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Newer Knowledge of Dairy Foods
Dairy Products in Human Nutrition
Milk and Other Milk Products Throughout Life
Milk and other dairy foods contribute to recommended nutrient intakes and promote health throughout life, from infancy through older adult years. Dietary nutrient intake recommendations for all age groups are currently being revised. In 1997, the National Academy of Sciences' Food and Nutrition Board of the Institute of Medicine released new dietary recommendations, called Dietary Reference Intakes (DRIs), for five nutrients related to bone health and other body functions: calcium, phosphorus, magnesium, vitamin D, and fluoride. In 1998, DRIs were published for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. For other nutrients, the 1989 Recommended Dietary Allowances (RDAs) remain in effect until updates are released. Refer to the Appendix (Tables 3: PDF 13k , 4: PDF 15k , 5: PDF 7k and 6: PDF 8k ) for current dietary recommendations for nutrients and average energy allowances for gender-age groups.
Infants
- Cow's milk (i.e., whole, 2% reduced fat, 1% lowfat, nonfat or skim, evaporated) is not recommended for infants during the first 12 months of life. Because of its low iron concentration and bioavailability, feeding cow's milk before introducing iron-containing solid foods increases the risk of iron deficiency anemia and possibly intestinal blood loss in infants with milk sensitivity. Human milk contains about the same amount of iron as cow's milk, but the iron in human milk is of higher bioavailability. A comparison of the nutrient content of human and fluid cow's milk is provided in Table 7: (PDF 7k) . In addition, feeding nonfat (skim), 2% reduced fat, and 1% lowfat cow's milk may cause infants to consume excessive amounts of protein due to the increased volume of milk consumed to satisfy caloric needs. Excessive protein intake increases the renal solute load and risk of kidney damage. During the first year of life, human milk or commercially prepared iron-fortified cow's milk-based formulas are recommended to support infants' rapid growth and development.
- Cow's milk allergy develops in less than 3% of infants. However, in most of these infants, the reactivity to cow's milk protein is usually outgrown by their third birthday. For infants with medically confirmed cow's milk sensitivity, a substitute hypoallergenic formula (e.g., protein hydrolysate) is recommended until at least one year of age. Eliminating allergenic foods from the mother's diet during pregnancy is unlikely to prevent food allergies in infants. To help delay or prevent food allergy in infants at high risk of atopic disease as a result of a family history, the American Academy of Pediatrics recommends the following: a) infants be breastfed exclusively for the first 4 to 6 months of age, b) solid foods not be fed until after 4 to 6 months of age, and c) cow's milk not be introduced until 1 year of age. Feeding a partially hydrolyzed whey formula or exclusively breastfeeding decreases risk of food allergy in high-risk infants.
- Cow's milk protein sensitivity has been suspected of contributing to infantile colic. However, scientific evidence fails to support this suggestion.
- Cheese may be introduced at about 4 to 6 months of age when solid foods begin to complement the infant's liquid diet. Cheese cubes/slices and cottage cheese are appropriate foods for self-feeding infants. Yogurt can be introduced to infants at about 8 to 10 months of age.
Children
- Cow's milk may be introduced to children over 1 year of age. However, because of children's need for foods of high nutrient density to support their growth and development, nonfat and lowfat milks or other fat-modified dairy foods are not recommended for children between the ages of 1 and 2. After the age of 2 years, the 1995 Dietary Guidelines recommend that children "gradually adopt a diet that, by about five years of age, contains no more than 30% of calories from fat." The American Heart Association and the American Academy of Pediatrics have issued similar statements. There is growing recognition that children need greater flexibility in their fat intake to meet their energy needs for growth, development, and activity.
- For young children, milk and milk products provide the majority of their calcium intake. Increasing calcium intake benefits bone health and helps to reduce young children's risk of lead toxicity.
- Consuming recommended intakes of calcium-rich milk and other dairy foods (3 to 4 servings/day) during childhood is an important determinant of peak bone mass and future risk of osteoporosis, as well as risk of bone fractures during childhood.
