Red raspberry and blood vessel function in healthy men
What it found
Eating red raspberries improved how well blood vessels widened in 10 healthy young men, lasting up to 24 hours.
The effect matched the amount of certain plant compounds found in their blood.
What they found
Studies in people
Blood vessel widening
Two hours after drinking either raspberry blend, the arm artery widened more than after the control drink. This improvement was still present 24 hours later, even after an overnight fast and a strict diet low in plant compounds.
Dose made little difference
The 200 g portion, containing 201 mg of total plant compounds, worked about as well as the 400 g portion with 403 mg. Eating twice as much did not lead to a bigger change in artery widening.
Blood pressure unchanged
Neither the 200 g nor the 400 g raspberry drinks changed blood pressure, pulse wave speed, or other measures of artery stiffness compared with the control drink at 2 or 24 hours.
Linked plant compounds
Ellagic acid levels in the blood rose at 2 hours and tracked with better artery widening. At 24 hours, urolithin A compounds made by gut bacteria tracked with the widening instead.
Gut bacteria differences
Eight of the ten men produced one set of urolithin compounds, while two produced another set. The authors noted a slight trend toward better artery widening in the larger group, but it was not statistically clear.
What the authors conclude
- They conclude that eating realistic amounts of red raspberries improves blood vessel function for at least 24 hours in healthy people.
- They suggest that gut bacteria play an important role by turning raspberry compounds into urolithins, which may drive the later benefits.
- They call for larger and longer studies to see if these short-term changes translate into real heart health benefits over time.
How it was done
Raspberries are popular and contain plant compounds linked to heart health in other foods, but no human study had tested their effects on blood vessels. The authors wanted to see if raspberries improve blood vessel function and which compounds might be responsible.
Ten healthy men aged 18 to 35 each took part in three test days. On different days they drank a blend made from 200 g or 400 g of frozen red raspberries, or a lookalike control drink without raspberries. Researchers measured how well an arm artery widened at the start, 2 hours later, and 24 hours later.
What it can’t tell you
- This trial only included 10 healthy young men, so the results may not apply to women, older adults, or people with existing health conditions.
- Because the study lasted only 24 hours per visit, it cannot show whether eating raspberries regularly leads to long-term heart benefits.
- The researchers linked urolithin levels to better blood vessel function but did not give pure urolithins alone, so they cannot prove those specific compounds caused the change.
Who paid
- Authors work at
- King's College London, UK; University Düsseldorf, Germany; Laboratory of Food & Health, Spain
The paper
- Title
- Plasma urolithin metabolites correlate with improvements in endothelial function after red raspberry consumption: A double-blind randomized controlled trial
- Type
- Randomised controlled trial
- Evidence
- Studies in people
- Summarised from
- Full text
- Cite
- Istas G, Feliciano RP, Weber T, et al (2018). Plasma urolithin metabolites correlate with improvements in endothelial function after red raspberry consumption: A double-blind randomized controlled trial. Archives of biochemistry and biophysics. doi:10.1016/j.abb.2018.05.016Free full textPubMed 29802820DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error