Nutrition Newsletter

Summer 1999

Prepared by:  Linda B. Bobroff, Ph.D., R.D., LD/N,  

FATS RATIO CRUCIAL TO LOWERING CHOLESTEROL

If you go on a low-fat diet, you will surely lower your cholesterol count, right?

Not necessarily, reports chemist Gary J. Nelson with ARS Western Human Nutrition Research Center.

Among 11 healthy men aged 20 to 35 who volunteered for a study led by Nelson, cholesterol levels didn't change significantly--regardless of whether the men were on a low-fat or high-fat stint. Fat calories made up 39 percent of the day's total calories in the high-fat menus, while accounting for only 22 percent during the low-fat regimen--meaning that fat calories were nearly cut in half for those days.

Why didn't such a drastic drop in fat intake lead to a similar decrease in cholesterol?
"Perhaps because we didn't change the ratio of fats: that is, saturated to polyunsaturated to monounsaturated," says Nelson. "We stayed with 28 percent saturated fat--the kind in healthful cooking oils. Other minor fatty acids made up the remaining 4 percent.
"These findings," Nelson says, "should be of interest both to people who are trying to lower their cholesterol and to health care providers advising patients on how to change their diets to improve their cardiovascular health."

For the experiment, all volunteers ate the high-fat diet for 20 days. Then, six volunteers ate low-fat meals for 50 days, while the other five volunteers ate the high-fat foods--whole milk instead of nonfat and cream cheese, not jelly on their breakfast bagels, for example. After that, the two groups crossed over to the opposite menus for the final 50 days of the study.
Nelson collaborated in the study with ARS chemist Perla C. Schmidt and Darsham S. Kelly at the Nutrition Center.--By Marsha Wood, ARS

Gary J. Nelson is at the USDA-ARS Western Human Nutrition Research Center, University of California, One Shields Ave., Davis, CA 95616; phone (530) 752-5356, fax (530) 752-8996.

Dietary Carbohydrate and Metabolic Control

A recent study found that a diet that emphasizes fruits, non-starchy vegetables, and dairy products may benefit patients with type 2 diabetes. Researchers developed an experimental meal containing carbohydrates that, upon digestion, resulted in relatively high amounts of the monosaccharides fructose and galactose and relatively low amounts of glucose.(Ingestion of fructose and galactose have been found to result in smaller increases in plasma glucose levels than ingestion of glucose.)

The experimental meal contained very little readily digestible starch, and large amounts of fruits and vegetables; nutrient content included 43% of energy as carbohydrate, 22% protein, and 34% as fat.

There were two comparison meals: one contained 55% of energy as carbohydrate with an emphasis on complex carbohydrates (starch), 15% as protein, and 30% as fat; the second had 40% of energy as carbohydrate, 20% as protein, and 40% as fat. Six men (aged 57 to 70 years) with type 2 diabetes treated by diet only ate identical test meals at 8 am, 12 noon, and 5 pm on 3 separate days; 1 type of meal was given on each test day in random order with a 2-day washout period between each type of meal. Changes in plasma glucose and insulin levels over 24 hours were significantly smaller after subjects ate the low-starch diet than after they ate the high-starch or high-fat diet. It will be interesting to see if future studies support these findings, and result in changes in dietary recommendations for persons with Type 2 diabetes.

Reference: Annals of Internal Medicine, Vol. 129, October 1, 1998.

Multivitamins, Folate and the Risk of Colon Cancer

In women, long-term use of multivitamin supplements containing folic acid may reduce risk of colon cancer. Subjects were 88,756 women enrolled in the Nurses' Health Study. They completed a semi-quantitative food frequency questionnaire (which included information about use of vitamin and mineral supplements), every 2 years between 1980 and 1994; during this time, 442 new cases of colon cancer were diagnosed.

Intake of folate in 1980 was inversely related to risk of colon cancer after adjustment for age, family history of colorectal cancer, aspirin use, cigarette smoking, body mass, physical activity level, and intakes of energy, red meat, alcohol, methionine, fiber, vitamin A, vitamin C, vitamin D, vitamin E, and calcium.

Among women who reported long-term use of multivitamin supplements containing folic acid, risk of colon cancer was significantly lower than among those who did not use multivitamins. Intake of folate from dietary sources was only slightly inversely related to risk of colon cancer.

