International journal of Sport Nutrition, 1992, 2, 351-365
Dietary Intake and Thiamin, Iron, and Zinc Status in Elite Nordic Skiers During Different Training Periods Mikael Fogelholm, Seppo Rehunen, Carl-Gustav Gref, Juha T. Laakso, Jari Lehto, lnkeri Ruokonen, and Jaakko-Juhani Himberg This study evaluated how different training periods affect dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. Subjects.were 17 skiers and 39 controls, ages 18-38 yrs. Dietary data were collected by 7-day food records at 3-month intervals. Coefficient of variation (CV) was used to indicate magnitude of seasonal changes. Energy intake for the year (28 food record days) was 3,802 kcallday (CV 19.1%) in male skiers, 2,754 kcallday (CV 3.7%) in male controls, 2,812 kcallday (CV 9.1%) in female skiers, and 2,013 kcallday (CV 5.9%) in female controls. CVs for thiamin, riboflavin, vitamin C, calcium, magnesium, iron, and zinc intake were 14.1-23.9% (male skiers), 2.9-15.0% (male controls), 4.8-24.5% (female skiers), and 4.3-1 1.5% (female controls). Seasonal changes in energy, carbohydrate, and micronutrient intakes reflected energy expenditure in male endurance athletes particularly. Erythrocyte transketolase activation coefficients and serum ferritin and zinc concentrations did not differ between skiers and controls. Seasonal variations in these biochemical indices of nutritional status were of the same magnitude in skiers and controls, despite large changes in skiers' physical activity. Daily, weekly, or seasonal variations in dietary intakes o r biochemical indices decrease the validity of an individual's nutritional status assessment (19, 23,43). On a group level, intraindividual day-to-day variations usually cancel out and a reasonably valid estimate of nutritional status is obtained (43). In contrast, seasonal or other long-term variations may cause systematic bias in cross-sectional nutritional assessment of a group (23, 38). Considerable seasonal variations in energy and nutrient intakes are likely
Fogelholm, Rehunen, Lehto, and Himberg are with the University of Helsinki, Depts. of Nutrition, Clinical Chemistry, Public Health, and Clinical Pharmacology, respectively. Gref is with the National Public Health Institute in Helsinki. Laakso and Ruokonen are with the MILA Laboratory in Helsinki. Request reprints from Mikael Fogelholm, Univ. of Helsinki, Dept. of Nutrition, SF-00710 Helsinki, Finland.
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in endurance athletes particularly, because the amount of their weekly physical activity depends on the training period (2). This might help explain the wide range in reported energy intake of male (2,47043,270 kcallday) and female (1,870-3,990 kcallday) endurance athletes (5, 7, 15, 16, 20, 27, 41,42, 45). Biochemical indices of nutritional status also may be affected by the amount of training or dietary intake, or both. Long-term variation in indicators of iron (2, 18, 24, 30, 32) and zinc status (8) has been found in endurance athletes. To our knowledge, seasonal variation in vitamin status has not been studied in an athletic population, even though suboptimal vitamin B status in athletes compared with sedentary controls has been reported (21). The purpose of this study was to evaluate how different training periods affected dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. From a methodological point of view, we studied whether 7-day food records and single blood samples were representative in describing the nutritional status of endurance athletes.
Methods This study was carried out between August 1989 and May 1990. Seasonal data comprising physical activity questionnaire, food records, and blood samples were collected in August (basic conditioning period for skiers), November (precompetition period), February (competition period) and May (off-period). This study was approved by the Ethical Committee of the Faculty of Agriculture and Forestry, University of Helsinki, Finland. Subjects
An informed consent was obtained from 12 male and 10 female Nordic skiers and from 21 male and 22 female controls, ages 18-38 years. Of the 65 subjects, 3 male and 2 female skiers and 2 male and 2 female controls withdrew from the study for personal reasons (n=9). Thus, 9 male and 8 female skiers and 19 male and 20 female controls completed this study. The participants' age, height, and weight ranges are presented in Table 1. Skiers, including five medalists from the Table 1 Characteristics of Subjects: Mean and Range of Individual Results Females
Males Skiers (9) M Range
Age, yrs Height,cm Weight,kg
27 180 73
24-33 175188 6&76
Controls (19) M Range
27 181 78
21-38 169-187 59-99
Skiers (8) M Range
25 165 58
1&30 159-172 53-63
Controls (20) M Range
24 164 58
18-32 150-175 49-67
Note. Height and weight as reported by subjects; seasonal variation in weight was not significant, P > 0.05.
