Are whole eggs a better choice than egg whites? A new study at the University of Illinois in Champaign finds the choice of whole eggs over egg whites makes a big difference in how well muscles recover after a workout.
Results of the study were reported in the American Journal of Clinical Nutrition.
So that widespread practice of throwing away egg yolks to maximize dietary protein may be counterproductive, according to lead researcher Nicholas Burd, a U of I professor of kinesiology and community health.
The study found people who consume 18 grams of protein from whole eggs or egg whites after engaging in resistance exercise differed dramatically in how their muscles build protein, a process called protein synthesis, during the post-workout period. Specifically, the post-workout muscle-building response in those eating whole eggs was 40 percent greater than those consuming an equivalent amount of protein from egg whites.
The yolks contain protein, along with key nutrients and other food components that are not in egg whites. Burd believes there is something in the yolks that boosts the body's ability to utilize protein in muscles.
"This study suggests that eating protein within its most natural food matrix tends to be more beneficial to our muscles as opposed to getting one's protein from isolated protein sources," said Burd.
In the study, 10 young men engaged in a single bout of resistance exercise and then ate either whole eggs or egg whites containing 18 grams of protein. Researchers administered infusions of leucine and phenylalanine (two important amino acids) to participants, which allowed the scientists to maintain and measure amino acid levels in participants' blood and muscles.
As part of the research project, the U of I poultry research farm developed eggs for the study that were isotopically labeled with leucine, allowing for precise tracking of where the food-derived amino acids ended up after participants ingested them. The team then took repeated blood and muscle biopsy samples to assess how the egg-derived amino acids were appearing in the blood and in protein synthesis in muscles before and after resistance exercise and eating.
With both whole eggs and the whites, about 60 to 70 percent of dietary amino acids were available in the blood to build new muscle protein. However, when researchers directly measure protein synthesis in the muscle, they found a different response — the whole eggs resulted in greater muscle-protein synthesis than the egg whites.
So, go ahead, hard boil or scramble that egg after your next workout. You may just see your muscles recover faster.
Q and A
Q: How do heating and freezing affect antioxidant levels in food?
A: Antioxidants are sensitive to heat and freezing seems to preserve antioxidant activity. However, different antioxidants are heat sensitive at different temperatures. For example, in tomatoes, 30 minutes of heating at 190 degrees causes a loss of 29 percent of vitamin C, but total antioxidant activity increases by 62 percent. The decline in antioxidant activity for vitamin C is offset by an increase in antioxidant activity of phytochemicals such as lycopene. Actually, antioxidant loss varies much more by cooking and preparation methods. Boiling generally decreases antioxidant levels of vegetable as the antioxidants leach into the water from the plant tissue during cooking. Stick with steaming or microwaving to retain more nutrients. — Tufts University Health & Nutrition Letter.
RECIPE
Sheet pan cooking seems to be all the rage at the moment. It's quick, easy on cleanup and brings out a wonderful roasted flavor. Here's a recipe for Sheet Pan Flank Steak with Salsa Verde from Cooking Light magazine.
Sheet Pan Flank Steak with Salsa Verde
1 (1 pound) flank steak, trimmed
1 teaspoon salt, divided
3/4 teaspoon black pepper, divided
6 tablespoons extra-virgin olive oil, divided
1 pound broccoli heads, cut into florets with stem attached
1 medium red onion, cut into wedges
1/4 cup chopped fresh flat-leaf parsley
3 tablespoons red wine vinegar
1 1/2 tablespoons chopped fresh oregano
1 tablespoons capers, chopped
1/4 teaspoon crushed red pepper
Preheat broiler with oven rack in top position. Place a rimmed baking sheet in oven. Sprinkle steak with 1/2 teaspoon salt and 1/2 teaspoon black pepper. Carefully remove pan form oven; add 1 tablespoon oil to pan, tilting pan to coat. Add steak ot pan; broil 5 minutes. Remove pan from oven, turn steak over. Add 1 tablespoon oil to pan around steak. Arrange broccoli and onion evenly around steak; sprinkle vegetables with 1/4 teaspoon salt and remaining 1/4 teaspoon pepper. Return pan to oven; broil until steak reaches 140 degrees, about 5 minutes. Place steak on a cutting board. Continue to broil vegetables until tender and lightly charred, about 5 minutes. Whisk together remaining 1/4 teaspoon salt, 1/4 cup oil, parsley, vinegar, oregano, capers and red pepper in a bowl. Cut steak against the grain into thin slices. Spoon parsley mixture evenly over steak. Serve with vegetable mixture. Serves 5; serving size: 3 ounces steak and 1 1/2 cups vegetables.
Per serving: 406 calories, 28 g protein, 11 g carbohydrate, 3 g sugars, 27 g fat, 4 g fiber, 635 mg sodium.
Charlyn Fargo is a registered dietitian at Hy-Vee in Springfield, Ill., and the media representative for the Illinois Academy of Nutrition and Dietetics. For comments or questions, contact her at charfarg@aol.com or follow her on Twitter @Nutrition Rd. To find out more about Charlyn Fargo and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.
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