Health Benefits of Walnuts
Walnuts, a rich source of the omega-3 fat, alpha-linolenic acid (ALA), improve artery function after a high fat meal and may be even more important in a Mediterranean-type diet than olive oil in promoting heart health, suggests a small study from Spain (Cortes B, Nunez I, J Am Coll Cardiol).
The study, funded by the California Walnut Commission and the Spanish Ministry of Health, looked at the effects on a number of markers of cardiovascular health of adding walnuts or olive oil to a fatty meal.
Twelve healthy people and 12 patients with high cholesterol levels were randomly assigned to eat either a high-fat meal (80 g fat, 35 per cent saturated fat) that also included 40 grams of walnuts or one that included 25 grams of olive oil (30 grams = 1 ounce). After one week, the participants eating walnuts were crossed over to olive oil and visa versa.
The researchers evaluated the activity of the subjects’ blood vessels after the meal, and looked at cholesterol and triglyceride levels, as well as markers of free radical (oxidative) stress and blood levels of asymmetric dimethylarginine (ADMA). AMDA is a by-product of the metabolism of the protein, arginine, that is said to interfere with the amino acid L-arginine, which is involved in the production of nitric oxide (NO). NO acts upon smooth muscle in blood vessels, causing them to dilate and thus increasing blood flow.
The researchers reported that blood flow in the brachial artery of the arm, (flow-mediated dilation) increased 24% in the subjects with high cholesterol after they ate the walnut-containing meal, while the olive oil-containing meal actually resulted in a 36% decrease in blood flow.
However, levels of cholesterol and triglycerides decreased in similar amounts after both meals. Blood levels of ADMA were not affected by either walnuts or olive oil. The fact that a single walnut meal positively affects postprandial vasoactivity further supports the beneficial effects of walnuts on cardiovascular risk, wrote lead author Berenice Cortés in the Journal of the American College of Cardiology.
E-selectin, a molecule that plays a role in cell adhesion-the process by which damaged cholesterol adheres to blood vessel walls to form plaques-also fell after the walnut meal. Many people forget that walnuts are an important part of the Mediterranean diet, providing numerous health benefits…Walnuts, unlike olive oil and other nuts, contain significant amounts of polyunsaturated fatty acids, specifically alpha-linolenic acid (ALA), an essential plant-based omega-3. They also provide antioxidants and L-arginine, components identified in past studies as potential nutrients that improve artery function., said Dr. Ross. Robert Vogel, a researcher from the University of Maryland, who did not participate in the study, commented: This demonstrates that the protective fat from walnuts actually undoes some of the detrimental effects of a high-saturated-fat diet, whereas a neutral fat, such as olive oil, does not have as much protective ability>,/q> This raises a very interesting issue because many people who eat a Mediterranean diet believe the olive oil is providing the benefits. But this research and other data indicate that’s not true…There are probably other factors in the diet, including that it is a relatively rich source of nuts. This is not to say that olive oil is bad, but it’s not the key protective factor in the Mediterranean diet, said Vogel.
This does not mean that simply eating a handful of walnuts can make up for an unhealthy diet. Consumers would get the wrong message from our findings if they think they can continue eating unhealthy fats provided they add walnuts to their meals, said study author Emilio Ros from the Universitat Autonoma de Barcelona. While this research clearly indicates that nuts are highly beneficial, they are only one component of the Mediterranean diet. Rich in vegetables, fruits, legumes, whole grains, fish and olive oil, as well as nuts, the Mediterranean diet includes literally thousands of protective vitamins, minerals and phytonutrients. It’s the combination of all these beneficial compounds that explains why this healthy way of eating is associated with longer life and protection against numerous diseases including cardiovascular disease, cognitive decline, and a number of cancers.
Food for Better Thought
Walnuts have often been thought of as a “brain food,” not only because of the wrinkled brain-like appearance of their shells, but because of their high concentration of omega-3 fats. Your brain is more than 60% structural fat. For your brain cells to function properly, this structural fat needs to be primarily the omega-3 fats found in walnuts, flaxseed and cold-water fish. This is because the membranes of all our cells, including our brain cells or neurons, are primarily composed of fats. Cell membranes are the gatekeepers of the cell. Anything that wants to get into or out of a cell must pass through the cell’s outer membrane. And omega-3 fats, which are especially fluid and flexible, make this process a whole lot easier, thus maximizing the cell’s ability to usher in nutrients while eliminating wastes–definitely a good idea, especially when the cell in question is in your brain.
