Preserve us from junk science
The results of nutrient analyses were simply compared with tabular standard values published by the USDA to substantiate claims of inherent nutritional superiority.
An article in the October/November edition of Mother Earth News claims that eggs derived from pasture-fed hens are more nutritious than eggs produced by hens maintained for commercial table egg production. The article bases the assertion of superiority on a spurious comparison. The average values of Vitamins A and E, Beta carotene, Omega-3 fatty acids, cholesterol and saturated fat were determined for samples of six eggs derived from 14 farms maintaining “free range” pasture-fed flocks.
The approach used by Mother Earth News is scientifically flawed since it is inappropriate to compare analytical results obtained from a specific laboratory with an arbitrary set of tabular values. There are obvious problems relating to the acquisition of samples from the subject farms. The hens were assumed to be brown-feathered strains obviously receiving supplementary feed over and above “bugs and grass.” This predicates a lack of homogeneity among farms. Individual values reported on the pools of six eggs display considerable variation despite the application of an arithmetic mean (average) value as the basis of comparison with the standard USDA values based on confined Leghorn hybrid hens.
For example, the article accepts the cholesterol content for “free-range” eggs to be 277 mg/100g egg. The range of values as presented in the article extends from 201 mg to 350 mg/100g. This presumes considerable differences in either nutrition of the hens among the farms comprising the comparison or in the analytical procedure applied. The article quotes a USDA cholesterol value of “423 mg/100g for confined birds.”
This is blatantly incorrect. The tabular values for cholesterol content as posted by the USDA Egg Nutrition Center and the American Egg Board are 212 mg and 213 mg respectively for a Large -grade egg. These values correspond to a theoretical content of 280 mg/100g egg which is considerably lower than the inflated and spurious value cited for the Mother Earth News comparison, invalidating their claim of “1/3 less cholesterol.” Recent refinements to the technique to extract cholesterol from yolk now yield actual values of approximately 185 mg for Large-grade eggs. In fact the cholesterol content of eggs is fixed when feeding conventional dietary ingredients. Reduction of cholesterol content is not possible without resorting to supplementing diets with drugs or additives which interfere with cholesterol synthesis. These compounds which are disallowed by the FDA as additives may reduce egg cholesterol for short periods but invariably result in marked reduction or cessation in egg production.
“Mother Earth” claims elevated values for Vitamins E and A for eggs derived from pastured hens compared to the tabular values for commercial product. Although these differences may be valid and ascribed to consumption of fresh vegetation, simple supplementation of commercial diets with these vitamins will increase the nutrient content of eggs derived from confined hens. Branded specialty eggs enriched with Vitamins A and E, folic acid, lutein and xanthophyll are available from both caged and non-confined commercial flocks. Specialty eggs are produced with nutrient levels of 1.3g saturated fat and omega-3 fatty acid content ranging from 100 mg to 600 mg/egg.Adherents to the “Birkenstock Lifestyle” are welcome to their dietary preferences and freedom to pay accordingly. Their supporters and guides should, however, refrain from practicing voodoo science to promote their prejudices against the commercial production of nutritious and safe food products supplied by the poultry industry.