Pasture feeding of hens has been shown to significantly increase the vitamin E content of their eggs. In a recent study comparing caged hens to hens foraging on grasses and legumes, vitamin E in the yolk of eggs from hens who foraged on pasture was about 200% higher than vitamin E, in the yolk of eggs from caged hens. Hens that foraged more on grasses than legumes developed about 25% more vitamin E in their eggs. Hens, of course, are omnivores and eat a wide variety of foods, including grasses, legumes, seeds, worms, grubs (insect larvae), and adult insects.
As a group, research studies on the health benefits of eggs have shown mixed results. Part of the difficulty that researchers encounter when trying to determine the pros and cons of egg intake is the tendency of participants to consume other foods high in fat and/or saturated fat along with eggs. For example, at breakfast meals in the U.S., eggs are often consumed together with bacon, sausage, or ham. This simultaneous consumption of eggs with other foods can make it difficult for researchers to separate out the specific influence of the eggs. In addition, from a calorie standpoint, two eggs typically provide only 150-175 calories—only 7-8% of a 2,000-calorie diet. This small amount can make it more difficult for researchers to pinpoint the role played by the eggs.
Another complicating factor in egg research is the fiber-free nature of eggs. Since fiber typically has a risk-lowering affect for cardiovascular disease, diabetes, and cancer, egg intake might show up as problematic in a diet that was otherwise very low in fiber, yet helpful in a diet that was otherwise rich in fiber.
We include eggs as one of our WHFoods because of the broad nourishment they provide, their unique combination of nutrients (including omega-3s, antioxidant minerals like selenium, and high biological value protein), and their low calorie cost. Eggs are a nutrient rich, natural, whole food. At the same time, research on eggs has not always shown them to provide health benefits, and in some situations (for example, individuals with type 2 diabetes who are trying to lower their risk of cardiovascular problems) eggs may not be appropriate as part of a routine meal plan. So even though eggs are a natural, nutrient rich whole food, we do not consider them mandatory in any meal plan.
If you do decide to consider the addition of eggs to your meal plan, we encourage you to take a close look at your overall diet. Could it use more protein? If so, eggs might make sense. Does it already have plenty of fiber? If not, it might make more sense to add a fiber-containing food rather than eggs. We're confident that in many diets, pasture-raised eggs can provide key nutrient benefits and lower your disease risk, despite some of the confusion that we've come across in the food science research.