Sugary, starchy diets are associated with chronic, low-level inflammation … as are obesity, metabolic syndrome, diabetes, dementia, and heart disease.
Chronic, “silent” inflammation is triggered and sustained by an excess of oxidizing free radicals in the body … an excess caused in turn by sugary, starchy, nutrient-poor diets.
Meals high in sugars and refined starches (e.g., white bread) typically raise body levels of oxidation and inflammation.
So it comes as welcome news that in a small clinical trial, strawberries appeared to dampen inflammation … despite their own sugar content and the inflammation-inducing effects of a starchy meal.
This does not mean, of course, that strawberries “neutralize” the ill effects of sugary, starchy diets.
But it adds to the substantial, growing evidence that berries are healthful, anti-aging “super foods”.
Small trial finds strawberry drink anti-inflammatory
The new trial involved 24 obese volunteers recruited by researchers from the Illinois Institute of Technology and the University of California-Davis (Edirisinghe I et al. 2011).
Obese people were chosen because they tend to have higher-than-normal levels of inflammation and less resistance to inflammation induced by sugars and refined starches.
The participants were divided into two groups: One received a strawberry-based drink and the other got an identical-looking, strawberry-flavored, placebo drink.
Critically, while the strawberry-based drink was rich in naturally occurring polyphenols – commonly called “antioxidants” (see our parenthetical clarification, below) – the placebo drink was polyphenol-free
Both groups drank their beverage along with a high-carbohydrate (moderate-fat) meal … the kind of repast known to raise blood levels of inflammation markers and insulin.
After drinking and eating, the volunteers' blood was tested for established “biomarkers” for inflammation – CRP, IL-6/10/18, MCP-1, and TNF-alpha – and for key polyphenol-type compounds in strawberries.
(The flavonoids and other polyphenols in fruits, tea, coffee, cocoa, and vegetables are commonly referred to as “antioxidants” … but that term is misleading. While they often display potent antioxidant powers in the test tube, most of these compounds' documented ability to reduce people's inflammation and oxidation levels is an indirect effect, flowing from their “nutrigenomic” influences on gene expression.)
As expected, blood levels of two strawberry compounds (pelargonidin sulfate and pelargonidin-3-O-glucoside) increased in the strawberry beverage group, compared with the placebo group.
And six hours after the meal, two key inflammation markers were substantially lower in the strawberry group, compared with people who downed the placebo drink: 25 percent lower levels of IL-6 and 13 percent lower CRP levels.
And compared with the placebo group, the strawberry group had less of a spike in insulin levels after the meal.
As the scientists wrote, “Collectively, these data provide evidence for favorable effects of strawberry antioxidants on postprandial [after-meal] inflammation and insulin sensitivity.” (Edirisinghe I et al. 2011)
As we'd expect – based on the indirect, nutrigenomic nature of polyphenols' damping effects on inflammation and oxidation – these reductions in inflammation markers appeared to follow detection of antioxidant impacts from the berry drink.
That makes sense, because although polyphenols tend to reduce expression of genes related to inflammation as well as oxidation, the latter exacerbates the former.
As the researchers noted, antioxidant activity – such as lower levels of LDL oxidation – appeared more quickly than the reductions in anti-inflammatory markers.
This finding dovetails with the fact that, as we said, inflammation can be triggered by the burst of oxidizing free radicals that can follow consumption of sugary, starchy foods.
The lesson? Enjoy berries as part of a balanced, whole foods diet … not as antidotes for poor diets.
Edirisinghe I et al. Strawberry anthocyanin and its association with postprandial inflammation and insulin. British Journal of Nutrition. Published online ahead of print. doi: 10.1017/S0007114511001176
Esposito K, Giugliano D. The metabolic syndrome and inflammation: association or causation? Nutr Metab Cardiovasc Dis. 2004 Oct;14(5):228-32.
Wisse BE. The inflammatory syndrome: the role of adipose tissue cytokines in metabolic disorders linked to obesity. J Am Soc Nephrol. 2004 Nov;15(11):2792-800. Review.