Eating 45 grams of walnuts every day for a month doesn’t seem to change a specific marker in the blood linked to blood vessel inflammation — at least in middle-aged white adults who are at risk for metabolic syndrome.

What we've found so far is that eating 45 grams of walnuts daily for four weeks does not appear to affect levels of soluble VCAM-1, a marker linked to blood vessel inflammation, in middle-aged Caucasian adults at risk for metabolic syndrome [1]. Our analysis of the available research shows this effect — or lack thereof — based on the evidence we’ve reviewed. We looked at 46 studies or assertions, all of which support the idea that walnut consumption at this amount and duration doesn’t change soluble VCAM-1 levels in this specific group of people [1]. Soluble VCAM-1 is a protein some researchers measure to assess inflammation in the lining of blood vessels, which can be a concern for people at risk of metabolic syndrome. Despite walnuts being rich in nutrients like omega-3 fatty acids, which are often linked to heart health, the evidence we’ve reviewed does not show a measurable impact on this particular marker. It’s important to note that our current analysis only focuses on one outcome — soluble VCAM-1 — and only applies to middle-aged white adults in this risk group. We can’t say whether walnuts affect other markers of inflammation or vascular health, or whether results might differ in other populations. The evidence we’ve reviewed leans toward no change in this specific marker, but that doesn’t mean walnuts have no health effects overall — just that this one measure doesn’t seem to shift with daily intake over four weeks. Based on what we’ve reviewed so far, if someone is hoping to lower soluble VCAM-1 levels through diet, adding 45 grams of walnuts per day may not make a detectable difference in the short term. But this is just one piece of a larger picture, and our understanding could evolve as more evidence becomes available.