Prions may cause Alzheimer's, says Nobel winner

``In all of these neurodegenerative diseases there are abnormal protein deposits,'' Prusiner pointed out in a plenary address at the annual meeting of the American Neurological Association.

Prions, tiny protein particles, are thought to be infectious agents spread through transplants or, it is speculated, through eating infected meat. They are best known as the cause of bovine spongiform encephalitis, or ``mad cow'' disease.

Prusiner, of the University of California at San Francisco, explained that prion infection causes proteins in the brain to change from a normal spiral conformation to an abnormal conformation called a beta-sheet. He suggested that prion-induced protein changes can be seen in the lesions characteristic of Alzheimer's disease.

``In Alzheimer's, this misfolding of proteins leads to plaques and tangles in the brain,'' Prusiner told meeting attendees. ``These are 'misprocessed' proteins.'' He speculated that prions may also be responsible for changes in other brain disease, for example, in ``Parkinson's disease there are Lewy bodies, while in frontotemporal dementia there are long fibrils of tau.''

Prusiner noted that ``something is pushing this process, although we don't know what it is. It's not a chronic infection like AIDS, and it may be 10 different things.'' The search is on, he said, for drugs that prevent prion-induced abnormal protein folding.

Home cooked meals can carry illness risk

This week at the ADA annual meeting, taking place in Atlanta, food experts released a survey showing that one out of three Americans ``believe it is common to get sick from the way food is handled or prepared at home.''

Each year, 33 million Americans contract a food-borne illness, and about 9,000 die, according to an ADA statement.

To raise consumer awareness about food safety, the ADA has joined with the ConAgra Foundation for a national campaign entitled ``Home Food Safety- It's in Your Hands.'' The campaign supports the goals of the President's Food Safety Initiative by highlighting specific steps that consumers can take to ensure the safety of their food.

Every individual is in control of food safety in their homes. But, ``even though people know what they should do, many times they're not doing it,'' said Edith Hogan, an ADA spokesperson, in a telephone interview with Reuters Health.

According to a survey of 1,000 ``household main meal preparers'' commissioned by ADA and ConAgra, 45% of individuals surveyed were aware of the dangers associated with improper hand washing before handling food, but many do not translate this knowledge into action. For example, the majority of the individuals surveyed gave themselves an ``A'' or ``B'' grade in safe food handling practices. Yet, 10% of those who gave themselves an ``A'' do not wash their hands with soap and water after touching raw meat, food safety experts note.

To ensure food safety, ADA and ConAgra recommend that consumers:

• make sure hands are washed frequently when preparing food.
• keep raw meats separate from cooked foods.
• make sure food is thoroughly cooked.
• refrigerate foods promptly at temperatures of 40F or below.

More information on the ADA is available at their website: http://www.eatright.org.

Vitamin E may reduce lung cancer risk in smokers

However, the researchers say that more study is needed to determine if taking supplements of the vitamin can reduce cancer risk.

``The results of this study showed that serum (blood) levels of vitamin E taken at the beginning of the study was associated with reduced lung cancer.'' lead study author Dr. Karen Woodson told Reuters Health. The research is published in the October 20th edition of the Journal of the National Cancer Institute.

Woodson, of the National Cancer Institute in Bethesda, Maryland, and colleagues there and at the National Public Health Institute in Helsinki, Finland utilized data from a cancer prevention study in Finland to identify vitamin E levels in 1,144 men with lung cancer.

The researchers report that high alpha-tocopherol serum levels at the beginning of the study, high dietary intake of alpha-tocopherol and high dietary intake of vitamin E were associated with a lower lung cancer risk.

The researchers attribute the decrease in cancer to vitamin E's antioxidant properties and anticancer properties.

Woodson and colleagues report that the men most likely to experience a benefit from high serum levels of alpha-tocopherol included those younger than 60, men who had smoked for less than 40 years and men who took vitamin E supplements containing alpha-tocopherol during the study.

The authors add that the findings ``reinforce the importance of adequate vitamin E status to lung cancer risk, particularly among smokers,'' and that ``supplementation may have provided the higher dosages possibly required for inhibition of'' the cell pathways that lead to cancer.

Despite these results, Woodson said in an interview with Reuters Health that ``the National Cancer Institute has never recommended taking supplements.'' She explained that ``other nutrients like you would get in a balanced diet may be likely to be needed as well for a number of reasons. Further, I would like to stress that the men who went on to take supplements didn't seem to have fewer lung cancers so we can't recommend that. We recommend quitting smoking.''

