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One of the most frequently asked questions I receive usually goes something like this: "Dr. Antonio, what’s your opinion of different protein sources? Can I just eat rice and beans and get the same benefits as drinking milk?" Usually, with a subtle chuckle, I say that if all proteins were the same, we’d all be lean and have abs that would make Jennifer Garner envious. Then I put on my serious face and say something scientifically profound like "Well, of course not."  

Let me elaborate. On the following pages, I’ll give you a snapshot of several popular protein sources. From this, you can pick and choose which are best for you. For starters, though, I will say with firm conviction that vegetable sources of protein are generally inferior to animal sources. Plant proteins are low in certain amino acids and are poorly digested. However, soy protein is one exception. With that protein preamble, let’s get to the meat of the issue.

Fish

The world according to Dr. Antonio puts fish as the single best protein source. But it’s not just the fact that fish is a complete protein and has some amazing benefits, but the healthy fat in fish (eicosapentanoic acid and docosahexanoic acid) is something that you won’t find in our land-dwelling brethren.

• Features and benefits: Eating fish improves your insulin sensitivity. Some investigators believe it’s related to the amino acid arginine. One investigation showed that a diet containing 1 percent arginine (similar to that found in cod protein) produces a lower blood insulin response 30 to 45 minutes after an intravenous glucose tolerance test. Others have theorized that the high lysine content of fish may also confer benefits. Ultimately, the increased insulin sensitivity means that you need less insulin to transport glucose and amino acids into your cells. Less insulin may mean less fat deposition.
• How to use it: Fish (especially cold water fatty fish like salmon, tuna and mackerel) should be the primary food protein that you eat. It has a great amino acid profile and confers health benefits—related to both the protein itself and the omega-3 fatty acids—that you just can’t find in other proteins.

Whey

Whey protein is the second most abundant protein derived from milk (casein is the most abundant milk protein). It’s found mainly in meal-replacement powders, protein powders and ready-to-drinks (RTDs).

• Features and benefits: Whey contains all of the essential amino acids and is particularly high in the branched-chain amino acids (leucine, isoleucine and valine) and glutamine (an immune-boosting amino acid). Whey is considered a "fast-acting" protein. If you consume a 30-gram serving of whey on an empty stomach, levels of blood amino acids peak about one hour afterward and return to pre-meal levels by three to four hours. This absorption profile makes whey a very anabolic protein. In fact, a whey protein meal produces a 68 percent increase in protein synthesis; however, it doesn’t blunt protein breakdown. (Casein protein does—more on that later.)
• How to use it: According to exercise physiologist John Berardi, Ph.D., founder of Science Link, "it’s best to consume a fast-acting protein like whey immediately after an intense workout." In fact, combining whey protein with a high-glycemic carbohydrate (e.g., maltodextrin) may be the ideal post-workout meal.

Casein

Casein is the main protein in milk. Besides drinking milk, you can obtain casein in various meal-replacement powders, protein powders and RTDs. Casein forms a curd in your stomach, which slows its digestion, making its absorption a bit slower than whey, hence, it’s designated a "slow-acting" protein.

• Features and benefits: Casein has a strong anti-catabolic effect. You might describe casein as the "opposite" of whey. They’re both great proteins but they act quite differently from one another. Casein has a lower anabolic effect (31 percent versus 68 percent) when compared to whey. However, casein has a very profound anti-catabolic effect, meaning that this protein inhibits protein breakdown. This has profound implications for the proper use of casein.
• How to use it: Because casein is digested slowly, it produces a slow but steady rise in amino acids. Blood levels peak about one to two hours after consuming casein and remains elevated for up to seven hours. According to sports nutritionist Jeffrey Stout, Ph.D., author of Supplements for Strength-Power Athletes, "casein is a great protein to take before going to bed. Because it’s absorbed slowly, you’ll get a nice stream of amino acids into your body. This will of course help you recover."

Soy

Soy is the best non-animal source of protein and is often accused of being inferior to animal-source protein because it can be limiting in the amino acid methionine. However, methionine supplementation in an adult’s diet is usually not necessary because at levels normally consumed, soy protein provides sufficient methionine. Though soy is not a normal staple in Americans’ diets, you can find various soy products (e.g., soy milk, soy-based protein powders) on your grocer’s shelves.