Epidemiological studies in various countries including the U.S. suggest a connection between increased rates of depression and decreased omega-3 consumption, and in children, the relationship between low dietary intake of omega-3 fats and ADHD has begun to be studied. A recent Purdue University study showed that kids low in omega-3 essential fatty acids are significantly more likely to be hyperactive, have learning disorders, and to display behavioral problems. In the Purdue study, a greater number of behavioral problems, temper tantrums, and sleep problems were reported in subjects with lower total omega-3 fatty acid concentrations. More learning and health problems were also found in the children in the study who had lower total omega-3 fatty acid concentrations.
Over 2,000 scientific studies have demonstrated the wide range of problems associated with omega-3 deficiencies. The American diet is almost devoid of omega-3s, except for nuts, such as walnuts, seeds and cold-water fish. In fact, researchers believe that about 60% of Americans are deficient in omega-3 fatty acids, and about 20% have so little that test methods cannot even detect any in their blood.
Help Prevent Gallstones
Twenty years of dietary data collected on over 80,000 women from the Nurses’ Health Study shows that women who eat least 1 ounce of nuts, peanuts or peanut butter each week have a 25% lower risk of developing gallstones. Since 1 ounce is only 28.6 nuts or about 2 tablespoons of nut butter, preventing gallbladder disease may be as easy as having a handful of walnuts as an afternoon pick me up, or tossing some walnuts on your oatmeal or salad.
A Source of Bio-Available Melatonin
Want a better night’s sleep? Try sprinkling your dinner’s tossed green salad, fruit salad or steamed vegetables with a handful of walnuts. Or enjoy a baked apple or poached pear topped with walnuts for dessert.
Melatonin, a hormone produced by the pineal gland, which is involved in inducing and regulating sleep and is also a powerful antioxidant, has been discovered in walnuts in bio-available form, making them the perfect evening food for a natural good night’s sleep.
Melatonin has been shown to help improve sleep for night shift workers and people suffering from jet lag, but maintaining healthy levels of this hormone is important for everyone over the age of 40 since the amount of melatonin produced by the human body decreases significantly as we age, and this decrease in antioxidant protection may be related to the development of free radical-related diseases later in life.
In a study published in Nutrition, Russell Reiter and colleagues at the University of Texas have not only quantified the amount of melatonin present in walnuts-between 2.5 and 4.5 ng/gram-but have demonstrated that eating walnuts triples blood levels of melatonin and also increases antioxidant activity in the bloodstream in animals.
The authors theorize that by helping the body resist oxidative stress (free radical damage), walnuts may help reduce the risk of cancer and delay or reduce the severity of cardiovascular disease and neurodegenerative diseases such as Parkinson’s or Alzheimer’s disease. Walnuts, best known as a heart-healthy nut, are also a rich source of another highly cardio-protective nutrient: omega-3-fatty acids, so Reiter and his team will next investigate possible synergy between walnuts’ omega-3 fats and melatonin. To us at the World’s Healthiest Foods, this sounds familiar theme in Nature’s symphony in which whole, wholesome foods each provide a wealth of nutrients whose harmony promotes our optimal health.
Omega-3-rich Walnuts Protect Bone Health
Alpha linolenic acid, the omega-3 fat found in walnuts, promotes bone health by helping to prevent excessive bone turnover-when consumption of foods rich in this omega-3 fat results in a lower ratio of omega-6 to omega-3 fats in the diet.(Griel AE, Kris-Etherton PM, et al. Nutrition Journal)
Other studies have shown that diets rich in the omega-3s from fish (DHA and EPA), which also naturally result in a lowered ratio of omega-6 to omega-3 fats, reduce bone loss. Researchers think this is most likely because omega-6 fats are converted into pro-inflammatory prostaglandins, while omega-3 fats are metabolized into anti-inflammatory prostaglandins. (Prostaglandins are hormone-like substances made in our bodies from fatty acids.)
In this study, 23 participants ate each of 3 diets for a 6-week period with a 3 week washout period in between diets. All 3 diets provided a similar amount of fat, but their ratio of omega-6 to omega-3 fats was quite different:
Diet 1 provided 34% total fat with omega-6 and omega-3 fats in amounts typically seen in the American diet: 9% polyunsaturated fats (PUFAs) of which 7.7% were omega-6 and only 0.8% omega-3 fats, resulting in a pro-inflammatory ratio of 9.6:1.
Diet 2, an omega-6-rich diet, provided 37% total fat containing 16% PUFAs of which 12% were omega-6 and 3.6% omega-3, a better but still pro-inflammatory ratio of 3.3:1.
