What is the optimum dose of wild blueberries to eat at a meal?
A single serving of blueberries can help mediate the arterial dysfunction induced by smoking a cigarette. Researchers investigated the effect of a single serving of frozen blueberries on young smokers. As you can see at 0:19 in my video Benefits of Blueberries for Artery Function, when you smoke a single cigarette, the ability of your arteries to relax naturally drops 25 percent within two hours. But, if you eat two cups of blueberries a hundred minutes before smoking, that same cigarette causes less than half the damage, demonstrating that a single, big serving of frozen blueberries could counteract the artery dysfunction induced by smoking. Of course, it should be noted that “blueberry consumption cannot be considered a means of preventing health consequences due to smoking; this can only be realized by smoking cessation and/or prevention,” i.e. not smoking in the first place.
Two cups of blueberries are a lot, though. Yes, you could easily drink them in a smoothie, but what do you think is the minimum dose to achieve that effect? We didn’t know until a group of British researchers decided to put it to the test. In order to do a double-blind study, they had to create a fake blueberry drink for the placebo control. They used a freeze-dried wild blueberry powder to give people the equivalent of three-quarters of a cup, one and a half cups, one and three-quarter cups, about three cups, or four cups of fresh wild blueberries. The researchers concluded that “blueberry intake acutely improves vascular [arterial] function…in an intake-dependent manner.” So what’s the optimal intake? As you can see at 1:32 in my video, nothing happened after the placebo. After eating one and three-quarter cups’ worth of blueberries, however, there was a big spike in artery function improvement within just one hour of consumption and that seems to be where the effect maxed out. Less than a cup is good, but between one and two cups seems better, with no benefit going beyond that in a single meal.
Can you cook them? What if you baked with them, for instance? As you can see at 2:00 in my video, the same remarkable improvement in artery function was seen with blueberries baked into a bun. The only difference is the spike happened an hour later, since solid food passes more slowly through your stomach.
If you eat blueberries week after week, you also get chronic benefits, in terms of reduced artery stiffness and a boost in your natural killer cells, which are one of your body’s natural first lines of defense against viral infections and cancer. How can blueberries have all these amazing effects if the anthocyanins—the blue pigments in blueberries purported to be the active ingredients—hardly even make it into our system? Indeed, women were given more than a cup of blueberries to eat, and the researchers couldn’t find hardly any in their bloodstream or flowing through their urine.
At 2:47 in my video, you can see a chart called a chromatogram. The spikes show all of the anthocyanin peaks in blueberries. Before eating blueberries, there is no sign of the pigments in the participants’ blood, which makes sense because they hadn’t been ingested. After one hour of eating them, however, you start to see the spikes appear, and, a few hours after that, they become a bit more distinct. All in all, though, just a few billionths of a gram per milliliter show up. So, “either anthocyanins are extremely potent and, therefore, active at low serum [parts-per-billion blood] concentrations…or their dietary occurrence or bioavailability has been underestimated.” Researchers decided to radioactively tag them and trace them throughout the body.
I show what happens at 3:28 in my video. Blueberry pigments are metabolized by our liver and our microbiome, the good bacteria in our gut, into active metabolites that are then absorbed into our system. So, it’s a team effort to benefit from berries, which would solve the mystery as to why researchers observed a second spike in benefits after consumption of a blueberry drink at six hours. Indeed, some of the metabolites peak in the bloodstream within an hour, but others ramp up more slowly, especially if the berries have to make it all the way down into the colon. What’s more, there aren’t only spikes at one hour and six hours after consumption. If you track them out even further, some go up more. Even a day later, we may be experiencing berry benefits as our gut bacteria continue to churn out goodies that get absorbed back into our system, feeding us as we feed them. Eating blueberries can so feed our good bacteria that eating them is like taking a natural probiotic, a win-win all around.
I’ve produced an extended series of videos on the latest berry research. They taste great and you get to live longer? That’s what plant-based eating is all about!
What else can blueberries do? Check out:
And for more on berries, watch:
What about fancier options, like açai berries? See:
Flashback Friday: How Much Fruit Is Too Much? Watch the video to find out.
What about all the fructose in fruit? See Flashback Friday: If Fructose Is Bad, What About Fruit?.
Within two hours of smoking just one cigarette, our arteries’ ability to relax naturally reduces by 25 percent. Eating two cups of blueberries a hundred minutes before smoking that cigarette results in less than half the damage. (But no one should smoke regardless of whether they eat blueberries.)
Researchers have found that intake of blueberries “acutely improves vascular [arterial] function…in an intake-dependent manner.”
Less than a cup is beneficial, but one to two cups seem better with no benefit to eating more than that in a single meal. The largest spike in improved artery function noted within an hour of consumption came with one and three-quarter cups’ worth of blueberries.
Baking blueberries achieves the same improvement in artery function, albeit with the spike occurring an hour later since solid food passes more slowly through the stomach.
Eating blueberries week after week gives us the chronic benefits of reducing artery stiffness and boosting natural killer cells that defend against viral infections and cancer.
Very little of the anthocyanins, the blue pigments in the fruit, appear in our blood after consuming blueberries, so the phytochemicals are either “extremely potent” or have “been underestimated.”
When researchers radioactively tagged and traced them throughout the body, they found that the anthocyanins are metabolized by our liver and good gut bacteria into active metabolites that are then absorbed into our system, which explains why there are numerous spikes in blueberry-induced benefits over a period—even a day later.
Blueberries can be thought of as natural probiotics. When we eat them, we’re also feeding our good bacteria.
What about the effects of other foods on artery function? Check out:
Michael Greger, M.D.
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