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Asthma and allergies are on the
rise in all industrialized nations. In the last decade, there has
been considerable interest in Europe about the relationship between
farm children and the lower incidence of allergies and asthma they
experience. Most researchers were working on the hypothesis that
farm children are exposed to more irritants at a young age and are
thus protected from asthma and allergies. However, by use of food
surveys and clinical tests, they found that farm milk (which is
usually whole unpasteurized milk), consumed early in the child's
life, provided substantial protection against asthma and allergies.
A cross-sectional survey conducted in rural areas of Austria, Germany,
and Switzerland, involving 2618 families with children ranging from
six to 13 years of age, found correlations that suggested substantial
protection against development of asthma, hay fever, and allergic
sensitization in children exposed to stables, farm milk, or both
in their first years of life.1 Researchers hypothesized that farm
milk, which is usually raw, contains more gram-negative bacteria.
Thus, the protective factor associated with consumption of farm
milk could be the ingestion of non-infectious microbial components,
with resultant changes to the gut flora.
Unpasteurized milk was associated with the protective effect on
skin prick test positivity in a Study of Asthma and Allergy in Shropshire,
UK.2 Eight hundred and seventy-nine children participated in the
skin prick test, and unpasteurized milk consumption was associated
with a significant 70% reduction in prevalence of skin prick sensitivity.
No other food included in the survey showed the consistent relationship
with reduced sensitivity of unpasteurized milk.
In view of the European studies of lower incidence of asthma and
allergies in farm children, another study was conducted in New Zealand.3
Two hundred and ninety-three rural children (ranging from seven
to ten years of age) were involved in the study. Skin prick tests
of eight common allergens were given, and parents completed questionnaires
about allergic and infectious diseases, place of residence, and
diet. Unlike in European studies, children in this study who lived
on farms had more hay fever, allergy rhinitis, asthma, and wheeze,
but the researchers still found that consumption of yogurt and/or
unpasteurized milk in the first years of life decreased the prevalence
of hay fever and allergic rhinitis at seven to ten years of age.
The authors hypothesize that this may be due to bacteria found in
yogurt and unpasteurized milk, which could stimulate the Th1 immune
response. Another hypothesis was that the unpasteurized milk had
a high fat content that may have provided protection from asthma,
hay fever, eczema, and allergic rhinitis.4 The authors concluded
that the consumption of whole milk, but not skimmed, was associated
with a decreased prevalence of asthma and allergies.
A large, cross-sectional multi-center study involving 14,893 children,
ranging from five to 13 years of age from five European countries,
showed that consumption of farm milk was associated with a statistically
significant inverse association with asthma, rhino conjunctivitis,
sensitization to pollen, food allergens, and horse dander.5 This
association was independent of any other farm-related exposures,
and no other farm-produced products were associated with a lower
prevalence of asthma and allergies.
There are several hypotheses that may account for the protective
effect of whole, unpasteurized farm milk. One hypothesis is that
the beneficial bacteria in the unpasteurized milk support the gut
flora and gut immune system and stimulate the Th1 immune response.
Another hypothesis is that raw milk is whole milk and thus provides
children the necessary fats for proper lung development and function.
Lung surfactants, the specialized phospholipids in the cell membranes
of the lungs, are 100% saturated fatty acids. Fresh farm milk differs
from milk that is commercially available because it has not been
separated and reconstituted at the milk factory to meet the industry
standard of 3.5% butterfat. The butterfat content in farm milk naturally
varies between breeds and diet. A third hypothesis involves the
nutritional superiority of grass-fed dairy products, the basis of
agriculture in most of the rural areas in these European studies.