Diet 3, which provided 38% in total fats, was an omega-3-rich diet, containing 17% PUFAs, of which 10.5% were omega-6 and 6.5% omega-3, resulting in an anti-inflammatory ratio of 1.6:1.
After each diet, subjects’ blood levels of N-telopeptides, a marker of bone breakdown, were measured, and were found to be much lower following Diet 3, the omega-3-rich diet, than either of the other two.
The level of N-telopeptides seen in subjects’ blood each diet also correlated with that of a marker of inflammation called tumor necrosis factor-alpha (TNF-alpha). Diets 1 and 2-the diets which had a significantly higher ratio of omega-6 to omega-3 fats-also had much higher levels of TNF-alpha than the Diet 3, which was high in omega-3 fats from walnuts and flaxseed. Practical Tip: Protect your bones’ by making anti-inflammatory omega-3-rich flaxseed and walnuts, as well as cold water fish, frequent contributors to your healthy way of eating.
Protective Omega-3 Levels Greatly Improved by Eating Just 4 Walnuts a Day
Enjoying just 4 walnuts a day significantly increased blood levels of the health-protective omega-3 essential fatty acids, alpha linolenic acid (ALA) and eicosapentaenoic acid (EPA), in 10 adults.
EPA, a longer-chain omega-3 fat, is already present in cold water fish, but is not found in nuts, which contain the shorter-chain omega-3 fat, ALA. Fortunately, as this study confirms, our bodies can make EPA from the ALA provided by walnuts, which are its richest source among all the nuts.
After a 2-week run-in period, during which no walnuts were eaten, blood levels of ALA and EPA were assessed, and study participants then ate 4 walnuts a day, in addition to their regular diet, for 3 weeks.
When blood tests were again run, significant increases in levels of ALA (from 0.23 to 0.47) and EPA (from 0.23 to 0.82) were seen. And levels of ALA and EPA remained elevated over subjects’ initial levels even after a final 2-week period during which no walnuts were eaten. This study, published in Nutrition, Metabolism and Cardiovascular Diseases, clearly shows that even a very simple change in diet can have highly beneficial and lasting effects on our health. Boosting your body’s supply of cardio-protective, anti-inflammatory omega-3 fatty acids couldn’t be any easier-just add a few walnuts to your morning cereal or daily salad or just grab a handful for an afternoon snack.
Eating Nuts Lowers Risk of Weight Gain
Although nuts are known to provide a variety of cardio-protective benefits, many avoid them for fear of weight gain. A prospective study published in the journal Obesity shows such fears are groundless. In fact, people who eat nuts at least twice a week are much less likely to gain weight than those who almost never eat nuts.
The 28-month study involving 8,865 adult men and women in Spain, found that participants who ate nuts at least two times per week were 31% less likely to gain weight than were participants who never or almost never ate nuts.
And, among the study participants who gained weight, those who never or almost never ate nuts gained more (an average of 424 g more) than those who ate nuts at least twice weekly.
Study authors concluded, “Frequent nut consumption was associated with a reduced risk of weight gain (5 kg or more). These results support the recommendation of nut consumption as an important component of a cardioprotective diet and also allay fears of possible weight gain.”
Practical Tip: Don’t let concerns about gaining weight prevent you from enjoying the delicious taste and many health benefits of nuts!
Spread some nut butter on your morning toast or bagel. Remember how many great childhood lunches involved a peanut butter and jelly sandwich? Upgrade that lunchbox favorite by spreading organic peanut butter and concord grape jelly on whole wheat bread. Fill a celery stick with nut butter for an afternoon pick-me-up. Sprinkle a handful of nuts over your morning cereal, lunchtime salad, dinner’s steamed vegetables. Or just enjoy a handful of lightly roasted nuts as a healthy snack.
Not the End of Walnut’s Health Benefits
Walnuts are a very good source of manganese and a good source of copper, two minerals that are essential cofactors in a number of enzymes important in antioxidant defenses. For example, the key oxidative enzyme superoxide dismutase, which disarms free radicals produced within cell cytoplasm and the mitochondria (the energy production factories within our cells) requires both copper and manganese.
Walnuts also contain an antioxidant compound called ellagic acid, which blocks the metabolic pathways that can lead to cancer. Ellagic acid not only helps protect healthy cells from free radical damage, but also helps detoxify potential cancer-causing substances and helps prevent cancer cells from replicating. In a study of over 1,200 elderly people, those who ate the most strawberries (another food that contains ellagic acid) were three times less likely to develop cancer than those who ate few or no strawberries.