She added that ``we would recommend eating a well-balanced diet in line with the Dietary Guidelines for Americans -- lots of fruits, vegetables, and whole grains, fat in the 30% or less category.''

``While it is tempting, based on the present data, to speculate that the administration of greater quantities of alpha-tocopherol... might have produced a substantial reduction in lung cancer incidence... only future studies... can shed light on this question,'' the team concludes.

The authors also call for further research to see if the same relationship between vitamin E and lung cancer holds for women. Woodson told Reuters Health that she expects to see similar results in women.

``The biology of lung cancer is thought to be essentially the same between men and women; (lung) cancer in both is thought to be due mainly to smoking,'' she commented.

SOURCE: Journal of the National Cancer Institute 1999;91:1738-1743.

Walking cuts diabetes risk

One hour per day of walking, or another form of moderately intense physical activity such as doing housework, can substantially reduce diabetes risk, similar to the reduction in diabetes risk linked to more vigorous exercise, such as running or jogging, report researchers.

Type 2 diabetes, also known as non-insulin dependent diabetes, is strongly associated with obesity. Losing weight is usually the first step in treating the disease.

``Our findings lend additional support to current guidelines from the Centers for Disease Control and Prevention and the National Institutes of Health that recommend that Americans should accumulate at least 30 minutes of moderate-intensity physical activity on most, preferably all, days of the week,'' write the team, led by Dr. Frank B. Hu of the Harvard School of Public Health in Boston, Massachusetts.

In the study, the investigators evaluated responses to questions about the intensity and duration of physical activity provided in 1986 by roughly 70,000 women participating in the Nurses Health Study. The women were free of heart disease, diabetes, and cancer at the time they answered the questions. During 8 years of follow-up, 1,419 women developed diabetes.

After taking into account known risk factors for diabetes, a relationship between physical activity and the risk of type 2 diabetes emerged. ``Increasing physical activity substantially reduced the risk of type 2 diabetes,'' Hu said in a telephone interview with Reuters Health. ``What is particularly interesting,'' he said, ``is that the risk reduction for moderate intensity activity such as walking is the same as that for more vigorous forms of activity such as running or jogging, if the energy expenditure is the same. Total energy expenditure is most important (factor).''

The finding that moderate exercise such as walking reduces the risk of diabetes just as more vigorous exercise does is ''reassuring,'' Hu and colleagues write in the JAMA paper. ''Walking is a physical activity that is highly accessible, readily adopted and rarely associated with physical activity-related injury,'' they note.

Obesity and a sedentary lifestyle are major risk factors for type 2 diabetes, Hu told Reuters Health. Physical activity can reduce the risk of type 2 diabetes through weight reduction and by helping the body use the hormone insulin more efficiently, he said.

It appears from this study, Hu added, that ``it doesn't matter how you (expend energy) as long as you do.''

SOURCE: Journal of the American Medical Association (JAMA) 1999;282:1433-1439.

Diet, exercise and other habits related to risk of colon cancer

To investigate the role that people's habits may play in the disease, Dr. Martha L. Slattery of the University of Utah in Salt Lake City and her colleagues there and elsewhere interviewed 1,993 men and women with colon cancer and 2,410 healthy 'control' subjects in northern California, Utah, and Minnesota. Their results are published in the October 15th issue of the American Journal of Epidemiology.

The interviews assessed study participants' age, sex, education, diet, physical activity, body size, family history of colorectal cancer, cigarette smoking, drinking, coffee consumption, and use of dietary supplements, aspirin, and other anti-inflammatory drugs.

Among both men and women, the investigators found, risk of colon cancer was linked to several lifestyle factors, even when participants' age was taken into account. Study participants who exercised more were less likely to have colon cancer. Diet was also an important risk factor in the study, especially for participants who were younger than 67 years of age. Those who ate a ``Western'' diet -- featuring high-calorie intake, animal proteins, red meats, high-fat dairy products, and sugar -- were at an elevated risk for colon cancer.

In contrast, those whose diet was characterized by low-fat dairy products and calcium were less likely to develop colon cancer.

Slattery and colleagues conclude that ``the importance of developing a lifestyle that incorporates vigorous physical activity appears to be universal to all groups evaluated and may be the most important component of a healthy lifestyle that decreases risk of colon cancer.''

SOURCE: American Journal of Epidemiology 1999;150:869-877.

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