Hello and welcome to Nutrition Facts. I’m your host, Dr. Michael Greger. Today, we’re going to explore smart nutrition choices based, naturally, on facts. Whenever there’s a new drug or surgical procedure, you can be assured that you and your doctor will probably hear about it because there’s a corporate budget driving its promotion; but, what about advances in the field of nutrition? That’s what this podcast is all about.
Today, we’re going to take a deep dive into açai berries. Açai berries are touted for their antioxidant power, but does that translate into increased antioxidant capacity of our bloodstream when we eat them? Here’s the story.
There are so many açai products on the market now, from frozen pulp in smoothie packs to freeze-dried powder and supplements. How is it eaten traditionally? Amazonian tribes cut down the tree, eat its heart, and then pee on the stump to attract a certain type of beetle that lays these monster maggots. And so, a few weeks later, you’ve got three or four pounds of these suckers; so, you can make some grub-kabobs. I think I’ll just stick with my smoothie pack.
“Despite being used for a long time as food” in the Amazon, only since the beginning of this century have “açaí berries…been the object of scientific research.” Four years ago, I reviewed that research, starting with in vitro studies that showed that açai could kill leukemia cells in a Petri dish at levels one might expect in one’s bloodstream eating a cup or two of açai pulp, or cutting the growth of colon cancer cells in half.
Unfortunately, subsequent studies published since then failed to find such benefit for that type of colon cancer, a different type of colon cancer, or an estrogen receptor negative form of breast cancer. An açai extract did appear to kill off a line of estrogen receptor positive breast cancer cells, but to achieve that level of açai nutrients in your breast, you’d have to sit down to like 400 cups of açai pulp.
That’s the problem with many of these Petri dish studies: they use concentrations that you could never realistically achieve in your bloodstream. For example, açai berries may exert a neuroprotective effect, blocking the buildup of amyloid fibers implicated in Alzheimer’s—but only at a dose reached drinking maybe 2,000 cups at a time; or, have an anti-allergy effect, or decrease bone loss—at a mere thousand cups a day.
But, I also talked about a clinical study in which folks were asked to drink less than a cup a day of açai in a smoothie, and appeared to get significant improvements in blood sugar, and insulin levels, and cholesterol. Now, there was no control group, and it was a small study, but there’d never been a bigger study to try to replicate it—until now.
Same amount of açai, for the same duration, but no significant improvements in blood sugars, insulin, or cholesterol. Huh? Why did this study fail to show the benefits seen in the first study? Well, this study was publicly funded—”no conflicts of interest”—whereas the first study was funded by an açai company, which always makes you suspect that maybe the study was somehow designed to get the desired result. And, indeed, the study participants were not just given açai smoothies, but explicitly told to avoid processed meat (like “bacon and hot dogs”). No wonder their numbers looked better at the end of the month.
Now, the new study did find a decrease in markers of oxidative stress in the participants’ bloodstream—a sign of how antioxidant-rich açai berries can be. Those that hock supplements love to talk about how açai consumption can “triple antioxidant capacity;” “triple the antioxidant capacity of [your] blood.”
And, if you look at the study they cite, yes, there was a tripling in antioxidant capacity of the blood after eating açai. But there was the same, or even better, tripling after just plain applesauce, which was used as a control, and is significantly cheaper than açai berries or supplements.
There was a new study showing significant improvements in artery function after eating açai berries, but any more than commoner fruits and vegetables? We’ll find out, next.
Here’s a closer look at the effects on artery function of açai berries, cooked and raw blueberries, grapes, cocoa, green tea, and freshly squeezed orange juice.
“Plant-based diets…have been found to reduce the risk of” some of our leading causes of death and disability. “Studies have shown that the longest living and least dementia-prone populations subsist on plant-based diets…” So, why focus on just this one plant for brain health and performance—açai berries? Well, “foods rich in polyphenols [appear to] improve brain health,” and açai berries have lots of polyphenols and antioxidants; so, maybe they’d help.
But, if you’re just looking at polyphenols, there are over a dozen foods that have more per serving, and it doesn’t have to be black elderberry. Regular fruits, like plums, have more; a few spoonfuls of flax seeds, a few squares of dark chocolate, or even just a cup of coffee, has more.
In terms of antioxidants, yes, açai berries may have ten times more antioxidant content than more typical fruits, like peaches and papayas; five times more than strawberries—but comparable to blackberries. In fact, blackberries appear to have even more antioxidants, and are cheaper and more widely available.
Ah, but açai berries don’t just have potential brain benefits—for example, protecting the lungs against “harm induced by cigarette smoke.” But you all remember that study, right? That’s the one where “addition of açai [berries] to cigarettes has a protective effect against emphysema in [smoking] mice.” That’s not very helpful. There’s this long list of impressive-looking benefits, until you dig a little deeper.
For example, I was excited to see “reduction of coronary disease risk due to [a] vasodilation effect,” but less excited when I pulled the study, and found out that they were talking about a “vasodilator effect…in [the] mesenteric vascular bed of the rat.” But, there hadn’t been any studies on açai berries and artery function in humans, until now.
