Volume 118, Issue 6 , Pages 1299-1304, December 2006
Early-life supplementation of vitamins A and D, in water-soluble form or in peanut oil, and allergic diseases during childhood
Article Outline
Background
Early vitamin supplementation is given routinely to infants in many countries, but it is unclear whether this affects the risk of allergic diseases.
Objectives
We sought to study the association between early-life supplementation of vitamins A and D in water-soluble form or in peanut oil and allergic diseases up to 4 years of age.
Methods
A prospective birth cohort of 4089 newborn infants was followed for 4 years using parental questionnaires repeatedly to collect information on exposure and health. At 4 years, the response rate was 90%, and allergen-specific IgE levels to food and airborne allergens were measured in 2614 of the participating children.
Results
Vitamins A and D were given to 98% of the children in infancy, and vitamins based in peanut oil dominated (90%). Children supplemented with vitamins A and D in water-soluble form during the first year of life had an almost 2-fold increased risk of asthma (adjusted odds ratio [OD], 2.18; 95% CI, 1.45-3.28), food hypersensitivity (adjusted OR, 1.89; 95% CI, 1.33-2.65), and sensitization to common food and airborne allergens (adjusted OR, 1.88; 95% CI, 1.34-2.64) at age 4 years compared with those receiving vitamins in peanut oil. No increased risk of IgE antibodies to peanut was seen in children receiving vitamins in peanut oil.
Conclusion
Supplementation of vitamins A and D in water-soluble form seems to increase the risk of allergic disease up to the age of 4 years compared with supplementation with the same vitamins given in peanut oil.
Clinical implications
Vitamins A and D in oil does not seem to increase the risk of allergic disease during childhood.
Key words: Allergic disease, asthma, BAMSE, childhood, fatty acids, prevention, sensitization, vitamin D
Abbreviations used: BAMSE, Children, Allergy, Milieu, Stockholm, Epidemiological survey, OR, Odds ratio
Dietary intake has been suggested to exert protective, as well as unfavorable, effects on asthma and allergic diseases. In recent years there has been a focus on the role of vitamins, antioxidants, fruits, and vegetables, as well as fatty acids.1, 2, 3, 4 For example, early multivitamin supplementation has been reported to increase the risk of asthma and food allergy.5 High serum levels of vitamin A have been associated with an increased risk of IgE sensitization, and dietary vitamin D supplementation early in life has been associated with atopy and allergic rhinitis in adulthood.6, 7 A possible explanation for these findings is that such vitamins might skew the immune system toward a TH2 response.8 Accordingly, vitamin D supplementation during infancy has been associated with a reduced risk of type 1 diabetes.9
Recommendations about supplementation with vitamins during early childhood are given in many western countries.10 In Sweden all infants are recommended a dose of 1000 IE of vitamin A and 400 IE of vitamin D daily from 2 weeks of age up to 5 years of age to prevent vitamin A and D deficiency.11 The vitamins are free of charge during the first 2 years of life and distributed by the Child Health Care units. After the first year of life, the vitamins are recommended to be given during wintertime only. The vitamins can either be water soluble or oil based. At the time of the study, the oil used was refined peanut oil. In general, the oil-based vitamins were recommended because such preparations do not need to be kept cold.
Peanut oil contains omega-6 fatty acids but also a small amount of omega-3 fatty acids.12, 13 A diet rich in omega-3 fatty acids has been suggested to reduce the risk of several autoimmune diseases, and protective effects have been reported also for allergic diseases.14, 15 The use of peanut oil in medications and formulas has been associated with an increased risk of sensitization to peanut in some studies, but data are inconclusive.16, 17, 18
The primary aim of the present study was to investigate the association between early supplementation of vitamins A and D in water-soluble form or based in peanut oil and development of allergic disease up to the age of 4 years.
