| ||What Your Doctor Is Reading || |
Update From the Medical Journals: April 2010
April 30, 2010
By Mary Pickett, M.D.
Harvard Medical School
What's the latest news in the medical journals this month? Find out what your doctor is reading.
For Better Cholesterol, Eat Less Sugar
Those spoonfuls of sugar in our daily diet are not only contributing to obesity and our risk for diabetes, they are bad for our cholesterol, says a study published in the April 21 issue of the Journal of the American Medical Association. Added sugars in our diet lower HDL (the "good" cholesterol), raise triglycerides and (at least for women) increase LDL (the "bad cholesterol").
The findings are based on diet information collected as part of the National Health and Nutrition Examination Survey (NHANES) 1999-2006. The survey included 6,113 adults who answered questions about added sugars in their diets. Added sugars include corn syrup, cane sugar, brown sugar and honey. They are found in processed foods and beverages, or added to foods at home. Added sugars do not include whole fruit and fruit juice.
The people in this study were divided into five groups from "low" to "high" based on how much sugar they ate. The "lowest" group got less than 5% of their calories from added sugar. The "highest" group ate an amount of added sugar that equaled 25% or more of their total calories. The higher the intake of added sugar for a group, the lower the group's average HDL cholesterol. A person who got at least 10% of total calories from added sugar was up to three times more likely to have low HDL as someone who took in half that much sugar. In the highest sugar group, the HDL was about 11 points lower on average.
It was shocking to find that on average, these adults ate 22 teaspoons of added sugar, which was 15.8% of their total daily calories. Other studies show similar rates of sugar consumption in recent years. Between 1970 and 2005, Americans increased their daily average intake of added sweeteners by 19%. Half of the recent increase in dietary sugar came from sweetened beverages, including sodas.
Most of the added sugar that we get in our diet is hidden in the form of sweetened drinks or processed or baked foods. A report published by the American Heart Association (AHA) in September 2009 said that soft drinks account for 33% of added sugar intake for Americans. Table sugars, candy, cakes, cookies, pies and fruit drinks together contribute 40%. The AHA estimates that a single 12-ounce soda has about 8 teaspoons of sugar.
This study adds to the evidence that dietary sugar can be harmful to our metabolism. Our metabolism is the rate at which our bodies expend energy or burn calories. In addition to cholesterol changes, sugar intake has been linked to high blood pressure, insulin resistance (the cause of type 2 diabetes), fatty liver and abdominal obesity. This collection of conditions is called the metabolic syndrome and has been linked with heart disease. Now it is time for us to cut down. A good place to start is to eliminate sweetened drinks.
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Drugs Lower Breast Cancer Risk, But Come With Side Effects
New information from an important study on breast cancer prevention suggests that two hormone medications may prevent breast cancer in high-risk women. The study was published in the journal Cancer Prevention Research online on April 19.
Women with a particularly strong family history of breast cancer have a 50% chance of developing breast cancer in their lifetimes. This severe risk can come from a family history of two close relatives (close relatives include a mother, sister, daughter, grandmother or aunt) who each had breast cancer before age 50. Women who carry the BRCA1 or BRCA2 gene have a 65% to 85% lifetime risk of developing breast cancer. In other words, a woman who has one of these genes is more likely to get cancer in her life than she is to avoid it.
The drugs used in the study were tamoxifen (Nolvadex or Tamone), which blocks the effect of estrogen, and raloxifene (Evista), which blocks some functions but imitates other functions of estrogen. The study included nearly 20,000 women. All of them had an above-average risk of breast cancer. More than 3 out of every 200 could expect to get breast cancer during the next 5 years.
They were randomly assigned to take either tamoxifen or raloxifene for five years. Doctors kept track of the women for seven years. The study found that tamoxifen reduced breast cancer risk about 50% during the time women were taking it. It probably has some benefit beyond that. Raloxifene, however, wasn't as effective as tamoxifen. For every four breast cancers that tamoxifen prevented, raloxifene prevented only three.
But raloxifene caused fewer serious side effects. During treatment tamoxifen tripled the risk of blood clots while raloxifene doubled the risk. Tamoxifen more than doubles the risk for uterine cancer. Raloxifene raises the risk, but by less. Both medicines increase stroke risk by about 50%.
Both drugs cause hot flashes, night sweats and vaginal discharge. Some women have other symptoms. About one out of four women dropped out of this major study because of side effects.
