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7 Benefits of Walnuts

May 19, 2014

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Story at-a-glance

  • One-quarter cup of walnuts provides more than 100 percent of the daily recommended value of plant-based omega-3 fats, along with high amounts of copper, manganese, molybdenum, and biotin
  • Walnuts may help reduce not only the risk of prostate cancer, but breast cancer as well
  • Walnuts contain the amino acid l-arginine, which offers multiple vascular benefits to people with heart disease, or those who have increased risk for heart disease due to multiple cardiac risk factors
  • Walnuts contain several unique and powerful antioxidants that are available in only a few commonly eaten foods
  • Walnuts may improve sperm quality, help with weight control, and offer support for brain health and Type 2 diabetes

Oftentimes, the simplest foods are best for your health, and this is certainly the case for nuts, in which Mother Nature has crafted a nearly perfect package of protein, healthy fats, fiber, plant sterols, antioxidants, and many vitamins and minerals. Among nuts, the case may be made that walnuts are king, as research shows they may boost your health in a number of ways at very easy-to-achieve "doses."

The History of the Humble Walnut

Walnuts belong to the tree nut family, along with Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts and pistachios. Each has its own unique nutritional profile. It's believed that the walnut tree dates as far back as 700 B.C. Walnuts were considered foods for the gods during the early Roman times, and were named after Jupiter – hence the scientific name Juglans regia.

The "English" walnut that everyone is familiar with today is native to India and regions around the Caspian Sea, and was named for the English merchants that carried it for trade around the world. Another variety, the black walnut, is native to North America, in the Appalachian region and central Mississippi valley.1 Eating just one ounce of walnuts a day ( about seven shelled walnuts) may be all it takes to take advantage of their beneficial properties. But what exactly are walnuts good for?

The 7 Best Benefits of Walnuts

The health benefits of walnuts lie in their high concentration of nutrients. According to “The Encyclopedia of Healing Foods,” walnuts not only contain impressive amounts of antioxidants and vitamin E, but are also rich in monounsaturated fats. It’s actually one of the few nuts that has alpha-linolenic acid and omega-3s.2

One-quarter cup of walnuts provides more than 100 percent of the daily recommended value of plant-based omega-3 fats, along with high amounts of copper, manganese, molybdenum and biotin. Some of the most exciting benefits of walnuts include:

1. Cancer-fighting properties — Walnuts may help reduce not only the risk of prostate cancer, but breast cancer as well. In one study, mice that ate the human equivalent of 2.4 ounces of whole walnuts for 18 weeks had significantly smaller and slower-growing prostate tumors compared to the control group that consumed the same amount of fat from other sources.

Overall, the whole walnut diet reduced prostate cancer growth by 30 to 40 percent. According to another study on mice, the human equivalent of just two handfuls of walnuts a day cut breast cancer risk in half, and slowed tumor growth by 50 percent as well.3

2. Heart health — Walnuts contain the amino acid l-arginine, which offers multiple vascular benefits to people with heart disease, or those who have increased risk for heart disease due to multiple cardiac risk factors. If you struggle with herpes, you may want to avoid or limit your intake of walnuts, as high levels of arginine can deplete the amino acid lysine, which can trigger herpes recurrences.

Walnuts also contain the plant-based omega-3 fat alpha-linolenic acid (ALA), which is anti-inflammatory and may prevent the formation of pathological blood clots. Research shows that people who eat a diet high in ALA have a reduced risk of coronary heart disease.4 Eating just four walnuts a day has been shown to significantly raise blood levels of heart-healthy ALA,5 and walnut consumption supports healthful cholesterol levels.

Separate research showed that eating just one ounce of walnuts a day may decrease cardiovascular risk,6 and among those at high cardiovascular risk, increased frequency of nut consumption significantly lowers the risk of death.7

3. Rare and powerful antioxidants — Antioxidants are crucial to your health, as they are believed to help control how fast you age by combating free radicals, which are at the heart of age-related deterioration. Walnuts contain several unique and powerful antioxidants that are available in only a few commonly eaten foods. This includes the quinone juglone, the tannin tellimagrandin, and the flavonol morin.8

Walnuts contain antioxidants that are so powerful at free radical scavenging that researchers called them "remarkable,"9 and research has shown that walnut polyphenols may help prevent chemically-induced liver damage.10

In another study, researchers found that nuts, especially walnuts, have potent antioxidant powers. Walnut polyphenols had the best efficacy among the nuts tested and also the highest lipoprotein-bound antioxidant activity. The researchers concluded:11

"Nuts are high in polyphenol antioxidants which by binding to lipoproteins would inhibit oxidative processes that lead to atherosclerosis in vivo. In human supplementation studies nuts have been shown to improve the lipid profile, increase endothelial function and reduce inflammation, all without causing weight gain."

