Do Walnuts Really Improve Artery Function?

Walnuts and Artery Function
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Good news for nut lovers: Eating at least one serving of walnuts per week may drop our chances of a cardiovascular-related death by 50%. However, 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 lowering cholesterol.

The ability of blood vessels to relax and open normally is considered an excellent barometer of underlying vascular health. For example, 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. So what effect do nuts have? A 2011 review in the journal Nutrition, Metabolism, and Cardiovascular Diseases found five clinical trials analyzing the effect of nut consumption on arterial function, and all three studies on walnuts showed an improvement in endothelial function measured in the arm. The study on pistachios also found a positive effect, but the study on hazelnuts was a wash.

A subsequent study on hazelnuts, however, did find a significant improvement in arterial function, so the data for hazelnuts is mixed, whereas two subsequent walnut studies (highlighted in my video, Walnuts and Artery Function) confirmed walnuts’ benefits. Therefore, eight studies to date have investigated the effect of nuts on brachial artery function; 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 nuts to replace foods in the diet known to have a negative effect on endothelial function. For example, in one study, walnuts replaced meat and dairy, which have been shown to be detrimental, so no wonder arterial function got better. When we do a study like that, we can’t tell if the benefits are because of the addition of the good stuff or the removal of the bad. In three of the other studies, nuts replaced olive oil, which tends to lead to a worsening of endothelial function. Therefore, in these four studies, the beneficial effects of the walnuts may have been exaggerated.

However, the other four studies just added nuts as a snack or with a meal, without replacing any specific foods, and found that nuts significantly improved arterial functioning. Given their association with longevity (see Nuts May Help Prevent Death), 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 eliminates nut consumption for millions of Americans.

What else can nuts do? See, for example:

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

Which type of walnut is better? Black Versus English Walnuts.

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

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.

  • Leslie

    Macadamia nuts….to high in saturated fat, in your opinion?

    Can abundance of both monounsaturated and polyunsaturated
    fats in the diet (from excess nuts by some many of us vegans!)
    suppress immune system, or compromise liver health?

    Thanks.

    • Joseph Gonzales R.D.

      Macadamia nuts are fine, but like all nuts and seeds their fat content is pretty high. Interestingly, a great video by Dr. Greger explains the research between nut intake and body weight. Make sure to checkout the bottom of the video’s “Doctors Note” to see more links and info. Lastly, a follow-up to that video is solving the mystery of the missing calories, which may also help.​

    • guest

      Of all nuts. macademia nuts have the lowest amount of linoleic acid. So, overloading with linoleic acid is an issue, macadamia nuts are the way to go. Macadamia nuts have more oleic acid than olives. So getting a lot of oleic acid without getting a lot of linoleic acid is important, macadamia nuts are a great choice. The downside is it’s the most expensive nuts.

  • Julie

    We purchase organic nuts directly from the farmers. This way the nuts are fresher, the consumer price is cheaper, and the farmer gets a larger profit. A google search will come up with US farms that ship directly to consumers. Since today’s article highlights walnuts: http://www.fillmorefarms.com/

    • Sheph

      Their prices are quite a bit higher than the walnuts I purchase at Costco. Plus, I’d have to buy too large a quantity to easily store in the fridge. What advantage would there be for me as the consumer in buying from this place?

    • Dommy

      After shelling each nutmeat piece is individually handled — without gloves? (!)
      http://www.fillmorefarms.com/wp-content/uploads/2012/04/P1010513.jpg

      Good grief.

  • Irene

    Hi Joseph, would walnuts help migraine sufferers?

    • A Migrainer

      Irene, I don’t know of walnuts having an affect on migraines unless you find they are a trigger but they do contribute to your over all health. And that is a good thing. The healthier the body the more able to deal with the migraine.

    • george

      Irene: Dr. Greger has a video on the remarkable effect of ginger on migraine.

  • Will

    I recall a vid where the good Dr. mentioned flax seed as a potent anti hypertensive…have there been any studies with flax seeds instead of walnuts or others nuts to measure the same cardio protective benefits?

    Also, how long would one have to be consuming walnuts to get the full impact of this?

    Thanks

  • David H

    which type of walnuts are best?

  • Ron

    ALERT: when I clicked on the letters in green above: Nuts May Help Prevent Death it took me to a commercial website: http://www.nutrtionfacts.org/video/nuts-may-help-prevent-death which is not affiliated with Dr. Greger or this site. It didn’t take me to the correct nutritionfacts video. It seems that someone has found a way to divert web traffic to certain bogus health websites selling products such as fish and other non-vegan foods.

    • Thea

      Ron: Wow, that’s amazing. I forwarded your post onto the NutritionFacts staff in order to bring it to their attention right away. Thanks for telling us about this!

