Protein: does the food source matter?

When someone says “protein” does the word “meat” pop into your mind?  This might happen even if you’re a committed vegetarian.  We’re practically hard-wired to think this way.  People who want to build muscle think meat or special protein supplements are essential.  Paleo dieters gorge on big portions of meat, thinking that’s how our primitive ancestors ate.  Plant proteins are dismissed as poor quality.  There’s a belief that protein from plant sources — legumes, nuts, whole grains, soy — is nutritionally irrelevant.   It’s not.

A new study suggests that, when it comes to protein food source it doesn’t matter if you eat meat, milk, fish or legumes.  For muscle mass, what does matter is amount of protein consumed.

Protein 101

Protein is essential for human health.  The official recommended intake for an adult is 0.8 grams per kilogram body weight per day.  Our bodies manufacture all the proteins we need, using the basic building blocks: amino acids.  We get those amino acid building blocks by consuming protein from food.  During digestion, proteins are broken down and the amino acids are absorbed and taken up by tissues to make necessary protein molecules.  There are 22 amino acids.  9 of these are essential meaning our metabolism cannot make them; they must be obtained from food.  Your metabolism can tweak some of those to produce the other 13 as necessary.

Not only do we need to consume amino acids, we need specific ratios of the 9 essentials for our unique human needs.  This is where the concept of protein quality comes in.  Some natural protein sources better match our ideal amino acid ratio than others.  Egg is one of the best matches.  Cow’s milk and soy are also good matches.  Plant proteins are not good matches.  The amino acid lysine is lacking in most grains; legumes lack methionine.  Put the two together in a meal and you have a higher quality protein.  Since most people eat mixed meals, protein quality of plant foods is naturally enhanced by default.

Meat Mania

Unfortunately, the meat-aholics have taken over the conversation about protein.  Weight loss and strength diets are all about meat, and lots of it, from low carb to Paleo.  We now have a protein supplement industry promoting the idea that protein from specific sources (whey, for example) is ideal for boosting muscle mass.  Occasionally you might see a story about a successful athlete who is vegan, but these people are treated more as exotic outliers.  The PR is all about meat for muscles.

This new study looked at food intake data for almost 3000 adults.  The people with the highest protein intakes had the most muscle mass.  It didn’t matter what the protein source was, animal foods or plant foods.  Protein from legumes or nuts was just as effective as protein from meat or eggs.  Interestingly, the higher end protein intake was about 1.8 grams per kilogram body weight, more than twice the recommended intake.  That finding itself is pretty interesting, because there’s some controversy about what protein recommendations should be.  The 0.8 g/kg/day recommendation is intended to cover basic metabolic needs, but there’s no consensus about optimal intake, whatever that might mean.   What’s optimal for a 22 year old male might not be optimal for a 55 year old female, yet the official recommendation is supposed to work for both people.  For older adults, sarcopenia, or loss of muscle mass, is a major concern.  Some researchers suspect that higher-than-recommended protein intakes might prevent this problem.

This study didn’t say anything about what an optimal protein intake might be.  But it did show that plant-sourced proteins are just as good as animal-sourced when it comes to muscle mass.  And that’s an important finding, for vegans and vegetarians, as well as for people moving away from meat-heavy diets.  For vegans, it’s important to include a sufficient variety of high protein plant foods in your daily diet: legumes (beans), nuts, whole grains, soy-based foods like tofu or soy milk, and possibly foods prepared with plant protein ingredients.  Vegetarians who eat dairy foods and eggs would have an easier time consuming plenty of protein.  You don’t need to eat meat to build muscle.  Those vegan athletes may be on to something.

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