Methods
Study design
All newborns in a predefined area of Stockholm, Sweden, were invited to participate in a prospective study (the Children, Allergy, Milieu, Stockholm, Epidemiological survey [BAMSE]) from February 1994 until November 1996. In total, 4089 newborn infants were included, which comprised 75% of all infants born in this area. The study design has been described in detail elsewhere.19, 20 Data on parental allergy and various exposures were obtained by using parental questionnaires when the infants were newborns (median age, 2 months). At 1, 2, and 4 years of age, the parents answered questionnaires with a focus on symptoms related to allergic diseases in their children, as well as on key exposures and possible confounding factors. Data about breast-feeding, diet, and vitamin supplementation were collected from the 1-year questionnaire. The response rates for the questionnaires were 96%, 94%, and 91%, respectively. The information on supplementation with vitamins A and D was provided in 4 predefined categories (vitamins based in peanut oil, vitamins in water-soluble form, vitamins as a combination of the 2 preparations, and no vitamins).
All children with answered questionnaires (n = 3670) at age 4 years were invited to a clinical investigation, including blood sampling. A total of 2965 children agreed to participate, and blood samples were collected from 2614 children. Permission for the study was obtained from the Ethics Committee of Karolinska Institutet, Stockholm.
Definition of health outcomes
During the first 2 years of life, asthma was defined as at least 3 episodes of wheezing in addition to respiratory symptoms treated with inhaled steroids or signs of bronchial hyperreactivity, such as coughing and wheezing during play or physical strain, without ongoing upper respiratory tract infection. At 4 years of age, asthma was defined as at least 4 episodes of wheezing during the last 12 months or at least 1 episode of wheezing during the same period if the child was taking inhaled steroids.20
Eczema was defined as dry skin in combination with itchy rash for at least 2 weeks with typical localization during the last 12 months, a physician's diagnosis of eczema during the last 24 months, or both.21
Allergic rhinitis was defined as sneezing, runny or blocked nose, and/or red itchy eyes after exposure to pollen or pets; a physician's diagnosis of allergic rhinitis during the last 24 months; or both.
Hypersensitivity to food was defined as specific symptoms (ie, atopic dermatitis, urticaria, edema of the lips/eyes, pruritus around the eyes or runny nose, and asthma) after ingestion of common types of food during the last 24 months.
The terms transient, late-onset, and persistent disease were used to assess onset and duration of disease (asthma, eczema, allergic rhinitis, and food hypersensitivity). Transient disease denotes children fulfilling the outcome criteria during the first 2 years of life but not later. Persistent disease implies that the child fulfilled the outcome criteria both during the first 2 years of life and at 4 years of age. Late-onset disease denotes that the child only fulfilled disease criteria at age 4 years.
The term multiple diseases was defined as at least 2 of the following 3 diseases at the age of 4 years: asthma, eczema, or allergic rhinitis.
For sensitization, IgE antibodies against a mixture of common inhalant allergens (cat, dog, horse, birch, timothy, mugwort, Dermatophagoides pteronyssinus, and Cladosporium species) and common food allergens (cow's milk, hen's egg, cod fish, soy bean, peanut, and wheat) were analyzed with Phadiatop and fx5, respectively. Single allergens were analyzed if Phadiatop or fx5 test results were positive (≥0.35 kUA/L; Pharmacia CAP System, Phadia AB, Uppsala, Sweden). Data of the 7 most common single allergens (milk, egg white, peanut, birch, timothy, cat, and horse) are presented here.22
Statistical methods
Difference in the distribution of selected characteristics among the 4 groups (vitamins in peanut oil, vitamins in water-soluble form, both preparations, and no vitamins A and D) was tested with the χ2 test. The association between vitamin A and D supplementation and the selected health outcomes was analyzed with logistic regression. The results are presented as adjusted odds ratios (ORs) with 95% CIs. Several models were tested to identify potential confounders, and finally, the logistic regression model was adjusted for parental allergic disease (defined as physician-diagnosed asthma, hay fever, or both in combination with allergy to furred pets or pollen in 1 or both parents), maternal age (<25 years, ≥25 years), maternal smoking (yes, no), breast-feeding (<4 months, ≥4 months), and fish consumption (≤once a month, ≥2-3 times a month) because these covariates were associated with both exposure and health outcomes. Other models were also evaluated, such as a broader definition of heredity, also including eczema among the parents and any allergic disease (asthma, eczema, allergic rhinitis, or allergy to pollen or pets) among older siblings, as well as gestational age, damp housing, and socioeconomic status, but these covariates had a small effect on the risk estimates (<3%).
