"We looked at macadamia nuts because they are not currently included in the health claim for tree nuts, while other tree nuts are recommended as part of a healthy diet," says Dr. Amy E. Griel, recent Ph.D. recipient in nutritional sciences. "Macadamia nuts have higher levels of monounsaturated fats, like those found in olive oil compared with other tree nuts."

The researchers used a controlled feeding study to compare a heart-healthy diet with 1.5 ounces , a small handful , of macadamia nuts to a standard American diet. The participants had slightly elevated cholesterol levels, normal blood pressure and were not taking lipid lowering drugs. Researchers randomly assigned participants to either the macadamia nut diet or the standard American diet and provided all meals for the participants for five weeks. The participants then switched diets and continued eating only food provided by the researchers for another five weeks.

The Healthy Heart diet with macadamia nuts did reduce total cholesterol, low-density lipoprotein cholesterol and triglyceride levels compared with the standard American diet.

"We observed a reduction in LDL similar to that seen with other tree nuts like walnuts and almonds," says Griel.

Individual calorie levels were used for each participant so that they did not gain or lose weight during the study. Both diets were matched for total fat, containing 33 percent calories from total fat. The Heart Healthy diet with macadamia nuts had 7 percent saturated fat, 18 percent monounsaturated fat and 5 percent polyunsaturated fat. The standard American diet had 13 percent saturated fat, 11 percent monounsaturated fat and 5 percent polyunsaturated fat.

The macadamia nut diet included macadamia nuts as a snack, mixed into meals, as a salad topping and in cookies and muffins.

"The total fat was the same in both diets," says Griel. "We substituted the macadamia nuts for other sources of fat and protein in the diet. For example, we could switch skim milk for 2 percent milk and add some macadamia nuts."

Macadamia nuts are native to Australia, but were imported to Hawaii and thrived. The first commercials crop of Hawaiian macadamia nuts was harvested in 1956.

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Dr. Lenore Arab, a nutritional epidemiologist in the David Geffen School of Medicine at UCLA, notes that the first coffee controversy dates back 430 years when in 1570 some monks petitioned the pope to condemn this drink, so popular among Muslims. Pope Clement VIII, liking how it kept the monks from falling sleep during mass, purportedly blessed it instead. The rest, including the United States, wholesale conversion to coffee following the Boston Tea Party, is history.

In reviewing the latest epidemiologic literature on cancers and coffee, Dr. Arab has found there to be close to 400 studies of the associations between coffee consumption and cancers various at various sites. The earlier controversy with regard to colon cancer was based on flawed analyses, she says. More thorough analyses and the accumulation of evidence suggest no negative effect on the incidence of colon cancer, and possible protective effects for adenomas of the colon as well as for rectal cancer and liver cancer. Mechanisms which might contribute to a possible anticarcinogenic effect include reduction in cholesterol, bile acid and neutral sterol secretion in the colon, increased colonic motility and reduced exposure of epithelium to carcinogens, the ability of diterpenes to reduce genotoxicity of carcinogens, and lower DNA adduct formation, and the ability of caffeic acid and chlorogenic acid to decreased DNA methylation. In other cancers - breast, ovarian, and prostate - the evidence is not suggestive of either risk or protection. There are two areas, says Dr. Arab, in which there is some evidence of increased risk: leukemia and stomach cancer. The evidence for the former is intriguing, for the latter insubstantial. She concludes that a systematic review of the newer data for liver, rectal, stomach cancer and for childhood leukemia is due.

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