Acai proponents claim that it's a top source of antioxidants, with benefits that include losing weight, enhancing the immune system, lowering cholesterol, boosting sexual perfor-mance, easing arthritis, improving digestion and even fighting cancer.
But what does the science say about this supposedly super-fruit?
One of the key claims made is that it's a superior source of antioxidants-those much-lauded free-radical fighters that prevent and repair cell-damage. However, there's mixed evidence for the antioxidant potency of these berries. While studies agree that acai is indeed a good source of antioxidants, it's not clear whether it's any better than the cheaper, more commonly available, antioxidant fruits such as blueberries and strawberries.
According to a study comparing several popular juice drinks available in the US, acai juice had only middling levels of antioxidants, which were less than those of pomegranate, grape, blueberry and black cherry juices, but more than cranberry, orange and apple juices (J Agric Food Chem, 2008; 56: 1415-22).
In another study from Spain and Brazil, comparing 11 different frozen fruit pulps, acai's antioxidant activity was ranked fifth-above pineapple and passion fruit, but below mango, strawberry and grapes (Cienc Rural, 2006; 36: doi: 10.1590/S0103-84782006000400037).
In contrast, an analysis of the anti-oxidant properties of freeze-dried acai fruit pulp and fruit skin powder (OptiAcai) found "an extremely high scavenging capacity" for free radicals-indeed, "by far the highest of any fruit and vegetable tested to date". Specifically, it showed a significantly high antioxidant capacity for scavenging peroxyl free radicals, involved in the development of tumors (J Agric Food Chem, 2006; 54: 8604-10). However, the study doesn't clarify whether the other fruits and vegetables referred to were tested in the same way as acai, so we don't know if it's a fair comparison.
Whether acai packs the biggest antioxidant punch remains to be seen, but what about its disease-fighting and health-boosting qualities? Surprisingly, not much research has been done in this area, and most of the studies that have been done are in animals. This means that the results may not necessarily apply to humans.
In one recent animal study, Brazilian researchers examined the benefits of acai on cholesterol in rats, and found that rats fed a high-fat diet supplemented with acai pulp had lower levels of total and non-HDL ('bad') cholesterol compared with the animals that only ate the high-fat diet. The findings suggest that acai-possibly because of its antioxidant activity-may reduce the risk of having high cholesterol (Nutrition, 2010; 26: 804-10).
US researchers tested the effects of acai pulp in fruit flies (Drosophila melano-gaster) fed a high-fat diet, and found that the flies supplemented with acai lived significantly longer than the non-supple-mented flies. Acai supplementation was also associated with beneficial changes in certain age-related genes. "Acai has the potential to antagonize the detrimental effect of fat in the diet and alleviate oxidative stress in aging," the researchers concluded (Exp Gerontol, 2010; 45: 243-51).
Acai might also reduce the risk of age-related neurodegenerative diseases such as Parkinson's and Alzheimer's. Scientists at the University of Caxias do Sul in Brazil discovered that pretreating rats with frozen acai pulp reduced the damaging effects of hydrogen peroxide (an oxidizing agent), causing less damage to the cere-bral cortex, hippocampus and cerebellum of the brain (J Med Food, 2009; 12: 1084-8).
Perhaps the most exciting acai study, however, is one that investigated the effects of the fruit on cultured human leukaemia cells in the lab. University of Florida researchers found that acai pulp extracts reduced cancer cell growth by up to 86 per cent-most likely by triggering a self-destruct (apoptosis) cell response (J Agric Food Chem, 2006; 54: 1222-9).
Although these findings are only preliminary, they are encouraging. According to study researcher Stephen Talcott, "Compounds that show good activity against cancer cells in a model system are most likely to have beneficial effects in our bodies."
However, acai is by no means unique in its cancer-fighting potential. Another American study of rats with chemically induced oesophageal cancer found that a number of different kinds of berries-including strawberries, blueberries and black and red raspberries, as well as acai-were equally capable of inhibiting tumour growth when added to the diet. No single berry proved to be any better than another (Pharm Res, 2010; 27: 1138-45).
The results so far are generally positive, but there is still a need for human clinical trials to confirm that acai berries can improve health and/or offer benefits for particular conditions. Although a couple of clinical trials have been carried out, they focused on the fruit's antioxidant capacity rather than its effects on health. Nevertheless, the studies-both involving 12 healthy volunteers, and both published in the same issue of the same journal-show that antioxidants from acai, whether consumed as a juice or a pulp, are readily taken up by the human body (J Agric Food Chem, 2008; 56: 7796-802; 8326-33).
Such findings are important as it's acai's antioxidants that are thought to be behind its beneficial effects in animal and laboratory studies. Clearly, though, more research is needed to determine whether the consumption of these berries will result in any disease-preventing and/or -treating health benefits, and to find the serving sizes needed to obtain a beneficial dose in people.
The bottom line
Considering the small amount of research that's been done so far, it's astonishing that so many websites are getting away with making such huge claims for this so-called miracle fruit. Whatever its possible merits, acai simply hasn't been proven to cure cancer, cut cholesterol, ease arthritis, assist weight loss or solve any other health problem in people.
The research is promising, but whether acai offers any benefits above and beyond those of other antioxidant-rich fruit and vegetables remains unanswered.
Perhaps we should take the advice of Wendy Marcason, a registered dietitian and part of the American Dietetic Association's Knowledge Center Team, who says: "Until the health benefits of the acai berry are scientifically proven, it seems more reasonable, cheaper and safer to get antioxidants from other fruit and vegetable sources" (J Am Diet Assoc, 2009; 109: 1968).
Factfile: Berry good
Although exotic berry types such as acai and goji berries have become popular in recent years, studies suggest that the more common berries, such as blueberries and strawberries, should not be overlooked.
u Scientists recently reported on the first human evidence that blueberries can boost memory and may even help to ward off dementia. Nine older-age adults with early memory decline were asked to drink around two cupsof a commercially available blueberry juice every day for two months, while a control group drank a beverage without blueberry juice. Tests taken before and after revealed that those who drank the blueberry juice showed significant improvements in learning and memory, leading the researchers to conclude that blueberries may offer neurocognitive benefits (J Agric Food Chem, 2010; 58: 3996-4000).
u In one test-tube study, extracts of six different kinds of berries-blueberry, blackberry, black raspberry, red raspberry, cranberry and strawberry-all were able to inhibit the growth of human mouth, breast, colon and prostate cancer cells. What's more, two of the extracts-black raspberry and strawberry-were able to stimulate apoptosis (cell death) in colon cancer cells (J Agric Food Chem, 2006; 54: 9329-39).
u A study involving 134,000 women and 47,000 men reported that people who regularly ate blueberries or strawberries had significantly reduced risks of developing hypertension (high blood pressure). The effect was stronger with blueberry than with strawberry consumption. Compared with people who never ate blueberries, those who had at least one serving of blueberries per week were 10-per-cent less likely to become hypertensive (Am J Clin Nutr, 2011; 93: 338-47).
WDDTY VOL. 22 NO. 1