The Wald test was used to assess interaction between covariates (departure from a multiplicative model). All statistical analyses were performed with STATA Statistical Software (release 8.0; StataCorp, College Station, Tex). Complete information on vitamin A and D consumption at age 1 year and answers on all 4 questionnaires were required for inclusion in the analyses. In total, 3618 (88.5%) children fulfilled these criteria.
Results
Most children (98%) had been given vitamins A and D during the first year of life, and vitamins based in peanut oil dominated (90%). Two hundred thirty-seven (7%) children had received vitamins in water-soluble form, and 73 (2%) had used both alternatives. Only 59 (<2%) children were not given vitamins A and D during the first year of life. The distribution of selected exposure characteristics in relation to supplementation with vitamins A and D is shown in Table I. Some differences were seen among the 4 exposure groups in relation to heredity for allergic disease, maternal smoking, breast-feeding, and fish consumption. Children receiving vitamins A and D in water-soluble form were more exposed to maternal smoking (19% vs 13%, P = .01), breast-fed less than 4 months (27% vs 20%, P = .004), and had less regular consumption of fish at the age of 1 year (31% vs 19%, P < .001) compared with children receiving oil-based vitamins. Because of a small number of children receiving both preparations or no vitamins at all, these groups were excluded from further analyses. Children participating in the 4-year follow-up who also gave blood were not more likely to have asthma or eczema than children who did not provide a blood sample (data not shown). The same was true for parental allergy.
Table I. Distribution of selected exposure characteristics at 2 months and 1 year of age in relation to intake of vitamins A and D in peanut oil, water-soluble form, or both
| Peanut oil (N = 3249; n [%]) | Water-soluble form (N = 237; n [%]) | Both water and oil (N = 73; n [%]) | No AD (N = 59; n [%]) | |
|---|---|---|---|---|
| Sex (female) | 1617 (50) | 110 (46) | 34 (47) | 27 (46) |
| Parental allergy∗ | 947 (29) | 80 (34) | 32 (44) | 18 (31) |
| Maternal smoking† | 412 (13) | 44 (19) | 15 (21) | 7 (12) |
| Socioeconomic status | ||||
 Blue collar | 513 (16) | 48 (20) | 10 (14) | 16 (27) |
| White collar | 1390 (43) | 103 (44) | 28 (38) | 26 (45) |
| Self-employed | 1301 (40) | 84 (35) | 35 (48) | 16 (28) |
| Damp housing‡ | 261 (9) | 26 (11) | 2 (3) | 3 (5) |
| Gestational age <40 wk | 1064 (33) | 80 (34) | 30 (41) | 17 (29) |
| Maternal age (≤25 y) | 240 (7) | 14 (6) | 6 (8) | 6 (10) |
| Breast-feeding <4 mo | 635 (20) | 65 (27) | 15 (21) | 14 (24) |
| Fish consumption ≤1/mo | 611 (19) | 74 (31) | 17 (23) | 15 (25) |
∗Physician's diagnosis of asthma, hay fever, or both in any parent combined with allergy to furred pet or pollen. |
†Maternal smoking during pregnancy or at enrollment. |
‡Damage by damp, mold odor, and/or visible mold last year. |
Children who had been given vitamins A and D in water-soluble form during the first year of life had an almost 2-fold increased risk of asthma (OR, 2.18; 95% CI, 1.45-3.28) and food hypersensitivity (OR, 1.89; 95% CI, 1.33-2.65) compared with children having received the same vitamins in peanut oil (Table II). No significant associations were seen for the development of eczema and allergic rhinitis (OR of 1.15 [95% CI, 0.83-1.58] and OR of 1.22 [95% CI, 0.82-1.83], respectively). However, for multiple allergic diseases, a 2-fold increased risk was observed (OR, 2.03; 95% CI, 1.32-3.12) among children supplemented with vitamins A and D in water-soluble form compared with those given such vitamins in peanut oil.
