Berry, berry unclearby Listener Archive
Big health claims are made for acai berries but do they actually stack up?
Question: Our local health shop has acai berry powders. I've heard acai berries are really high in antioxidants and help with lots of health problems. Is this true or just sales hype?
A small purple berry from the Brazilian Amazon, the acai berry (pronounced ah-sigh-ee) sounds terribly exciting, and far trendier than a granny smith apple from Hastings. The internet is awash with glowing claims about acai berries, saying they have more antioxidants than any other food and that their unique nutritional properties help with arthritis, cancer, weight loss, high cholesterol and even erectile dysfunction. Fact or sales fiction?
In 2006, US Department of Agriculture (USDA) researchers announced that OptiAcai freeze-dried berries had the highest antioxidant activity of any fruit or vegetable they'd tested, with an Orac value of 102,700 per 100g. Orac, or oxygen radical absorbance capacity, is a measure of a substance's antioxidant activity.
Not all acai powders have such high Orac values, though, says nutritional biochemist Carolyn Lister, from Plant & Food Research. "We've tested acai powders that have much lower activity." So, too, has the USDA. The second highest Orac value found, for another freeze-dried acai powder, was just 15,500 per 100g.
Putting that in perspective, kiwifruit has antioxidant activity of 862 Orac units per 100g and an apple 2500-3000 units. But you're more likely to consume 100g of fresh fruit than of acai powder, so let's talk Orac units per serving. The humble granny smith apple (weighing about 130g) provides about 3900 Orac units per 100g, so per apple you'd consume about 5070 units. A scoop of freeze-dried acai berry powder is about 5g, manufacturers variously recommending 1-3 scoops at a time, so a top-grade acai powder would provide 5135-15,405 units, whereas a lower grade powder would provide 775-2325 units.
Our body doesn't absorb all the antioxidants in food; determining how much is an emerging research area. A 2008 clinical trial published in the Journal of Agriculture and Food Chemistry confirmed that humans absorbed a portion of the antioxidants in acai pulp/juice, although an apple sauce used for comparison caused a similar increase in blood antioxidant levels. "It's not the highest quality study," says Lister. Unfortunately it's one of the only human clinical trials of acai berries.
"There are some animal studies showing health benefits in rats in terms of inhibiting tumour progression, reducing the development of age-related neurodegenerative diseases, antagonising the detrimental effect of fat in the diet and alleviating oxidative stress in ageing. However, how these relate to effects in humans is unclear, as levels [of acai powder] given were quite high," says Lister. Animal and in-vitro studies are useful pointers, but we need more human clinical trial data to form a clearer picture.
Acai berries may be a good source of antioxidants, dietary fibre and healthy fats, but the health claims made for them are unproven. Compare that with the humble apple. Apples are a rich source of phytochemicals that have strong antioxidant activity, inhibit cancer cell proliferation and lower cholesterol in laboratory studies. Also, in population-wide studies, apple consumption is associated with a reduced risk of some cancers, cardiovascular disease, asthma and diabetes. And although human clinical trial data for apple health effects is equally scarce, it's worth considering the price difference - freeze-dried acai powder is about $1.50 a scoop, whereas a granny smith apple has the same quantity of Orac units for about 50c.
Eating more fresh fruit is a commitment most of us can meet financially and practically - whereas research shows people struggle to commit long term to taking dietary supplements. And it's important to think long term about the nutrients you consume.
"In most cases you do need regular to moderate consumption to have a benefit," says Lister, "rather than just taking intense amounts for a short period. They're low-level effects that accumulate over time to have a benefit." So perhaps an apple a day will keep the doctor