Most teen pregnancies undernourished
Fewer than one-third of pregnant adolescents met the dietary standards for iron, zinc, magnesium, calcium, and vitamins D and E from food sources, even when they had access to US food programs such as Women, Infants and Children (WIC), in a study of patients from Cincinnati prenatal clinics of a University Hospital. Only 6 percent met the recommended amounts of iron. Yet the 97 pregnant adult women studied had even lower intake of calories and 11 nutrients than did the 59 pregnant teens. About 80 percent reported they took prenatal vitamins. (Giddens JB, Krug SK, Tsang RC, et al. Pregnant adolescent and adult women have similarly low intakes of selected nutrients. J Am Dietetic Assoc 2000;100:1334-1340.)
Benefits of low-fat diet questioned
Older women who eat low-fat, high-carbohydrate diets may have higher risk of ischemic heart disease than those who eat high-fat, low-carbohydrate diets. Ten postmenopausal women ate two diets of equal calories for 3 weeks each. The low-fat diet contained 60 percent of calories in carbohydrate and 25 percent fat. The high-fat diet contained 40 percent carbohydrate and 45 percent fat. Both had 15 percent protein.
For the low-fat diet period, high density lipoprotein cholesterol was significantly lower (the "good" cholesterol), and plasma trigglyceride, very-low-density lipoprotein (VLDL-TG), VLDL-cholesterol, and insulin levels were significantly higher than with the high-fat diet. Because all of these changes would increase risk of ischemic heart disease in post-menopausal women, the researchers say it seems reasonable to question the wisdom of recommending low- fat, high-carbohydrate diets for women after menopause. (Jeppesen J, et al. Effects of low-fat, high-carbohydrate diets on risk factors for ischemic heart disease. Am J Clin Nutr 1997;65:1027- 1033)
Calorie intake same for larger persons
It's finally official: there's little or no correlation between weight and calorie intake. Calorie intake fails to predict weight, and vice versa. Statistics from the Healthy Eating Index show that adults with a body mass index of 20 or less and those with a BMI greater than 30 have similar calorie intakes, as do the two categories between. For instance, for men age 18 to 74, of those who eat less than 60 percent of recommended calories, 3 percent have a BMI of 15- 20, 36 percent a BMI of 20-25, 43 percent a BMI or 25-30, and 17 percent a BMI over 30. Of those who eat 120 percent of recommended calories, the figures are, respectively, 3 percent, 46 percent, 41 percent, and 10 percent. These percentages are about the same as the percent of men in each category, with actually fewer of the heaviest men having a high calorie intake.
Thus, since total calorie intake, Recommended Dietary Allowance of nutrients, and apparently percent fat in the diet, showed almost no relation to BMI, weight factors were omitted from the final statistics provided in the Healthy Eating Index brochure. This index, the nation's "report card" on how Americans are eating is based on national intake data, compiled by the Center for Nutrition Policy and Promotion. (Healthy Eating Index, Table 10. July 19, 1998. Center for Nutrition Policy and Promotion, United States Department of Agriculture; www.usda.gov.fcs.cnpp.htm)
CHO converts to fat within fat tissue
The amount of carbohydrate that converts to fat is still controversial in humans, as is the extent to which this takes place in the liver rather than adipose tissue. Research with five male volunteers at the University of Texas suggests the liver plays a minor role, and instead, that fat tissue is the main site for conversion of excess carbohydrate calories.
Three tracer-infusion studies were performed on each subject during four days of carbohydrate overfeeding through glucose infusion. Indirect calorimetry showed that after only one day the men were accumulating fat. By the fourth day of overfeeding, after the glycogen stores were saturated, it appeared that all the excess glucose converted to fat. (Aarsland A, D Chinkes, R Wolfe. Hepatic and whole-body lipogenesis in humans. Am J Clin Nutr 1997;65:1774-1782)
Over the past three decades, adult Americans have dramatically lowered the percent of fat in the diet from about 45 percent in 1965 to 34 percent in 1995. For women age 19 to 50 this has been a real decrease from about 83 grams per day in 1965, to 73 in 1978, to 62 in 1989, and holding quite steady since then at about 62-65 grams. Men in the same age group decreased fat consumption from 139 grams in 1965, to 113 in 1978, to 96 in 1989, and have increased to about 100-101 grams since then. Thus for men, but not women, the percent of calories from fat continued to decrease even as daily grams of fat intake increased slightly after 1990.
Food intake analysis shows an increase in calories since 1990 is due to increased consumption of grain products, certain soft drinks and alcoholic beverages. Average calorie intake of women is slightly below 1,800 calories, considerably less than the recommended 2,200 calories per day for women in this age group. Average intake for men is about 2,700 calories, also somewhat less than the 2,900 calories recommended. (Is total fat consumption really decreasing? Nutrition Insights 5, USDA Center for Nutrition Policy and Promotion, April 1998)
Meatless diets put athletes at risk
Menstrual abnormalities and the female athlete triad are linked to the meatless diets that are common among female athletes, warns an article in The Physician and Sportsmedicine. One study cited reported menstrual irregularities in 26.5 percent of vegetarian women, compared with 4.9 percent in nonvegetarian women. Another compared 9 regularly menstruating runners with 8 amenorrheic runners and found 44 percent of the menstruating runners ate red meat, while none of the amenorrheic runners did. Still another study showed that, of 13 amenorrheic runners, 12 were vegetarians, and 8 had eating disorders. Only 3 of the 19 menstruating runners were vegetraians, and none had eating disorders.
The review shoed that even though intake of iron and calories was the same, female runners who ate a modified vegetarian diet (less than 100 grams of red meat per week) had significantly lower iron levels than those who regularly ate red meat. One study showed that female runners who did not eat meant, chicken, or fish had protein levels below the recommended minimum for encurance athletes.
