Scientific Update

A Review of Recent Scientific Papers Related to Vegetarianism

By Reed Mangels, PhD, RD, FADA

This issue's Scientific Update will focus on recent studies of changes in the American diet due to factors like fast food consumption and increased snacking.

Americans Eating More Fast Food and Other Meals Prepared Away From Home

What portion of the food dollar is spent on food prepared away from home? a) 20%, b) 33%, c) 47.5%. If you chose 47.5%, you are correct. Nearly half the money we spend on food is spent on food prepared away from home. What effect does this have on the amount and quality of food that Americans eat? Let's look first at where we are eating. The largest portion of calories from foods eaten away from home comes from fast food establishments. Young men aged 18-39 years get 17% of their total calories from fast food; adults in general average 12% of calories from fast food, 10% from restaurants, and 11% from other places, including cafeterias, bars, others' homes, and vending machines. Thus, food prepared away from home represents a major part of many people's diets. This increased use of food prepared away from home has marked effects on nutrition. For example, the fat content of foods eaten at home averages around 32% of total calories; food eaten away from home is higher in fa t–close to 38% of total calories. Foods eaten away from home also contribute more saturated fat and cholesterol, and have slightly more sodium. Home-prepared foods are higher in fiber, calcium, and iron. Our reliance on convenience foods has serious health implications. If you're pressed for time, we hope that you'll consider some of the suggestions for quick and easy vegan meals found in this issue of Vegetarian Journal.

Guthrie JF, Lin B-H, Frazao E. 2002. Role of food prepared away from home in the American diet, 1977-78 versus 1994-96: changes and consequences. J of Nutr Educ and Behav 34:140-150.

Changes in Diets of Adolescents and Young Adults

Two recent studies have focused on the eating habits of American adolescents and young adults. This is partially because of the rapid increase in obesity in these age groups. Young adults especially are establishing dietary patterns, independent of their parents, that may persist for the rest of their adult years. The first study examined young adults' snacking habits. Snacks provide a higher percentage of total calories than they have in the past, partly because the snacks today are higher in calories and partly because snacking is more frequent. Snacks providing the highest percentage of calories include desserts, soft drinks, and beer. The calories coming from high-fat, salty snacks have doubled between 1977-78 and 1994-96.

The second study surveyed where adolescents and young adults get their food and the types of food they commonly eat. For both adolescents and young adults, between 1977-78 and 1994-96 (the most recent years for which data are available), there has been a marked increase in the use of salty snacks, candy, soft drinks, fruit drinks, alcohol, French fries, cheeseburgers, pizza, and Mexican food. Fewer calories come from meals and snacks eaten at home, and more come from meals and snacks eaten at restaurants and fast food places.

The authors of the first study recommend making changes in the types and amounts of foods chosen as snacks by young adults. The authors of the second study recommend improving the quality of food eaten away from home and educating young adults and adolescents about healthful food choices when eating out. Another option seems to be to educate consumers about quick and easy food choices at home that are lower in fat, calories, and sodium and higher in fiber and vitamins and minerals than foods commonly chosen when eating out.

Nielsen SJ, Siega-Riz AM, Popkin BM. 2002. Trends in food location and sources among adolescents and young adults. Prev Med 35:107-113.

Zizza C, Siega-Riz AM, Popkin BM. 2001. Significant increase in young adults' snacking between 1977-2011 and 1994-2011 represents a cause for concern. Prev Med 32:303-310.

You Don't Have to Eat Meat to Build Muscle

Does the source of protein make a difference in older men who are beginning an exercise program? To find out, researchers placed 21 men, around 65 years old, on either a diet containing beef as a key protein source or a lacto-ovo vegetarian diet with soy as the primary source of protein. The men followed their assigned diets for 12 weeks, during which time they participated in a weight-training program. Both groups had relatively high protein intakes of around 0.5 grams of protein per pound of body weight (1.03 to 1.17 g/kg body weight). Both groups showed improved strength and increased muscle size with no difference between the groups. These results suggest that older men can build muscle successfully without eating meat.

Haub MD, Wells AM, Tarnopolsky MA, Campbell WW. 2002. Effect of protein source on resistive-training-induced changes in body composition and muscle size in older men. Amer J of Clin Nutr 76:511-517.

An Apple a Day…

There are many reasons to eat fruits and vegetables. A recent study from Finland suggests that flavonoids, found in fruits and vegetables, can reduce risk of chronic disease. Flavonoids often work as antioxidants and can protect against oxidative damage that may lead to heart disease, cancer, and diabetes. Flavonoid intakes of more than 10,000 people were measured and their rates of various diseases close to 30 years later were assessed. The death rate from heart disease was lower in those with higher flavonoid intakes. Of all the dietary sources of flavonoids, apples appeared to be most associated with reduced risk of death from heart disease. Stroke rates were also lower with higher intakes of flavonoids. Prostate cancer and breast cancer risk appeared to be lower with higher intakes of certain flavonoids. Flavonoids, and their apparent effects on a number of chronic diseases, provide another reason to eat generous amounts of fruits and vegetables.

Knekt P, Kumpulainen J, Jarvinen R, et al. 2002. Flavonoid intake and risk of chronic diseases. Amer J of Clin Nutr 76:560-568.

Poor Bone Health Seen in New Zealand Children with Low Calcium Intakes

A recent study from New Zealand suggests that if children do not get enough calcium, their bones suffer. Researchers studied 50 children, 3-10 years old, who avoided cow's milk for a variety of reasons, including milk intolerance, dislike, and “lifestyle choice.” Few children used calcium supplements or fortified calcium products, like juices or soymilk, so that their total calcium intake was around 400 milligrams per day. This is approximately half the recommended level of calcium for younger children and less than 1/3 of the recommended level of calcium for 9-13 year olds. The children who avoided cow's milk were compared to other children living in the same area and were found to be shorter, have smaller skeletons, and lower bone density. Lower bone density in adulthood increases the risk of osteoporosis. Children with low bone density may be at increased risk of breaking bones. Close to a quarter of the children in this study who avoided cow's milk had a history of bro ken bon es. This seems high, although no comparison was made with the group drinking cow's milk. This study illustrates the importance of adequate calcium intake in childhood. Good sources of calcium for those who avoid dairy products include calcium-fortified soymilk, orange juice, and other juices; calcium-set tofu (tofu prepared with calcium sulfate, which contains more calcium than tofu made with nigari); and dark green vegetables, like kale and turnip greens.

Black RE, Williams SM, Jones IE, Goulding A. 2002. Children who avoid drinking cow milk have low dietary calcium intakes and poor bone health. Amer J of Clin Nutr 76:675-680.