The question was simple: If we provide a healthy, balanced diet, but fewer calories, can we extend life span and improve the quality of life in old age?
The study of the animals on a restricted diet - and a control group allowed to eat freely - is far from over. But the initial results support a growing body of evidence that life span can be extended and killers of the elderly, such as diabetes, can be held at bay through dietary intervention. The results, which Kemnitz calls a "backbone of knowledge," will lead to new approaches to treating and averting the complications of old age in humans. Issues of aging and the elderly are urgent as America's elderly population continues to balloon. Not only will there be many more elderly within the next 30 years as baby boomers mature, but improvements in medicine, diet, public health, education and income levels are helping people live longer. By the year 2020, one-fourth of Americans will be older than 60, and the average life expectancy will be 82 for women and 74 for men. The Wisconsin primate study focuses on two groups of middle-aged monkeys that are nearly identical except for diet. One group is allowed to eat freely while the other is provided a diet with 30 percent fewer calories than the control group. The study is exploring how diet influences physiological functions such as metabolic rate, vision, immune function, physical activity and glucose tolerance. In terms of aging, rhesus monkeys are a lot like people, says Kemnitz. They get the same diseases, and as the study progresses and the animals enter the stage of life where the visible signs of aging begin, they will provide a novel window into the process of growing old. "They are in a phase of life now where we would expect age-related diseases to emerge," says Kemnitz. "In fact, four of the animals in the control group have impaired glucose tolerance and one of those has developed full-blown diabetes and requires daily insulin therapy. None of the food-restricted animals are showing glucose regulatory problems."
By tweaking the timing and modifying parts of the cheesemaking procedure, UW dairy researchers are coming up with ways to make low-fat cheese that retains most of the taste of its more sinful cousin.
with texture ranging from hard and rubbery to soft and pasty. Milkfat, milk proteins, cheese cultures and aging time interact to produce the rich flavors and textures of good cheese. Today, a good 25- percent reduced-fat Cheddar approximates the taste of mild full-fat Cheddar. But cutting the fat content even more - such as by 50 percent - poses a challenge, explains Mark Johnson, senior scientist at the Center for Dairy Research. The more fat you take out, the trickier the cheese chemistry gets. Some of the so-called "non-fat cheese" sold today barely resembles cheese, he says. Johnson and colleague Carol Chen have developed a recipe for 50-percent reduced-fat Cheddar that holds its own in side-by-side comparisons with full-fat Cheddar. The recipe tweaks the timing and modifies parts of the cheesemaking procedure, but requires no special equipment. Any cheesemaker making full-fat Cheddar cheese should be able to use it, they say. Consumer response to reduced-fat Cheddar right now is lukewarm, Chen says. People are buying it, but that's because a trip down the grocery aisle doesn't provide a side-by-side taste test with full-fat Cheddar. When compared with its full-fat counterpart, Chen says, reduced-fat Cheddar is missing true Cheddar flavor and has off-flavors. "We think our reduced-fat Cheddar can stand up to mild to medium full-fat Cheddar in side-by-side comparisons," Chen says. In fact, their reduced-fat cheese passed muster with a tough bunch of cheese tasters in the Food Science Department's Sensory Analysis Lab. And when tested on an even tougher group - visitors to the World Dairy Expo - common comments likened it to aged Cheddar, and tasters wanted to know where to buy it. To introduce people to high-quality reduced-fat cheese, Chen and Johnson plan to sell this Cheddar at the Babcock Hall Dairy Store on the UW campus. The cheese should have a nine-month shelf life or better, say the researchers. As it ages, it will develop a balanced Cheddar flavor, rather than the off-flavors of some reduced-fat cheeses. Taking a molecular approach to cheese flavor, food microbiologist Jim Steele is identifying the enzymes that generate Cheddar flavor com-pounds. These enzymes are produced by bacteria in starter cultures - the mixes of microbes that commence the cheesemaking process. Certain strains of bacteria can speed flavor development and reduce bitterness. Using molecular biology techniques, Steele creates a derivative of the original strain that lacks one enzyme. By compar-ing the original strain with the derivative, he learns whether that enzyme affects flavor development. In another study, Steele has removed genes from a good mozzarella starter organism and put them into a good Cheddar starter. In the resulting starter, the enzyme that helps eliminate bitterness is 100 times more prevalent - an important finding for producing reduced-fat Cheddar.
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