- Healthy older adults (and possibly middle-aged ones too) require more than RDA protein levels for frailty and mortality prevention. The optimum: .45 grams per pound — .54 grams per pound of body weight daily (see Part I, "Protein: The Mortality Protector").
- Protein timing, quantity, and combining with exercise are essential ingredients in the vitality recipe (see Part II, "Protein + Exercise: Perfect Partners in Mortality Prevention").
Fundamentally, this means that, according to medical experts worldwide, every day, a 120-pound woman 65+ would best eat 54 — 65 grams of protein—and a 180-pound man who exercises would best pump up to nearly 100 grams. (See the full charts in Part I.)
So, do you know…
- If you are getting enough protein?
- How much protein is in your favorite foods?
- What healthy foods (of different types) have the most protein?
- Why vegetarians, vegans, and meat eaters need to mix their proteins?
To help you answer these questions, below you’ll find Honest Health News' "Pump Up Your Healthy Proteins Chart." But first, here’s a protein primer to help you understand the chart numbers and smartly enrich your diet.
All Proteins Are Not Alike
Proteins—which are essentially long chains of amino acids—vary in their amino acid make-up. Some are considered "full," meaning they contain all the "essential amino acids," [pullquote-right] "Proteins vary in how well our bodies digest them." [/pullquote-right] those the body cannot produce alone. Our bodies need the full spectrum of essential amino acids to create new cells and repair others, as well as to help build bone, muscles, cartilage, and skin. All proteins, even full ones, will have different proportions and quantities of essential and non-essential amino acids.
Proteins also vary in how well our bodies digest them. If the digestibility isn’t high enough, then the body doesn’t fully utilize the essential amino acids it has, even if you’re eating a full protein.
What, then, defines a good protein? In short, as Dr E. Boutrif, Senior Officer, Food Quality and Consumer Protection Group, FAO (Food and Agriculture Organization of the United Nations), puts it: "Good quality proteins are those that are readily digestible and contain the essential amino acids in quantities that correspond to human requirements. "
In other words, consuming just any group of proteins to reach the daily protein target numbers in and of itself is not sufficient for health.
Important Yet Imperfect Protein Quality Raters
Over the years, medical experts developed various scoring systems to measure protein quality, including Protein Efficiency Ratio, Biological Value, and the Protein Digestibility-Corrected Amino Acid Score (PDCAAS). Of the three, only PDCAAS is still widely and respectfully used, because:
- The Protein Efficiency Ratio was measuring a protein’s ability to support growth in young, rapidly growing rats, and researchers assumed those values correlated to humans [pullquote-right] "The Protein Efficiency Ratio in large part measures the amino acid requirements of the rat rather than the human." [/pullquote-right] —but after many decades, it became apparent that, as Dr. E. Boutrif explains, "PER in large part measures the amino acid requirements of the rat rather than the human." Basically, PER overestimates the human value of some animal proteins and underestimates the human value of other vegetable proteins, since, Boutrif says, "the rat appears to have a much higher requirement for [certain] amino acids than… the human. "
- Biological Value (BV) was measuring how efficiently the body consumes individual proteins by calculating what percentage of nitrogen in a given protein [pullquote-right] "Biological Value was measuring a protein’s maximum potential rather than human requirements." [/pullquote-right] is used to create body tissue—but doesn’t consider all the factors that influence protein digestion, Jay R. Hoffman and Michael J. Falvo point out in the Journal of Sports Science and Medicine. In addition, BV measures a protein’s maximum potential rather than human requirement levels.
- In contrast, PDCAAS, the Protein Digestibility-Corrected Amino Acid Score, measures both the required amino acid contents of the protein and a person’s ability to digest it—an apt measurement in light of the above-noted understanding that "good quality proteins are those that are readily digestible and contain the essential amino acids in quantities that correspond to human requirements." [pullquote-right] "PDCAAS considers the amino acid needs of 2- to 5-year-olds, the most nutritionally demanding age group." [/pullquote-right] Adopted both by the US Food and Drug Administration (FDA) and the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO), PDCAAS essentially calculates the quality of a protein based on the amino acid requirements—adjusted for digestibility—from which 2- to 5-year-olds, who are deemed the most "nutritionally demanding" age group, can grow and maintain body tissue. The highest possible PDCAAS score is a 1.0, meaning that after the protein is digested, it provides 100% or more of the essential amino acids required by 2- to 5-year-olds—and, presumably, the rest of us.
