies and most were funded by the US-based manufacturer of the supplement.

Most importantly, the researchers did not monitor the participants’ food intake or exercise levels during the trials. This makes it possible that some other factor may have contributed to the participants’ weight loss.

It is also important to remember that while a supplement or medication might help with short-term weight loss, long-term success in maintaining a lower weight requires cutting back on the calories taken in, increasing physical activity and having support from others.

• Dónal O'Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He authored Alternative Medicine: The Christian Handbook,Updated and Expanded Edition, Zondervan, 2007