Category: Prior Clinic Blog
STUDY: Workouts alter way lipids circulate through body, study finds
JOURNAL: New England Journal of Medicine
AUTHORS: Dr. William E. Kraus
ABSTRACT: Need another reason to exercise? Scientists have discovered it makes cholesterol less dangerous.
A new study found that even modest exercise changes the size and density of cholesterol-carrying proteins so they do less damage. And the benefits occur even if people’s total amount of cholesterol and their weight stay the same.
COMMENTARY: Staying active has many health benefits, but improving cholesterol is not usually considered one of them. People who exercise often lose weight, and while that can improve their cholesterol levels, exercise by itself was thought to have little or no effect.
Workouts fail to lower LDL, the dangerous form of cholesterol, and only rigorous exercise can nudge up HDL, the good form that protects against heart attacks.
PROTEIN PARTICLES ALTERED
But the study, by Dr. William E. Kraus of Duke University, found a new way that exercise can affect cholesterol — by altering the number and size of the particles that carry cholesterol through the bloodstream.
“People in the exercise field have always wondered why it doesn’t affect total cholesterol and LDL,” Kraus said. “We always knew low levels of exercise are helpful. This helps solve that paradox.”
His work, published in the New England Journal of Medicine, is the latest chapter in an evolving view of cholesterol’s effects. A generation ago, doctors worried only about the total amount of cholesterol. Later, the importance of the main subtypes, especially HDL, became apparent. Now experts are turning their attention to the physical structure of cholesterol in the bloodstream.
Cholesterol is an essential fat, or lipid. It circulates through the body by attaching to protein particles. Cholesterol appears more likely to clog the arteries when it is carried by small, dense protein particles than when it is moved by relatively large, fluffy ones.
The latest study finds that people who exercise develop these bigger particles, even if their total amount of cholesterol stays the same.
“Using this analysis shows clearly that exercise has beneficial effects that are not revealed by standard tests,” said Dr. Ronald M. Krauss of the Lawrence Berkeley National Laboratory, who studies the protein particles.
MODERATE EXERCISE BENEFICIAL
The study, conducted at Duke and East Carolina University, involved 111 sedentary, overweight men and women. They were randomly assigned to three exercise groups: the equivalent of walking 12 miles a week, jogging 12 miles a week or jogging 20 miles a week. All were instructed to eat enough to keep their weight constant.
They found that the cholesterol effects of walking and jogging 12 miles were the same, while jogging 20 miles resulted in more pronounced changes.
Measuring protein particle size is sometimes done in large medical centers, but it is not part of standard physicals. Kraus said he expects the tests, which cost two or three times more than standard cholesterol tests, to become more widely used.
Dr. Joann Manson, head of preventive medicine at Harvard’s Brigham and Women’s Hospital, noted that exercise has already been found to have many other benefits for the heart, including improvements in blood pressure, blood sugar, clotting and inflammation.
Studies show that briskly walking 30 minutes a day can lower the risk of heart disease by 30 percent to 40 percent.
STUDY: Lower cancer risk with dietary antioxidants
JOURNAL: Gastroenterology 2002;123:985-991.
AUTHORS: Dr. Mauro Serafini
ABSTRACT: The total dietary intake of antioxidants is inversely associated with the risk for developing cardia and distal gastric cancer, European researchers report.
COMMENTARY: For the first time this shows that the total antioxidant capacity of the diet is inversely associated with the risk of developing gastric cancer.
In people exposed to abnormal bio-radical loads, such as smokers and Helicobacter pylori-infected individuals, the increased need for antioxidant equivalents seems even more important.
Dr. Serafini and colleagues collected data on 505 patients newly diagnosed with gastric adenocarcinomas and on 1116 controls to assess their dietary habits for the 20 years before the survey. To convert food frequency into antioxidant potential, Dr. Serafini's team used the total radical-trapping antioxidant potential of different plant foods.
"We believe that the total antioxidant capacity concept is a more complete measurement of the counteracting forces in the multi-factorial pathological process towards invasive gastric adenocarcinoma," Dr. Serafini explained. This approach may provide a new tool for investigating the relationship between dietary antioxidants and oxidative stress-induced cancer pathology, he said.
The researchers also accounted for cancer risk from exposure to higher oxidative stress, including smoking and Helicobacter pylori infection, according to their report.