Reference: Annals of Internal Medicine, Vol. 129, October 1, 1988.

Calcium Poor Diets Studied: How Low Do They Go?

Adolescent girls with calcium-poor diets, as well as their dairy-loving counterparts, are helping scientists learn more about calcium metabolism in a study called Project: Healthy Bones.

Although bone development has been shown to peak during puberty, dietary surveys suggest that the average 9- to 18-year-old consumes only 700 to 800 milligrams of calcium per day. One in 5 consumes half that much or less.

Calcium recommendations for this age group are 1300 milligrams per day, or the equivalent of just over four cups of milk.

"Little is known regarding the consequences of calcium intakes less than 500 milligrams per day during puberty," said Dr. Steven Abrams, an associate professor of pediatrics at Baylor College of Medicine in Houston. Although Abrams believes that girls' bodies might be able to adapt to lower levels of calcium, the degree of adaptation is unknown. It's also possible that ethnicity influences adaptation. Previous studies have shown that African-American girls absorb calcium more efficiently and form new bone at a faster rate than Caucasian girls.

The study will involve 60 African-American and Caucasian girls between the ages of 9 and 13, half with adequate amounts of calcium in their diets and half with calcium-poor diets. Girls with adequate diets will be put on a low-calcium regime for 20 days. Those with calcium-poor diets will receive initial nutrition counseling and calcium supplements for six months. Abrams points out that reducing the amount of calcium in an adolescent's diet for a short time is quite safe and does not affect overall bone growth.

To measure adaptation, the girls' initial bone density and calcium tracer tests will be compared to those undergone at the end of the study.

Abrams believes that the information gathered might help physicians better assess the risk associated with calcium-poor diets among adolescent girls and customize dietary recommendations for specific populations.

Girls enrolled in the study will receive a Healthy Bones T-shirt and a stipend. For more information, contact Dee Dee Powledge at (713) 798-7085. To learn more about the calcium needs of children, visit the Web site at: http://www.bcm.tmc.edu/cnrc

Source: Nutrition and Your Child, Spring 1999.
Reprinted with permission from the USDA/ARS Children's Nutrition Research Center at Baylor College of Medicine.

Lycopene and Tomatoes

"Lycopene may help reduce the risk of prostate and cervical cancer." At least that's what a full page ad for a popular brand of tomato ketchup claims. And even though most of us don't know it, this ketchup also happens to be "America's favorite source of lycopene." When compared to other tomato products on a per ounce basis, the ketchup has up to 5 times more lycopene than fresh tomatoes, according to the ad.

So does this mean we should all start pouring ketchup on everything? A recent review looked at the intake of tomatoes and blood lycopene level in relation to the risk of various cancers. In all, 72 studies were reviewed and 57 of these found that higher levels of tomato intake or blood lycopene levels was associated with a lower risk of cancer; in 35 studies the association was statistically significant. The strongest association was for a lower risk of cancers of the lung, stomach and prostate gland. In no study was there a statistically significant relationship in the opposite direction. The author points out that because the data are from observational studies, one can't assume a cause and effect relationship.

While lycopene, a type of carotenoid, may account for or contribute to these benefits, a direct benefit has not been proven. It could be that other compounds in tomatoes alone or interacting with lycopene may be important. The author notes that the evidence regarding dietary intake and lycopene blood concentrations reflects consumption of tomatoes and tomato products rather than purified lycopene supplements. Until more is known about any drug-like properties of lycopene, he emphasizes it is premature to recommend use of concentrated lycopene supplements for any health benefit.

While ketchup is a source of lycopene, if you calculate the amount on a per serving, rather than per weight, basis, there are some other sources to consider. A cup of tomato juice has 6 times more lycopene than a tablespoon of ketchup, a medium size tomato can have up to 3 times more, a cup of watermelon has 2 times more and ½ grapefruit has 1½ times more.
Regardless of the source of lycopene, the results do add further support to the recommendations to increase fruit and vegetable consumption, including tomatoes and tomato-based products.

References: Giovannucci, E. Tomatoes, tomato-based products, lycopene, and cancer: Review of epidemiologic literature, Journal of the National Cancer Institute, 9(4): 317-331, February 17, 1999.

Nguyen and S. Schwartz. Lycopene: Chemical and biological properties. Food Technology, 53(2): 38-45, February 1999.

