Food intake of patients with atopic dermatitis

ARTICLE

The number of patients with atopic dermatitis (AD) has increased over the last two decades [1, 2]. Nowadays it is estimated that 10 to 15% of the population will be affected by AD at some time during their life [2]. AD is a multifaceted, chronically relapsing disease, which often begins in early infancy and is characterized by pruritus and typical distribution of the cutaneous lesions [3].

In spite of a considerable lack of knowledge about the etiopathogenesis of AD, currently there exist well known triggering factors [4]. Among those are nutritional factors which are widely discussed in the scientific literature [5]. In addition, using varying types of diets improvement of AD was seen in 10-30% of the cases [5-7]. In some studies, even stronger effects with dietary changes occurred, covering more than 50% of the subjects [8-11].

There is also the observation that food intolerance and the prevalence of AD coincide. This observation was mostly derived from studies among children. It was found that, in double-blind, placebo controlled, food challenge studies, cutaneous, gastrointestinal and respiratory symptoms were seen in up to 30% of patients with AD [12-15]. Open food challenges caused exacerbation of AD in up to 80% [16, 17]. For example, between 20 to 48% of children ingesting orange, tomato, sweets, soft drinks, chocolate, pineapple, egg, fish, and milk have been reported to react to that food [18].

Dietary issues also affect AD patients because of more or less scientifically based dietary advise for AD treatment from lay press releases, magazine cover stories and newspapers [5, 19]. Accordingly, many AD patients follow some - even restrictive - diets [18]. Therefore nutrient deficiencies and even malnutrition in children with AD consuming restrictive diets were observed [9, 18, 20-23]. However, no investigations have been performed so far to examine whether such risk also exists in adult AD patients.

We therefore examined the food intake in a series of patients with AD with particular consideration of self-reported food intolerance. Those patients reporting intolerance of specific food items ("symptomatic") were compared in terms of food intake with patients not reporting such intolerance ("asymptomatic"). It may be possible that symptomatic patients represent a group with nutrient deficiencies that deserves particular clinical attention.

Material and methods

Study population

All German patients with AD, who were referred to two wards of the Department of Dermatology and Allergy, Davos, Switzerland, between July and December 1996 formed the study population (n = 120). All incoming patients were examined by at least two dermatologists. AD diagnosis was evaluated and finally established according to the criteria of Hanifin and Rajka [24]. The severity of the AD was evaluated by the SCORAD-Index [25].

The study subjects were referred to the Department by dermatologists, allergists and general practitioners. The subjects were members of the general social security system of Germany, covering more than 85% of the population. Severity of disease, lack of sufficient home care, or inability to conduct self treatment were reasons for being referred to the specialized hospital in Switzerland.

Study design

Informed consent for a dietary study was asked from the eligible patients. Only 4 of the patients refused. The remaining 116 patients received on the day of admission a food-frequency questionnaire (FFQ) to fill in during the next two days. The FFQ was applied previously in a large cohort study in Germany and tested for its validity and reliability on different occasions [25-27]. The FFQ covered the intake of 146 food items. For this study, the intake of only 28 food items was of interest and selected for statistical analysis because of their potential role as aggravating factor for AD or provoking food intolerance [18, 29]. After having filled in the FFQ, the study patients were interviewed for signs of intolerance against the 28 food items using a standardized questionnaire. They were asked food item by food item whether they experienced previously and/or also currently oral-allergy-syndromes, pruritus, urticaria/angioedema, aggravation of AD, gastrointestinal symptoms, respiratory symptoms and other symptoms.

We are used the following terms in the publication: other meat includes non-pork meat; other fruits includes all fruits except apples, pears, oranges and kiwis; other raw vegetable includes all raw vegetables except tomatoes, green or red peppers and garlic; other cooked vegetable includes all cooked vegetables except tomatoes, green or red peppers and garlic; other nuts includes all nuts except hazelnuts and peanuts.

