I EXPERIMENTAL NUTRITION THE VALIDITY OF 24-HOUR DIETARY RECALLS The 24-hour dietary recall is a frequently used tool for assessing nutrient intake. A study in the elderly suggests that both over and under reporting of foods consumed limits the sensitivity of this tool for detecting changes in intake. Key Words: dietary recall, nutrient intake, elderly, nutrition survey methodology
The methodology used in diet surveys has increasingly come under scrutiny as to its reliability and validity. When food and nutritive intake derived from diet surveys is used to generate policy decisions and statements about nutritional status of groups it is important that the sampling techniques used have a reasonable degree of accuracy and precision if erroneous conclusions are not to be drawn and perpetuated. Young, in a frequently cited study,’ compared 24-hour dietary recalls with a seven day record and diet history to assess the amount of variation in nutrient intake between these three dietary sampling techniques. The results indicated that none of the three gave similar values for individual intake, but that 24-hour recall would yield approximately the same values as the seven day record when used with groups of 50 persons or more and when a 10 percent error factor could be tolerated. The shorter, more economical 24-hour method has become the most frequently used diet survey technique. Young did not study the validity of the three methods, only whether these methods gave similar values and not if the values themselves were accurate. A technique may be precise or replicatable and yet not accurate. Few studies have been done to assess whether 24-hour recall is accurate in measuring actual food intake. Madden2in a 1976 study attempted to measure the internal validity of the 24-hour recall method by comparing, for the same meal, nutrient values derived from weighed dietary intake to nutrient values derived from 24-hour 310 NUTRITION REVIEWS / VOL. 34, NO. 10 /OCTOBER 1976
recall. The study used the lunch meal served to 76 elderly subjects at a congregate meal site. The subjects were unaware they were being observed and studied for memory recall. Actual intakes for energy and seven nutrients (protein, calcium, iron, vitamin A, thiamine, riboflavin and ascorbic acid) were computed, using Agricultural Handbook 8 , from a duplicate sample of the lunch meal with observed plate wastes subtracted. The subjects were interviewed within 24 hours after their intake was observed. Health and disability questions were asked along with a 24-hour diet recall in order to obscure the fact that the real purpose of the interview was to evaluate diet recall memory. Only the lunch portion of the 24-hour recall was used to calculate recall intake. The data showed a significant difference by a paired T test only for calories, in which recall intake underestimated actual intake. Regression analysis showed, however, a significant difference between actual and recalled intake for three nutrients: protein, calories and vitamin A, for which small intakes tended to be overreported and large intakes under-reported. Madden states that this corroborates similar results found by Linusson et al. where the group mean from recall underestimated actual intake. Madden makes the observation that this would seldom result in a difference being reported where none existed but it could result in a false negative. The importance of this observation lies in the use of diet survey data to evaluate the diet impact of a nutritional supplementation program. If Madden’s data are correct then this sampling technique may not be sufficiently sensitive and may fail to discern a difference where a difference actually exists. Since Madden’s population group was comprised entirely of the
elderly, the question may be raised that the under-reporting was due in large part to memory fraility in the aged. Campbell’s study3 on the effect of memory on 24-hour recall data between institutionalized older and younger people demonstrated that the older group did recall significantly less calories than did the younger population group. Memory per se, however, cannot explain the simultaneous over-reporting of small amounts and underreporting of large amounts, a phenomenon Madden characterizes as “Talking a good diet.” F i d a n ~ ain , ~a review of sources of error in diet surveys, comments on the similar problem of suppression or distortion of memory in regard to that which is not socially acceptable. It would be of value to see additional validity studies done on a young population group where memory is not such an important variable. These studies attempting to assess the extent and magnitude of sampling errors are im-
portant in that generalized statements about the nutritional status of groups can only be as precise as the least exacting measurement method. Clearly, methodological research is needed in order to develop more exacting techniques. 0