Dietary Intake in Nordic Skiers
/
353
1989 World Championships in Lahti, Finland, were international class elite athletes who had trained regularly for at least 5 years. Controls were healthy young adults, mostly university students, who were not involved in competitive sports. Five skiers (71%) and 10 controls (50%) were taking oral contraceptives.
Downloaded by Ryerson Univ on 09/16/16, Volume 2, Article Number 4
Activity and Dietary Assessment
An index for seasonal leisure aerobic energy expenditure was calculated from physical activity questionnaires (17). Subjects were queried about their participation in 15 types of leisure and sports activities for 1 month. Activities were classified according to their intensity, expressed in terms of MET (work metabolic rate /resting metabolic rate) (17, 46). Leisure energy expenditure index (MET x hrslday) was calculated by adding the product of MET (intensity) and hrslday (time spent on different activities). An estimation of leisure energy expenditure was obtained by multiplying the index by resting metabolic rate (RMR), which was calculated from the following equations (wt = weight, kg) RMR,,,,,,, (kcallh) = (879 + 10.2 x wt) / 24 (36) RMRfemal,, (kcallh) = (795 + 7.18 x wt) / 24 (37) Subjects kept a 7-day food record for a nonconsecutive 2-week period in August, November, February, and May. Food recording was divided into two parts: a 3-day period, Sunday to Tuesday, was followed by a 4-day period, Wednesday to Saturday. In order to increase compliance, there was a 1-week interval between the recording periods. Participants were instructed on how to complete the food consumption records with exact descriptions and amounts of all foods and drinks consumed. Amounts were estimated using household measurements (glasses, cups, tablespoons, slices, etc.), deciliters, or estimated grams. Drawings were given with the instructions in order to help estimate weights. The records were mailed to the first author. Four male athletes and one female athlete did not return food records. Daily energy and nutrient intakes were calculated by a computer program developed in the Department of Nutrition, University of Helsinki (1). The main part of the food composition data was obtained from Finnish food analyses and was completed from different international food composition tables. Dietary Supplements. In general, subjects were not allowed any dietary supplements during the study. To prevent nutritional deficiencies, subjects with serum fenitin concentration
Dietary Intake and Thiamin, Iron, and Zinc Status in Elite Nordic Skiers During Different Training Periods Mikael Fogelholm, Seppo Rehunen, Carl-Gustav Gref, Juha T. Laakso, Jari Lehto, lnkeri Ruokonen, and Jaakko-Juhani Himberg This study evaluated how different training periods affect dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. Subjects.were 17 skiers and 39 controls, ages 18-38 yrs. Dietary data were collected by 7-day food records at 3-month intervals. Coefficient of variation (CV) was used to indicate magnitude of seasonal changes. Energy intake for the year (28 food record days) was 3,802 kcallday (CV 19.1%) in male skiers, 2,754 kcallday (CV 3.7%) in male controls, 2,812 kcallday (CV 9.1%) in female skiers, and 2,013 kcallday (CV 5.9%) in female controls. CVs for thiamin, riboflavin, vitamin C, calcium, magnesium, iron, and zinc intake were 14.1-23.9% (male skiers), 2.9-15.0% (male controls), 4.8-24.5% (female skiers), and 4.3-1 1.5% (female controls). Seasonal changes in energy, carbohydrate, and micronutrient intakes reflected energy expenditure in male endurance athletes particularly. Erythrocyte transketolase activation coefficients and serum ferritin and zinc concentrations did not differ between skiers and controls. Seasonal variations in these biochemical indices of nutritional status were of the same magnitude in skiers and controls, despite large changes in skiers' physical activity. Daily, weekly, or seasonal variations in dietary intakes o r biochemical indices decrease the validity of an individual's nutritional status assessment (19, 23,43). On a group level, intraindividual day-to-day variations usually cancel out and a reasonably valid estimate of nutritional status is obtained (43). In contrast, seasonal or other long-term variations may cause systematic bias in cross-sectional nutritional assessment of a group (23, 38). Considerable seasonal variations in energy and nutrient intakes are likely
Fogelholm, Rehunen, Lehto, and Himberg are with the University of Helsinki, Depts. of Nutrition, Clinical Chemistry, Public Health, and Clinical Pharmacology, respectively. Gref is with the National Public Health Institute in Helsinki. Laakso and Ruokonen are with the MILA Laboratory in Helsinki. Request reprints from Mikael Fogelholm, Univ. of Helsinki, Dept. of Nutrition, SF-00710 Helsinki, Finland.
