Research On The Vitamin A Requirements Of The Long-haul Truck Drivers

BackgroundLong-distance freight drivers often need to drive with low-light conditions, so need good night vision to ensure the night-time driving safety. Vitamin A constitutes the important component of light-sensitive material within the visual cells and plays a critical role in the night vision. Lack of vitamin A could cause the dark-adapted ability decline, significantly affect night vision. While previous studies of this research group found that these drivers showed poor nutritional status of vitamin A. The cause of the poor vitamin A,on one hand is the shortage of vitamin A intake (far below the recommended nutrient intake (RNI) of China Nutrition Society, less than 50%RNI); on the other hand, long-time driving in the low light or dark conditions the consumption and requirements of vitamin A long haul freight drivers is obvious higher than the general populations, such as the requirements of vitamin A of radar operator is 1590μgRE, and aviator's is 1500-3000p.gRE. Therefore, this study were designed and conducted by dietary survey, serum retinol detection, dark-adapted time and visual field detection to estimate the vitamin A status comprehensively. We are intended for improving the vitamin A malnutrition status of the long-haul truck drivers and exploring the relationship between the different vitamin A intakes and vitamin A nutrition status by different dose vitamin A supplementation treat, so as to explore the appropriate requirements of vitamin A of the long-haul truck drivers and provide a theoretical data and reference basis for the formulation of the vitamin A recommended nutrient intake. ObjectiveThe objective of the study was to improve the vitamin A malnutrition status of the long-haul truck drivers and explore the relationship between the different vitamin A intakes and vitamin A nutrition status by different dose vitamin A supplementation treat, so as to explore the appropriate requirements of vitamin A of the long-haul truck drivers and provide a theoretical data and reference basis for the formulation of the vitamin A recommended nutrient intake.Subjects and methods 1. Research objectsSubjects were long-haul truck drivers who often drive at night (an average of not less than 4 hours night-time driving and the driving time is more than 8 hours in a day), whose dark adaptation time more than 30 seconds or physiological blind spot area expanded, no eyes diseases, no digestive diseases, not experienced vitamin oral supplementation in nearly one month. There were 134 long haul truck drivers surveyed, including 60 drivers met the inclusion criteria who all are male, aged 23～56 years, came from three big international logistics companies in Shanghai.2. Dietary survey methods2.124h recall dietary surveyThree days 24-hour food recalls were conducted in two working days and a resting day, which assist by plenty of three-dimensional food models (as a present from Shanghai Gong Rong food model Manufacture Company), to survey the food consumptions and daily nutrient intakes situation of the long haul drivers by 30 samples. Average daily nutrient intakes were calculated on the basis of Chinese food composition Tables (Institute of Health,2002).2.2 Food frequency questionnaireA food frequency questionnaire with vitamin A (includingβ-carotene) containing foods was conducted so as to grasp the status of foods intake frequency, meal patterns and food intake habits and so on. Several preliminary experiments were undertaken before the formal experiment.3. Serum retinol detection and relative dose responseFasting blood samples were obtained from long-haul truck drivers who participate the intervention study. Fasting intravenous blood (5 ml) was drawn from each subject at morning before breakfast (whose retinol serum level signed as A0), using negative pressure vacuum pipe (10ml).Then each subjects were supplemented about 495μgRE retinol orally and then work as usual.5 hours later, blood samples were drawn again from subjects (whose retinol serum level signed as A5). All the blood samples were immediately placed on ice in light-free jars and then transported to the laboratory (within 4 h of the last blood sample). On arrival at the laboratory the blood samples were immediately divided into fractions and stored at-80°. Serum level of retinol was determined by the RDR and HPLC method. RDR calculated formulation is as following:RDR= (A5-A0/A0)*100%. It was reported as positive when RDR value is more than 20%, which means the lack of the liver vitamin A storage.4. Overweight and obesityAll subjects were