Due to their high fat content, nuts traditionally have been viewed as an indulgent food. They're commonly used in confections, ice cream, snacks and baked goods, but also have found a place in entrees, salads and side dishes. With more research coming out supporting nuts' health benefits, formulators may consider using them in functional foods.
Studies support the idea that nuts should become a regular part of a healthy diet. They offer protein, fiber, vitamin E, folate, and many vitamins and minerals. They also derive a high percentage of their calories from fat, but it is polyunsaturated and monounsaturated fat.
The International Tree Nut
Council sponsored a recent conference called "Making the Claim for
Nuts" at the Georgetown University Center for Food and Nutrition
Policy. Summaries of some of the presentations highlight the latest
research on nut nutrition.
Cardiovascular HealthBoth epidemiological and clinical studies indicate that eating nuts benefits cardiovascular health. Gary Fraser, professor of epidemiology, Loma Linda University, has conducted several dietary studies of more than 34,000 Seventh Day Adventists living in California. The results of a six-year study showed that people who ate five or more servings of nuts per week experienced 50% fewer heart attacks than non-nut eaters did. Subjects consumed the nuts of their choice, which included tree nuts or peanuts. Thirty percent reported eating peanuts. Twelve-year findings with this population yielded similar results.
Dr. Joan Sabaté, M.D., Ph.D., professor of nutrition and chairman, Dept. of Nutrition, School of Public Health, Loma Linda University, found that people who ate moderate amounts of walnuts had lower blood cholesterol levels. In his first clinical study, he randomly placed 18 healthy young men on two mixed natural diets. The diets were identical, except that in one, 20% of the calories from fat were derived from walnuts. Those on the walnut diet had reductions of 12.4% in total cholesterol, 16.3% in low density lipoprotein (LDL) cholesterol and 4.9% in high density lipoprotein (HDL) cholesterol. They also exhibited a lowering in the ratio of LDL to HDL.
In another of Sabaté's studies, 49 men and women with a mean age of 56 years who had polygenic hypercholesterolemia participated in a randomized, crossover feeding trial. The control diet was a Mediterranean diet. The experimental diet was similar in energy and fat content, but walnuts replaced approximately 35% of the energy from fat. The walnut diet produced mean reductions of 4.1% in total cholesterol level, 5.9% in LDL cholesterol and 6.2% in lipoprotein (a).
"We served the whole nut because we were interested in the effect of whole foods served as commonly consumed," explains Sabaté. "The main reason for the cholesterol reduction was the nature of the fat. Walnuts are high in polyunsaturated fat that contains alpha-linolenic acid, which is a precursor of the omega 3 fatty acids found in fish oil. The decrease in cholesterol was even greater than predicted because of other components that may contribute, like fiber and protein."
In a study involving peanuts and peanut products, Penny Kris-Etherton, professor of nutrition, Pennsylvania State University, showed that eating a diet that includes polyunsaturated and monounsaturated fat can be heart-healthy. Her group performed a randomized, double-blind crossover study to look at the cardiovascular disease risk of five different diets. These included the Average American Diet, the American Heart Association Step II lowfat diet and three diets high in monounsaturated fatty acids (MUFA). The high MUFA diets contained 34-36% fat and relied on olive oil, peanut oil or peanuts and peanut butter.
Results showed that the three high MUFA diets lowered total cholesterol 10% and LDL cholesterol 14% without lowering HDL cholesterol. The Step II lowfat diet lowered total cholesterol and LDL cholesterol by comparable amounts, but it also reduced HDL cholesterol. The Step II diet raised triacylglycerol concentrations--a risk factor for cardiovascular disease--while the high MUFA diets lowered it.
Wanda Morgan, Ph.D., associate
professor of human nutrition and food science at New Mexico State
University, asked test subjects on self-selected diets to supplement
their diets with 68 g of pecans every day. The control group refrained
from eating nuts. The pecan eaters lowered their LDL cholesterol
by 6% at the end of eight weeks. This was in spite of the fact that
the pecan eaters ate more fat each day than the control subjects.
Cancer PreventionAlmonds showed promise in preventing colon cancer in a study conducted by Paul Davis, associate research nutritionist, Department of Nutrition, College of Agriculture and Environmental Science, University of California-Davis.
He fed high-fat diets to rats that were primed to develop colon cancer. One of the diets contained 20% almonds and the other cellulose as a control. The rats developed Aberrant Crypt Foci, (ACFs), which are early markers for colon tumor development. The animals fed almonds had far fewer ACFs than did those fed the control diet.
"Almonds appear to inhibit
the formation of ACFs, precancerous lesions, which are red flags
for colon cancer," reports Davis. "The study was done to question
the assumption that people should avoid nuts. Nuts, in fact, contain
a variety of potentially healthy components such as monounsaturated
and polyunsaturated fats, minerals and proteins that are especially
high in arginine, an amino acid that the immune system uses as a
messenger. We don't know which compound, or more likely, combination
of compounds, in the whole nut is causing the reduced colon cancer
risk we saw, but the results certainly suggest that nuts may have
a role in cancer prevention."
Weight ControlSnacking on nuts does not lead to weight gain. In fact, it may help people stick to their weight loss programs for a longer time, according to a study conducted at Brigham and Women's Hospital in Boston under the direction of Kathy McManus, director of nutrition. She placed subjects in a weight loss program on two plans, one a lowfat diet and the other a moderate fat diet. In the moderate fat diet, the subjects could snack on the nuts of their choice.
The subjects on both plans lost about 10 pounds. However, those on the lowfat diet began to gain a small amount of weight back after one year. In contrast, the group on the moderate fat diet did not gain back any weight. More subjects on the moderate fat diet remained with the program for the full 18 months. PF