An important question when eating red raspberries is know how well the polyphenols are absorbed into the bloodstream to maximize their antioxidant and health promoting properties.
Red raspberry contains anthocyanins have been suggested to have several health promoting properties including cardioprotection, anti-inflammation, and anti-cancer.
The major criticism of anthocyanins from raspberry are that they are poorly absorbed and are unable to promote healthy outcomes.
A new study published in the journal Free Radical Biology and Medicine reveals a more sophisticated story than simply saying ‘anythocyanins are not well absorbed’.
This is especially important when we see evidence that anthocyanins can improve health outcomes in clinical trials yet the blood levels are very low.
In another clinical trials blueberries have been found to convert to different polyphenols after you eat them.
To help understand what happens when these compounds are absorbed a study was undertaken in healthy volunteers and blood and urine was analyzed to understand how these antioxidants are broken down.
Here are the study details:
Red raspberries, containing ellagitannins and cyanidin-based anthocyanins, were fed to 9 human volunteers and metabolites appearing in plasma and urine were analyzed by UHPLC-MS.
After an overnight fast, volunteers consumed 300 grams off homogenized raspberries.
Blood samples were collected before (0 h) and after raspberry consumption at 30 minutes, 1, 1.5, 2, 3, 4, 5, 6, 8, and 24 hr.
| Table 1. Polyphenols in red raspberries used in the study | |
| (Poly)phenolic compounds | μmol per 300 g raspberries |
| Total anthocyanins | 292±10 |
| Total ellagic acids | 6.3±0.3 |
| Total ellagitannins | 251±3 |
| Total (poly)phenols | 553±19 |
Here are the results:
Blood levels (i.e. plasma) of anthocyanins were sub nanomolar per liter (i.e. super low)
Metabolites (i.e. anthocyanins that were modified in our body) appeared in the urine and blood (i.e. plasma) about 1 to 1.5 hr after intake.
18 metabolites were identified represent about 15% of the intake.
Take away message:
The breakdown or metabolism of anthocyanins happens very quickly. In fact, it begins as soon as the anthocyanins enter the mouth and can be further metabolized by enzymes in the digestive tract and by bacteria in the tract. The key to figuring out the health benefits is to understand how anthocyanins are metabolized as these are the compounds found in the blood and urine. At least 18 metabolites discovered in this study and likely many, many more of these compounds represent only the tip of the iceberg of ‘active’ metabolites that need to be studied.
New insights into the bioavailability of red raspberry anthocyanins and ellagitannins. Free Radical Biology and Medicine. 2015 Dec;89:758-69.
His research on plant medicine has led to more than 45 publications and abstracts.This research has been presented at international meetings in the USA, France, Turkey, Peru, Israel, Austria, and Italy.
Categories: Antioxidant, Clinical Trials, Food
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