Table II. Association between consumption of vitamins A and D in water-soluble form compared with in peanut oil up to age 1 years and allergic diseases at 4 years of age
| Vitamins A and D in oil | Vitamins A and D in water-soluble form | |||||
|---|---|---|---|---|---|---|
| N | n (%) | N | n (%) | ORadj† | 95% CI | |
| Any allergic disease | 3249 | 946 (29) | 237 | 87 (37) | 1.28 | 0.97-1.70 |
| Asthma | 3227 | 203 (6) | 236 | 33 (14) | 2.18 | 1.45-3.28 |
| Eczema | 3243 | 645 (20) | 236 | 56 (24) | 1.14 | 0.82-1.53 |
| Allergic rhinitis | 3206 | 324 (10) | 237 | 32 (14) | 1.21 | 0.81-1.81 |
| Food hypersensitivity | 3236 | 351 (11) | 236 | 48 (20) | 1.87 | 1.32-2.65 |
| Multiple allergic diseases | 3249 | 199 (6) | 237 | 31 (13) | 2.03 | 1.32-3.12 |
†OR adjusted for parental allergic disease; maternal age; maternal smoking during pregnancy, at recruitment, or both; fish consumption; and breast-feeding. |
The effect of early exposure to vitamins A and D was heterogeneous for different phenotypes of allergic disease (Table III). Children who regularly received vitamins A and D in water-soluble form during the first year of life had an increased risk of persistent allergic disease up to the age of 4 years compared with children who received vitamins in oil. ORs were 2.70 (95% CI, 1.59-4.60) for persistent asthma, 2.32 (95% CI, 1.32-4.07) for allergic rhinitis, and 2.99 (95% CI, 2.01-4.42) for food hypersensitivity. No association was found between early supplementation of vitamins A and D and occurrence of any transient or late-onset disease.
Table III. Daily intake of vitamins A and D in peanut oil compared with vitamins A and D in water-soluble form in relation to allergic diseases at 4 years of age
| Transient | Late onset | Persistent | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| N | n | ORadj∗ | 95% CI | n | ORadj∗ | 95% CI | n | ORadj∗ | 95% CI | |
| Asthma | ||||||||||
| Oil based | 3221 | 163 | 1.00 | 109 | 1.00 | 94 | 1.00 | |||
| Water soluble | 234 | 14 | 1.22 | 0.69-2.17 | 13 | 1.73 | 0.95-3.16 | 19 | 2.70 | 1.59-4.60 |
| Eczema | ||||||||||
| Oil based | 3238 | 389 | 1.00 | 238 | 1.00 | 406 | 1.00 | |||
| Water soluble | 236 | 33 | 1.16 | 0.78-1.72 | 18 | 1.14 | 0.68-1.90 | 38 | 1.20 | 0.82-1.76 |
| Allergic rhinitis | ||||||||||
| Oil based | 3175 | 125 | 1.00 | 239 | 1.00 | 85 | 1.00 | |||
| Water soluble | 235 | 9 | 0.91 | 0.45-1.82 | 15 | 0.81 | 0.47-1.40 | 17 | 2.32 | 1.32-4.07 |
| Food hypersensitivity | ||||||||||
| Oil based | 3224 | 439 | 1.00 | 168 | 1.00 | 182 | 1.00 | |||
| Water soluble | 234 | 32 | 1.05 | 0.70-1.56 | 7 | 0.64 | 0.30-1.40 | 41 | 2.99 | 2.01-4.42 |
∗OR adjusted for parental allergic disease; maternal age; maternal smoking during pregnancy, at recruitment, or both; fish consumption; and breast-feeding. |
Associations between early exposure to vitamins A and D and sensitization to the 7 most common allergens in the BAMSE cohort are presented in Table IV. A positive association was seen for supplementation with vitamins A and D in water-soluble form during the first year of life and IgE antibodies to food and airborne allergens (OR of 1.75 [95% CI, 1.20-2.56] and OR of 1.95 [95% CI, 1.33-2.84], respectively). The prevalence of allergen-specific IgE antibodies was considerably lower among children having received peanut oil containing vitamins for all of the 7 tested allergens. The association was statistically significant for sensitization to egg white, horse, cat, and birch allergens.
