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One egg packs 6 grams of protein into only 70 calories. But don't toss out the yolk. Nearly half an egg's protein, as well as iron, vitamin A, and phytonutrients lutein and zeaxanthin, are in the yolk. Studies show that eating eggs doesn't adversely affect bad LDL cholesterol levels, while eating some cholesterol is necessary for healthy testosterone production. 

Choose organic, free-range eggs for fewer pesticides and more omega-3 fatty acids than eggs from caged birds. Protein power: Excellent.