- In addition to calcium, milk and other dairy foods are nutrient-dense foods providing protein, vitamins, and minerals necessary for children's growth and development. According to a recent analysis of dietary sources of nutrients in the diets of U.S. children, milk was the number one source of calcium, magnesium, and protein, and a major source of zinc, vitamin A, and folate. Milk and milk products provided nearly 70% of the calcium in the diets of children ages 6-11. Vitamin D-fortified milk is the primary food source of vitamin D in the U.S. This vitamin plays an important role in calcium absorption and metabolism. Two 8-ounce servings of vitamin D-fortified milk provide the amount of vitamin D currently recommended for children of all ages (200 IU/day).
- Three servings per day of Milk Group foods are recommended for children ages 1 to 3. The portion sizes recommended for young children are smaller than adult servings. For young children 1 to 3 years of age, a serving is about two-thirds of typical serving size, or about 6 ounces of milk or yogurt and about 1 ounce of cheese. As young children grow older during the preschool years, larger servings of Milk Group foods are recommended. Children ages 4 to 8 should consume 3 servings from the Milk Group with a serving consisting of 8 ounces of milk or yogurt and 1.5 to 2 ounces of cheese ( Table 8: PDF 261k ).
- Intake of milk and other Milk Group foods such as cheese may reduce children's risk of tooth decay. Components in cheese or milk such as protein (casein, whey), lipids, calcium, and phosphorus may be responsible for the caries protective effect of dairy foods.
- Unfortunately, many children do not consume the recommended number of servings of milk and other dairy foods.
Adolescence
- Intake of milk and milk products (e.g., cheese, yogurt) during adolescence is important to meet calcium needs for building bone mass and strength. Optimizing the amount of bone deposited during adolescence is considered to be the most effective strategy to reduce the risk of osteoporosis in later years. Increasing calcium intake during the five-year period from age 11 to 16 years coincides with a time when substantial bone accretion occurs.
- In addition to calcium, intake of milk and milk products contributes other nutrients. When the nutrient intakes of adolescent girls (13-18 years) who drank milk were compared to nutrient intakes of girls who did not drink milk, milk-drinkers were found to consume 80% more calcium, 59% more vitamin B12, 56% more riboflavin, 38% more folate, 35% more vitamin A, 24% more of each vitamin B6 and potassium, and 22% more magnesium than did non-milk-drinking teenagers.
- To meet their calcium needs of 1,300 mg/day, 4 servings of Milk Group foods/day are recommended for children and teenagers ages 9-18 ( Table 8: PDF 261k ). Few adolescents consume the recommended number of servings of dairy foods/day. According to a recent USDA survey, only 10% of adolescent girls and 30% of adolescent boys met the recommendations for dairy food intake. Boys ages 12-19 consume an average of about 1.25 servings of milk/day, whereas girls consume only about .75 of a cup, less than one serving.
- Without consuming dairy foods, it is difficult for adolescents to meet recommended intakes of calcium and vitamin D. Moreover, intake of dairy foods improves the nutrient adequacy of the diet without necessarily increasing total calorie or fat intake, body weight, or percent body fat.
- For pregnant adolescents, adequate dairy food intake during pregnancy helps to preserve bone mass and meet nutrient needs. The National Academy of Sciences recommends 1,300 mg calcium/day for both pregnant and lactating adolescents, or the equivalent of 4 servings of milk, yogurt, or cheese.
Adults
- During adulthood, intake of dairy foods such as milk, cheese, and yogurt provides essential nutrients needed for body maintenance and helps to reduce the risk of major chronic diseases.
- Adequate intake of calcium-rich dairy foods helps adults 19-50 years meet their calcium recommendation of 1,000 mg/day, an amount equivalent to about 3 servings of Milk Group foods. Meeting calcium needs throughout the adult years is important to maintaining bone mass between the time peak bone mass is reached (generally by 30 years of age) and menopause in women or about age 50 in men. For older adults over age 50, meeting the calcium recommendation of 1,200 mg/day helps to reduce bone loss and risk of osteoporosis. Unfortunately, calcium intake is low for many older adults, especially females, in large part because of their low intake of dairy foods.
