If you're at risk for heart disease, swapping out saturated fats for healthier fats like walnuts or olive oil for six weeks might help your blood pressure and cholesterol, but it won’t make your arteries more flexible in the short term.

If you're an adult with mild obesity, swapping out saturated fats (like butter) for healthier fats from walnuts or vegetable oils for six weeks might lower your blood pressure by about 5 or 6 points — and how your body processes food could affect how much it drops.

Eating walnuts or using vegetable oils instead of foods with saturated fats can lower bad cholesterol in people at risk for heart disease—by about 5 to 7%.

Eating a small handful of walnuts every day for a month doesn’t seem to make arteries more flexible in healthy young guys, according to this claim.

If you're at risk for heart disease, swapping out saturated fats for healthier fats from walnuts or vegetable oils won't raise a specific blood marker (called Lp(a)) that's linked to heart problems.

If you're at risk for heart disease, swapping some fatty foods for whole walnuts every day for six weeks might lower an important type of blood pressure by a small but meaningful amount — even if your top blood pressure number doesn't change.