But We Can’t Give PDCAAS Itself a Perfect Score
PDCAAS can help us. It can improve our protein choices by revealing potential amino acid holes in our diet. For example, whereas proteins from certain animal sources, such as eggs and milk/whey/casein, receive a perfect 1.0, [pullquote-right] "The proteins in legumes, vegetables, fruits, and starches don’t have perfect scores." [/pullquote-right] meaning they contain all nine of the essential amino acids in sufficient quantities and are well digested by the body, the proteins in legumes, vegetables, fruits, starches, and cereals don’t individually attain that perfect amino acid score (more on this later). As Gertjan Schaafsma observes in a 2012 PDCAAS overview published in the British Journal of Nutrition, "The advantages of the PDCAAS are its simplicity and direct relationship to human protein requirements."
Nonetheless, PDCAAS is an imperfect instrument. Among the reasons Schaafsma gives:
- It’s based on minimum amino acid requirements for tissue growth and maintenance, and therefore doesn’t necessarily reflect optimum amino acid intake.
- It assumes that a given food’s score is independently accurate, and doesn’t take into account [pullquote-right] "Certain foods common in animal feed have been shown to lead to amino acid losses in the body." [/pullquote-right] how other foods might affect it. For example, so-called anti-nutritional factors, found in certain protein sources, among them soybean meal, peas, and fava beans, have been shown to lead to amino acid losses. This is very relevant for animal protein consumers because these foods are common in animal feed.
- Because of the simplified scoring system and each protein’s unique amino acid composition, PDCAAS doesn’t offer the rest of us enough information to figure out how exactly to close any essential amino acid gaps in our diet.
All this said, PDCAAS is nonetheless the best scoring system for protein quality available to date.
PDCAAS in Practice
Working with the imperfect instrument we have, here are 3 ways to apply it when using the "Pump Up Your Healthy Protein Chart with PDCAAS Values Chart" (to follow):
[dropcap]1[/dropcap] Eat protein foods with 1.0 or nearly 1.0 PDCAAS values, so at some meals your body is (at least in principle) getting all the amino acids it needs to function. Although PDCAAS figures are not currently available for every animal or fish protein, animal proteins tend to be full proteins and come closer to 1.0 scores. However, there are good, full, 1.0 PDCAAS proteins for vegans and vegetarians, too.
[dropcap]2[/dropcap] Eat an extensive variety of protein foods, including foods with less than perfect PDCAAS values. This is imperative for folks whose main sources of protein consist of legumes, nuts, seeds, and wheat, all of which have amino acid digestibility scores considerably below 1.0 (more on this to come). Meat eaters would also be wise to mix their proteins at meals because of anti-nutrient factors in animal feed which might downgrade those proteins.
[dropcap]3[/dropcap] After exercising, eat protein foods with 1.0 PDCAAS values, and especially those high in the amino acid leucine, to maximize your body’s ability to build muscle mass. (See Part II, "Exercise + Protein—Perfect Partners in Mortality Protection" for exercise and protein study-tested options in older adults.)
How To Be a Healthy Plant-Based Protein Eater
Vegetarians and vegans have two essential protein challenges:
[dropcap]1[/dropcap] Whereas animal proteins are considered complete, meaning they contain all the essential amino acids, as we’ve discussed, vegetable sources usually lack one or more essential amino acids. Typically, vegetable sources do not score high on PDCAAS; they also score lower on the older Biological Value and Protein Efficiency Ratio systems.
Here, the best approach is clear: Eat a variety of vegetables, fruits, grains, and legumes to increase your chances of ingesting sufficient quantities of all the essential amino acids. Remember: In the PDCAAS system, [pullquote-right] "Vegetarians and vegans: Protein diversity is your best protection." [/pullquote-right] if you eat one food with a .74 rating and another with a .53 score together, it does not mean you’ve reached over 1.0 and therefore covered all your amino acid bases. It could be that both these foods are low in the same amino acids your body needs to function. Protein diversity is your best protection.
[dropcap]2[/dropcap] Whereas animal proteins are normally digested easily in the body, vegetable proteins are generally less digestible, which means the body isn’t maximizing the use of those vegetable proteins' amino acids. And, it turns out, there is a presumption underlying the daily recommended protein consumption numbers [pullquote-right] "Vegetable proteins are generally less digestible in the body." [/pullquote-right] we’ve discussed—the assumption of good quality and digestibility in those proteins.
In one small study, published in the journal Nutrition in 2011, 21 young adult vegetarian women who filled out food logs for 4 days had total dietary protein digestibility scores of 82% on average, which differed significantly from the 88% protein digestibility Daily Reference Intake (DRI) score, the general reference value used to assess nutrient intakes of healthy people.
