When designing an evidence-based nutrition course, or researching an evidence-based lecture, I am continuously surprised to learn how little real data exists for seemingly basic concepts in nutrition. Many times this is due to the absence of an patentable product or any other economic incentive to fund the research – no one will fund a clinical trial comparing whey protein versus egg whites, for example, because a positive result for either will yield marketing data for any company’s whey or egg white products – and sometimes the absence of data simply means the question is not particularly important and worthy of research (as in the above example).
Protein seems to fall into this category, for we are concerned about the sufficiency of our protein intake to a degree that is unwarranted: parents worry about providing enough protein for their children, athletes fuss over providing substrates for lean muscle production, and protein is the one food group that is routinely invoked by name: “be sure to eat your protein, Sweetheart.” One never hears, “Eat your fat” or “Did you get enough carbs today?” These concerns are unwarranted because the average American diet contains 50% – 100% more protein than the recommended daily allowance (RDA). This is an inexact science, however, and it has not been shown what protein intake is ideal. Vegetarian and vegan diets average 10–11% protein, and represent RDA guidelines; whereas, the opposite end of the protein spectrum contains paleo diet and strict USDA food pyramid adherents at 35% or more. For otherwise healthy individuals, even these high levels of protein are perfectly fine, although most diets in this range, thankfully, usually represent a brief fad diet phase.
We may not understand what amount of protein is ideal, but we are, unfortunately, very knowledgeable about the consequences of too little protein. Kwashiorkor and marasmus are two conditions characterized by protein deficiency that are much too common in our world.
Even though the average person need not concern themselves with seeking sources of food rich in protein, there remain several topics on protein worth investigating, including: complete versus incomplete sources of protein, global health perspectives on the sustainability of contemporary meat production, and the topic I will discuss further now, the concept that protein should not be considered in isolation of its nutritional package. Unlike for fats or carbohydrates, there are no foods that are anywhere near 100% protein. Chicken breast, at 30% protein, is as rich a source of protein as there is, and foods considered high in protein are more typically in the range of 15–25%. The remaining fractions in a given food comprise the nutritional package, the various fats and carbohydrates that characterize that food. Foods with otherwise comparable amounts of protein can have very different packages, as illustrated in the table below that I assembled using the SELFNutritionData database for 100g portions of beef chuck, kidney beans,English walnuts, and wild Atlantic salmon:
Although roughly comparable in protein, these four packages vary to the extreme in regards to calories, carbohydrate type and content, and fat subtypes and content. Consider the following observations about these packages:
- Calorie differences are predominantly a function of fat content: walnuts, at 654 kcal/100g, are more than 65% fat. Kidney beans, at 60% carbohydrate, are only 333 kcal/100g.
- Packages of animal protein contain no carbohydrates or sugars; thus their appeal for the Atkin’s diet.
- Legumes and many other vegetables and nuts contain significant amounts of carbohydrates, but nearly half these carbs are in the form of dietary fiber.
- Walnuts contain as much saturated fat as beef, but also contain 67 times the amount of polyunsaturated fats.
- Outside of algae, plants contain insignificant levels of omega-3 fatty acid, docosahexaenoic acid (DHA), which is only found at high levels in seafood. Many plants contain the essential omega-3 fatty acid alpha-lenolenic acid (ALA), which we convert (poorly) into DHA. Walnuts are unique among nuts as a rich source of ALA.
- Cholesterol is found only in animal-based foods.
My intent is not to label these protein packages as good or bad, simply that such differences need to taken into consideration. As the scientific evidence concerning healthful versus detrimental effects of mono-, poly-, and saturated fatty acids and carbohydrate consumption accumulates, our view of what constitutes a beneficial package of protein changes.
For those seeking a way to include more nuts in your diet, you will not find a more attractive package than my Give Peace a Chance Walnut Granola; it comes with the added benefit of keeping your appetite at bay until lunchtime.
This article was originally published on the Georgetown Food Studies Blog. Republished here with permission of the author, Georgetown University Professor of Pharmacology and Physiology, Thomas Sherman. Professor Sherman is a contributing author to the GUWellness blog, exploring topics like food as medicine, nutrition, metabolism, exercise and appetite.