Downloaded by Ryerson Univ on 09/16/16, Volume 2, Article Number 4
352
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Fogelholm, Rehunen, Gref, et a/.
in endurance athletes particularly, because the amount of their weekly physical activity depends on the training period (2). This might help explain the wide range in reported energy intake of male (2,47043,270 kcallday) and female (1,870-3,990 kcallday) endurance athletes (5, 7, 15, 16, 20, 27, 41,42, 45). Biochemical indices of nutritional status also may be affected by the amount of training or dietary intake, or both. Long-term variation in indicators of iron (2, 18, 24, 30, 32) and zinc status (8) has been found in endurance athletes. To our knowledge, seasonal variation in vitamin status has not been studied in an athletic population, even though suboptimal vitamin B status in athletes compared with sedentary controls has been reported (21). The purpose of this study was to evaluate how different training periods affected dietary intake and biochemical indices of thiamin, iron, and zinc status in elite Nordic skiers. From a methodological point of view, we studied whether 7-day food records and single blood samples were representative in describing the nutritional status of endurance athletes.
Methods This study was carried out between August 1989 and May 1990. Seasonal data comprising physical activity questionnaire, food records, and blood samples were collected in August (basic conditioning period for skiers), November (precompetition period), February (competition period) and May (off-period). This study was approved by the Ethical Committee of the Faculty of Agriculture and Forestry, University of Helsinki, Finland. Subjects
An informed consent was obtained from 12 male and 10 female Nordic skiers and from 21 male and 22 female controls, ages 18-38 years. Of the 65 subjects, 3 male and 2 female skiers and 2 male and 2 female controls withdrew from the study for personal reasons (n=9). Thus, 9 male and 8 female skiers and 19 male and 20 female controls completed this study. The participants' age, height, and weight ranges are presented in Table 1. Skiers, including five medalists from the Table 1 Characteristics of Subjects: Mean and Range of Individual Results Females
Males Skiers (9) M Range
Age, yrs Height,cm Weight,kg
27 180 73
24-33 175188 6&76
Controls (19) M Range
27 181 78
21-38 169-187 59-99
Skiers (8) M Range
25 165 58
1&30 159-172 53-63
Controls (20) M Range
24 164 58
18-32 150-175 49-67
Note. Height and weight as reported by subjects; seasonal variation in weight was not significant, P > 0.05.
Dietary Intake in Nordic Skiers
/
353
1989 World Championships in Lahti, Finland, were international class elite athletes who had trained regularly for at least 5 years. Controls were healthy young adults, mostly university students, who were not involved in competitive sports. Five skiers (71%) and 10 controls (50%) were taking oral contraceptives.
Downloaded by Ryerson Univ on 09/16/16, Volume 2, Article Number 4
Activity and Dietary Assessment
An index for seasonal leisure aerobic energy expenditure was calculated from physical activity questionnaires (17). Subjects were queried about their participation in 15 types of leisure and sports activities for 1 month. Activities were classified according to their intensity, expressed in terms of MET (work metabolic rate /resting metabolic rate) (17, 46). Leisure energy expenditure index (MET x hrslday) was calculated by adding the product of MET (intensity) and hrslday (time spent on different activities). An estimation of leisure energy expenditure was obtained by multiplying the index by resting metabolic rate (RMR), which was calculated from the following equations (wt = weight, kg) RMR,,,,,,, (kcallh) = (879 + 10.2 x wt) / 24 (36) RMRfemal,, (kcallh) = (795 + 7.18 x wt) / 24 (37) Subjects kept a 7-day food record for a nonconsecutive 2-week period in August, November, February, and May. Food recording was divided into two parts: a 3-day period, Sunday to Tuesday, was followed by a 4-day period, Wednesday to Saturday. In order to increase compliance, there was a 1-week interval between the recording periods. Participants were instructed on how to complete the food consumption records with exact descriptions and amounts of all foods and drinks consumed. Amounts were estimated using household measurements (glasses, cups, tablespoons, slices, etc.), deciliters, or estimated grams. Drawings were given with the instructions in order to help estimate weights. The records were mailed to the first author. Four male athletes and one female athlete did not return food records. Daily energy and nutrient intakes were calculated by a computer program developed in the Department of Nutrition, University of Helsinki (1). The main part of the food composition data was obtained from Finnish food analyses and was completed from different international food composition tables. Dietary Supplements. In general, subjects were not allowed any dietary supplements during the study. To prevent nutritional deficiencies, subjects with serum fenitin concentration
