How might berries improve human health, healthy aging, and quality of life? Maybe, due to their anti-inflammatory effects, since inflammation can be an underlying contributing factor in the “development, progression, and complication” of a number of chronic diseases. Higher intake of anthocyanins, the brightly-colored pigments in berries, has been associated with anti-inflammatory effects, which may be “a key component” underlying the associated reduction in chronic disease risk. But these are all just associations. You can’t prove cause and effect until you put it to the test.
A double-blind, randomized, placebo-controlled trial found that blueberry smoothies could turn off inflammation genes. (This is measuring the expression of pro-inflammatory genes in white blood cells taken from individuals before and after six weeks of drinking placebo smoothies with no blueberries.) They got worse over time. Six weeks later, more inflammatory chemicals pouring out, whereas the blueberry group started out about the same at week zero, but six weeks of daily blueberries and, the expression of inflammatory genes went down.
“In addition to attenuating inflammation,” they demonstrate that “blueberry consumption was able to significantly decrease the levels of free radicals” in their bloodstream: no change in the placebo group, but after six weeks of blueberry smoothies, the amount of free radicals in their blood was extinguished by half. Okay, but does all that antioxidant and anti-inflammatory power actually translate into clinical benefits? For example what is the effect of blueberry consumption on recovery from excessive weight lifting-induced muscle damage?
A randomized crossover study: a blueberry smoothie or antioxidant-matched placebo smoothie five and 10 hours prior to, and then 12 and 36 hours after, exercise-induced muscle damage. The smoothies were about a cup and a half of frozen strawberries, a banana, and apple juice, or without the berries, but dextrose and vitamin C added to match it for calories and antioxidant power. Even so, the blueberries worked better at mopping up free radicals. Here’s the oxidative stress without the blueberries: it goes up and stays up. But, with the blueberries, it comes right down. Yeah, but what we care about is the recovery of muscle strength, so you can jump right back into training. Same drop in peak torque 12 hours later, but a day later, significantly faster restoration of peak muscle strength, demonstrating that the ingestion of blueberries can accelerate recovery — something that may be especially relevant to athletes who compete over successive days.
That’s all well and good, but what about using berries to treat inflammatory diseases like arthritis? Yes, they may have protective effects against arthritis in a rat — significantly reducing “paw volume”— how swollen their paw gets when you inject it with some inflammatory irritant. But there had never been any human arthritis berry studies, until now.
Remember that amazing study where strawberries alone could reverse the progression of precancerous lesions? The strawberries were dramatically downregulating pro-inflammatory genes. Give strawberries to diabetics for six weeks, and not only does their diabetes get better, their C-reactive protein levels, a marker of systemic inflammation, drops 18%. Even just a single meal can help. Have people eat a largely unhealthy breakfast, and the level of inflammatory markers goes up over the next six hours, but less so if you added just five large strawberries to the meal.
So, can “strawberries improve pain and inflammation” in confirmed knee osteoarthritis? No fair that the title ruined the suspense, but yes, osteoarthritis patients randomized to get like a pint and a half of strawberries a day for 12 weeks and yeah, certain inflammatory markers plummeted on the strawberries. But did they actually feel any better? Significant reductions in constant pain, intermittent pain, and total pain. The “first clinical study on the effects of…berries” on human arthritis, and found that a “simple dietary intervention, the addition of berries to one’s diet, may have a significant impact on pain, inflammation, and overall quality of life in obese adults with [osteoarthritis].”