asked to worn only light clothes and with barefoot before stand in the health meter. Body mass index (BMI=weight(kg)/height2(m2)) criterion standard: <18.5(underweight); 18.5～23.9 (normal); 24～27.9 (overweight);≥28 (obese).5. Dark adaptometryYA-Ⅱdark adaptometry was used in Dark adaptation detection. The range of normal values of the equipment was pre-performed by healthy control subjects. Steps of the detection:five minutes of pre-adaptation→two minutes of highlight exposure→identify the direction of the marker—rrecord the time by the equipment runner.6. Visual field detectionSubjects, whose dark-adapted time is beyond 30 seconds (especially the time extended longer) were selected to detect the visual field. Test is carried out in the dark room, conducted by the professional ophthalmic doctors from a big hospital in Shanghai. Testing equipment:OCTOPUS 101 automatic perimeter (Interzeag, Haag Streit Switerland). Normal physiological blind spot area is about a diameter about 6°while mean defect (MD) normal range is between-2-2dB and loss variance (LV) is 0～6dB2.7. Randomization grouping and intervention methods60 subjects who met the inclusion criteria were randomly grouped into control group(12 persons), low-dose group(11 persons), middle-dose group(10 persons), the higher-dose group (14 persons) and the highest-dose group(10 persons) through the random numbers from random number table. Intervention dose and conduct ways as following(Table 1). Vitamin A capsules (5000IU, H37023082) was from Qingdao double-whale medicine company. While the placebo is the vitamin E(10mg, H31022238), whose size and shape is similar to the vitamin A capsule.8.On-site supervision and quality control All the subjects were signed informed consent before the survey and receive certain compensation when survey finished. Researchers release whole bottle of vitamin A capsules or placebo (post the label marked the use methods on the bottle surface by a transparent waterproof plastic). Through daily SMS by mobile, weekly telephone interviews and follow-up remind, track, supervise and guide them to supplement capsules so that subjects were supplemented following request on time and could solve the possible problem in time.9. Data statistical analysisAll data entered by two staffs, and check out by another staff in the end. Descriptive statistics including means, medians, standard deviations, quartile range. Correlation analysis including Pearson correlation (normally distributed data) and Spearman's rank correlation (non-normal distributed data). Multiple samples comparison including single-factor analysis of variance (normally distributed data) and rank test (non-normal distributed data). All the data were analyzed using the SPSS 13.0 statistical software package.Results1. Sample featureThere were 134 long-haul truck drivers investigated from three big international logistics companies of Shanghai. All of them are male. Mean age and occupational age of these long-haul truck drivers is 35.56±7.07 (18～56) and 9.49±5.52 (3～28) respectively, there are 84.7%(115) drivers whose age is between 25 and 45 years and driving history beyond 5 years reached 85.2%. Based on BMI measurements for 134 subjects, no one was underweight; 52 were normal; 67 (50.0%) were overweight and 15 (11.2%) were obese. There are 49 drivers completed intervention out of 60 subjects entered into the intervention trial, whose average age is 36.13±6.58 (23～52) with occupational age mean 10.20±4.70 (3～28) and BMI 24.74±2.98 (19.90-33.06), what is more, there are no significantly difference among the different supplemented-dose group.2. Vitamin A intakes and nutrients resourceThere were 30 drivers sampled from 60 subjects join the dietary survey. The result shows as following:The average VA intake per day is just 367μgRE, far below the RNI; Dietary intake is irregular and difficult to guarantee three meals a day; Dietary structure is irrational with high consumption of high energy food and animal foods and low consumption of plant food. The food rich in vitamin A such as animal liver, dark vegetables and fruits, daily products intake was generally much low. There is a obvious shortage intake of vitamin A (less than 50%RNI).3. Dark adaptation timeThe average dark-adapted time of the 134 drivers is 32 seconds,56.7%dark adaptation time is extended (more than 30 seconds).All the dark-adapted times of the subjects (60) who enter into the intervention trial are beyond 30 seconds. There were 49 intervention results were taken back. There were significantly different between the prior to and after the intervention(P<0.01). Before the intervention