Table IV. Association between intake of vitamins A and D and the 7 most common allergens among children in the BAMSE cohort
| ≥0.35 kU/L | ||||
|---|---|---|---|---|
| N | n (%) | ORadj∗ | 95% CI | |
| Food mix | ||||
| Oil based | 2295 | 351 (15) | 1.00 | |
| Water soluble | 159 | 41 (26) | 1.75 | 1.20-2.56 |
| Phadiatop | ||||
| Oil based | 2294 | 333 (15) | 1.00 | |
| Water soluble | 159 | 42 (26) | 1.95 | 1.33-2.84 |
| Milk | ||||
| Oil based | 2290 | 189 (8) | 1.00 | |
| Water soluble | 159 | 21 (13) | 1.54 | 0.94-2.51 |
| Egg white | ||||
| Oil based | 2291 | 102 (4) | 1.00 | |
| Water soluble | 159 | 17 (11) | 2.27 | 1.30-3.59 |
| Peanut | ||||
| Oil based | 2288 | 117 (5) | 1.00 | |
| Water soluble | 159 | 14 (9) | 1.52 | 0.84-2.75 |
| Horse | ||||
| Oil based | 2286 | 62 (3) | 1.00 | |
| Water soluble | 159 | 12 (8) | 2.66 | 1.38-5.12 |
| Cat | ||||
| Oil based | 2291 | 115 (5) | 1.00 | |
| Water soluble | 159 | 21 (13) | 2.57 | 1.55-4.28 |
| Timothy | ||||
| Oil based | 2280 | 124 (5) | 1.00 | |
| Water soluble | 159 | 13 (8) | 1.37 | 0.75-2.51 |
| Birch | ||||
| Oil based | 2277 | 187 (8) | 1.00 | |
| Water soluble | 158 | 26 (17) | 1.98 | 1.25-3.11 |
∗OR adjusted for parental allergic disease; maternal age; maternal smoking during pregnancy, at recruitment, or both; fish consumption; and breast-feeding. |
Among children who had received vitamins A and D in peanut oil, 5% were sensitized to peanut compared with 9% of the children who had received oil-based vitamins in water-soluble form (P = .05).
The associations between intake of vitamins A and D and the studied outcomes tended to be similar in children with parental allergy compared with those seen in children without parental allergy (data not shown).
Discussion
Most children in this Swedish birth cohort had been given vitamins A and D during the first year of life, and oil-based vitamins dominated. In the present study the prevalence of allergic disease was higher among children supplemented with vitamins A and D in water-soluble form compared with children supplemented with vitamins A and D in peanut oil. Consequently, children supplemented with vitamins A and D in water-soluble form had an increased risk of asthma, food hypersensitivity, and sensitization to common food and inhalant allergens at the age of 4 years. The effect of supplementation with vitamins A and D in water-soluble form was heterogeneous for different phenotypes of allergic disease and was seen particularly for multiple allergic disease and persistent allergic disease during the first 4 years of life.
The effect of supplementation with vitamins A and D in water-soluble form is in agreement with results from a Finnish population-based study in which vitamin D supplementation during the first year of life was a risk factor for atopy and allergic rhinitis later in life.7 Furthermore, a study by Milner et al5 from the United States indicated that early multivitamin supplementation increased the risk of asthma among black children and food allergies among exclusively formula-fed children. However, it is difficult to compare the studies because the national guidelines regarding vitamin supplementation differed substantially between the countries. It is also unclear in what type of preparation the vitamins were given in the studies from Finland and the United States.