The study was approved by the local Ethical Committee of Davos.

Statistical analysis

The study population was first described according to criteria relevant in this context. The symptoms were related to the specific food items and each participant was categorized as symptomatic or asymptomatic to this food item. The average amount of intake by food item and by symptomatic and asymptomatic patients was calculated and presented as median and 25 and 75 percentile. The Mann-Whitney U test was used to evaluate group differences for significance. P-values less then 0.05 were considered as statistical significant. SAS 6.12 was used for statistical analysis.

Results

The group of 116 patients consisted of 98 women and 28 men. They had a mean SCORAD-Index of 42 (± 18) and an average BMI of 24 kg/m² (± 4). Seventy-two per cent were non-smokers and 29% had a school education of 10 years or longer. The average age was 35 years (± 11). The youngest participant was 17 years old, the oldest 62.

A considerable number of patients (92%) reported symptoms provoked by at least one of the 28 food items. If categories of symptoms were individually considered, the following distributions were found: pruritus (80% of patients), oral-allergy symptoms (50%), aggravation of AD (48%), gastrointestinal symptoms (18%), respiratory symptoms (17%), articaria/angioedema (8%), and other symptoms (6%). Regarding individual food items the range went from 3% for other meat to 57% for oranges (Table I). More than 20% of the AD patients reported that they were symptomatic in relation to the following food items: oranges, other fruits, hazelnuts, apples, other nuts, alcoholic drinks, dairy products, tomatoes, fish, spices/herbs, kiwis, and peanuts.

Differences in specific food intake between symptomatic and asymptomatic patients are displayed in Table I. Median consumption of dairy products, fish, egg, and pork consumption of symptomatic patients was highly significantly decreased compared to asymptomatic patients. Median other meat consumption was also decreased in symptomatic patients, but the difference did not reach statistical significance. Also with respect to fruit consumption, symptomatic patients consumed highly significantly less oranges, other fruits, apples, kiwis, and pears than asymptomatic patients.

The only vegetable item being significantly different between symptomatic and asymptomatic patients was green or red pepper. Amounts of intake of garlic and tomatoes were lower in symptomatic subjects, without reaching statistical significance. There were almost no differences in celery, other raw vegetable and other cooked vegetable consumption between symptomatic and asymptomatic patients.

Peanut and hazelnut intakes were significantly lower in symptomatic patients, whereas the consumption of other nuts was somewhat lower but did not reach statistical significance. There was no difference in soy consumption between symptomatic and asymptomatic patients. Symptomatic patients ate less wheatbread, ryebread and cereals, however these differences were not statistically significant. Bakery product consumption of symptomatic patients was considerably and significantly less as compared to asymptomatic patients. There was no difference in intake of spices/herbs including camomile. Symptomatic patients consumed more coffee/tea and less alcoholic drinks; however, these differences reached no statistical significance.

Discussion

This study was designed to examine the prevalence of subjective food intolerance in AD and how this affects food consumption. The intake of 28 food items in AD patients with and without symptoms was studied. We found in symptomatic AD patients, as compared to asymptomatic patients, a significantly decreased intake for several of these food items. The studied food items covered most food groups except sugar, fats and oils.

The study was performed in a hospital specialized in treatment of AD patients, who have proven refractory against usual ambulatory therapy [30]. Despite the advantage of a standardized diagnosis, the source population was not identifiable. However, we are convinced that our patients are representative of many other patients suffering from AD and, at least, are comparable to the patients under clinical treatment or surveillance. This study represents a nearly complete series of patients over half a year.

The food-frequency questionnaire was tested for its validity and reliability. The strength of the FFQ-method is seen in the ranking of subjects. Scaling bias might have been present in this instrument, leading to food specific over- or underestimation. However, this type of bias does not affect the conclusions of this study because they are based on internal comparison between subgroups of the study population. The advantage of this method was clearly seen in its easy application, in particular in a clinical setting with and its previous validation.