4. Weight control — Adding walnuts to your diet can help you to maintain your ideal weight over time. In one review of 31 trials, those whose diets included extra nuts or nuts substituted for other foods lost about 1.4 extra pounds and half an inch from their waists.12 Eating walnuts is also associated with increased satiety after just three days.13

5. Improved reproductive health in men — One of the lesser-known benefits of walnuts is their impact on male fertility. Among men who consume a Western-style diet, adding 75 grams (a bit over one-half cup) of walnuts daily significantly improved sperm quality, including vitality, motility, and morphology.14

6. Brain health — Walnuts contain a number of neuroprotective compounds, including vitamin E, folate, melatoninomega-3 fats and antioxidants. Research shows walnut consumption may support brain health, including increasing inferential reasoning in young adults.15

One study also found that consuming high-antioxidant foods like walnuts "can decrease the enhanced vulnerability to oxidative stress that occurs in aging," "increase healthspan," and also "enhance cognitive and motor function in aging."16

7. Diabetes — The beneficial dietary fat in walnuts has been shown to improve metabolic parameters in people with Type 2 diabetes. Overweight adults with Type 2 diabetes who ate one-quarter cup of walnuts daily had significant reductions in fasting insulin levels compared to those who did not, and the benefit was achieved in the first three months.17

Walnut Nutritional Facts

Walnuts are a mainstay in the Mediterranean diet, and there have been numerous reports about their health benefits. Nutritionally speaking, they're one of the most impressive nut varieties you can consider. For example, there's 4.3 grams of protein in a cup of walnuts and 3.8 grams of carbohydrates. Take a look at walnut nutrition facts below.18

Walnut Nutrition Facts

Serving Size: 1 cup (7 nuts), in shell, 28 grams
  Amt. Per
Serving
% Daily
Value*
Calories 183 9%
Calories from Fat 153  
Total Fat 18.3 g 28%
Saturated Fat 1.7 g 9%
Trans Fat 0 g
Cholesterol 0 mg 0%
Sodium 0.6 mg
Total Carbohydrates 3.8 g 1%
Dietary Fiber 1.9 g 8%
Sugar 0.7 g  
Protein 4.3 g 9%
Vitamin A 5.6 IU
Calcium 27.4 mg   3%

*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.

Why You Should Eat the Walnut Skin

The outermost layer of a shelled walnut — the whitish, flakey (or sometimes waxy) part — has a bitter flavor, but you should resist the urge to remove it. It's thought that up to 90 percent of the antioxidants in walnuts are found in the skin, making it one of the healthiest parts to consume.19 To increase the positive impacts on your health, look for nuts that are organic and raw, not irradiated or pasteurized.

It’s important to note that walnuts are highly perishable and their healthy fats easily damaged. If you're purchasing shelled walnuts in bulk, avoid those that appear shriveled, smell rancid, or that you cannot verify are fresh.

Walnuts should be stored in an airtight container in your refrigerator or freezer, whether they are shelled or unshelled. Walnuts are great as a quick snack, but if you're not a fan of their flavor, you can still get their therapeutic benefits by blending them into smoothies. Or you can try one of the other healthful nuts available.

You can further improve the quality of walnuts by soaking them in water overnight, which will tend to lower some of the enzyme inhibitors and phytic acid. After soaking, you can dehydrate them at a low temperature of around 105 to 110 degrees Fahrenheit until they are crispy again, as they are far more palatable when they are crunchy.

How to Toast Walnuts

Toasting walnuts is also a great way to give them a delicious crunch. While I recommend consuming walnuts raw, indulging in toasted walnuts occasionally is all right, as long as they’re eaten in moderate amounts. According to The Spruce Eats, doing this not only removes their bitterness, but also draws out their earthiness. Toasted walnuts have an intensity and delicious aroma that gives any dish a whole new level of flavor.

