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Back to Health Concerns

Understanding the Relationship Between Milk Products and Asthma

Although the belief that drinking milk exacerbates asthma symptoms can be traced back to ancient traditional Chinese medicine, scientific evidence to date fails to support this hypothesis. Furthermore, emerging data shows that milk products, especially regular-fat milk products, may have a protective role against asthma.

Highlights

  • The intake of regular-fat milk products could offer a protective effect against asthma and asthma symptoms;
  • Maternal consumption of regular-fat yogurt appears to have a protective effect for children;
  • Consumption of whole milk and butter appears to result in decreased risk of asthma in children and adults;
  • Vitamin D deficiency may be associated with a greater asthma disease burden.

Introduction

Milk products have a long history of association with asthma, and it is not uncommon for people, and sometimes even health professionals, to believe that it is necessary to avoid dairy products in the case of asthma. However, emerging data from the current literature shows that milk products, especially regular-fat milk products, may play a protective role against asthma. The components in milk products that may be beneficial include fat and vitamin D.

The Evidence

A 2012 prospective cohort study of 61,909 pregnant women (at approximately the 25th week of gestation) examined the relationship between dairy intake (whole milk, semi-skimmed milk, total milk, full-fat yogurt, low-fat yogurt and total dairy) and childhood asthma at the age of 18 months and 7 years:1

  • After adjusting for maternal age, smoking, breastfeeding, parity, physical activity, total energy intake as well as other relevant factors, maternal consumption of regular-fat yogurt at any intake appeared to have a protective effect against infant asthma;
  • Whole milk (> 5 glasses/day) was associated with a 15% decrease in the risk of asthma at 18 months, but an increased risk of 24% was observed for ever asthma (identified using the International Classification of Diseases criteria) before the age of 7;
  • Consumption of semi-skimmed milk and low-fat yogurt increased the risk of asthma at 18 months by 6% to 8% for intakes > 1 serving/day versus no intake of these foods (in a dose-respondent manner, for semi-skimmed milk). While a 26% increase in the risk of ever asthma was observed for the same consumption of low-fat yogurt, the results were no longer significant for semi-skimmed milk;
  • No association was found for total dairy product and milk intakes.

In two studies published in 2012 and 2011 respectively,2,3 which used data from the 1996 Type 1 Diabetes Prediction and Prevention (DIPP) Nutrition Study—a population-based cohort study—, infants with a high to moderate genetic risk for type 1 diabetes were assessed for asthma incidence at age 5 in relation to maternal dietary intakes during pregnancy (2,680 mother-child pairs) and lactation (1,798 mother-child pairs):2,3

  • Maternal consumption of milk, butter and milk products during pregnancy and lactation was not related to asthma incidence at age 5;
  • After adjustments for several factors such as sex, duration of gestation, maternal age and maternal asthma or allergic rhinitis, maternal margarine consumption during lactation was shown to increase the risk of asthma by 96%;2
  • Low maternal intakes of alpha-linoleic acid and total n-3 polyunsaturated fats during pregnancy were shown to increase the risk of asthma at age 5 by 66% to 70%, while a higher intake of saturated fat and palmitic acid was found to have a protective effect against asthma (45% to 50% decreased risk);3
  • Lower arachidonic acid intakes during pregnancy had a protective effect against asthma incidence in offspring.3

A 2007 nested case-control study, comprised of 723 children between 8 and 10 years, 246 of whom were diagnosed with asthma, found that infrequent milk consumption (< 2 times/week) doubles the risk of asthma in girls only. While overweight status alone increases the risk of asthma by 39%, the combination of infrequent milk consumption and overweight results in a 3.6-fold increase in the risk of asthma.4

Data from 2978 children participating in a 2003 PIAMA birth cohort study revealed the following:5

  • Daily consumption of regular-fat milk at the age of 2 resulted in a 46% to 47% reduction in the risk of ever asthma and recent asthma at the age of 3 when compared to consumption of less than once a week;
  • A 75% lower risk of recent asthma was observed with daily butter consumption;
  • No association could be established for daily milk product intake.

Data from a large U.S. national study (NHANES III) showed that vitamin D deficiency (< 10-30 ng/mL serum vitamin D) is associated with a greater burden of asthma, in that people with respiratory tract diseases and low vitamin D levels may have higher odds of respiratory tract infections (48% higher in the winter, when dairy is the main source of vitamin D, compared to spring).6

Potential Mechanisms

Milk fat appears to be protective against asthma, although the exact mechanisms remain to be elucidated. The components of milk that could play a role are different fatty acids as well as antioxidants or other micronutrients.

Conclusions

Emerging scientific evidence indicates that the consumption of regular-fat milk products may reduce the risk of asthma, but further research is needed to provide more definitive answers, particularly regarding the role of specific milk products and low-fat milk products.

More studies are also needed to clarify how vitamin D may decrease the risk of respiratory tract infections in people with asthma.

Keywords: butter , dairy , asthma , respiratory tract infection , milk , vitamin D


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