A double-blind placebo controlled food challenge is recognized as the gold standard for the diagnosis of food intolerance. This was not required in our investigation aiming at the food avoidance-nutritional status relationship. This is important to remember because the rate of perception is about 4-5 times higher than the rate proven by a double-blind placebo controlled food challenge.

About 92% of our patients reported subjective food intolerance to at least one out of the 28 food items. This high percentage did not allow us to evaluate differences in nutrient intake between symptomatic vs. asymptomatic patients in general. We therefore discuss our results in respect of possible dietary deficiencies on the basis of the consumption of particular food groups.

We did not analyse specific-IgE or -IgG toward inhalant- or food-allergens, because the primary goal of the study was the description of possible nutrient deficiencies in patients with atopic dermatitis and less the immunological pathogenesis of the cases.

The study revealed that animal products like egg, dairy products, pork and fish were significantly less consumed in the symptomatic group. Of particular concern is the fact that 25% of all AD patients reported intolerance to fish and consumed virtually no fish. The consequence is a lower intake of n - 3 fatty acids (eicosapentanoeinc acid). According to different studies these substances may have a positive effect on AD [31-33]. The underlying mechanism may be a favorable modulation of the immune system by n - 3 fatty acid metabolites [34-36]. Hence, this particular group of patients may experience a negative effect by lack of n - 3 fatty acids and a supplementation may even be considered in this case. Furthermore, a sufficient supply of n - 3 fatty acids is considered to protect against cardiovascular disease [37-39].

Moreover, it should not be neglected that fish is a major source of iodine and vitamin D [40]. There exist several reports on patients with AD consuming restricted diets and experiencing iodine deficiency with goiter [23]. Therefore, care should be taken to prevent iodine deficiency by supplementation, e.g. with iodized salt and to prevent vitamin D deficiency by adequate exposure to sunlight/UV-B phototherapy or supplementation [21, 41].

Around one quarter of the patients had a dramatically low intake of milk and dairy products. These foods contribute around 60% of dietary calcium in western diets [40] and a higher risk of osteoporosis in a significant segment of patients can be deduced. This is in accordance with earlier reports, describing AD children consuming calcium deficient diets [21, 42] and even suffering from rickets [20].

Interestingly, meat did not range among the foods avoided to a major degree in our patients. This is in agreement with a former report describing nutrition behavior in children with AD [21]. It is hard to understand why so many of the symptomatic AD patients opted to avoid pork; there is no rational argument against pork - except for very rare cases of pork-specific allergy [43, 44] - to the best of our knowledge.

Between 16 and 58% of the symptomatic patients consumed significantly less of all fruit items than their asymptomatic counterparts. These fruit items are a major source of vitamin C in our diet [40]. Vitamin C is also a relevant source of antioxdidative potential [45] - particularly in the case of a chronic inflammatory disease [5]. It is noteworthy that one earlier study [21] did not find reduced ascorbate intake in atopic children, yet a case report observed ascorbate deficiency [20]. In order to diagnose and prevent specific nutrient deficiencies we are currently determining plasma levels of vitamins and minerals in another group of AD patients.

Interestingly, 17% of our symptomatic patients avoided green or red pepper. It is of note that a recent report described a higher intestinal permeability following consumption of this food [46]. This may be followed by an enhanced sensitization against oral allergens. This finding therefore raises the question whether AD patients experienced clinical improvement of their disease by avoiding green or red pepper.

CONCLUSION

From our data one can conclude that in symptomatic AD patients supplementation of the diet with specific nutrients may become mandatory. This is particularly pertinent for calcium, iodine, vitamin C and n - 3 fatty acids. It should kept in mind that consultations with dieticians are recommended for patients with AD and food intolerance.

Acknowledgements

The authors acknowledge gratefully the assistance with statistical analysis of W. Bernigau and helpful discussions with C.A. Barth from the German Institute of Human Nutrition.

Article accepted on 25/2/01

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