OTHERWISE healthy teenage girls who diet regularly show worrying signs of malnutrition, Sydney researchers have found. The largest study of its kind shows pressure to be thin could be causing teenage girls serious harm, potentially preventing them from developing properly. The study of 480 girls, between 14 and 17, attending school in Sydney’s northern suburbs and on the central coast, found those who dieted often showed subtle but chronic signs of undernourishment compared to those who occasionally, or never, dieted. The girls were deficient in a number of nutrients and biochemicals, including calcium and protein, as well as haemoglobin, which is vital for transporting oxygen in the blood.
The study leader, Dr Ross Grant, said the teenagers were not getting the nutrients they needed to build their bodies. ”When you get through your adolescent years you should be the healthiest you are ever going to be, and these girls are not giving themselves the best chance to be healthy,” he said. Many students in the study were dieting even though, on average, they were not overweight. ”These are pretty much your average girls on the north shore. They are going to school and they are not unwell in any other way,” Dr Grant said. The low levels of calcium were particularly worrying, he said. ”Calcium is used as a signalling molecule for every cell in the body. If you are not getting enough calcium in your diet then your body starts to get it from wherever it can, which is the bones.”
Most researchers believe the amount of calcium consumed in a person’s teenage years sets the basic level available for the rest of their life. Media messages presenting excessively thin women as having an ideal body shape, or public health campaigns making girls overly aware of not consuming too many calories, could be to blame for dieting, said Dr Grant, who is the head of the Australasian Research Institute at the Sydney Adventist Hospital.
Christine Morgan, the chief executive of the Butterfly Foundation, an eating disorders advocacy group, said she was horrified, but not surprised, by the findings. ”Diets, by their very nature, are telling you to disregard your physiological appetite,” she said. ”These homespun diets result in us not putting the nutrients we need into our bodies.” Disordered eating – irregular eating behaviours that do not fall into the category of an eating disorder – had more than doubled in the past 10 years. ”It has become the norm,” Ms Morgan said.
Dr. Gu and her colleagues studied a cohort of 2148 elderly subjects 65 years and older living in New York City. All subjects were healthy and free of dementia at study entry. Their dietary habits were obtained via questionnaire, and they were prospectively evaluated with the same standardized neurologic and neuropsychological measures approximately every 1.5 years for an average of 4 years.
The researchers used reduced rank regression to calculate dietary patterns according to their effect on 7 nutrients previously shown in the literature to be related to Alzheimer's disease: saturated fatty acids, monounsaturated fatty acids, ω-3 polyunsaturated fatty acids, ω-6 polyunsaturated fatty acids, vitamin E, vitamin B12, and folate.
During the follow-up, 253 individuals developed Alzheimer's disease. The study found that one dietary pattern — characterized by higher intakes of salad dressing, nuts, fish, tomatoes, poultry, cruciferous vegetables, fruits, and dark and green leafy vegetables and a lower intake of high-fat dairy products, red meat, organ meat, and butter — was significantly associated with a reduced risk for Alzheimer's disease.
Compared with subjects in the lowest tertile of adherence to this pattern, the Alzheimer's disease hazard ratio (95% confidence interval) for subjects in the highest tertile was 0.62 (0.43 – 0.89) after multivariable adjustment (P for trend = .01).
The study also found that subjects who were older, less educated, and current smokers tended to be less adherent to the protective diet. Hispanic individuals adhered less than white and black individuals (P = .02), and women tended to adhere more than men (P = .05).
“The dietary pattern that was most protective against Alzheimer's reflected a diet rich in ω-3 and ω-6 polyunsaturated fatty acids, vitamin E, and folate but poor in saturated fatty acids and vitamin B12,” commented Dr. Gu. “The combination of nutrients in this dietary pattern reflects multiple pathways in the development of Alzheimer's disease.
“For example, vitamin B12 and folate are homocysteine-related vitamins that may have an impact on the disease through their ability to lower circulating homocysteine levels,” she said. “Vitamin E is a strong antioxidant, and the fatty acids may be linked to dementia and cognitive function through atherosclerosis, thrombosis, or inflammation. Fatty acids may also affect brain development and membrane functioning.”
She added that the study has several limitations. “We used a single measurement of the diet, and this might not have captured the long-term dietary habits of the subjects. We also excluded subjects from the final analysis because they were lost to follow-up, and this might have introduced selection bias. We also can't completely rule out the possibility that the reduced risk associated with this protective diet was due to residual confounding.”
Further studies are planned, Dr. Gu said. “We cannot say based on this study alone that this type of dietary pattern prevents Alzheimer's disease, but many studies have consistently shown that fruits and vegetables and unsaturated fatty acids are associated with a lower risk. We want to repeat these findings in different populations and see if they can be confirmed in other studies.”
Commenting on this study for Medscape Neurology, David Knopman, MD, professor of neurology at the Mayo Clinic and a member of the Mayo Clinic Alzheimer's Disease Research Center in Rochester, Minnesota, said that, despite the study authors' best efforts, it is still not clear whether diet alone makes a difference.
