Eating a handful of walnuts every day for a month doesn't seem to help improve cholesterol or other blood fats in middle-aged white adults who are at risk for metabolic syndrome.

What we've found so far suggests that eating 45g of walnuts daily for four weeks may not improve blood lipid levels in middle-aged adults at risk for metabolic syndrome. Our analysis of the available research shows this based on one key assertion drawn from 46 supporting studies [1]. We analyzed the evidence to see whether daily walnut consumption has an effect on cholesterol and other blood fats in this group. The assertion we reviewed states that a month of eating a handful of walnuts each day does not appear to lead to improvements in blood lipid measures among middle-aged white adults who are at risk for metabolic syndrome [1]. This finding is based entirely on studies that support this conclusion, with no studies found that refute it. It’s important to note that while the evidence we’ve reviewed leans toward no benefit for blood lipids in this specific group, the data is limited to one assertion. We cannot say whether results might differ in other populations, with longer durations, or in people with different health backgrounds. Also, the evidence does not address other potential benefits of walnuts, such as effects on inflammation, blood pressure, or blood sugar control. Our current analysis shows that, for this specific question, the available research does not support a meaningful improvement in blood fat levels from eating walnuts daily over four weeks. But this is just one piece of a larger puzzle. As we continue to review more studies, our understanding may change. Practical takeaway: If you're eating walnuts hoping to improve your cholesterol or blood fats in a month, the evidence we’ve reviewed so far suggests you might not see a change — at least in the short term and for this group of people.