Lynden, WA – Feb. 10, 2016 – Red raspberries are naturally rich in polyphenols, and as a result of research recently published in Free Radical Biology and Medicine and The Journal of Functional Foods, scientists are now beginning to understand how and why these polyphenols may offer human health benefits.

According to researcher Dr. Alan Crozier, at the Department of Nutrition, University of California, Davis, “In order to further study the potential health benefits of red raspberry consumption, it is important to first understand how the body metabolizes raspberry polyphenols, and the mode of action of the bioactive compounds that underlie these potential protective effects.”

Polyphenols are a class of phytochemicals. Polyphenols in red raspberries include: anthocyanins, flavan-3-ols, procyanidins, flavonols, ellagitannins, and hydroxycinnamates. [1-3]

Animal and cellular studies examining how phytochemicals may work at the molecular level, suggest that certain phytochemicals may help slow age-related declines which can also impact a person’s disease risk. A growing body of research is focused on how some phytochemicals may offer protection against some cancers, heart disease, stroke, high blood pressure, cataracts, osteoporosis and other chronic health conditions [4]. While current evidence is promising, additional long term studies are needed to establish the role of berry polyphenols in the prevention of specific health conditions. [5-7]. 

Assessing Bioavailability of the Active Compounds in Raspberries

Dr. Crozier and colleagues were interested in the fate of ellagitannins and anthocyanins, the compounds thought to be involved in beneficial health effects, following ingestion of the berries by human volunteers. Their study, published in Free Radical Biology and Medicine [8] looked at how these phytochemicals are metabolized by the body once ingested.

To determine this, researchers asked human volunteers to consume 300 grams of raspberries (a little over 2 cups) and then have their blood and urine samples analyzed over a 24 hour period. Analysis of these samples by high performance liquid chromatography and mass spectrometry showed an array of phytochemicals metabolites in the blood: some that peaked in the blood within 1-1.5 h, others at 6 h and still other metabolites peaking at 24 h after raspberry consumption. The work of Crozier and colleagues illustrate the complex metabolism of raspberry phytochemicals and that they are absorbed in the small intestine and the colon, which play an important role in the bioavailability of both anthocyanins and ellagitannins.

“The information discovered in our research is of importance as it enables other investigators to test these metabolites in cell-based model systems relating to cardiovascular function, colonic health and various cancers, in order to determine the mode of action of the bioactive compounds. This is critical to understanding the potential effects of raspberry consumption,” says Dr. Crozier, lead author of the study.

Reducing Inflammatory Response

A second study [9] published in the May 2015 Journal of Functional Food looked at how the metabolites of ellagitannins, called urolithins, were able to reduce the inflammatory response in rat heart muscle cells exposed to high glucose concentrations – a model which mimics a condition common in people with diabetes mellitus and hyperglycemia (high blood sugar). Overtime, this inflammation produces oxidative stress and may play a role in the development of diabetic cardiomyopathy, which can lead to heart failure. The results of this research suggest that ellagitannin-rich foods such as red raspberries, pomegranates, blackberries, strawberries and walnuts may support heart cell function. However, additional research is needed in order to determine if these compounds would have the same effect in humans.

“While this study shows the potential of ellagitannins/urolithins’ ability to help maintain normal function in the diabetic heart, further human studies are needed,” said Dr. Danielle Del Rio at the Department of Food Science, University of Parma, Italy. “In particular, the influence of a mix of circulating metabolites on the inflammatory scenario should be taken into account, and specifically designed intervention studies aimed at assessing the impact of ellagitannin-rich food sources on markers for inflammation should be performed.”

Further studies looking at the effects of red raspberries on reducing risk for conditions such as diabetes, cardiovascular disease, and other chronic diseases are currently in progress through grants funded by the National Processed Raspberry Council.

About the National Processed Raspberry Council

Created in 2013, the National Processed Raspberry Council (NPRC) represents the processed raspberry industry and is supported by assessments from both domestic producers and importers. NPRC’s mission is to conduct nutrition research and promote the health benefits of processed raspberries. The NPRC is responsible for marketing processed raspberries in the U.S. and is committed to promoting the growth of the entire industry. Processed raspberries are frozen at the peak of ripeness to lock in flavor and nutrition. Visit redrazz.org for more information, and follow us on our social media channels: on https://twitter.com/red_razz , https://www.facebook.com/redrazz, https://instagram.com/red_raspberries; or https://www.pinterest.com/razzrecipes.

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3. Mullen W, Yokota T, Lean MEJ, Crozier A. Analysis of ellagitannins and conjugates of ellagic acid and quercetin in raspberry fruits by LC-MSⁿ. Phytochemistry 2003, 64, 617-
4. Academy of Nutrition and Dietetics Complete Food and Nutrition Guide. John Wiley & Sons Inc. 2012, pp. 153-
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9. Sala R, Mena P, Savi M, Brighenti F, Crozier A, Miragoli M, Stilli D, Del Rio, D. et al. Urolithins at physiological concentrations affect the levels of pro-inflammatory cytokines and growth factor in cultured cardiac cells in hyperglucidic conditions. Journal of Functional Foods 2015, 15, 97–105.