The city of Belem in northern Brazil has a population of about 2,000,000. It would be very interesting to find out if its inhabitants have an unusually low incidence of illnesses such as cancer, arteriosclerosis or Alzheimer’s disease. Why? Because the city is dotted with some 3000 “acai points” where people line up to purchase a slurry made from the pulp of the fruit of the acai (a-sigh-yee) palm tree. Over 200,000 liters of the thick purple sludge are consumed every day, which is more than the amount of milk that is drunk in the city. And, at least if you listen to some of the North American advertisers who have begun to import the juice of the acai berry, it has fantastic anti-inflammatory, anti-bacterial, anti-mutagenic and, above all, antioxidant properties! “Nature’s perfect fruit,” boasts one distributor. “The Amazon’s Viagra,” brags another. Little surprise then that North Americans, in constant search for the next miracle that will help them beat the clock, are shelling out in excess of $40 for a bottle of juice made from the acai berry which has “more antioxidants than any other edible berry on the planet.”
One thing we can say for sure about antioxidants is that they help sell products. Just festoon a label with “source of antioxidants” and the food, beverage, or dietary supplement flies off the shelves. That’s because researchers have shown that antioxidants can neutralize those nasty free radicals that form in our bodies as a result of breathing oxygen. And those free radicals have been linked with a number of human illnesses. So, it stands to reason that if we can curtail their activity, we’ll be better off. Fruits and vegetables are the main sources of antioxidants in our diet, and the prevailing opinion is that it is their antioxidant content that is responsible for the health benefits seen in populations with a high intake of plant products. But trials using antioxidant supplements have repeatedly failed to show positive results. Fruits and vegetables contain dozens of compounds that have potential physiological activity and it seems that it is a blend of these that is required for health benefits. In other words, the whole is somehow greater than the sum of its parts.
There is no doubt that antioxidants in our diet are important, but the relevance of a single food or drink having more or less of these compounds is questionable. What matters is our total antioxidant intake. On a weight basis, acai berries may have a higher concentration of antioxidants than apples, but it is certainly easier to load up on apples. But there is another important issue. The antioxidant potential of a food is determined by a laboratory measurement. One common method relies on generating free radicals by means of a chemical reaction in the presence of alpha-keto-gamma-methiolbutyric acid (KMBA). (How’s that for a tongue twister!) Free radicals attack KMBA, breaking it down and releasing ethylene gas in the process. Ethylene can then be identified and quantified by an instrumental technique known as gas chromatography. Addition of a food extract containing antioxidants to the mix neutralizes free radicals and therefore reduces the amount of ethylene gas released, thereby providing a measure of “antioxidant potential.”
It is such measurements that fuel the claim of acai berries being a particularly good source of antioxidants. However, a laboratory flask is a far simpler system than the human body. We don’t know how well the antioxidants in a given food are absorbed into the bloodstream and we don’t know that in the complex molecular environment of the body they have the same free radical neutralizing effect as in the lab. And we certainly don’t know that whatever activity they have is enough to prevent any disease. The only way to know that is by means of a controlled trial. Give a large group of people a regular dose of acai juice, while another similar group takes a placebo. The follow them for years and monitor disease patterns. Nobody has done this, therefore any health claim for acai is plain conjecture.
Of course this doesn’t mean that the possible health-promoting properties of acai berries should not be investigated further. Any food with a high antioxidant potential merits investigation. A recent study at the University of Florida, for example, showed that acai berry extracts destroyed a high percentage of leukemia cells in culture dishes. Interesting, but not all that unusual. Extracts of mangoes and grapes do the same. In any case, this is a long, long way from showing that such extracts have any effect on leukemia cells in the body. But such studies are enough to supply the ammunition that some unethical marketers use to hype the “anti-cancer” effect of acai juice. Maybe they need to learn a lesson from the promoters of Xango, a mangosteen juice product that was all the rage before the company received a warning letter from the FDA. Claims of anti-tumour benefits, lowering of blood pressure and prevention of hardening of the arteries are not supported by science, said the letter. In fact such claims can only be made on behalf of a drug, and as such, the product would require FDA approval, which of course is contingent on providing supporting evidence. Again, this is not to say that compounds in mangosteen such as the much talked-about xanthones, may not eventually turn out to have health benefits. But claiming that the juice can ward off disease is unproven, at best.
The chance that mangosteen or acai juice can make a significant contribution to our antioxidant status is slim. Better to concentrate on getting five to ten servings of common fruits and vegetables every day. Where acai berries have a real potential, though, is in helping the economy of Belem, where approximately 110,000 tons of fruit are worked up commercially every year, leaving behind 100,000 tons of seeds. These, like the fruit, have high antioxidant potential but have little commercial application. Perhaps extracts can be used as preservatives in foods, and it may even turn out that concentrates may have a therapeutic potential. But if that turns out to be the case, you will hear about it from the New England Journal of Medicine, or some other such peer-reviewed publication, and not from you neighbour who has become involved in selling acai juice through a multi-level marketing scheme.