- Meeting calcium needs with vitamin D-fortified milk helps adults, particularly older adults, meet their need for vitamin D. For adults aged 51-70 years, 10 ug (400 IU) per day of vitamin D is recommended. For adults older than 70 years, 15 ug (600 IU) per day of vitamin D is recommended ( Table 3: PDF 13k ). Vitamin D-fortified milk contains 400 IU (10 ug) of vitamin D per quart. Studies indicate that increasing older adults' intake of calcium and vitamin D, which enhances calcium absorption, reduces age-related bone loss and the risk of fractures.
- For older adults, milk and other dairy foods are nutrient-dense foods that supply not only calcium and vitamin D (if fortified), but also other important nutrients such as vitamin B12, riboflavin, and protein. Also, milk and other dairy foods are easy to consume (i.e., do not require much chewing), relatively economical, have a high water content, and require minimal preparation -- all of which are important considerations for older adults.
- Intake of dairy foods improves the nutrient adequacy of adults' diets without necessarily increasing total calorie or fat intake, body weight, or percent body fat.
- A lowfat diet including 3 servings of lowfat dairy foods and 8 to 10 servings of fruits and vegetables per day reduces blood pressure in adults with high normal blood pressure, according to the NHLBI-funded DASH (Dietary Approaches to Stop Hypertension) trial. The National Institutes of Health, in its Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure , recommends the DASH diet as the first line of defense against hypertension.
- Consuming lowfat dairy foods to reach approximately 1,500 mg of calcium per day has been demonstrated to normalize changes in the colon believed to be precancerous in adults at high risk of colon cancer. Several components in dairy foods, including calcium, vitamin D, sphingolipids, conjugated linoleic acid (CLA), butyric acid, protein, and lactic acid bacteria are identified as potential anticarcinogenic agents.
- Intake of dairy foods, because of their calcium content, may help to alleviate symptoms of PMS (premenstrual syndrome) in women, and possibly protect against hearing loss in older adults.
- Adults, like children, are not consuming recommended servings per day of dairy foods. A USDA survey found that Americans are only consuming 1.5 servings (1 serving from milk and .5 serving from cheese) each day from the Milk Group -- an amount slightly more than half of the 2 to 3 servings per day recommended. Only 23% of those surveyed met the recommendations for dairy food intake.
Pregnancy and Lactation
An intake of 3 to 4 servings per day of milk and milk products is important during pregnancy and lactation to meet calcium and other nutrient needs. Meeting calcium recommendations helps to maintain maternal bone density, mineralize infant bone, regulate blood pressure and prevent pre-eclampsia, as well as provide a readily available source of calcium in breast milk during lactation. Dietary calcium recommendations during pregnancy and lactation are the same as for nonpregnant or nonlactating women of the same age.
Therapeutic Diets
Milk and milk products have an important place in many therapeutic diets. Consult the American Dietetic Association and/or dietetic manuals for complete information.
- Sodium-restricted Diets . As mentioned above, intake of a lowfat diet including lowfat dairy foods and rich in fruits and vegetables (i.e., the DASH diet) reduces blood pressure. This diet is likely to be associated with fewer compliance problems than salt-restricted diets which are difficult to follow for many patients. Nutrients in dairy foods such as calcium, potassium, and magnesium have been demonstrated to reduce blood pressure. Increasing calcium intake is effective in offsetting the salt-induced increase in blood pressure in salt-sensitive individuals. Also, intake of calcium-rich foods such as dairy foods is advantageous considering that salt-restricted diets are often limited in other essential nutrients such as calcium, iron, magnesium, and vitamin B6. Most milks provide about 50 to 60 mg sodium/100g. With the exception of dry curd cottage cheese, which has only 13 mg sodium/100 g, other cheeses contain 300 mg (cream cheese) to 1,430 mg (Process American cheese) sodium/100g. For about 15% of the population that is salt-sensitive, a variety of low-sodium cheeses is available. Low-sodium cheeses contain 140 mg sodium per serving ( Table 9: PDF 11k ). To be labeled sodium-free, a food must contain 5 mg or less sodium per serving. Efforts are underway to improve the flavor and other characteristics of sodium-reduced cheeses.