You can toast walnuts either in the oven or on the stove, depending on the amount you’re using. Oven toasting is best for larger servings, while the stovetop is better if you’re preparing only a handful or so.20

How to Roast Walnuts in the Oven

1. Preheat the oven to 375 degrees F. While waiting, line a baking sheet with parchment paper and spread the walnuts over it in a single layer. Make sure not to overcrowd the nuts, and add space in between to allow hot air to evenly circulate.

2. Place walnuts in the oven and roast for five to 10 minutes or until they start to brown and smell toasted. Check them after the first five minutes, as they can go quickly from roasted to burnt.

3. Pull them out as soon as the color has changed. Let cool before chopping them or using in recipes.

How to Toast Walnuts on the Stove

1. Place a frying pan over medium-high heat. No oil needed.

2. Add the walnuts, spreading them in a single layer. Let toast for five minutes or until they start to brown. Make sure to watch them closely and stir frequently to evenly brown them.

3. Transfer to a plate or baking sheet and let them cool evenly.

Enjoy These Walnut Recipes

Like other tree nuts, walnuts can be used in a variety of ways, from smoothies to salads to main dishes. You can also give desserts a nutty flavor with a handful of walnuts. Check out these recipe ideas:

Basil Walnut Pesto

Ingredients:

1/4 cup coarsely chopped walnuts

1 cup packed fresh basil leaves, rinsed and dried

4 tablespoons freshly grated Parmigiano-Reggiano

1/4 cup good extra virgin olive oil

1 large garlic clove

A big squeeze of fresh lemon juice

Salt and pepper to taste

Procedure:

1. In a food processor, pulse the walnuts and basil together.

2. Add garlic and olive oil, then pulse again.

3. Add lemon juice, cheese, and salt and pepper, pulsing continuously until just blended.

4. Scrape the sides down and pulse again for a few more times.

If not using immediately, place in an airtight container in the refrigerator to prolong shelf life.

(Recipe from Epicurious21)

Beet Salad With Walnuts and Goat Cheese

Ingredients:

2 bunches medium beets, (about 1 ½ pounds) tops trimmed

Kosher salt and freshly ground black pepper

2 tablespoons red wine vinegar

1/3 cup extra-virgin olive oil

1/2 cup walnuts

1 bunch arugula, trimmed and torn

1/2 medium head escarole, torn

4 ounces goat cheese, (preferably aged goat cheese) crumbled

Procedure:

1. Put the beets in a saucepan with water to cover and season generously with salt. Bring to a boil over high heat and cook until fork tender, about 20 minutes. When the beets are cool enough to handle, peel them – the skins should slide right off with a bit of pressure from your fingers. If they don't, use a paring knife to scrape off any bits that stick. Cut each beet into bite-sized wedges.

2. Whisk the vinegar with salt and pepper, to taste, in a large bowl. Whisk in the olive oil in a slow steady stream to make a dressing. Toss the cut beets in the dressing; set aside to marinate for at least 15 minutes or up to two hours.

3. Preheat the oven to 350 degrees F. Spread the nuts on a baking sheet and oven-toast, stirring once, until golden brown, about eight minutes. Cool.

4. Toss the arugula and escarole with the beets and divide among four plates. Scatter the walnuts and goat cheese on top. Serve.

(Recipe from The Food Network22)

Make Sure You Don’t Have a Walnut Allergy

Unfortunately, people who have food allergies cannot indulge in tree nuts for the risk of suffering severe symptoms. Food allergies occur when the body’s immune system mistakenly attacks proteins in food and treats them as a threat. It releases a number of chemicals, which then leads to severe allergic reactions.23

Similar to peanuts, tree nuts may also trigger allergic reactions, so if you have this condition, it’s best to stay away from any type of nut to keep yourself safe. According to the American College of Allergy, Asthma and Immunology, tree nut allergies usually last a lifetime, with fewer than 10 percent outgrowing this condition. Symptoms include:24

Itching of the throat, mouth, skin, eyes or any other area

Pain and cramps in the abdominal region

Nausea and vomiting

Diarrhea

Swallowing difficulties

Nasal congestion or a runny nose

Shortness of breath

Anaphylaxis (this is a potentially life-threatening reaction that affects your breathing and can lead to shock)

If you suffer from a tree nut allergy, or any type of food allergy, make sure that you check the label of any food you buy to ensure that it’s safe for you to eat. Prepare meals at home as much as possible, so you know what goes in your food. If dining out in restaurants, always ask about the ingredients to make sure you’re not putting yourself at serious risk.

