The article opens with - "Protein is a critical part of a healthy diet and the right amount helps with everything from higher energy to stronger muscles. The trick is knowing the healthiest sources of protein and the right amounts for your body."
So far, so good.
To lend credibility the article offers advice from Elisa Zied, a Registered Dietian and spokesperson for the American Dietetics Association. She correctly includes the reasons why we need protein in our diet, "protein provides the building blocks for our bones, muscles, skin, cartilage, and blood, and helps us make enzymes and hormones that keep our bodies functioning. Protein is the most filling or satiating of all the nutrients and can therefore potentially help us curb our calorie intake and help us achieve or maintain a healthier body weight. Protein can also boost energy by stabilizing our blood sugar levels throughout the day."
Zied's advice is good until she points to which sources of protein provide the best nutritional bang: Zied recommends about five and a half one-ounce equivalents of meat and beans each day in a 2,000 calorie diet. The following equals a 1-ounce equivalent of meat/beans:
- 1 ounce of fish, poultry, or beef
- 1/4 cup beans
- 1 tablespoon of peanut butter or 1/2 ounce (2 tablespoons) nuts
- 1 egg
Three cups of beans per week is the recommended amount, and a great option for vegetarians. "These are great sources that give iron, zinc and healthy fiber which can fill you up as well," said Zied, and also supply folate and antioxidants. She points out, though, that they are very filling and high in calories, so a portion is 1/4 cup.
The quality of protein is measured by its amino acid content. Foods rich with the full spectrum of "essential amino acids" are better than those which have one or more "limiting amino acids" - that is they lack a high enough level of one or more amino acids and therefore require one to eat more or eat another food limited in an amino acid to make up the shortfall. Foods that provide good levels of all the essential amino acids are considered "complete proteins," whereas foods that have a limiting amino acid are considered "incomplete proteins."
Foods are rated according to the Protein Digestibility Corrected Amino Acid Score (PDCAAS). This is a method of evaluating the protein quality based on the amino acid requirements of humans. A PDCAAS value of 1 is the highest, and 0 the lowest. Some ratings of commons foods include eggs (1.0), casein (1.0), milk (1.0), whey (1.0), beef (0.92), kidney beans (0.68), lentils (0.52), peanuts (0.52), wheat (0.25).
So, what's wrong with her list of foods?
The one-ounce equivalents aren't the same for quality protein content. In fact, they're not even close due to the limiting amino acids in the beans, peanut butter and nuts, and also the fact that these items provide less protein per ounce than the eggs, fish, poultry or beef.
Since the article is highlighting the importance of protein, let's take a look at some important differences in each food above and dispel some of the myths put forth.
1. "[P]rotein provides the building blocks for our bones, muscles, skin, cartilage, and blood, and helps us make enzymes and hormones that keep our bodies functioning."
This is the critical reason we need quality protein in our diet each day. When you choose foods with complete proteins, you have a better chance of meeting your requirements for essential amino acids - and you'll consume less calories in the process too - than if you choose foods with limiting amino acids.Just how different is the amino acid profile between two foods?
Take a look at the difference between the egg and a tablespoon of peanut butter:
- Calories: 74/94
- Phenylalanine 0.339g/0.209g
- Valine 0.428g/0.169g
- Tryptophan 0.277g/0.138g
- Isoleucine 0.335g/0.142g
- Methionine 0.190g/0.049g
- Histidine 0.154g/0.102g
- Arginine 0.409g/0.483g
- Lysine 0.455g/0.145g
- Leucine 0.541g/0.262g
Not only does the peanut butter cost you 20-calories more, it's "limited" because of the low level of methionine, and except for arginine, provides much less of every other animo acid considered "essential" - that is, required by humans. In fact, you'd have to eat almost 4-tablespoons of peanut butter, costing you 364-calories, to overcome the limiting amino acid in peanut butter.
2. "These are great sources that give iron, zinc and healthy fiber which can fill you up as well," said Zied, and also supply folate and antioxidants. She points out, though, that they are very filling and high in calories, so a portion is 1/4 cup.
The above statement is a bit misleading, and might lead one to think that eggs, beef, poultry or fish do not contain similar nutrients. This time, let's look at the eggs nutrients and 1/4 cup of pink beans:
- Calories: 63/74
- Calcium: 22mg/26mg
- Iron: 0.97mg/0.92mg
- Zinc: 0.41mg/0.55mg
- Phosphorus 70mg/95mg
- Selenium 0.6mg/15.8mg
- Riboflavin 0.02mg/0.24mg
- Vitamin B-6 0.07mg/0.07mg
- Folate 71mg/24mg
- Vitamin E 0.43mg/0.48mg
- Vitamin B-12 0.00/0.64mg
- Vitamin A 0.00/242IU
- Vitamin D 0.00/17IU
With the exception of folate (which you should be getting plenty of from your vegetables) the egg provides more important nutrients than the 1/4 cup of beans! And, like the peanut butter, the amino acid profile of the beans falls short when compared with an egg. To overcome the limiting amino acid in beans, and consume more nutrients, you'd have to eat more than three 1/4 servings - costing you 211-calories - and you'd still not consume any Vitamin D, A or B-12 and still not consume as much selenium or riboflavin as you would with an egg.
3. Zied recommends about five and a half one-ounce equivalents of meat and beans each day in a 2,000 calorie diet.
This is one recommendation I take issue with repeatedly as it fails to provide adequate intake of complete protein. Because the current dietary recommendations base intake of carbohydrate, protein and fat on percentage of calories this type of simplistic advice is provided again and again without considering the potential danger to the individual following the advice.
Quite frankly, for most men 5.5-ounces of protein-rich foods in a day is simply inadequate, regardless of the source, for overall total protein intake at the end of the day. For a good number of women, it's also inadequate - especially if one is choosing incomplete protein sources more than complete protein sources, which is currently the recommendation (eat more plant based foods instead of aminal foods).
The Institutes of Medicine (IOM) consider quality protein to be critical and are clear in their recommendations - protein must provide adequate intake of all indispensible amino acids and care must be taken when protein sources are limited in amino acid content. In addition, they set the minimum intake of complete protein at 56g for men and 46g for women. And, let's be clear - that's "complete" protein, not "total protein" in a day from all sources. They also carefully calculated amino acid requirements based on quality protein intake for each of the essential amino acids which is based on miligrams (mg) of amino acid required for each gram (g) of protein consumed.
So, just how risky is the advice to consume just 5.5-ounces of meat and beans with the emphasis on the beans?
In a single day eating 3-ounces of cooked beef (ground, lean, broiled), 1/4 cup of pink beans, a tablespoon of peanut butter and 1/2 ounce of almonds would fulfill the recommendation based on "ounce equivalents" but falls short on actual protein consumed - just 30g - and is deficient in essential amino acids, specifically falling short for phenylalanine and methionine. Including the beef simply wouldn't overcome the limiting amino acids in the other foods. If you followed the advice and consumed no other "protein-rich foods" - that is no more beans or eggs or meats - but relied on other foods like vegetables, fruits, and grains to round out your menu and provide your calories, you'd still fall short for protein and amino acids no matter how many calories you ate.
The bottom line is that when it comes to protein in your diet - quality counts!
Not only will you cosume complete proteins with eggs, meats, poultry, fish, and dairy, you'll also consume higher amounts of vitamins and minerals critical for good health. These foods are and should be recommended as the "gold standard" for quality protein and should be your first choice for protein!