Walnuts & Artery Function

Walnuts & Artery Function
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Not eating walnuts may double our risk of dying from heart disease (compared to at least one serving a week)—perhaps because nuts appear to improve endothelial function, allowing our arteries to better relax normally.

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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Not eating walnuts may double our risk of dying from heart disease, compared to at least one serving a week. But, walnut consumption may only drop our cholesterol levels about 5%. How could we get a 50% drop in cardiac mortality from just a 5% drop in cholesterol? Walnuts must have some other heart-protecting benefits, besides just lowering cholesterol—such as improving arterial function.

This review found five clinical trials analyzing the effect of nut consumption on the ability of our arteries to relax and open normally—considered “an excellent ‘barometer’ of underlying vascular health.” Even after controlling for other risk factors, 80% of those with better-than-average arterial function survived cardiac event-free over the years, whereas 80% of those with below-average dilation didn’t.

And so, what effect do nuts have? All three studies on walnuts showed an improvement in endothelial function, arterial function—this so-called flow-mediated dilation measured in the arm. The one study on pistachios also found a positive effect, but the one study on hazelnuts was a wash. A subsequent study on hazelnuts, though, did find a significant improvement in arterial function, so the data on hazelnuts is mixed—whereas two subsequent walnut studies, however, confirmed walnuts’ benefits.

So, eight studies to date on nuts and brachial artery function, and seven out of eight showed a significant improvement in arterial function; one showed a negligible effect; and none found nuts made things worse. Half the studies, though, used the added walnuts to replace foods in the diet known to have a negative effect on endothelial function.

For example, in this study, walnuts replaced meat and dairy, which have been shown to be detrimental, so, no wonder arterial function got better. When you do a study like that, you can’t tell if the benefits you’re seeing is because you’re adding good stuff, or getting rid of the bad.

And, in three of the other studies, nuts replaced olive oil, which tends to lead to a worsening of endothelial function—thereby exaggerating the beneficial effects of the walnuts, from here to here.

But, the other four studies, like this one, that just added nuts “as a snack or with a meal,” without replacing any specific foods, found nuts “significantly improved [arterial] functioning.” And, given their association with longevity, I encourage everyone to eat an ounce of nuts a day—unless, of course, you’re allergic. Only about 1% of people report nut allergies, but still, that’s a significant “downside of [nut] consumption” for millions of Americans.

Please consider volunteering to help out on the site.

Images thanks to Alex Ex and J.Dncsn via Wikimedia, and angels aguirre via flickr

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

Not eating walnuts may double our risk of dying from heart disease, compared to at least one serving a week. But, walnut consumption may only drop our cholesterol levels about 5%. How could we get a 50% drop in cardiac mortality from just a 5% drop in cholesterol? Walnuts must have some other heart-protecting benefits, besides just lowering cholesterol—such as improving arterial function.

This review found five clinical trials analyzing the effect of nut consumption on the ability of our arteries to relax and open normally—considered “an excellent ‘barometer’ of underlying vascular health.” Even after controlling for other risk factors, 80% of those with better-than-average arterial function survived cardiac event-free over the years, whereas 80% of those with below-average dilation didn’t.

And so, what effect do nuts have? All three studies on walnuts showed an improvement in endothelial function, arterial function—this so-called flow-mediated dilation measured in the arm. The one study on pistachios also found a positive effect, but the one study on hazelnuts was a wash. A subsequent study on hazelnuts, though, did find a significant improvement in arterial function, so the data on hazelnuts is mixed—whereas two subsequent walnut studies, however, confirmed walnuts’ benefits.

So, eight studies to date on nuts and brachial artery function, and seven out of eight showed a significant improvement in arterial function; one showed a negligible effect; and none found nuts made things worse. Half the studies, though, used the added walnuts to replace foods in the diet known to have a negative effect on endothelial function.

For example, in this study, walnuts replaced meat and dairy, which have been shown to be detrimental, so, no wonder arterial function got better. When you do a study like that, you can’t tell if the benefits you’re seeing is because you’re adding good stuff, or getting rid of the bad.

And, in three of the other studies, nuts replaced olive oil, which tends to lead to a worsening of endothelial function—thereby exaggerating the beneficial effects of the walnuts, from here to here.

But, the other four studies, like this one, that just added nuts “as a snack or with a meal,” without replacing any specific foods, found nuts “significantly improved [arterial] functioning.” And, given their association with longevity, I encourage everyone to eat an ounce of nuts a day—unless, of course, you’re allergic. Only about 1% of people report nut allergies, but still, that’s a significant “downside of [nut] consumption” for millions of Americans.

Please consider volunteering to help out on the site.

Images thanks to Alex Ex and J.Dncsn via Wikimedia, and angels aguirre via flickr

Doctor's Note

This helps explain why Nuts May Help Prevent Death.

What else can nuts do? See, for example:

Don’t nuts make us fat, though? You may be surprised—see Nuts & Obesity: The Weight of Evidence.

Which type of walnut is better? See Black vs. English Walnuts.

What about the phytates in nuts–do we need to soak or toast them? See:

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