Featured article in the Fall 2019 Issue of Nutrition Close-Up; written by Mickey Rubin, PhD
There has been considerable debate recently around the topic of protein quality, particularly regarding the best way to measure protein quality1 as well as the relative importance of dietary protein quality as it relates to important health outcomes, such as muscle loss with aging.2
While this discussion is important and will no doubt continue as research in this area evolves and new measures for protein quality are developed,3 less attention is often given to the important contribution of protein foods to overall nutrient adequacy. Commonly consumed protein foods contribute to nutrient intake, diet quality, and nutrient adequacy, independent from their contributions to total protein intake.4
Protein foods provide important micronutrient diversity. Foods within the protein foods group provide B vitamins (e.g., niacin, vitamin B12, vitamin B6, and riboflavin), selenium, choline, phosphorus, zinc, copper, vitamin D, and vitamin E just to name a few.5
For example, meats provide the most zinc, while poultry provides the most niacin.5 Seafood provides the omega-3’s eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA). Eggs provide the most choline of any commonly consumed protein food, while nuts and seeds provide vitamin E, and soy and legumes are sources of copper, manganese and iron.5 Indeed, if we focus just on the protein that is provided by the protein foods group, we are missing the larger picture of what these foods contribute to healthy diet patterns.
Nutrient-Dense Eggs Make Important Contributions to the Diets of Americans of All Ages
Eggs are a prime example of a protein food that should be just as appreciated for their micronutrient contribution to healthy eating patterns as they are for their macronutrient contribution. Analysis of NHANES 2003-2012 reveals that in adults ≥19 years, whole egg consumption is associated with a higher likelihood of meeting or exceeding recommendations for several micronutrients, including nutrients identified by the 2015-2020 Dietary Guidelines as Nutrients of Public Health Concern such as vitamin D, calcium, and iron. Egg consumption is also associated with higher likelihood of meeting the recommendations for other underconsumed nutrients such as choline.6 Importantly, egg consumption was not associated with serum total cholesterol or LDL cholesterol in this analysis.
In fact, several lipid related risk factors were improved with higher egg consumption, including triglycerides, the triglyceride to HDL-cholesterol ratio, and the total cholesterol to HDL-C ratio.6 NHANES data in infants and toddlers ages 6-24 months revealed that those who consume eggs have greater intakes of choline, lutein + zeaxanthin, α -linolenic acid, DHA, vitamin B12, phosphorus, and selenium. Egg consuming infants and toddlers also had higher intakes of total fat, monounsaturated fat, saturated fat, and sodium, but also lower added sugar and total sugar compared to non-consumers of eggs. Importantly, egg consumption in infants was associated with longer recumbent length when compared to nonconsumers of eggs.7
Findings in children and adolescents ages 2-18 years showed a similar story, revealing those who consume eggs have greater intakes of protein, polyunsaturated, monounsaturated and total fat, α-linolenic acid, DHA, choline, lutein + zeaxanthin, vitamin D, potassium, phosphorus, and selenium compared to non-egg consumers.8
Plant vs. Animal or Plant and Animal?
Perhaps all too often the nutrition conversation regarding protein foods has turned to a debate between animal and plant protein sources. However, both animal and plant protein sources provide essential nutrients that are important for healthy dietary patterns. The emphasis away from animal source protein foods is generally evidenced by the association of some of these foods with cardiovascular risk, although randomized controlled studies show that nutrient-dense diets containing animal protein can improve cardiovascular disease risk factors,9 and animal source foods like eggs may have nutrients important for other outcomes such as neurocognitive development.10
The 2015–2020 DGA recommends adopting healthy eating patterns that contain a variety of protein foods, including seafood, lean meats and poultry, eggs, legumes, nuts, seeds, and soy products. A recent editorial by Dr. Wayne Campbell of Purdue University uniquely captured the idea that eating protein foods does not have to be an either or proposition, stating that “debates pitting meats against protein-rich plant foods seem less useful to consumers than helping both omnivores and vegetarians understand the health properties of the foods they choose to consume and educating them to include a variety of suitable protein-rich foods within healthy eating patterns.”11