Source: Reprinted from DNS Alert, March/April 1999.

Eating Out and Nutrition

Increasingly, America's family dining table is not at home, but at a fast food outlet or restaurant. In 1970, 26% of the total food dollar was spent away from home; by 1996, that number had risen to 39%. So while we are spending more on eating out, a new report from the USDA says the nutritional content of meals eaten away from home is failing to keep pace with nutritional improvements in home-prepared foods.

Compared with home-prepared foods, food made outside of the home contains more of the nutrients that Americans over-consume, such as fat and saturated fat, and less of those that they under-consume, such as calcium, fiber, and iron.

The report, Away-from-Home Foods Increasingly Important to Quality of American Diets, finds

The frequency of dining out rose by more than two-thirds over the past two decades, from 16% of all meals and snacks in 1977-78 to 27% in 1995.

Fat contributed 31.5% of calories in home foods, but 37.6% in away-from-home foods. While the percentages of calories attributed to fat and saturated fat in both home and away-from-home foods have been falling in recent years, the decline has been sharper among home-prepared foods.

The fiber content of away-from-home foods was 25% less than that of home foods.
Calcium content of home foods was close to the nutritional benchmark, but away-from-home foods were more than 20% below the benchmark.

Low iron intake is common among teenage girls and young women, who face the highest requirements and typically have low food consumption. For this group, food eaten away from home had an iron density of 29% below the nutritional benchmark.
Meals served in school cafeterias tended to be lower in total fat and higher in calcium and dietary fiber than other meals eaten away from home.

This report, published by USDA's Economic Research Service, says nutrition education programs should focus more on helping consumers understand the dietary implications of away-from-home dining, and how to make more healthful food choices when eating out.

The report is available at: http://www.ers.usda.gov/publications/aib749/   or by calling 1-800-999-6778.

Reference: USDA news release, 2/19/99 CNI Nutrition Week, 2/19/99

"Phyt-ing" Cancer

All fruits and vegetables make a contribution to our overall health. But we know that certain types of produce are particularly important in reducing cancer risk.

Cruciferous Vegetables

Cruciferous vegetables contain a substance called sulforaphane and other phytochemicals that appear to reduce cancer risk. These compounds trigger enzymes that may block damage to your cells' DNA by various carcinogens. Cruciferous vegetables include broccoli, cauliflower, kale, Brussels sprouts, cabbage, bok choy, kohlrabi, and collard, mustard and turnip greens.

Garlic and Onions

Sulfur compounds, called allyl sulfides are the active, possibly cancer-risk reducing components in garlic and onions. They trigger enzymes that can help promote the excretion of carcinogens from the body.

Orange and Grapefruit Juice

Oranges, and grapefruits contain vitamin C and flavonoids, which act as antioxidants. Antioxidants help to reduce adverse effects of free radicals. (Free radicals are compounds formed in our bodies during normal metabolism.)

Soy

Soy foods are high in phytochemicals called isoflavones. Isoflavones block activity of hormones, including estrogen, in some cells. Diets high in soy products are associated with lower rates of cancers of hormone related cancers like breast, endometrial and prostate cancer. A variety of soy foods are becoming more popular: soy milk, tofu, tempeh, miso, and some meat-substitute products.

Tomatoes and Tomato Sauce

Tomatoes are high in the phytochemical lycopene, a powerful antioxidant. Lycopene is one of the colorful carotenoids, plant pigments found in a variety of fruits and vegetables. Lycopene may have an even more potent ability to stop cancer cells from proliferating than beta-carotene, another carotenoid and vitamin A precursor. A diet high in tomatoes (especially when cooked) and tomato sauce has been associated with decreased risk of stomach, colon, and prostate cancer.

Source: John Hopkins Inteli Health Web site at: http://www.intelihealth.com 

5 A DAY FOR NUTRA CEUTICALS

Phytochemicals are substances in foods that may not be nutrients, but provide health in a variety of ways. To get a variety of phytochemicals (as well as nutrients and fiber) in your diet, eat foods from the following groups often:

• Garlic, onions, leeks, chives
• Cruciferous vegetables (e.g., broccoli, cabbage, Brussels sprouts)
• Citrus fruits and berries
• Legumes
• Dark green and yellow vegetables

Source: LaChance, P. Florida Dietetic Assn. Annual meeting, July 1999.

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