Eating walnuts helps your blood vessels work better by improving blood flow, and this benefit happens even if your cholesterol doesn't change.
Evidence from Studies
Supporting (2)
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Effects of walnuts consumption on vascular endothelial function in humans: A systematic review and meta-analysis of randomized controlled trials.
The study looked at whether eating walnuts helps blood vessels work better, and it found that they do. This supports the idea that walnuts improve blood vessel function.
Effect of walnut consumption on markers of endothelial function in adults: A systematic review and meta‐analysis of randomized controlled trials
The study found that eating walnuts improves blood vessel function, which matches the claim. We don’t know from this study if it’s because of something other than cholesterol changes, but the main effect is supported.
Contradicting (2)
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Effects of walnut consumption on blood lipids and other cardiovascular risk factors: a meta-analysis and systematic review.
The study looked at how walnuts affect cholesterol, but not how they affect blood vessel function directly, so it can't confirm or deny the claim about improved blood flow.
Effect of moderate walnut consumption on lipid profile, arterial stiffness, and platelet activation in humans
The study looked at whether eating a small amount of walnuts daily helps blood vessels work better, and found no improvement—even though cholesterol didn’t change.
Gold Standard Evidence Needed
According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.