|MadSci Network: Agricultural Sciences|
Aloha, Michelle, Regarding your question about white/brown eggs. Chickens characteristically lay either white OR brown eggs (or even some other color, like green). This is pretty much due to the genetics of the breed of chicken, although I imagine that diet can have a minor effect on the color of the shell. So white chickens generally lay white eggs, whether they are on the farm or in mass-production facilities. Brown chickens (like Rhode Island Reds) lay brown-shelled eggs...these may be what you think of as 'farm chickens.' As to the cholesterol content of the egg, I guess the best way to state the answer is that a chicken egg is a chicken egg is a chicken egg. The cholesterol is found in the yolk; cholesterol is a fat-like compound that they human body can make easily, so there is no official recommendation for a minimum intake in your diet. The average egg yolk contains about 220 mg; there is never any differentiation in nutrient tables as to white vs. brown eggs...or any other color shell, for that matter. The difference that you might have noticed in the color of the egg yolk is due to other compounds, not to cholesterol; and, the color is partially due to the diet that the chicken has been eating. Vitamin A-like compounds (carotenes) may impart more yellow to the yolk. These compounds are found throughout the plant kingdom...and chickens, especially free-range/farm chickens would have more access to these plants (like dandelions?). Egg producers sometimes add these compounds to the food formulated and fed to 'factory chickens' to make the yolks more yellow, too. Some nutritionists seem to think that cholesterol in food is a problem, so you will see some recommendations to keep the cholesterol level in your diet to about 300 mg/day (about the amount 1.5 egg yolks...a yolk contains about 220 mg). However, since your body makes the stuff, limiting or restricting cholesterol in your diet (eggs, butter, meats) will only upregulate your body's production to some genetically preset level, for most people. The cholesterol level that doctors measure when you have a cholesterol screening done is the cholesterol in lipoproteins, which are in your blood. This has little relationship to the cholesterol that you have eaten. Actually, this cholesterol (in lipoproteins) is more affected by quantity and quality of fat in your diet, your level of exercise, genetics, and a few other factors...not so much by dietary cholesterol. This is an unfortunate and pervasive bit of misinformation that I'd like to see cleared up for the public. One last bit of egg-trivia: a duck egg, which is somewhat bigger than a chicken egg (70 g, as compared to 50 g) has 620 mg cholesterol/yolk; a goose egg (144 g) has 1227 mg cholesterol/yolk !!...and a quail egg (9 g) has 76 mg cholesterol/yolk. So can you figure out which of the four has the most cholesterol/g egg? Enjoy!
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