They found that for both cardia and distal cancer the dietary intake of antioxidant equivalents reduced cancer risk (odds ratio 0.65 for the highest quartile of total antioxidant potential).
When Dr. Serafini's team adjusted the data for smoking, they found a more robust dose-response relationship of antioxidant potential to gastric cancer risk. People who never smoked and who had the highest antioxidant intake had the lowest cancer risk.
Among those who had H. pylori infection, the odds ratio for developing gastric cancer varied from 0.66 to 0.56 from the lowest to the highest antioxidant potential.
STUDY: Study shows increased risk of breast cancer
JOURNAL: Annals of Internal Medicine
AUTHORS: Dr. JoAnn Manson
ABSTRACT: Women who drink alcohol and take hormones are at almost double the risk of breast cancer, researchers with a large ongoing study say.
COMMENTARY: Previous studies have shown that women who have more than a drink a day raise their risk of breast cancer, and that hormone replacement therapy also increases the cancer risk.
The Nurses’ Health Study assessed the risk of the two factors combined. Researchers said the good news is that alcohol and estrogen together do not greatly magnify the danger through interaction. Some scientists were concerned that might be the case.
Instead, what they found is that a postmenopausal woman who has a lifetime breast cancer risk of 4 percent could increase the risk to 8 percent if she drinks and takes hormones.
“The public health message is that the two will substantially increase your risk of breast cancer and you might want to be particularly vigilant about having both of these risk factors,” said study co-author Dr. JoAnn Manson of Brigham and Women’s Hospital.
During the study years of 1980-94, 1,722 women developed breast cancer. Women who took hormones for at least five years but drank no alcohol increased their risk of breast cancer by about 30 percent, as did women who did not take hormones but consumed more than one drink a day.
For women who took hormones and drank alcohol, the risk nearly doubled.
For those women who still take hormones, a good compromise would be to consume no more than one drink of red wine a day at the most. That way, women can still get the cardiovascular benefits of moderate alcohol use while eliminating the increased breast-cancer risk.
STUDY: Effect exaggerated in overweight, sedentary women
JOURNAL: Journal of the National Cancer Institute
AUTHORS: Dr. Charles Fuchs
ABSTRACT: A diet high in white bread, white rice and potatoes puts women at much higher risk of pancreatic cancer — especially if they are overweight and do not exercise much.
COMMENTARY: Previously, the only known risk factor for pancreatic cancer, which kills 30,000 people a year in the United States, was smoking.
The take-home message for women who are overweight and sedentary is that a diet high in starchy foods may increase their risk of pancreatic cancer.
Substituting less starchy vegetables such as broccoli for potatoes and rice and snacking on fruit are some simple steps they can take to reduce this potentially serious health risk.
STUDY: Flax good prostate food
JOURNAL: Urology 2002;60:000-000.
AUTHORS: Dr. Wendy Demark-Wahnefried
ABSTRACT: In mice genetically engineered to develop prostate cancer, a diet supplemented with flaxseed, which is rich in omega-3 fatty acids and fiber, inhibits the growth and development of prostatic carcinoma.
COMMENTARY: A team of scientists from Duke University in Durham, North Carolina reports these findings in the November issue of the journal Urology.
The Duke team randomized 135 male 5- to 6-week-old transgenic mice to a normal mouse diet, the control group, or to a mouse diet supplemented with 5% flaxseed, the experimental group. The animals were sacrificed either at 20 or 30 weeks.
Three percent of flaxseed-fed mice did not develop prostate cancer at all. All of the control mice developed the disease.
According to the team, significant between-group differences in tumor growth and development were evident. Tumor weight was 1.9 grams in flaxseed-fed mice compared with 3.6 grams control mice (p = 0.0005). Tumors in flaxseed-fed mice were also "significantly less aggressive" than tumors in control mice (p = 0.01) and had a higher rate of apoptosis (p < 0.0001).]
While not reaching statistical significance, the prevalence of lung and lymph node metastases was lower in flaxseed-fed than control-fed mice.
This study builds on two other studies published recently by the Duke team. In a pilot study reported in July 2001, they found that men with prostate cancer who ate a low-fat diet supplemented with ground flaxseed for 34 days saw a drop in testosterone and a trend toward lower prostate specific antigen (PSA) level. The diet was well tolerated.
In another study, published in November 2001, flaxseed-derived lignans blocked the growth of three distinct human prostate cancer cell lines.
Adding flaxseeds to the diet would be a wise step toward promoting prostate health.