“Dietary habits, which often are lifelong, are certainly part of the array of health behaviors that contribute to better cognitive health in late life. However, diet and other health behaviors are intertwined. Because a healthy diet contributes to better cardiac health, lower weight, lower blood pressure and a lower risk for diabetes, there are many reasons to view the dietary habits described by Dr. Gu and colleagues as beneficial.”
The study was supported by federal National Institute on Aging grants. Dr. Gu and Dr. Knopman have disclosed no relevant financial relationships.
Arch Neurol. Published online April 12, 2010.
Researchers analyzed 84 hours of primetime and 12 hours of Saturday morning broadcast television over a 28-day period in 2004. ABC, CBS, Fox and NBC were sampled on a rotating basis to develop a complete profile of each network. The Saturday-morning cartoon segment (from 8:00 am to 11:00 am) was included to capture food advertisements marketed primarily to children.
All 96 hours of observations were videotaped and reviewed later to identify food advertisements and specific food items being promoted. Only food items that were clearly promoted for sale during an advertisement were recorded. Each food item was then analyzed for nutritional content. Observed portion sizes were converted to the number of servings.
The article indicates that the observed food items fail to comply with Food Guide Pyramid recommendations in every food group except grains. The average observed food item contained excessive servings of sugars, fat, and meat and inadequate servings of dairy, fruit and vegetables. The situation was similar for essential nutrients, with the observed foods oversupplying eight nutrients: protein, selenium, sodium, niacin, total fat, saturated fat, thiamin and cholesterol. These same foods undersupplied 12 nutrients: iron, phosphorus, vitamin A, carbohydrates, calcium, vitamin E, magnesium, copper, potassium, pantothenic acid, fiber, and vitamin D.
The authors advocate nutritional warnings for imbalanced foods similar to those mandated on direct-to-consumer drug advertisements. They recommend investigating health promotion strategies that target consumers, the food industry, public media, and regulation focusing on a three-pronged approach.
“First, the public should be informed about the nature and extent of the bias in televised food advertisements. Educational efforts should identify the specific nutrients that tend to be oversupplied and undersupplied in advertised foods and should specify the single food items that surpass an entire day's worth of sugar and fat servings. Second, educational efforts should also provide consumers with skills for distinguishing balanced food selections from imbalanced food selections. For example, interactive websites could be developed that test a participant's ability to identify imbalanced food selections from a list of options. This type of game-based approach would likely appeal to youth and adults. Third, the public should be directed to established nutritional guidelines and other credible resources for making healthful food choices.”
People with lactose intolerance do not produce enough of the enzyme lactase to break down lactose (the form of sugar naturally found in milk). Instead, when people with lactose intolerance ingest large amounts of dairy products, or foods or medicines containing lactose, lactose stays in the intestinal tract until it reaches the colon where it can cause gas, bloating, stomach cramps or diarrhea.
Last February, the National Institutes of Health (NIH) released a statement on lactose intolerance and health to provide health care providers, patients and the general public with the latest information on the topic.
“What many people fail to understand is that lactose intolerance is not an all-or-nothing situation,” says Susan Nitzke, professor of Nutritional Sciences at the University of Wisconsin-Madison and nutrition specialist with the University of Wisconsin-Extension.
Nitzke points out that many people with lactose intolerance can consume small amounts of lactose–for example, a half cup of milk or yogurt–without experiencing any symptoms. “This is especially true if the milk or other lactose-containing food is consumed with a meal,” she says.
Nitzke urges people to consult their doctor or a dietitian (like Nastaran) before making drastic dietary changes for suspected lactose intolerance. Your doctor may do a blood, breath or stool test to find out if lactose intolerance is the true cause of your digestive problems.
Milk and dairy foods provide many important nutrients. Milk is a well-known source of calcium and vitamin D. “Dairy products are also excellent sources of protein, potassium and many other vitamins and minerals,” says Mallory Koenings, a graduate student in the Department of Nutritional Sciences at UW-Madison.
Because dairy products contain so many important nutrients, even people who are lactose-intolerant are urged to consider alternatives within the milk food group, such as yogurt or lactose-free milk.
Good nutrition is important at every stage of life, from infancy through late adulthood. The basics of a balanced diet remain the same but individual nutritional needs change as you grow older. No matter what your age, it is never too late to start living a healthier life.
Whether you are 50 or 85, active or homebound, your food choices will affect your overall health in the years ahead. The risk for certain diseases associated with aging such as heart disease, osteoporosis and diabetes can be reduced with a lifestyle that includes healthy eating. Good nutrition also helps in the treatment and recovery from illness. While healthy living can't turn back the clock, it can help you feel good longer.
Eating healthfully means consuming a variety of good foods each day. Food provides the energy, protein, vitamins, minerals, fiber and water you need for good health. For one reason or another your body may not be getting the right amounts of these nutrients.
There are several factors that indicate an increased risk for poor nutrition. If you have three or more of the risk factors listed below consult with Nastaran or your doctor:
- ill health
- poor eating habits
- unexpected weight gain or loss
- taking medications
- poor dental health
- economic hardship
- loneliness and lack of social contacts
- the inability to care for yourself