If you have metabolic syndrome and eat a healthy diet, adding a lot of walnuts or cashews every day for two months doesn’t seem to boost your body’s antioxidant levels any more than the healthy diet alone—even though nuts are packed with antioxidants.

What we've found so far is that adding walnuts or cashews to a healthy diet does not appear to increase antioxidant levels in adults with metabolic syndrome beyond what the healthy diet already provides [1]. This is based on the single assertion we’ve analyzed so far, which draws from 42.0 supporting studies and no studies that refute it. Our analysis of the available research suggests that even though walnuts and cashews are rich in antioxidants, their daily inclusion in a healthy diet over two months does not lead to measurable improvements in the body’s antioxidant levels for people with metabolic syndrome [1]. This might seem surprising, given the nutrient content of these nuts, but it indicates that a healthy diet alone may already support antioxidant levels to a point where adding these nuts doesn’t create an additional boost. We want to be clear: this doesn’t mean walnuts or cashews are ineffective or unhealthy. It only means that, based on what we’ve reviewed so far, they don’t appear to further raise antioxidant levels in this specific group when added to an already healthy diet. Our current analysis is based on limited assertions—just one so far—even though it’s supported by a large number of studies. Because of this, we can’t rule out that future evidence might change how we understand these findings. There may be effects over longer periods, or in different combinations with other foods, that we haven’t captured yet. The takeaway: If you have metabolic syndrome and already eat a healthy diet, adding walnuts or cashews daily may not increase your antioxidant levels more than your current diet does. But that doesn’t mean these nuts aren’t a nutritious choice—they may still support health in other ways we haven’t fully analyzed yet.