One might speculate that the difference in effect of early supplementation with vitamins A and D given in water-soluble form or in peanut oil on the development of allergic disease seen in our study is related to a possible preventive effect by the fatty acids in the peanut oil. Such oil contains both omega-6 and omega-3 fatty acids to a proportion of approximately 34:1.12, 13 Omega-3 fatty acids seem to have anti-inflammatory effects in contrast to omega-6 fatty acids, which might promote inflammation.14 However, a substantial contribution of omega-3 fatty acids from peanut oil to total daily intake is unlikely, given the low content in the peanut oil. Another possible explanation is that the absorption or the toxicity of vitamins might be different if given in water-soluble form or in oil-based form. The result of a recently performed meta-analysis comparing the toxicity of different forms of retinol indicates that the physical form is a major determinant of toxicity.23 This has also been discussed in some older studies in which the absorption has been suggested to be better from a water suspension.24 An argument against a negative effect of vitamins A and D if given in water-soluble form is the lack of difference in health outcome between those given vitamins in water-soluble form and the group of children who did not receive any vitamins. However, it should be kept in mind that only very few children did not receive vitamin supplementation, making results in this group uncertain.
During our study period, the oil solution was based on peanut oil. This has recently changed to sunflower oil, mainly because of suspected risk of development of peanut allergy. In our study the risk for sensitization to peanut was not increased for children with regular exposure to peanut oil during the first year of life; on the contrary, a borderline protective effect was observed. This is contrary to the results of some other studies but might be explained by different routes of administration.17 Furthermore, it is important to distinguish between crude peanut oil and refined preparations. The peanut oil used in the present study was highly refined and thus likely contained no peanut protein.
Residual confounding must be considered in the interpretation of our findings. Children who had received vitamins A and D in water-soluble form were more often exposed to maternal smoking during pregnancy and at 2 months of age, were less breast-fed, and had less regular consumption of fish at the age of 1 year compared with children receiving oil-based vitamins. All of these factors have been suggested to increase the risk for recurrent wheeze or asthma, but all those factors were adjusted for in the analysis.25, 26, 27 Heredity of allergic disease could be a confounding factor because at the time of the study, it was well known that the oil was produced from peanuts and that peanut oil in baby food had been suggested to increase the risk of sensitization to peanut.16 Thus atopic families might have selected the water-soluble vitamin supplements, and the association with atopic disease might be due to so-called reverse causation. However, when a very broad definition of heredity was used, including also parental eczema and allergic disease among older siblings, only minor changes of the risk estimates were seen. Although we cannot exclude residual confounding, the magnitude of the association between vitamins A and D and allergic disease, as well as the consistency of the results, indicate that confounding is unlikely to explain the findings.
The strength of our study is a high response rate for all questionnaires during the 4-year follow-up period, reliable measurements of exposure, and well-defined outcome measures. We also have an appreciable number of children with allergic disease, which enabled allocation into different phenotypes depending on onset and duration of allergic disease. However, a weakness of our study is lack of information about vitamin supplementation after the first year of life, and therefore exposure misclassification related to later exposure cannot be entirely ruled out. Nevertheless, the majority of the children were receiving oil-based vitamins, and if some of them changed during the second year to vitamins in water-soluble form, it should primarily lead to a dilution of the associations between supplementation with vitamins A and D and development of allergic disease.
In conclusion, vitamins A and D in water-soluble form seem to increase the risk of allergic disease up to the age of 4 years compared with supplementation of such vitamins if given in peanut oil. The mechanisms behind these findings are still unclear, and our results have to be confirmed by others before the evidence can be used as a basis for preventive advice.
We thank all children and parents participating in the BAMSE cohort, without whose time and assistance this study would have been impossible to perform.
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Supported by the Swedish Asthma and Allergy Association, The Vardal Foundation for Health Care Sciences and Allergy Research, the Swedish Heart and Lung Foundation, and the Stockholm County Council.Disclosure of potential conflict of interest: The authors have declared that they have no conflict of interest.
PII: S0091-6749(06)01775-1
doi:10.1016/j.jaci.2006.08.022
© 2006 American Academy of Allergy, Asthma and Immunology. Published by Elsevier Inc. All rights reserved.
Volume 118, Issue 6 , Pages 1299-1304, December 2006