A cow's diet is one of the largest influences on the content
and composition of the milk fat and the fat-soluble micronutrient
components of the dairy products. Grass-fed dairy products are higher
in vitamin E,6 omega 3 fatty acids,7 and the natural trans fat conjugated
linoleic acid.8 Dairy products rich in conjugated linoleic acid
have been associated with a lower risk of heart disease, obesity,
diabetes, and cancer.9
Sanitary conditions and animal health are a large concern when consuming
unpasteurized dairy products. Well-managed dairy farms with grass-fed
cattle provide a more nutrient-dense product and have significantly
lower bacteria counts and environmental pathogens, offering a safe
option for unpasteurized milk consumption.10 Also, stainless steel
equipment and closed loop milking systems are common dairy management
practices that offer protective measures from exposure to harmful
bacteria and pathogens. Today, certified raw milk sold legally in
Connecticut and California cannot exceed 10,000 bacteria per ml.
Pasteurized milk can contain 50,000 per ml before pasteurization
and 15,000 per ml after pasteurization.11
There is strong evidence that whole, unpasteurized dairy products
support healthy gut flora, the immune system, and proper lung development
that provide young children protection from asthma and allergies.
The health care community should provide support to grass-based
dairy farms by educating their patients about nutritionally dense,
raw, grass-based milk products. This endorsement could help revitalize
our rural communities and provide a solid preventative measure towards
childhood asthma and allergies.
Notes
1. Riedler J, Braun-Fahrlander C, Eder W, Schreuer M, Waser M, Maisch
S, Carr D, Schierl R, Nowak D, von Mutis E, ALEX Study Team. Exposure
to farming in early life and development of asthma and allergy:
a cross –sectional survey. The Lancet.
358; Oct. 2001: 1129-1133.
2. Perkin MR, Strachan DP. Which aspects of the farming lifestyle
explain the inverse association with childhood allergy? Journal
of Allergy and Clinical Immunology. 2006;117:1374-81.
3. Wickens K, Lane JM, Fitzharris P, Siebers R, Riley G, Douwes
J, Smith T, Crane J. Farm residence and exposures and the risk of
allergic diseases in New Zealand children. Allergy.
2002:57;1171-1179.
4. Von Ernestine OS, von Mutis E, Illi S, Baumann L, Bohm O, von
Kries R. Reduced risk of hay fever and asthma and allergic sensitization.
Allergy. 2000;30:187-193.
5. Waser M, Michels KB, Bieli C, Pershagen G, von Mutis E, Ege M,
Riedler J, Schram-Bijkerk D, Brunekreef B, van Hage M, Lauener R,
Braun-Fahrlander C and PARISFAL Study Team. Inverse association
of farm milk consumption with asthma and allergy in rural and suburban
populations across Europe. Clinical and
Experimental Allergy.2007 May; 37(5): 661-70.
6. Kay JK, Roche JR, Kolver ES, Thomson NA, Baumgard LH. A comparison
between feeding systems (pasture and TMR) and the effect of vitamin
E supplementation on plasma and milk fatty acid profiles in dairy
cows. Journal of Dairy Research.2005
Aug; 72 (3):322-32.
7. Hauswirth CB, Scheeder M, Beer JH. High n-3 fatty acid content
in alpine cheese, the basis for an alpine paradox. Circulation.2004;
109:103-107.
8. Dhiman TR, Anand GR, Satter LD, Pariza MW. Conjugated linoleic
acid content of milk from cows fed different diets. Journal
of Dairy Science 1999 Oct; 82 (10): 2146-56.
9. Belury M. Dietary conjugated linoleic acid in health: physiological
effects and mechanisms of action. Annual
Review of Nutrition. 2002 (22): 505-31.
10. Goldberg JJ, Wildman EE, Pankey JW, Kunkel JR, Howard DB, Murphy
BM. The influence of intensively managed rotational grazing, traditional
continuous grazing and confinement housing on bulk tank milk quality
and udder health. Journal of Dairy Science.
1992;75: 96-104.
11. A Campaign for Real Milk. Which do you choose? Available at:
http://www.realmilk.com/whichchoose.html.
Accessed March 12, 2008.
Martha Pickard, MS, Human Nutrition
Ag/Grazing Program Coordinator
Adirondack North Country Association
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