1. C.M. Young, G.C. Hagan, R.E. Tucker and W.D. Foster: A Comparison of Dietary Study Methods. II. Dietary History vs. Seven-Day Record vs. 24-Hour Recall. J. Am. Dietet. Assn. 28: 218221, 1952 2. J.P. Madden, S.J. Goodman and H.A. Guthrie: Validity of the 24-Hour Recall. J . Am. Dietet. Assn. 68: 143-147, 1976 3. V.A. Campbell and M.I. Dodds: Collecting Dietary Informationfrom Groups of Older People. J. Am. Dietet. Assn. 51: 29-33, 1967 4. F. Fidanza: Sources of Error in Dietary Surveys. Bibl. Nutrition Diet. 20: 105-113, 1974
TOXIC EFFECTS OF FLUORIDE IN ENAMEL FORMATION Excessive levels of fluoride ingestion during development of the rat incisor led to a reduced rate of enamel formation, as evaluated by the amount of protein in the matrix formed in the ten day experimental period. In addition, the distribution of amino acids in the organic matrix formed during fluoride administration changed with a significant increase in amino acids with charged polar R groups and a significant decrease in hydrophobic amino acids. Key Words: fluoride, enamel, protein, matrix, amino acids, mineralization
The ingestion of excessive amounts of fluoride during tooth development has been known to cause abnormalities in the enamel which is being formed during that period. Indeed, the ameloblast, the cell which forms enamel, is believed to be the most sensitive cell in the body to excessive fluoride. In man, excessive fluoride beyond the amount needed for optimal reductions in dental caries incidence leads to the formation of mottled enamel, chronic endemic dental fluorosis, for which various levels of severity were described by Dean.’ In the rat, excessive fluoride leads to abnormalities in enamel formation, including the lack of pro-
duction of the orange iron-containing pigment in the enamel of the incisor which is so characteristic of the incisor teeth of all rodents, and also a hypomineralized zone at the time of fluoride administration.2 While the gross pathology of mottled enamel has been known for 70 years, and the recognition that excessive fluoride was the causative agent came over 40 years ago, no satisfactory explanation of the mechanism is yet available. Indeed, relatively little attention has been given to determining the mechanism. Kruger and co-workers in Australia have had special interest in this subject. Three intraperitoneal injections of fluoride at approximately 7 mg fluoride per kilogram of body weight on the fourth or fifth postnatal day in rats caused large conNUTRITION REVIEWS I ’OL.34, NO. 10 I OCTOBER 1976 311
The methodology used in diet surveys has increasingly come under scrutiny as to its reliability and validity. When food and nutritive intake derived from diet surveys is used to generate policy decisions and statements about nutritional status of groups it is important that the sampling techniques used have a reasonable degree of accuracy and precision if erroneous conclusions are not to be drawn and perpetuated. Young, in a frequently cited study,’ compared 24-hour dietary recalls with a seven day record and diet history to assess the amount of variation in nutrient intake between these three dietary sampling techniques. The results indicated that none of the three gave similar values for individual intake, but that 24-hour recall would yield approximately the same values as the seven day record when used with groups of 50 persons or more and when a 10 percent error factor could be tolerated. The shorter, more economical 24-hour method has become the most frequently used diet survey technique. Young did not study the validity of the three methods, only whether these methods gave similar values and not if the values themselves were accurate. A technique may be precise or replicatable and yet not accurate. Few studies have been done to assess whether 24-hour recall is accurate in measuring actual food intake. Madden2in a 1976 study attempted to measure the internal validity of the 24-hour recall method by comparing, for the same meal, nutrient values derived from weighed dietary intake to nutrient values derived from 24-hour 310 NUTRITION REVIEWS / VOL. 34, NO. 10 /OCTOBER 1976
