Are animal proteins more easily absorbed than vegetable proteins?
But that’s no reason to choose animal protein over plant protein.
The difference in absorption is small, usually about 10 to 20 percent lower from plants than from animals, and it would only be a concern if our diet has barely enough protein to meet needs – about 0.8 grams per kilogram of body weight, or about 10 percent of daily calories.
For adults in the United States and other wealthy countries, protein intake is usually above what we need—about 15 percent of daily calories on average—so the difference in absorption between animal and plant proteins is largely negligible.
One of the reasons why there is so much confusion about this topic has to do with amino acids. Proteins are strings of 20 amino acids, which are the building blocks for muscles, other body components, hormones, antibodies, and enzymes that control our metabolism. Nine of these amino acids cannot be produced by our body and are called essential because we need to get them through food.
A common argument for consuming animal proteins is that they are “high quality” and “complete” compared to plant proteins, in terms of their essential amino acids.
Let’s start with the idea of protein quality. This nutritional concept is based on a mixture of specific amino acids that maximize the growth of young mice and other mammals. But maximizing growth is not a problem for adults. By this definition of protein quality, eggs and milk rank first, but are not dramatically higher than most plant-based protein sources, and beef protein is actually similar to soy protein.
You also don’t have to worry about whether plant proteins are “complete”. It is a myth that plant foods do not contain all essential amino acids and that we must eat complementary proteins such as rice and beans in the same meal for optimal results. In fact, if we eat a variety plant foods in our dietthe total mixture of amino acids is not significantly different from what would we get from eating animal proteins.
Concerns have been raised that antinutrients such as phytates, lectins and oxalates in plant foods may reduce the absorption of essential nutrients.
In a poor population with a high intake of starchy foods and low dietary diversity, consuming a lot of phytate may contribute to some mineral deficiencies. But in the context of a more varied diet, such as in the United States, this does not seem to be a problem.
Phytates may contribute to many of the health benefits of plant foods due to their antioxidant activity, and higher phytate intake is associated with overall good health and lower risk of kidney stones.
Focus on the protein pack
Most Americans don’t need to worry about any of these issues—digestive efficiency, amino acid content, anti-nutrients—because we don’t consume protein in isolation or from a single food. These differences would only become important for someone on the threshold of protein deficiency.
For everyone else, the health effects of the entire protein package are more important.
When we eat beef, we get protein, essential minerals and vitamins, yes, but we also get hefty doses of saturated fat, cholesterol and other heart disease risk factors, with very little of the beneficial polyunsaturated fat.
With plant-based proteins such as nuts or soy foods, we get good amounts of fiber and polyunsaturated fats, a different mix of essential minerals and vitamins, and many other compounds that appear to have health benefits.
Making room for more plants
We can best understand the health effects of protein-containing foods by using randomized trials to assess their short-term effects on disease risk factors, such as blood cholesterol and blood pressure, and epidemiological studies to assess their long-term effects on specific disease risks and overall mortality.
Our research group conducted prospective analysis of more than 130,000 men and women who were followed for up to three decades. Total dietary protein was not associated with total mortality or other outcomes, but mortality increased with higher consumption of animal protein and decreased with higher amounts of plant protein.
Although some evidence suggests that total protein requirements may be higher in older age, the same pattern a favoring of plant proteins was observed in the elderly when the outcome was poor.
Protein and calorie needs increase with pregnancy and among serious athletes, but with no clear advantage of animal versus plant sources. For those who feel “better” with more animal protein, I suggest slowly incorporating more nuts and soy into their meals, which can also be satisfying and delicious.
The benefits go beyond improving your health. At this point in human history, it is also important to consider the role of food choices in preserving a sustainable planet for future generations. Although eliminating the use of fossil fuels is the highest priority, we have little hope of avoiding disaster unless we also change our diet to be more plant oriented.
Although this would be a big change for many Americans, the traditional diets of Asia, Africa, Latin America, and the Mediterranean region provide plenty of flavor and attractive examples.
This does not mean that we have to eliminate steak or parmesan cheese from our diet, or go vegan, although that is an option that some would like to pursue. Research has shown that the child with about two servings of food of animal origin per day can be both healthy and sustainable. This might mean a cup of yogurt plus 3 to 4 ounces of chicken or fish.
So instead of large servings of animal protein at every meal, focus on adding more plant-based protein to your plate, such as lentils, tofu, chickpeas, peanuts, nuts and beans. Make your diet as varied as possible, include a wide variety of fruits, vegetables and whole grains. Not only is this a smart dish, but it can also unlock new flavors and exciting dishes. The benefits include better personal health now — and hope for future generations.
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