The tour, entitled "There's A Nut In Nutrition", explained the latest nutritional research into the health benefits - and in particular the cardiovascular health benefits - of adding Hi Oleic peanuts to your diet.

Prof Penny Kris-Etherton first became interested in cardiovascular nutrition when she started her post-graduate research in 1973. She completed her Ph.D in human nutrition at the University of Minnesota in 1978 and then did post-doctoral research into lipid metabolism at Stanford University.

Prof Kris-Etherton (pictured above with husband and fellow researcher Terry Etherton) is currently the Distinguished Professor of Nutrition at the Department of Nutritional Sciences at Pennsylvania State University.

She began doing feeding studies to study cardiovascular disease risk factors in the mid-1980s and started including peanuts in her research in the early 1990s after she was contacted by the Peanut Institute of Georgia. "They contacted me just at a point where we were very interested in the amount of fat in the diet - both low fat and moderate fat, so it was just perfect in terms of the timing ... what I really wanted to look at in terms of the next research question," she said. In 1999, Prof Kris-Etherton published her landmark study to determine whether peanut products - a rich source of monunsaturated fatty acids - affected cardiovascular disease risk factors.

This paper, entitled "High-monounsaturated fatty acid diets lower both plasma cholesterol and triacylglerol concentrations", was published in the American Journal of Clinical Nutrition. 

All the diets lowered total cholesterol and the bad "LDL" cholesterol in the subjects tested. 

"However the low-fat diet lowered the good cholesterol more than the others," Prof Kris-Etherton said. 

"And the key thing is that the low-fat diet increased triglycerides. 

So is there any difference between eating peanuts (which are actually a legume) and tree nuts?

"All nuts for the most part are low in saturated fat and high in unsaturated fat," Prof Kris-Etherton said.

"Peanuts are high in monosaturated fats and have a good amount of polyunsaturated fats in them. 

"One of the key characteristics of peanuts is that they are a good source of plant protein. Other nuts have small amounts but peanuts have a substantive amount.

"And then you have to look at the other nutrients. 

"Peanuts are a source of arginine and that's been shown to have all sorts of beneficial effects. One of the key ones is that it is a pre-cursor of nitric oxide. Nitric oxide has a vasodilatory response which means it just kind of 'opens up' the arteries."

And what about Hi Oleic peanuts?

"Hi Oleic peanuts have a fatty acid profile which is quite similar to olive oil. Olive oil has this wonderful reputation of being a very healthy oil," Prof Kris-Etherton said. 

"Now interestingly, Hi Oleic peanuts are also a little bit lower in saturated fats compared with regular peanuts and that is a very good characteristic.

"They are higher in monounsaturated fatty acids (MUFA) and a little bit lower in polyunsaturated fatty acids (PUFA)."

Prof Kris-Etherton said the distinguishing characteristic of Hi Oleic peanuts was they were "really high" in MUFA but also lower in saturated fats.

"So you get the big increase in monos at the expense of saturated fats," she said.

Metabolic Syndrome

How do diets high in MUFA affect Metabolic Syndrome - the cluster of conditions which includes obesity, insulin resistance and abnormal blood fat levels? 

"Increasing MUFAs can help with some of the distinguishing clinical characteristics that define Metabolic Syndrome," Prof Kris-Etherton said.

"The key thing is an increase in triglyceride levels. 

"A low-fat diet increases triglyceride levels and that is really bad - a risk factor for heart disease.

"Across the board people know that if you decrease the fat, you increase triglyceride levels and you lower the good cholesterol (HDL cholesterol). "In contrast, a moderate diet high in MUFA decreases triglycerides and increases the good cholesterol.

"I think definitely for some people - people who have high trigyclerides and don't have a normal blood cholesterol profile - the message is you've got to increase the monounsaturated fats.

"Metabolic Syndrome is really on the increase. Statistics in Australia show 275 people per day are getting diabetes in Australia ... that's amazing. And so it's also saying that as Metabolic Syndrome is a precursor (to diabetes) there are a lot of people in Australia that have Metabolic Syndrome."

Prof Kris-Etherton was co-author of a paper "Improved diet quality with peanut consumption" published in the Journal of American College of Nutrition in 2004.

So why do peanuts improve diet quality? 

"Peanuts are a rich source of a lot of vitamins and minerals and people who consume peanuts have better intakes of all these vitamins and minerals," Prof Kris-Etherton said. 

The research also showed that peanut consumers also have a better intake of calcium.

Peanuts are also a good dietary source of Vitamin E and magnesium.

"Magnesium is a nutrient that has recently come into the limelight because Western diets are poor in magnesium. A low intake of magnesium is associated with a lot of the criteria used to define Metabolic Syndrome," Prof Kris-Etherton said. 

"I think peanuts can really help in terms of getting some of the nutrients that can help prevent and protect against a lot of the chronic diseases that Australians are suffering from (just like Americans) ... cardiovascular disease, diabetes and Metabolic Syndrome."

The Physicians Health Study showed an inverse relationship between consuming peanuts and sudden cardiac death."Consuming peanuts as little as twice per week can decrease risk of sudden death by about 40% or so," Prof Kris-Etherton said. 

"That's an amazing finding. Just twice a week!" 

Peanuts are a low-GI (glycemic index food).

"I have a paper that Peter (Adelaide University nutritional researcher Professor Peter Howe, pictured at right) gave me that just came out about a year ago," Prof Kris-Etherton said.

"What it shows is that peanuts can help attenuate glycemic response to a meal.

"When you eat a sandwich you get a peak in blood glucose levels and then a decline after that. Well peanuts can attenuate (ie stretch) that response, that is keep the energy levels higher for longer.

"When blood glucose peaks, it causes insulin to be produced to respond to that increase. This causes glucose levels to decrease and then people become hungry soon afterwards. 

"I use the example at breakfast where somebody just eats cereal and skim milk. By 10 o'clock or 10:30 they're starved. That's in part related to the post-prandial glucose response that causes a decrease in glucose - a quick decrease - so they're hungry pretty soon thereafter. 

"Including peanuts with a meal like that, or peanut butter, decreases that blood glucose curve and response. 

"There are two things, I think, that are really important: One is that peanuts are a low GI food so that eaten alone, they don't cause a high glycemic response. 

"But the other thing that's really important is that when eaten with a meal, peanuts help to attenuate a hyper-glycemic response. I think that's something that's really new and a good message to get out. It'll help people control their calories. 

"That's a key thing ... and we're talking about obesity again and how it relates to diabetes and metabolic syndrome and heart disease."
 

"Well it's a good fat, we know that now. 

"People who are fat-phobic need to appreciate that low-fat meals might not have staying power. 

"If you add a little bit of peanuts to them, it really helps. You get to the next meal without feeling ravished and so hungry that you overeat ... so they help with calorie control."
 

"I think I'd like to do something looking at the role of peanuts in a meal with all sorts of other good foods and what they do to the post-prandial response," she said. 

"Oftentimes when we do studies we do them with subjects fasting. But most of the time we're in a post-prandial state. We eat breakfast, we eat lunch and then we eat dinner ... in the US we eat five times a day! So for the most part our blood levels represent what we've just eaten. 

"I'd like to see how peanuts effect blood response throughout the day."
 

Presentation by Prof Kris-Etherton

Presentations by other speakers

Prof Kris-Etherton's biography

Research by Prof Kris-Etherton