    • Laurie

      quite subtle, but note the spelling differences!

  • Coclesmary

    I’m allergic to raw walnuts, once roasted they are fine. Does anyone know if the benefit remains?

    • MCPeters

      I remember seeing a video on this site in which Dr. Greger says that roasted nuts are better for you than the raw ones, but I can’t remember if that applies to all nuts.

      • Coclesmary

        Well that’s encouraging, Not much else I can do, so I’ll try them.

  • mbglife

    I clicked on the hyperlinked word, lead, in the past and read the study abstract. It talked about the results relative to a very high fat meal, not as absolute results in and of themselves. What does this mean about the results as a practical matter?

  • PLA

    Perhaps this benefit of walnuts (and nuts in general) is due to magnesium? I’d love to see Dr Greger do some videos/articles on Magnesium and Dr Carolyn Dean’s book “The Magnesium Miracle” . Incredible book and information. I found my answer to most of my health issues in her book. One differnce between her and Dr Greger is that she says studies show that it is ‘oxidized’ cholesterol that does harm, not unoxidized cholesterol. So if dietary cholesterol is not damaged through heat, is it still important to keep cholesterol levels down to 135 total or lower as Dr Greger suggests or is it possible that unoxidized cholesterol does not accumulate in the arteries?

    • Sharon Stewart

      My cardiologist was very concerned about my cholesterol level being 280, even though I have been a vegan for over two years. I am one of the lucky ‘high cholesterol from genes’ recipients. Every one of my siblings have stents and take statins, which is why I became a vegan. I recently had the dye catheter test done because it looked like the stress/echo test showed problems. My arteries are clean as a whistle!! Left the doctor speechless. She said I still need to take statins to keep the vessels from hardening. I informed her the walnuts do the same thing, and her response was still take the statins. No thank you, I’ll just keep eating vegan!

      • Veganrunner

        Sharon you had an Angiogram and the results were all clear with 280? That is wonderful. And that is what we hear again and again. Some people can’t get cholesterol down ever though they are diligent with the diet. I would think your testimonial will give others in the same situation hope that the WFPB diet is still the right way to go even if the numbers are off!

        Great story!!! I love these! And the walnut answer to your MD is priceless!

      • jCarol

        Good for you, Sharon! It’s hard to stand up to some docs – they sometimes forget that we each own the bodies in which our souls reside!

        My husband and I became vegans partly because of two movies (“Forks Over Knives” and “Vegucated”) and partly because I read “The Truth About Statins” by Barbara Roberts. Like you, we have no interest in going down the pharmaceutical path.

        We’ve gotten out of the habit of eating walnuts, but after reading this article as well as your story, I’ll be putting the nut bowl back out!

  • Lazer Wolf

    The first paragraph is a complete non-sequitur. A 5% reduction in cholesterol in no way corresponds to a 5% reduction in mortality, unless you assume some linear relationship, which is perverse. Maybe a 5% reduction in cholesterol would lead to an 80% reduction in mortality, or maybe to a 0% reduction in mortality. Or maybe reducing cholesterol would like to an increase in mortality. There’s no logical basis to assume 5% reduction in cholesterol corresponds to 5% reduction in mortality.

    • Joseph Gonzales R.D.

      Hi Lazer. I am reading the first paragraph differently. He’s not saying a 5% reduction in cholesterol led to a 5% reduction in mortality, I think Dr. Greger is saying he’s not sure why walnuts only seem to drop cholesterol by 5% when other studies have found walnuts may drop our chances of a cardiovascular-related death by 50%. They are two different studies. The point was that other factors besides lowering cholesterol seem to play a role in arterial health. Let me know if that makes sense and if I’m thinking right?

  • Rodrigo Cardoso

    To share with your Portuguese speaking friends: http://nf.focoempatico.net/nozes-melhoram-a-funcao-arterial/

  • omar pantaleon

    Hi Dr. Greger, I started in a plant based diet about two months ago. The first month was a really good start with no changes in weight or any other measures, but I started noticing changes in the second month. During the second month I started to gain weight and I noticed this because of my 2 inch increase around my waist. I was wondering if changing the percentage of fats consumed in my diet could help me, let’s say like a vegan ketogenic diet. I consume now approximately 2500-2600 calories every day with a 80/10/10 (carbohydrates, protein, fats) percentage aproximately, I am also a very active person. My excircising routines consist of 1 hour of weightlifting and 20 minutes of cardio for days a week, 1 hour of power yoga two days a week and 30-40 minutes of cardiovascular activity 1 day a week. My current weight is 186 at 5 feet and 8.5 inches of height. I don’t know if I should return to a non vegan diet, since it provided me with better results, please help me the last thing I want to do is return to a non vegan diet, but it is seriously concerning the amount of fat that I am gaining. I thank you in advance for any help that you can bring me.

