What is African mango?
African mango, also known as Irvingia gabonesis, is a fleshy West African fruit commonly used in traditional Nigerian and Cameroonian cooking. In fact, it's the seed of this fruit, known as the 'dika nut', that is extracted for use in supplements.
After being featured on the Emmy-Award-winning Dr Oz Show in the US, demand for African mango soared, and there are now scores of websites selling the supplement as a natural weight-loss aid. But are the claims for this product backed up by hard evidence?
Weighing the facts
Unlike some so-called 'slimming pills' on the market, there are several credible scientific studies of African mango that appear to support the hype. Most of them have been conducted by Judith Ngondi and her colleagues at the University of Yaound'e in Cameroon.
In one 2005 study, which was double-blind and randomized-considered the 'gold standard' of scientific evaluation-the team gave 40 obese volunteers either African mango supplements (around 3 g daily of the seed extract) or a placebo (oat bran) for four weeks. The supplements were taken in divided doses one hour before meals, and the participants were instructed to follow a low-fat diet consisting of 1800 calories.
At the end of the study, the researchers reported that those who took the African mango supplement lost 5.3 per cent of their body weight, while the control group lost only 1.3 per cent-a difference that was statistically significant. Waist and hip measurements were also significantly reduced in the African mango group. Moreover, the supplement group saw their blood pressure and LDL ('bad') cholesterol levels decrease, while their HDL ('good') cholesterol increased. No such changes were reported in the placebo group.
The use of African mango extract "should be further encouraged for the purposes of control of dietary lipids [fats] as well as for weight reduction", the researchers concluded (Lipids Health Dis, 2005; 4:12).
In another randomized, double-blind trial, Ngondi and colleagues used a more highly developed African mango seed extract-which they called 'IGOB131'-and studied its effects on a group of overweight and/or obese individuals for 10 weeks. Just over 100 volunteers were split into two groups: one took 150 mg of IGOB131 30-60 minutes before lunch and dinner, while the other took a placebo.
The researchers reported significant improvements in body weight, body fat and waist circumference in the IGOB131 group compared with the placebo group. What's more, they noted that the treated group also had improved blood glucose and cholesterol levels as well as other markers of the metabolic syndrome (the term used for a group of specific risk factors that raise your risk of heart disease and other health problems, such as diabetes and stroke). The researchers concluded that Irvingia gabonensis extract may prove to be a useful tool in dealing with the emerging global epidemics of obesity, high cholesterol, diabetes and other associated conditions (Lipids Health Dis, 2009; 8: 7).
The University of Yaound'e researchers also trialled the use of African mango extract in combination with another plant-derived weight-loss extract, Cissus quadrangularis, a member of the grape family. Again, a group of overweight individuals were studied for 10 weeks in a randomized, double-blind study.
Cissus quadrangularis supplements alone were found to significantly reduce all of the variables studied-body weight, body fat, waist size, total blood cholesterol, LDL cholesterol and fasting blood glucose. But when the supplements were given in combination with the African mango pills, there were even greater reductions (Lipids Health Dis, 2008; 7: 12).
So, how does African mango apparently help weight loss? Initially, it was thought that the high fibre content of the seeds was responsible for the beneficial effects. High-fibre foods are known to keep you feeling fuller for longer, so it could be that African mango works by making you feel full and eat less.
The fibre content can also explain its effects on cholesterol. As the University of Yaound'e researchers explained, "Like other soluble fibres, Irvingia gabonensis seed fibre can bind to bile acids in the gut and carry them out of the body in the faeces, which requires the body to convert more cholesterol into bile acids. This can result in the lowering of blood cholesterol as well as other blood lipids" (Lipids Health Dis, 2005; 4: 12).
However, more recent research suggests that African mango's positive effects aren't just down to the fibre content alone. Laboratory studies indicate that these special seeds could also affect fat cells by reducing fat-cell growth and increasing the breakdown of fats. Moreover, the supplement may have a beneficial impact on the hormones leptin and adiponectin, both of which play key roles in fat metabolism and appetite regulation (Lipids Health Dis, 2008; 7: 44).
Not a magic bullet
Although some supplement manufacturers and advertisers have jumped on this scientific evidence as 'proof' that African mango works, others are far more sceptical. Dr Tanya Edwards on the Dr Oz Show pointed out that the University of Yaound'e researchers, who've conducted the only weight-loss clinical trials on African mango so far, have a vested interest in the company making the product.
"More independent studies likely need to be done by independent researchers," she said on the Dr Oz website (www.doctoroz.com).
She also reveals the "underwhelming" results she has seen from using the supplements herself and from recommending them to patients. "A few patients lost a few pounds, but it has not been the magic bullet I had hoped for. And with continued use, I have not lost any more weight," she reported.
On the upside, there have been no significant side-effects associated with African mango supplements. The most common ones appear to be headache, difficulty sleeping and flatulence, but more research is needed to establish the long-term safety.
Ultimately, if you're looking for a helping hand with your weight loss, you're probably better off choosing a more well-researched supplement for now (see WDDTY vol 22 nos 5 and 6), and keeping an eye out for more African mango studies in the future.
Factfile: Beyond weight loss
Some research suggests that African mango may be useful not just for weight loss and lowering cholesterol, but for a variety of other health problems.
- Fighting infections. Extracts from the stem bark of Irvingia gabonensis were found to have potent antimicrobial activity in test-tube studies. "The obtained results confirmed the use of Irvingia gabonensis in the treatment of bacterial and fungal infections," the researchers concluded (J Ethnopharmacol, 2007; 114: 54-60). Another study reported that the leaves and roots of the tree also have effective antibacterial properties (Afr J Med Med Sci, 2008; 37: 119-24).
- Killing pain. In West Africa, the Mende tribe of Sierra Leone uses the stem bark of I. gabonensis to relieve pain, so researchers at Ahmadu Bello University in Nigeria decided to test this natural painkilling remedy in the lab. The researchers found that a water-based extract of powdered tree-stem bark had similar analgesic properties to those of the painkilling drug morphine in protecting mice from heat-induced pain (J Ethnopharmacol, 1995; 45: 125-9).
- Treating diabetes. University of Benin researchers conducted a clinical trial of an African mango seed supplement in 11 patients with type 2 diabetes. After a month of taking 4 g/day of the supplement, there were significant reductions in the patients' blood glucose levels, as well as other positive biochemical effects (West Afr J Med, 1990; 9: 108-15). Similar results had been reported by the same researchers in an earlier study (Enzyme, 1986; 36: 212-5).
- Easing diarrhoea. In a mouse study, a leaf extract of I. gabonensis was found to protect against castor oil-induced diarrhoea (Indian J Exp Biol, 2004; 42: 787-91). These results, however, may not necessarily be seen in humans.
WDDTY Vol. 22, 12. March 2012