Friday Favorites: Benefits of Blueberries for Artery Function

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

“A single serving of blueberry [can help mediate the] arterial dysfunction induced [by smoking a cigarette].” They “investigated the effect of a single serving of…frozen blueberr[ies on] young smokers.” Smoke a single cigarette, and the ability of your arteries to relax naturally drops 25% within two hours. But, eat two cups of blueberries a hundred minutes before, and that same cigarette causes less than half the damage, demonstrating that “a single [big] serving of…frozen blueberry could counteract the [artery] dysfunction induced by smoking.” However, 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” stopping smoking, or even better, not smoking in the first place.

Two cups of blueberries is a lot, though. Yeah, you could easily chug those down in a smoothie, but what’s like the minimum dose? We didn’t know, until a group of British researchers decided to put it to the test. To enable them to do a double-blind study, they had to create a placebo control fake blueberry drink. So, they used a freeze-dried wild blueberry powder to give people the equivalent of three-quarters of a cup of fresh wild blueberries, one and a half cups, one and three-quarters, about three cups, or four cups. They concluded “[b]lueberry intake acutely improves [artery] function in a[n] intake-dependent manner.”

Okay, so what’s the optimal intake? After the placebo, nothing happens. But, after eating one and three-quarter cup’s worth of blueberries, a big spike in artery function improvement within just one hour of consumption. And, that seems to be where the effect maxes 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 put them in a blueberry pie or something? The same remarkable improvement in artery function baked into a bun—just spiking an hour later, since solid food passes more slowly through your stomach.

And, then, if you eat blueberries week after week, you get chronic benefits too, 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. But wait a second; 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? 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.

Here’s what’s called a chromatogram, with the spikes showing all the little anthocyanin peaks in blueberries. Here’s your blood before eating blueberries: obviously no sign of the pigments. After one hour, you start to see them appear, and a few hours after that, they become a bit more distinct. But, all in all, just a few billionths of a gram per milliliter show up. So: “Either anthocyanins are extremely potent, and, therefore, active at low [parts-per-billion blood] concentrations or [somehow] their bioavailability has been underestimated.” So, researchers decided to radioactively tag them and trace them throughout the body.

What happens is that blueberry pigments are metabolized by our liver and our microbiome—the good bacteria in our gut—into these active metabolites that are then what’s absorbed into our system. So, it’s kind of a team effort to benefit from berries.

And, that would solve this mystery as well. Anyone notice this second spike in benefits over here at six hours? How does that make sense? Well, 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. And, it’s not just spikes at one hour and six hours. If you track them out even further, some go up even more. So, like a day later, we may still 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 it’s like taking a natural probiotic: a win-win all around.

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• Del Bo' C, Porrini M, Fracassetti D, Campolo J, Klimis-Zacas D, Riso P. A single serving of blueberry (V. corymbosum) modulates peripheral arterial dysfunction induced by acute cigarette smoking in young volunteers: a randomized-controlled trial. Food Funct. 2014;5(12):3107-3116.
• Rodriguez-Mateos A, Rendeiro C, Bergillos-Meca T, et al. Intake and time dependence of blueberry flavonoid-induced improvements in vascular function: a randomized, controlled, double-blind, crossover intervention study with mechanistic insights into biological activity. Am J Clin Nutr. 2013;98(5):1179-1191.
• Rodriguez-Mateos A, Del Pino-García R, George TW, Vidal-Diez A, Heiss C, Spencer JP. Impact of processing on the bioavailability and vascular effects of blueberry (poly)phenols. Mol Nutr Food Res. 2014;58(10):1952-1961.
• McAnulty LS, Collier SR, Landram MJ, et al. Six weeks daily ingestion of whole blueberry powder increases natural killer cell counts and reduces arterial stiffness in sedentary males and females. Nutr Res. 2014;34(7):577-584.
• Mazza G, Kay CD, Cottrell T, Holub BJ. Absorption of anthocyanins from blueberries and serum antioxidant status in human subjects. J Agric Food Chem. 2002;50(26):7731-7737.
• Wu X, Cao G, Prior RL. Absorption and metabolism of anthocyanins in elderly women after consumption of elderberry or blueberry. J Nutr. 2002;132(7):1865-1871.
• Czank C, Cassidy A, Zhang Q, et al. Human metabolism and elimination of the anthocyanin, cyanidin-3-glucoside: a (13)C-tracer study. Am J Clin Nutr. 2013;97(5):995-1003.
• Vendrame S, Guglielmetti S, Riso P, Arioli S, Klimis-Zacas D, Porrini M. Six-week consumption of a wild blueberry powder drink increases bifidobacteria in the human gut. J Agric Food Chem. 2011;59(24):12815-12820.
• Cassidy A, Minihane AM. The role of metabolism (and the microbiome) in defining the clinical efficacy of dietary flavonoids. Am J Clin Nutr. 2017;105(1):10-22.

Image credit: veeterzy via Unsplash. Image has been modified.

Motion graphics by Avocado Video.