    • Steven Jodoin

      since your above your desired weight, i’m no doctor, but what I do is replace one high carb meal with a super veggie salad mix or something. If your gaining weight you are consuming over your required maintenance calories. If normally you eat 2500-2600Cal try and aim for 2200. It takes a while but I’ve been working out and on a plant based diet for a year now and starting to get amazing results.. takes some tweaking and getting to know your own body more then you ever thought possible!

    • Julie

      Omar, have you increased the amount of wheat products since going vegan? Modern wheat has been so hybridized that it is now radically different from ancient wheat. This major difference has many negative implications for our bodies, weight gain and appetite stimulation being two of them (The book “Wheat Belly” does a great job of explaining this). Also listen to your body for the amount of carb, fat, protein that it wants at each meal. You may have been unwittingly forcing the wrong nutrient mix.

      • Thea

        Julie: Wheat Belly is not a source I would consider reputable. Here is some more info about the book if you are interested. The following website is anti-gluten and even they see problems in the “science” behind Wheat Belly:
        http://noglutennoproblem.blogspot.com/2012/03/wheat-belly-busted.htm
        Or check out:
        https://www.drmcdougall.com/misc/2014nl/jan/smoke.htm

        I do agree that increases in wheat “products” can be a problem regarding weight gain. But only in the sense that you are likely talking about highly processed products like say crackers. In that case, we are talking about calorie dense foods and thus the issue is about calorie density and lost of nutrients, not that the food happens to have some wheat in it. If you were talking about wheat berries as a part of whole plant food diet, then I’d have to disagree with you that the wheat has anything to do with weight gain.

    • largelytrue

      What do you actually eat and how is this different from before? What was your weight two months ago? Have you checked that your adiposity has been increasing through some other independent and hopefully more reliable means? An increase in gut content and glycogen storage can account for pretty significant weight change as one changes macronutrient ratios independent of any change in fat/lean tissue as such.

      One thought is that you may be eating at a very high calorie density. I think this is so is because 1 cup of cooked brown rice is about 220 calories. 2200 calories of brown rice would be 10 cups, or more than 2 liters. Eating something like brown rice, you’d be getting in more than a 2 liter soda bottle full of brown rice every day, which is a lot of bulk to work through, before considering the additional 300-400 calories to make up the rest of your estimated total, and the possibility that you may be underestimating calorie intake or the calorie contribution of additional colonic fermentation. I find it a little unlikely that you are eating only to the point of satiety if we’re considering brown rice as the approximate calorie density of your diet.

    • Thea

      omar: I had a response similar to largelytrue in content. If you are really gaining fat, then you are getting too many calories. But that does NOT mean that you have to go hungry! You should be able to eat your whole food plant diet until you are full and get the exact right amount of calories. The key to getting to this sweet spot is to understand and utilize the concept of calorie density (not to worry about your nutrient percentages).

      In the following free youtube video, you can learn about the concept of calorie density and something about human biology and get some useful tips on how to apply it. This speaker is one of the main experts who appears in the Forks Over Knives video. He is well respected and also often works in the McDougall programs. This video is well worth your time (and it is amusing):
      https://www.youtube.com/watch?v=xAdqLB6bTuQ

      Jeff Novick has an excellent complementary talk, which I highly recommend for greater understanding of the topic and more tips:
      http://www.amazon.com/Calorie-Density-More-Weigh-Less/dp/B003ASP6JE/ref=sr_1_2?ie=UTF8&qid=1439583407&sr=8-2&keywords=calorie+density

      Hope that helps.

    • Veganrunner

      Hi Omar,
      Have you been eating a lot of tofu? When I first went vegan I thought I was supposed to eat tofu and tempi (neither of which I particularly love). If you look at the label you will see that a serving size is rather small. If you eat 1/2 of a package you are consuming a lot of calories. Now I rarely eat those food products. But I do love edamame.

    • Veganrunner

      Omar I just came across this Q and A. Excellent. Really good advice about oil, tofu amounts etc.
      http://youtu.be/sR09A_eDsiM

    • Tom Goff

      Is the weight gain actually fat or is it muscle?

    • S Slavin

      How are you even getting to 2500 calories with a plant based diet…? Where do the calories come from? What are you using for carbs, since that must be the main source of calories for you?

  • Christina Thomaz

    I read that it is not good to eat walnutrs if you take Synthroid. Can I eat walnuts in the evening if I take Synthroid in the morning?