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Special edition: Nuts, pulses and legumes

Omega-3 content sets walnuts apart from other tree nuts

By Hank Schultz , 27-Mar-2014
Last updated on 27-Mar-2014 at 15:34 GMT

Almost all of the walnuts grown in the US are grown in California, but the state supplies only about 40% of the world's walnut crop. Photo courtesy of the California Walnut Board.
Almost all of the walnuts grown in the US are grown in California, but the state supplies only about 40% of the world's walnut crop. Photo courtesy of the California Walnut Board.

Now that the mania about fat in the diet is mostly over the story has become that some fats are good. And as far as fat-rich tree nuts go, the story is: They’re all good. But walnuts have a leg up on their tree nut competitors in that they are the only source among tree nuts of the very best of fats: omega 3s.

Walnuts also have a very interesting mix of polyphenolic compounds to go with the fat content.  It’s a mix whose health effects have been studied by many researchers, including Dr Sujatha Rajaram, PhD, of Loma Linda University in California.

“Walnuts stand alone because it is the only tree nut that has omega-3 in it,” Rajaram told FoodNavigator-USA. 

Mix of cardioprotective effects

Rajaram who is a professor of nutrition in the school of public health at the university, has  studied the nut extensively, including matching it up against the big boys in the omega-3 game: EPA and DHA.

“We compared walnuts with fatty fish—salmon. They both carry omega 3 fatty acids. We looked at blood lipids and cholesterol. We found that if you want to lower cholesterol, walnuts are better, and if you want to lower tryiglycerides, salmon is better,” she said.

“People always talk about EPA and DHA. The conversion ration of ALA into EPA is very low, it is about 3% to 5%. But we were concerned about whether ALA by itself had intersting health effects,” she added.

But walnuts have those other compounds in them, too, such as the mix of phytonutrients in their skins. Rajaram said researchers are interested in those, too.

“With walnuts it’s not just about the omega-3. There are some phytonutrients with very interesting profiles that are very powerful antioxidants. They combine synergistically with the omega 3. What we are hoping to show in the future is that the combo of omega-3, phytonutrients and vitamin E in walnuts has some combined effects,” Rajaram said.

Diet recommendations

Connie Diekman is a dietician in clinical practice who serves on the California Walnut Board’s scientific advisory committee. When advising her patients on diet, Diekman says tree nuts are always part of the conversation. And one recent paper, published in the journal Food & Function, found that while all nuts were good, walnuts were potenially superior  because of their polyphenolic content.

“When you look at the health benefits, I have to put walnuts at the top of that list because they are a good source protein, a good source of fats and they have a moderate amount of carbohydrates,” she said.

“Most people find they cannot eat enough at three regular meals to keep them full.  So rather than snacking on empty calories I recommend they make the shift to something that provides calories but is also nutrient rich.  And with walnuts, because of the unique presence of omega-3, it makes it easier to make that recommendation,” Diekman said.

Addressing public health concerns

But not only are walnuts a good way to snack healthily, they also address some critical public health concerns, Diekman said.

“If you go the next step, the research continues to grow on their health benefits, in cardiovascular risk reduction, in brain health, in the prevention of certain types of cancers.  And as it relates to disease in society, those are also the health conditions of most concern,” she said.

The biggest application of walnuts continues to be as an occasional food eaten out of hand, whether raw or roasted, Diekman said.  But work done at the walnut board and elsewhere continues to find new menu options, whether in baked goods, as an addition to stir frys or an ingredient in more complex formulations.

“A great opportunity has come from the idea that nuts don’t have to be just snack foods. With their texture, protein and fiber the tree nut category provides such a nice mouth feel addition to a meal. As a dietician, I’m always looking for how do you help the consumer make this part of their eating plan. Who cares what the science says if you can’t get people to eat it?” Diekman said.

And walnuts are hardy as an ingredient, too. Rajaram said in her research the team supplied walnuts in various forms and found that there was no diminution of health benefits with different preparation methods.

Market considerations

Almost all of the walnuts in the United States are grown in California.  But unlike some other tree nuts, the US does not supply the lion’s share of the world crop.  Walnuts are a much more globalized supply picture.

“The thing that one has to remember is that unlike almonds, where more than 80% of the world’s supply comes from California, with walnuts it’s only about 40%,” said Don Barton, president of Gold River Orchards in Oakdale, CA.  Barton represents the fourth generation of his family to grow walnuts in the state.

“China’s crop is neck and neck with California depending on the year and who you talk to,” Barton said. “In the second tier are countries like Turkey, Ukraine and Chile.  And some walnuts are grown in western Europe,” he said.

Another anomly of the walnut market is where the nuts are consumed.  As well as being one of the two major growers, China is the world’s leading consumer of walnuts, Barton said. 

“China has been a major buyer, and is the largest importer of California walnuts,” Barton said.  This is true for a number of reasons.

“In the US and in many other countries when you think of snacking nuts the most popular is almonds.  Not true in China.  There the tree nut of choice is walnuts,” he said. “It is an important part of their diet.  They believed in the health benefits of walnuts long before the studies that have been published in the past 20 years.”

“As the economy has grown and the middle class has broadened the demand for walnuts has risen.  There are a lot of walnuts that are roasted and eaten out of hand in China, but there are also industrial buyers that are using walnuts as an ingredient in value-added foods,” Barton said.

And finally, walnuts have an application in China that doesn’t as yet exist in the West, Barton said.

“They have a healthy drink where they grind the walnuts and add it to soy.  It is sort of a greyish-white color. It is very popular over there,” he said.

Supply concerns

The continued demand from China (and a crop there rumored to be lower than average) has pushed the price of walnuts up about 10% during the most recent selling period, which extends from September into about late January, Barton said.  California's 2013 crop was only slightly off the previous year, but the same might not be true for this year’s crop as a result of the crushing drought that has cast a pall over all of California’s agriculture.

“I think the walnut industry is in better shape than almonds or pistachios and the reason is that walnuts are predominantly grown in the Sacramento Valley and the east side of the San Joaquin Valley.  Those areas have better water supplies. The acquifer levels are higher when you are closer to the mountains. Still, there is going to be some impact this year.  The crop might off 5% to 10%,” he said.

Strong demand

The vicissitudes of weather are always part of the picture for any agricultural crop.  The drought aside, the long-term outlook for walnuts is excellent, Barton said.  Demand from China can only be expected to rise, and Barton credits the promotional work done by the California Walnut Board for supporting demand for the ingredient worldwide.

“I think that the underlying driver is the health research that has been ultimately sponosored by the growers through the California Walnut Board. It has developed a robust cadre of university researchers who are publishing anywhere from three to seven or eight studies per year that continue to show not only heart health but whole body health benefits like bone health, brain health and pre-diabetic conditions,” Barton said.

"It really has had a tremendous impact worldwide. The underlying demand is increasing and acreage is increasing in all growing areas including China," he said.

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