Women who know their breast cancer risk is very high might consider this aggressive preventive strategy. Some might consider surgery to remove both breasts. A 2009 study from the United Kingdom suggested that about 40% of women with a BRCA gene choose to have both breasts surgically removed to prevent cancer.
Deciding which, if any, preventive strategy is right for you is quite personal,difficult and requires courage. The side effects from tamoxifen and raloxifene are worrisome and bothersome. This makes it challenging to decide whether to use medicine for prevention, even for women at high risk.
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More News in Brief
- Sleep Apnea Increases Risk for Stroke. According to a new study, strokes are more common among people who have interruptions in their breathing at night. This problem is called obstructive sleep apnea. The study was published online March 25 in the American Journal of Respiratory and Critical Care Medicine. People with obstructive sleep apnea briefly stop breathing when they sleep. The tongue and throat muscles become too relaxed during sleep. They collapse together and obstruct the airway. This causes a surge of adrenaline that raises blood pressure. Oxygen drops to low levels during these episodes, which usually occur many times each night during deeper sleep. Researchers enrolled 5,422 adults in the study who had no history of stroke. They were 40 years and older. A sleep test determined whether they had sleep apnea. During nine years of observation, 193 people had a stroke. Men with moderate to severe sleep apnea were three times as likely to have a stroke as those with mild or no sleep apnea. Only women with severe sleep apnea were at higher risk for stroke. Researchers are guessing that the sex difference may be because men often begin having sleep apnea at a younger age. It's estimated that 12 to 18 million Americans have sleep apnea. Many people are unaware they have the condition. The most common way to treat sleep apnea is with a "CPAP" (continuous positive airway pressure) mask and machine. It is worn at night to help keep the air passages open by blowing light air pressure.
- Body-Building Steroids Weaken the Heart Muscle. Anabolic steroids, also known as "body-building steroids," damage the heart, according to a new, very small study. This side effect was not widely known before. The study appeared in the April 27 issue of Circulation: Heart Failure. Researchers looked at the pumping action of the heart in 19 male weight lifters using echocardiograms. Their average age was 40. They had similar exercise habits, heart attack risk factors, and had been weight lifting for similar amounts of time. Twelve men in the study had taken body-building steroids on a weekly basis for about nine years. All of the men had roughly equal body mass index scores (calculated from weight and height). But the steroid users had more muscle mass on average. Ten out of 12 men who were long-term steroid users had weak systolic (squeezing) function of the heart. With each squeeze, there was less blood leaving the left ventricle. Only one of the seven non-steroid users had reduced systolic heart function. If these findings are confirmed with a larger study, 83% of long-term steroid users could have damaged heart function. Steroid users also had abnormal diastolic (refilling) heart function. This is a sign that the heart muscle is becoming stiff; this prevents a normal amount of blood to fill the ventricles between beats. More research is needed to confirm the findings of this small study. But it is a warning to athletes that if they use steroids to build muscle, they are risking serious long-term side effects.
- Institute of Medicine Recommends Aggressive Steps to Control Salt in the American Diet. The Institute of Medicine (IOM) is a branch of the National Academy of Sciences and a non-profit advisory group to the government. It has focused its research on the connection between salt and health. Salt increases the risk for high blood pressure, heart disease, stroke and death. In 2008, the U.S. Congress asked the IOM to recommend strategies for reducing sodium intake among Americans to levels recommended in the Dietary Guidelines for Americans. On April 20, the IOM issued a 480-page report called Strategies to Reduce Sodium Intake in the United States. The report recommends that our government act quickly to take aggressive steps to get Americans to eat less salt. One strategy includes new regulations that would require food processors, packagers and restaurants to lower the salt in their food. The IOM's plan would lower the "allowed" quantity of salt for processed foods in several stages, so Americans can more easily adjust to a less salty taste. Some of the strategies recommended by the IOM are creative and some might say extraordinary. One example is to reclassify salt's status the U.S. Food and Drug Administration so that it stays on the U.S. Food and Drug Administration's "generally recognized as safe" list only if it is within specified low levels. The IOM also recommends that 24-hour urine collections be taken when the government conducts the next National Health and Nutrition Examination Survey (NHANES). The urine would give an exact measure of the daily salt intake for a sample of Americans.
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Mary Pickett, M.D. is an Associate professor at Oregon Health & Science University where she is a primary care doctor for adults. She supervises and educates residents in the field of Internal Medicine, for outpatient and hospital care. She is a Lecturer for Harvard Medical School and a Senior Medical Editor for Harvard Health Publications.