• Features and benefits: It’s been shown that soy protein is comparable in digestibility to other high-quality protein sources such as meat, milk, fish and egg. According to Darryn Willoughby, Ph.D., an associate professor of exercise physiology at Texas Christian University, "soy protein’s powerful antioxidant capabilities provide significant health and anti-cancer benefits. This is probably due to the presence of isoflavones, saponins, phytic acid and protease inhibitors." In fact, a recent study found that a soy-based meal-replacement formula was "effective at lowering body weight, fat mass and reducing LDL cholesterol."
• How to use it: Soy is best used as a part of a meal-replacement powder. Alternatively, soy products (e.g., soy milk, tofu, miso soup) are wonderful foods as well.

Milk

Milk isn’t just for kids. There is an assortment of bioactive peptides that have been identified in milk which may improve your overall health, as well as provide the amino acids needed for active individuals.

• Features and benefits: Milk contains all of the essential amino acids. Undenatured cow’s milk contains 74 percent casein protein, 18 percent whey protein, 3 percent glycomacropeptide, 3 percent proteose peptone and 2 percent miscellaneous proteins. And you thought it was only good for dunking chocolate chip cookies! According to the Journal of Dairy Science, "bioactive peptides [in milk] may function as health care products, providing therapeutic value for either treatment of infection or prevention of disease." Keep in mind that if you’re trying to get lean, stay away from whole milk and stick to skim.
• How to use it: Milk and apple pie, is there a better combination? Actually, skim milk is an excellent food source that’s perfect as an evening protein supplement. Because the majority of the protein in milk is casein (a "slow" protein), you’ll get a slow and sustained elevation of amino acids throughout the night while you sleep. This will ensure that your body has the amino acids it needs to facilitate muscle recovery.

Beef

There’s nothing better than throwing a big fat steak on the grill and smelling the mouthwatering aroma as it cooks. However, the fat content between different kinds of beef can be quite variable.

• Ground beef: 70 percent lean, 30 percent fat
• Ground chuck: 80 percent lean, 20 percent fat
• Ground round: 85 percent lean, 15 percent fat
• Ground sirloin: 90 percent lean, 10 percent fat

An easy way to remember which beef source has the least fat content is to remember that those at the beginning of the alphabet (ground Beef) have the most fat and those near the end of the alphabet (ground Sirloin) have the least.

• Features and benefits: Beef contains all of the essential amino acids. Moreover, beef is an excellent protein source and is loaded with zinc and iron as well. Remember the acronym ZIP (for zinc, iron, protein). Also, beef isn’t as bad as its reputation. For example, a study published in Nutrition found that two groups of overweight women who exercised and consumed a restricted-calorie diet with either lean beef or chicken as the main protein source both demonstrated similar weight loss as well decreases in body fat percentage, total cholesterol and LDL cholesterol. The key is that you need to consume lean beef!
  
   
• How to use it: Beef can be eaten as part of your regular diet (perhaps once or twice per week).

Chicken

Chicken is a great protein source and is perhaps the single most consumed dietary protein. Like beef, the fat content of chicken can vary dramatically especially if you eat the skin. For instance, a 100-gram serving of light meat chicken with skin contains 222 calories and 10.85 grams of fat compared to 173 calories and 4.51 grams of fat if you remove the skin. That’s 141 percent more fat (with skin)!

• Features and benefits: Chicken contains all of the essential amino acids. Because of its complete amino acid profile, it’s a favorite amongst fitness enthusiasts. I’d recommend that you eliminate the skin from chicken (unless you’re tring to gain weight). Similar to lean beef, chicken consumption as part of a well-rounded diet can help decrease total cholesterol and LDL cholesterol.
• How to use it: Chicken is a favorite amongst athletes. It’s best you consume chicken as part of your regular meals.

Eggs

Which came first, the chicken or the egg? The egg, of course! Remember in your biology class that egg-producing animals (i.e., dinosaurs) existed long before chickens cock-a-doodled on this earth. And it wasn’t too long ago when eggs (and perhaps milk) were the favorite protein source of athletes. For a while there, eggs got a bad (an undeserved) rap for having too much fat. Well, eggs are a great source of protein and the yolk is chock-full of vitamins and minerals. Some consider the amino acid profile of eggs to be the best of all food sources. Think about it, you’re basically eating an entire animal. I know that’s not a pretty analogy, but you get the point!

• Features and benefits: Eggs are a rich source of thiamine, riboflavin, pantothenic acid, folic acids, vitamin B12, biotin, vitamin D, vitamin E and phosphorus. Seems like a complete food, right? Not only is egg protein great, but it’s very affordable. According to Chris Mohr, R.D., a doctoral student at the University of Pittsburgh, "Where else can you get 80+ grams of protein—the content of about a dozen eggs—for under a dollar?"
• How to use it: Egg white omelets (three to five egg whites with one whole egg) are an excellent food.