Most Nuts Are a Wonderful Food

You can't really go wrong when choosing nuts to eat, as long as you pay attention to quality. Look for nuts that are organic and raw, not irradiated, pasteurized or coated in sugar. One exception is peanuts, which are technically in the legume family. My main objections to peanuts are that they tend to:

Distort your omega-3 to omega-6 ratio, as they are relatively high in omega-6

Be frequently contaminated with a carcinogenic mold called aflatoxin

Be one of the most pesticide-contaminated crops

My favorite nuts are raw macadamia and pecans, as they provide the highest amount of healthy fat while being on the lower end in terms of carbs and protein. Most nuts' nutritional makeup closely resembles what I consider to be an ideal ratio of the basic building blocks: fat making up the greatest amount of your daily calories, followed by a moderate amount of high-quality protein and a low amount of non-vegetable carbs.

And this is precisely why they're recommended as one of the best sources of healthy fats in my nutrition plan. The main fatty acid in macadamia nuts is the monounsaturated fat oleic acid (about 60 percent). This is about the level found in olives, which are well known for their health benefits. I have been consuming macadamia nuts and pecans almost daily since I started lowering my overall protein intake about a year ago.

The following list shows the nutrition facts in grams per one ounce for your most common tree nuts (one ounce of nuts equates to just over 28 grams, or about a small handful):25

Tree Nut Fat (grams per ounce) Protein (grams per ounce) Carbohydrates (grams per ounce)
Macadamias 22 2 4
Pecans 20 3 4
Pine nuts 20 4 4
Brazil nuts 19 4 3
Walnuts 18 4 4
Hazelnuts 17 3 5
Cashews 13 4 9
Almonds 14 6 6
Pistachios 13 6 8

Frequently Asked Questions (FAQs) About Walnuts

Q: How many calories are in walnuts?

A: One ounce of walnuts (100 grams) contains 183 calories.

Q: Are walnuts good for the brain?

A: Yes. The neuroprotective compounds in walnuts, which include vitamin E, folate, melatonin, omega-3 fats and antioxidants may support brain health.26

Q: Are walnuts good for the liver?

A: Yes. According to research, polyphenols found in walnuts may help prevent chemically-induced liver damage.27

Q: Are walnuts good for weight loss?

A: Walnuts may support your weight management efforts. One review found that including extra nuts in meals or substituting nuts for other foods allowed the participants to lose 1.4 extra pounds and half an inch from their waists.28

Q: Can you eat too many walnuts?

A: Tree nuts like walnuts contain protein, and if consumed in excessive amounts, this can lead to effects such as weight gain, elevated blood sugar and kidney stress. Since walnuts are in the middle range in terms of protein (4 grams of protein per 1 ounce), it's OK to eat them daily, as long as the amounts are kept in moderation.

Q: Do walnuts go bad?

A: Yes. Walnuts are highly perishable and the fats they contain can be damaged easily. It's best to buy it with the skins on. If you're buying shelled walnuts, stay away from those that are shriveled or smell rancid.

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Sources and References

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  • 2 "The Encyclopedia of Healing Foods," 2010
  • 3 WebMD Health News, April 21, 2009
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  • 11 Food Funct. 2012 Feb;3(2):134-40.
  • 12 American Journal of Clinical Nutrition April 17, 2013
  • 13 Obesity (Silver Spring). 2010 Jun;18(6):1176-82.
  • 14 Biology of Reproduction August 15, 2012
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  • 16 J Nutr. 2009 Sep;139(9):1813S-7S.
  • 17 Eur J Clin Nutr. 2009 Aug;63(8):1008-15.
  • 18 SelfNutritionData, Nuts, walnuts, english [Includes USDA commodity food A259, A257]
  • 19 World’s Healthiest Foods, Walnuts
  • 20 The Spruce Eats, April 16, 2018
  • 21 Epicurious, September 24, 2015
  • 22 Food Network, Beet Salad with Walnuts and Goat Cheese
  • 23 NHS Choices, May 16, 2016
  • 24 American College of Allergy, Asthma & Immunology, Tree Nut Allergy
  • 25 Nuthealth.org
  • 26 Br J Nutr. 2012 May;107(9):1393-401.
  • 27 J Agric Food Chem. 2008 Jun 25;56(12):4444-9.
  • 28 American Journal of Clinical Nutrition April 17, 2013
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