the dark-adapted time mean of each group is 36.00,36.50,43.50,45.00,43.50 respectively and exist no significantly difference (P=0.39) among them. While there are significantly difference (P<0.01) among different groups with whose average dark-adapted time is 34.00,30.00,22.50, 18.00,16.00, respectively(from control to the highest-dose group). It was found that there are significantly difference among the middle-dose group or the above and the control group or low dose group respectively (P=0.01,< 0.01,<0.01), but there are no significantly difference among he middle-dose group and the above themselves (p=0.56, 0.17,0.35), also is the control and low-dose group (P=0.64).4. Visual field detectionThere were 38 drivers from the 60 subjects received the visual field detection by OCTOPUS 101 automatic perimeter. It was found that 55.26%(21) drivers'physiological blind spot area (8.26±5.21.°) were expanded(> 6°), with 13.16%(5) mean defect (0.97±1.67dB) and 26.32%(10) loss variance (5.12±3.61dB2) is too large. After the comprehensive analysis of the computer procedure, we found there were 39.48%(15) visual field defect. 5. Serum retinol RDR%valuesWe toke back 38 pairs serum samples in this trial. Statistical analysis showed the average value of the RDR%of these drivers is 9.57±10.79, andⅠ-Ⅴis 31.96±59.22, 21.06±38.00,18.57±15.31,5.20±12.28,4.38±5.48 respectively, and there were significantly difference of RDR%values among different groups. The percent of RDR% >20%ofⅠ,ⅡandⅢare 66.7%,28.9%,16.7%respectively, while the others is< 20%.Discussion and suggestionAcoording to the comprehensive evulation of VA status of long haul truck driver through diet survey, serum retinol,dark-adapted time and physiological blind spot area and so on, we select the drivers whose VA intake is less than 50%RNI and poor in the dark adaptation and visual field as subjects.Then there are 60 drivers who met the inclusion criteria and were randomly grouped into control group,low-dose group,middle-dose group, the higher-dose group and the highest-dose group through the random numbers from random number table. In the end we took back 49 results and statistical analysis shows there are no significantly difference in the age, driving experience among these different groups before the intervention which means homogenesis. We remind, track and supervise subjects for supplementation by daily SMS and weekly follow-up during the intervention study. Based on the previous research experience on the VA requirements study of other occupational people, we select the dark-adapted time and relative dose response to research the VA requirements of long haul truck driver.Results showed that the VA nutritional status of long haul truck driver could be improved by VA supplementation, the dark-adapted time and RDR value reached normal range when drivers supplemented 952μgRE VA, in conjunction with the VA intake basal value (367μgRE), the VA requirements of long haul truck driver is 1319μgRE, which is higher than the general population whose VA requirements is 800μgRE, but less than the radar operators(1590μgRE). Meanwhile, the results of the study play an important role in the diet guidance and formulation of VA RNI of long haul truck driver in the future. According to the study, we suggest that it is the time to take attention to the health problem of the long-haul truck drivers, some feasible measures should be made out to ensure the health and nutrition of Long-haul truck drivers. The long-haul truck drivers could be taught to make a better choice in choosing foods, such as, eat more natural vegetality foods other than these deep processing products, eat more food which is rich in the vitamin A.Conclusions1. The incidence rate of overweight and obesity of long-haul truck drivers is much higher than the general population in China. More than a half of drivers in this study are overweight or obese.2. There were severe problems resided in long-haul truck drivers'daily diet. The food rich in vitamin A such as animal liver, dark vegetables and fruits, daily products intake was generally much low. There is a obvious shortage intake of vitamin A (less than 50%RNI).3. The dark-adapted time and visual field situation of long-haul truck drivers cannot be optimistic. It is necessary to detect the long-haul truck drivers" vision regularly.4. The appropriate requirement of vitamin A of long-haul truck drivers is higher than the general population in China, based on this study it is approximately 1319μRE, which supply the reference value to the formulation of VA RNI of long haul truck driver or other similar workers in the future.