Many reviews and meta-analyses about blueberries ignore one critical question: “Are blueberries good for your immune system?” So yesterday, I hoped the newest study of blueberries’ health benefits would broach this topic.
Hot off the press, the paper covered much of the same material I’ve researched recently. Its formal title:
Effects of Berry Anthocyanins on Cognitive Performance, Vascular Function and Cardiometabolic Risk Markers: A Systematic Review of Randomized Placebo-Controlled Intervention Studies in Humans
A quick review immediately impressed me with the Dutch research team’s conclusions. They associated berry anthocyanin intake with:
- significant improvements in memory, and positive effects on attention, psychomotor speed, and executive function.
- improved vascular function (specifically, vascular endothelial function.)
- significant positive effects on blood pressure.
Unfortunately, their review also overlooked the question, “Are blueberries good for your immune system?”
So the best I could do was to find…
Research Answering “Are Blueberries Good for Your Immune System”
As limited as studies on blueberries and immunity are, a recent one headed by nutritionist Michèle Rousseau of Quebec’s Université Laval Nutrition Center investigated the fruit’s impact on “immune-related pathways.”
The eight-week, randomized, double-blind, placebo-controlled trial split 49 participants into two groups consuming either freeze-dried highbush blueberry powder or a placebo (fake) powder.
Before and after the trial, the researchers measured the participants’ fasting blood gene expression and plasma metabolic profiles.
The blueberry-powder group experienced “significant changes in the expression of 49 genes and in the abundance of 35 metabolites.” All the changes were “clustered in immune-related pathways.”
In other words, the blueberry powder directly impacted the participants’ immune systems.
The Dutch research review also investigated an earlier six-week trial of blueberries’ impact on natural killer (NK) cells. As the immune system’s first responders, natural killers stand ready to destroy any virus-or cancer-infected cell.
The trial’s 25 sedentary adult participants consumed either a blueberry powder or a placebo. Those receiving the blueberry powder experienced:
- an increase in NK cell numbers
- a reduction in augmentation index (the arterial stiffness affecting systolic BP)
- lower aortic systolic pressure
Are Blueberries Good for Your Immune System if you are an Athlete?
My personal favorite among studies on blueberries and the immune system? It required 25 well-trained athletic subjects to race for 2.5 hours at ~72-percent maximum oxygen consumption.
Six weeks before the run, half of them began eating 250 grams (1.5 cups) of blueberries daily. Then, one hour before the race, they ate 375 grams (2 cups).
Did the berries give them a competitive edge over the non-blueberry group?
Absolutely! Both groups started the race with a similar number of NK cells – around 2 billion.
By the time they crossed the finish line, the immune systems of the blueberry-stoked group had kicked into high gear and doubled their NK cell counts to around 4 billion.
The non-blueberry competitors’ NK cell counts went backward, dropping by half to ~1 billion. The oxidative stress and inflammatory effects of racing seemed to overwhelm their immune systems!
If You Have MetS, Are Blueberries Good for Your Immune System?
Finally, another randomized, double-blind, placebo-controlled trial also found that blueberries could “exert immunomodulatory effects and attenuate oxidative stress and inflammation in adults with MetS.”
The coolest aspect of the MetS study was the researchers’ discovery that blueberries’ benefits are far-reaching. In their words:
“Our findings from this study demonstrate that blueberry consumption was able to significantly decrease the levels of free radicals in the whole blood.”
Meaning the berries’ immune system benefits ripple through your entire body.