recall. The study used the lunch meal served to 76 elderly subjects at a congregate meal site. The subjects were unaware they were being observed and studied for memory recall. Actual intakes for energy and seven nutrients (protein, calcium, iron, vitamin A, thiamine, riboflavin and ascorbic acid) were computed, using Agricultural Handbook 8 , from a duplicate sample of the lunch meal with observed plate wastes subtracted. The subjects were interviewed within 24 hours after their intake was observed. Health and disability questions were asked along with a 24-hour diet recall in order to obscure the fact that the real purpose of the interview was to evaluate diet recall memory. Only the lunch portion of the 24-hour recall was used to calculate recall intake. The data showed a significant difference by a paired T test only for calories, in which recall intake underestimated actual intake. Regression analysis showed, however, a significant difference between actual and recalled intake for three nutrients: protein, calories and vitamin A, for which small intakes tended to be overreported and large intakes under-reported. Madden states that this corroborates similar results found by Linusson et al. where the group mean from recall underestimated actual intake. Madden makes the observation that this would seldom result in a difference being reported where none existed but it could result in a false negative. The importance of this observation lies in the use of diet survey data to evaluate the diet impact of a nutritional supplementation program. If Madden’s data are correct then this sampling technique may not be sufficiently sensitive and may fail to discern a difference where a difference actually exists. Since Madden’s population group was comprised entirely of the
elderly, the question may be raised that the under-reporting was due in large part to memory fraility in the aged. Campbell’s study3 on the effect of memory on 24-hour recall data between institutionalized older and younger people demonstrated that the older group did recall significantly less calories than did the younger population group. Memory per se, however, cannot explain the simultaneous over-reporting of small amounts and underreporting of large amounts, a phenomenon Madden characterizes as “Talking a good diet.” F i d a n ~ ain , ~a review of sources of error in diet surveys, comments on the similar problem of suppression or distortion of memory in regard to that which is not socially acceptable. It would be of value to see additional validity studies done on a young population group where memory is not such an important variable. These studies attempting to assess the extent and magnitude of sampling errors are im-
portant in that generalized statements about the nutritional status of groups can only be as precise as the least exacting measurement method. Clearly, methodological research is needed in order to develop more exacting techniques. 0
1. C.M. Young, G.C. Hagan, R.E. Tucker and W.D. Foster: A Comparison of Dietary Study Methods. II. Dietary History vs. Seven-Day Record vs. 24-Hour Recall. J. Am. Dietet. Assn. 28: 218221, 1952 2. J.P. Madden, S.J. Goodman and H.A. Guthrie: Validity of the 24-Hour Recall. J . Am. Dietet. Assn. 68: 143-147, 1976 3. V.A. Campbell and M.I. Dodds: Collecting Dietary Informationfrom Groups of Older People. J. Am. Dietet. Assn. 51: 29-33, 1967 4. F. Fidanza: Sources of Error in Dietary Surveys. Bibl. Nutrition Diet. 20: 105-113, 1974
TOXIC EFFECTS OF FLUORIDE IN ENAMEL FORMATION Excessive levels of fluoride ingestion during development of the rat incisor led to a reduced rate of enamel formation, as evaluated by the amount of protein in the matrix formed in the ten day experimental period. In addition, the distribution of amino acids in the organic matrix formed during fluoride administration changed with a significant increase in amino acids with charged polar R groups and a significant decrease in hydrophobic amino acids. Key Words: fluoride, enamel, protein, matrix, amino acids, mineralization
The ingestion of excessive amounts of fluoride during tooth development has been known to cause abnormalities in the enamel which is being formed during that period. Indeed, the ameloblast, the cell which forms enamel, is believed to be the most sensitive cell in the body to excessive fluoride. In man, excessive fluoride beyond the amount needed for optimal reductions in dental caries incidence leads to the formation of mottled enamel, chronic endemic dental fluorosis, for which various levels of severity were described by Dean.’ In the rat, excessive fluoride leads to abnormalities in enamel formation, including the lack of pro-
duction of the orange iron-containing pigment in the enamel of the incisor which is so characteristic of the incisor teeth of all rodents, and also a hypomineralized zone at the time of fluoride administration.2 While the gross pathology of mottled enamel has been known for 70 years, and the recognition that excessive fluoride was the causative agent came over 40 years ago, no satisfactory explanation of the mechanism is yet available. Indeed, relatively little attention has been given to determining the mechanism. Kruger and co-workers in Australia have had special interest in this subject. Three intraperitoneal injections of fluoride at approximately 7 mg fluoride per kilogram of body weight on the fourth or fifth postnatal day in rats caused large conNUTRITION REVIEWS I ’OL.34, NO. 10 I OCTOBER 1976 311