- Lactose Intolerance . For lactose maldigesters, or individuals with low levels of lactase, the enzyme necessary to digest lactose (milk's sugar), milk and other dairy foods need not necessarily be eliminated from the diet. Many individuals with lactose intolerance (i.e., those who develop abdominal symptoms following intake of lactose) can consume 2 cups of milk, one at breakfast and another at dinner, without developing symptoms. In fact, lactose maldigesters can consume a dairy-rich diet providing 1,500 mg calcium (e.g., 2 cups of milk, 1 cup of yogurt, and 2 ounces of cheese). Moreover, consuming lactose-containing foods such as milk may improve tolerance to lactose. Lactose maldigesters can also alter the type of dairy food consumed. Many cheeses (e.g., Cheddar, Swiss, American) contain considerably less lactose than milk ( Table 10: PDF 10k ). Also, many cultured dairy foods, such as yogurt, that contain "live, active" bacteria are generally well tolerated. Tolerance to other cultured dairy foods such as sweet acidophilus milk depends on the strain of bacteria used, among other factors.
- Dairy Food and Drug Interactions . In patients treated with first-generation monoamine oxidase (MAO) inhibitors for medical conditions such as depression or cancer, intake of tyramine-containing foods including some cheeses led in some cases to headaches, nosebleeds, and increased blood pressure. Various amines, such as tyramine, are formed in cheese during ripening. Tyramine is normally degraded during metabolism. However, MAO inhibitors can interfere with or delay the inactivation of tyramine and related amines. As a result, these amines are absorbed and can persist in body fluids for a considerable period of time, leading to the above described adverse symptoms. The tyramine content of cheeses varies widely among different types of cheese and even among the same types. Generally, soft unripened cheeses such as cream and cottage cheese contain negligible, if any, tyramine. However, Cheddar cheese, aged sufficiently to become sharp, has a higher tyramine content. Refer to Table 11 (PDF 7k) for the tyramine content of specific cheeses. Newer MAO inhibitors do not result in adverse reactions with dietary components. Also, some individuals are more susceptible to MAO inhibitor-tyramine interactions than are others. Patients treated with MAO inhibitors should consult their physician and a registered dietitian for advice regarding the kinds and quantities of cheeses that may be included in their diet.
References
Food and Nutrition Board, Institute of Medicine, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride . Washington, D.C.: National Academy Press, 1997.
Food and Nutrition Board, Institute of Medicine, Standing Committee on the Scientific Evaluation of Dietary Reference Intakes. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline . Washington, D.C.: National Academy Press, 1998.
Food and Nutrition Board, Commission on Life Sciences, National Research Council. Recommended Dietary Allowances, 10th Edition . Washington, D.C.: National Academy Press, 1989.
American Academy of Pediatrics, Committee on Nutrition. The use of whole cow's milk in infancy. Pediatrics 89 : 1105, 1992.
American Academy of Pediatrics, Committee on Nutrition. Pediatric Nutrition Handbook , 4th ed. Elk Grove Village, Ill.: American Academy of Pediatrics, 1998.
U.S. Department of Agriculture, Agricultural Research Service. USDA Nutrient Database for Standard Reference. Release 12. Nutrient Data Laboratory, 1998. http://www.ars.usda.gov/main/main.htm
Miller, G.D., J.K. Jarvis, and L.D. McBean. Handbook of Dairy Foods and Nutrition . 2nd ed. Boca Raton, Fla., 1999.
American Academy of Pediatrics, Committee on Nutrition. Hypoallergenic infant formulas. Pediatrics 83 : 1068, 1989. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Nutrition and Your Health: Dietary Guidelines for Americans . 4th edition. Home and Garden Bulletin No. 232. Washington, D.C.: USDA/DHHS, 1995.
American Heart Association, Nutrition Committee. Dietary guidelines for healthy American adults. Circulation 94 : 1795, 1996.