Although it is theoretically possible to compete athletically on a meatless diet, the researchers emphasize thtere is risk. They recommend that female athletes who call themselves vegetarians be screened for disordered eating and amenorrhea, and if either is found, for osteoporosis. The American College of Sports Medicine recently published a position statement on the female athlete triad. ( Loosli AR, Ruud JS. Meatless diets in female athletes: A red flag. The Physician and Sportsmedicine. 1998;26:45-48,55)
Milk down, soft drinks up for teens
Soft drink consumption has nearly tripled since 1967, and now comprises more than one-third of all refined sugars in the diet, says a Center for Science in the Public Interest report. Soft drinks now provide the average American with 7 teaspoons of sugar per day. The most avid drinkers are 12- to 29-year-old males. One out of 10 teen males who drink soda pop consumes seven or more cans per day, and one-fourth drink five cans or more. Teen girls are not far behind. Of pop-drinkers, 10 percent of 13- to 18-year-old girls drink five cans or more, and one-fourth drink 3.5 cans. By contrast, 20 years ago, the typical boy or girl consumer of soft drinks (at the 50th percentile) drank only two-thirds of a can per day.
As teens have doubled or tripled their consumption of soft drinks, they have cut their milk intake by nearly half. Both boys and girls now drink twice as much soda pop as milk. Teen boys drink an average of 2 2/3 cups per day and only 1 1/4 cup of milk. Girls average 1 1/2 cup of soft drinks and less than 1 cup of milk. Heavy consumption of soft drinks is associated with low intake of calcium, magnesium, ascorbic acid, riboflavin, and vitamin A and with high intake of calories, fat, and carbohydrate. It is a likely factor in the increase in obesity for both children and adults, says the report. Aggressive marketing by the soft drink industry is seen as a factor. (Center for Science in the Public Interest, October 21, 1998, Website: www.cspinet.org/sodapop/liquid_candy.htm)
Protein triggers thermogenesis
Stimulating or suppressing heat seems to be an important way the body regulates energy balance to keep weight stable. In a review of research on diet-induced thermogenesis (DIT), Michael Stock, a noted British researcher in the field, shows that an unbalanced diet -- particularly one either high or low in protein -- results in high levels of DIT. In overfeeding studies, much of the excess energy is dissipated as heat. Yet there is great individual variation. Stock shows that individual differences in DIT are much more marked when calorically dense high- or low-protein diets are fed, and predicts this could be a sensitive test in determining who may be resistant to obesity and who is susceptible.
He suggests that DIT may have evolved as a mechanism for dealing with nutrient-deficient or unbalanced diets. Thus, it may be a way of enriching nutrient-poor diets (low protein) by disposing of excess energy. The disposal of this excess energy, once fat is restored, helps prevent obesity, which is a hazard to survival in the wild, exposing the individual as more vulnerable. (Stock M. Gluttony and thermogenesis revisted. Int J Obes 1999; 23:1105-1117)
TV ads fail nutrition test
Television today is a major source of nutrition confusion and misinformation. A recent study finds half the nutrition-related information in TV commercials aired in top-rated prime- time network shows and viewed heavily by 2- to 11- year-olds is misleading or inaccurate.During 17.5 of prime-time hours, one-fourth were spent on commercials (4.3 hours).
Of the 700 commercials shown, one-third contained nutrition-related information, an average of 13 commercials every hour, and half of this was questionable. High-sugar foods were presented as being a healthy breakfast choice. A dietary supplement ad implied the product was needed to ensure proper growth and development. Nearly half of medicine commercials included nutrition references, such as that cough drops are superior because they contain honey. Other ads promoted behaviors not recommended by nutrition educators. Eating a whole bag of a snack food was encouraged because it was lowfat. A heartburn drug ad suggested that eating too much or eating high-fat foods is no problem because a pill can prevent heartburn pain.
Most of the health and beauty aids commercials also contained misleading information, such as that shampoos and cosmetics contain vitamins and other nutrients vital to healthy hair and skin. Public service announcements were virtually absent from prime-time TV. While the impact of all this on food intake has not been fully studied, the researchers report that studies do suggest that beer and cigarette advertisements increase the likelihood that youth will drink alcohol or smoke. (Byrd-Bredbenner C, Grasso D. What is television trying to make children swallow? J Nutr Ed 2000;32:187-195)
When foods are restricted, kids want more
Parents who try to control how much and what foods their children eat may find their efforts backfiring. Their children tend to eat more when not hungry, to choose the very foods being restricted, and may feel intense guilt about eating. In a study of 197 girls age 4 to 7 and their parents, Leann Birch, PhD, of Pennsylvania State University, and colleagues continue their research on child feeding practices. After eating a standard lunch, when not hungry, the girls were offered free access to snack foods. Their intake ranged from 0 to 436 calories, and the more restrictive the parents, the more the girls ate and the stronger were their negative feelings.
About half the girls reported negative feelings about eating too much or whether their mother or father would find out. Feelings of eating "too much" were not affected by how much they ate, but rather by whether they felt this food was disallowed. The study measured parental food restrictions, as well as the girls' feelings about eating, hunger, fullness, food preferences. Cited was other research by this group that suggests when children's attention is drawn to a food but their access restricted, they view that food as highly attractive, associate it with parental disapproval, but have less control over their eating of it. In another study they found high parental control of foods is associated with young children's inability to regulate calorie intake, and that this in turn is related to childhood obesity. (Fisher JO, Birch LL. Parents' restrictive feeding practices are associated with young girls' negative self-evaluation of eating. J Am Diet Assoc 2000;100;1341-1346.)