Give some overweight men a smoothie containing about two-thirds of a cup of frozen açai pulp, and a half a banana, versus an artificially-colored placebo smoothie with the banana but no açai; you get a significant improvement in artery function within two hours of consumption, which lasts at least for six hours. That one- or two-point bump is clinically significant. Those walking around with just a point higher go on to have 13% fewer cardiovascular events, like fatal heart attacks.
You can get the same effect from wild blueberries, though, about a point-and-a-half bump two hours after wild blueberry consumption—an effect peaking and plateauing at about one-and-a-half cups of blueberries, with two-and-a-half or three-and-a-half cups showing no further benefits.
What about cooked blueberries? Here’s the same wild blueberry drink effect we saw before. But what if you baked the blueberries into a bun, like a blueberry muffin? Same dramatic improvement in artery function.
Cocoa can do it, too. One tablespoon of cocoa gets you about a point, and two tablespoons is like a whopping four points—that’s like double the berries.
One-and-a-quarter cups worth of multicolored grapes gave a nice boost in artery function, but enough to counter an “acute endothelial insult”—a sudden attack on the vulnerable inner layer of our arteries? They decided on a sausage-and-egg McMuffin meal; they weren’t messing around. Without the grapes, that meant cutting artery function nearly in half within an hour, and the arteries stayed stiffened and crippled three hours later. But, eat that McMuffin with all those grapes, and hardly any effect.
Eat a meal with hamburger meat, and artery function drops after the meal. But, eat that same meal with some spices, including a teaspoon and a half of turmeric, and your artery function gets better.
What about orange juice? Four cups a day for four weeks, and no change in artery function.
Want a beverage that can improve your artery function? Green tea. Two cups of green tea, and you get that same cocoa effect, nearly four points within just 30 minutes. And, that same crazy effect you get with green tea, you get with black tea. Twice as powerful an effect as the açai berries.
So, why focus on just that one plant? Well, the real reason, presumably, is that the author owns a patent on an açai-based dietary supplement.
An independent study of the effects of açaí berries was recently published, including studies on immune function, arthritis, and metabolic parameters.
An “Evidence-Based Systematic Review of Açaí” berries was recently published by the Natural Standards Research Collaboration, an impartial scientific body that refuses to take support from product manufacturers—cited by the World Health Organization as one of the most authoritative sources on such matters.
What did they find? Whenever a new purported superfood hits the market, the first thing researchers tend to do is look at its chemistry, such as antioxidant capacity, which was done back in 2006. Based on one measure, it had “the highest [antioxidant capacity] of any food reported to date”—a remarkable finding I reported at the time, arguing that, despite its cost, frozen açaí pulp represented one of the best antioxidant bangs for one’s buck. But, still, we didn’t know what it did outside of a test tube.
The next step is to go from test tube to Petri dish, and try it out on some human cells. They dripped the concentration of açaí berry phytonutrients one would expect in one’s bloodstream after eating them on some blood cancer cells taken from a woman with leukemia, and saw a dramatic rise in cancer cell mortality—in fact, about twice what was found previously, using similar concentrations of hibiscus tea, on the same cancer.
Açaí was also found to boost immune cell function at extremely low doses. Sprinkle some açaí berry powder on them, and they gobble more. With no açaí for breakfast, the white blood cells were able to engulf about 140 yeast; but, in the presence of a tiny amount of berry powder, they engulfed closer to 200. Slowly but surely, researchers began piecing together the mechanism by which açaí affected cellular function.
Still no human studies, though. Researchers moved from cells to animal models. Who could forget the “Addition of açaí…to cigarettes has a protective effect against emphysema in mice.” Instead of adding berries to their cigarettes, though, it might be easier to just encourage the mice to quit smoking. But then, finally, starting in 2011, studies on actual people.
“Pain Reduction and Improvement in Range of Motion After Daily Consumption of an Açaí” in about a dozen folks with painful conditions, like osteoarthritis. After three months, antioxidant levels went up, and pain levels went down—though since there was no blinded control group drinking like some artificially açaí-flavored Kool-Aid, the placebo effect could not be excluded.
And, finally, one last pilot study. The “Effects of Açai on Metabolic Parameters.” Ten overweight folks were given two packs of frozen açaí pulp every day for a month. And, even though they were allowed to take it with sugar, their fasting blood sugars dropped, as did their insulin levels, and cholesterol. And, it significantly blunted the sugar spike caused by a standardized meal—all without any observed adverse effects. In fact, the only theoretical concerns cited in the new review may be that it might work too well. If you’re on diabetic blood sugar-lowering medications, it could potentially drop your blood sugar too low; or, if you have an autoimmune disease, or are on immunosuppressants, it could stimulate your immune system too much.
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Thanks for listening to Nutrition Facts. I’m Dr. Michael Greger.
This is just an approximation of the audio content, contributed by Allyson Burnett.