American Academy of Pediatrics, Committee on Nutrition. Cholesterol in childhood. Pediatrics 101 : 141, 1998.
Groziak, S.M., and G.D. Miller. Dietary guidelines for children: where are we heading? J. Nutr. 128 : 1836, 1998.
National Dairy Council. Calcium Counseling Resource . http://www.nationaldairycouncil.org
Subar, A.F., S.M. Krebs-Smith, A. Cook, and L.L. Kahle. Dietary sources of nutrients among U.S. children, 1989-91. Pediatrics 102(4) : 913, 1998.
U.S. Department of Agriculture, Agricultural Research Service. Pyramid Servings Data, Results from USDA's 1994-1996 Continuing Survey of Food Intakes by Individuals . Riverdale, Md.: U.S. Department of Agriculture, February 1999. http://www.ars.usda.gov/main/main.htm
Fleming, K.H., and J.T. Heimbach. Consumption of calcium in the U.S.: food sources and intake levels. J. Nutr. 124 : 1426s, 1994.
U.S. Department of Agriculture, Agricultural Research Service. Data tables: Results from USDA's 1994-96 Continuing Survey of Food Intakes by Individuals and 1994-96 Diet and Health Knowledge Survey, 1997 . http://www.barc.usda.gov/bhnrc/foodsurvey/home.htm (February 1999)
Appel, L.J., T.J. Moore, E. Obarzanek, W.M. Vollmer, L.P. Svetkey, F.M. Sacks, G.A. Bray, T.M. Vogt, J.A. Cutler, M.M. Windauser, P-H Lin, and N. Karanja. A clinical trial of the effects of dietary patterns on blood pressure. N. Engl. J. Med. 336 : 1117, 1997.
Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. The Sixth Report of the Joint National Committee on Prevention, Detection, and Treatment of High Blood Pressure. Arch. Intern. Med. 157 : 2413, 1997.
Holt, P.R., E.O. Atillasoy, J. Gilman, J. Guss, S.F. Moss, H. Newmark, K. Fan, Y. Yang, and M. Lipkin. Modulation of abnormal colonic epithelial cell proliferation and differentiation by low-fat dairy foods. JAMA 280 : 1074, 1998.
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Thys-Jacobs, S., P. Starkey, D. Bernstein, J. Tian, and the Premenstrual Syndrome Study Group. Calcium carbonate and the premenstrual syndrome: effects on premenstrual and menstrual symptoms. Am. J. Obstet. Gynecol. 179 : 444, 1998.
Johnson, M.A., D.K. Houston, J. Edmonds, R.J. Nozza, K. Shea, M. Cutler, R.D. Lewis, C. Modlesky, and E.W. Gunter. Age-related hearing loss is associated with poor bone health and low calcium intake in women. FASEB J. 12(5) : A 878, 1998.
ASPEN Reference Group. Dietitian's Patient Education Manual. Volumes 1 & 2. Gaithersburg, Md.: Aspen Publ., Inc., 1997.
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U.S. Department of Health and Human Services, Food and Drug Administration. Code of Federal Regulations, Title 21, Part 133, Cheeses and Related Cheese Products. Washington, D.C.: U.S. Government Printing Office. April 1998, pp. 294-346.
McBean, L.D., and G.D. Miller. Allaying fears and fallacies about lactose intolerance. J. Am. Diet. Assoc. 98 : 671, 1998.
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Suarez, F.L., J. Adshead, J.K. Furne, and M.D. Levitt. Lactose maldigestion is not an impediment to the intake of 1500 mg calcium daily as dairy products. Am. J. Clin. Nutr. 68 : 1118, 1998.
McCabe, B.J. Dietary tyramine and other pressor amines in MAOI regimens: A review. J. Am. Diet. Assoc. 86 : 1059, 1986.
Walker, S.E., K.I. Shulman, S.A.N. Tailor, and D. Gardner. Tyramine content of previously restricted foods in monoamine oxidase inhibitor diets. J. Clin. Psychopharmacol. 16: 383, 1996.
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