Update From the Medical Journals: April 2010
April 30, 2010
By Mary Pickett, M.D.
What's the latest news in the medical journals this month? Find out what your doctor is reading.
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.
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.
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.