The study authors explained that whereas previously DRI expert panels had recommended adjusting iron, zinc, and calcium Daily Reference Intake numbers for vegetarians to account for decreased bioavailability, they did not change protein DRI numbers because they assumed vegetarians were getting about 50% of their protein from animal (dairy/egg) sources. But in the vegetarian study, only about 21% of the women’s protein came from animal sources.
Given this digestibility discrepancy, vegetarians and vegans might be best served by serving themselves even higher quantities of protein. That was the conclusion of the study authors: "This research suggests that the protein DRI for vegetarians consuming less than the expected amounts of animal protein (45% to 50% of total protein) may need to be adjusted from 0.8 to about 1.0 g/kg to account for decreased protein bioavailability"—in other words, from .36 grams to .45 grams/pound of body weight.
As careful readers no doubt know, however, the recommended daily protein numbers for older adults are already higher than .45 grams/pound.
It’s Difficult To Say What’s Healthy with Certainty
Food science appears to be as complex, and possibly as individualized, as proteins. Many foods we select and foods we shun can seem to help and, sometimes, to hurt us:
- Meat-based diets may be high in complete and easily digestible proteins, but as Hoffman and Falvo point out in "Protein: Which Is Best?," "Some health professionals [are] concerned about the amount of saturated fat common in these foods compared to vegetable sources… [pullquote-right] "Patients with cardiovascular disease who followed the Mediterranean diet had an overall lower risk of mortality from all causes." [/pullquote-right] If elevated protein does come primarily from meats, dairy products, and eggs, without regard to fat intake, there likely would be an increase in the consumption of saturated fat and cholesterol." At the same time, the 2014 Health Professionals Follow-Up Study and the Nurses' Health Study found that patients with cardiovascular disease who followed the Mediterranean diet had an overall lower risk of mortality from all causes, and this diet contains some meat—approximately 4 ounces' worth per day. And while we know that eating 5 or more servings of vegetables a day is heart and life healthy, to date, no study has compared the health outcomes of meat vs. pesco-vegetarian vs. vegetarian vs. vegan eaters who all eat 5+ servings of produce daily.
- Vegetarian diets offer many health benefits—when properly done, vegetarianism is associated with a reduced risk of cardiovascular disease, diabetes, and cancer, according to a 2014 review, "Health Benefits and Risk Associated with Adopting a Vegetarian Diet." However, a poorly planned vegetarian diet can results in protein deficiency, anemia, and much more.
- Individual foods can be just as controversial. To point to just a few on the "Pump Up Your Healthy Proteins Chart" below, textured vegetable protein (TVP), a meat alternative produced from soy flour in which proteins are isolated, has a PDCAAS perfect protein rating of 1.0, but is questioned by some because it is highly processed, contains the chemical hexane, and is derived from soy. Soy in general, which has a perfect 1.0, has mixed reviews: Some studies have shown it improves heart health and reduces blood pressure, but other heart studies had conflicting results; some studies point to an association between soy intake and breast cancer risk and others come to opposite conclusions.
In a nutshell, there’s a lot researchers don’t know about protein. Meanwhile, here’s an active reference chart to help you make the most of what they—and you—do know now. Use often and stay strong.
*Protein Notes: Foods in each section are displayed from greatest to lowest overall protein gram count. Most foods low in protein grams are not displayed, but a few are shown to showcase product differences in digestibility and amino acid levels. This is not an exclusive list; some healthy and protein-rich sources may not appear. Different brands sometimes have widely divergent amounts of protein even in the same serving or portion size. These are estimates or averages based on the USDA National Nutrient Database and specific package labels; check yours for more accurate, personalized figures. Most portion sizes are based on the manufacturer’s suggested serving size. Some readers may disagree with the suggested healthy varieties, and some of the food literature is open to debate. In addition, some foods are healthier for some individuals than others; check with your doctor for the best protein sources for you.
** PDCAAS Notes: Protein Digestibility-Corrected Amino Acid Score values are shown wherever available based on the primary literature. Other information and research sources sometimes report different PDCAAS scores for the same foods. PDCAAS scoring sources include: beef, black beans, casein, egg, milk, peanuts, soy protein, wheat gluten, and whey protein; vegetables, potatoes, fresh fruits, dried fruits, legumes, chickpeas, and soybeans.Pumping Up #Protein. Best foods for meat eaters and #vegans. Click To Tweetby