What does protein do for your body? Plant vs animal sources, and other FAQs answered

Ever hear your stomach grumbling even though you just ate? Your meal or snack might not have been as balanced as you think. Combining complex carbohydrates with protein and fat is the best recipe for satiety and success, experts previously told USA TODAY.

If you're trying to increase your protein intake, there's more than just meat to choose from. While that and dairy are popular choices, almost 90% of Americans do not eat the recommended amount of seafood and more than 50% do not get enough nuts, seeds and soy products, according to the Dietary Guidelines for Americans.

What is the healthiest protein to eat?

Though animal protein sources pack more protein in smaller quantities, plant protein may be better for your overall health, says Theresa Gentile, a registered dietitian nutritionist who is a spokesperson for the Academy of Nutrition and Dietetics.

She points to a recent study published in the American Journal of Clinical Nutrition, which found that regularly consuming plant protein, more so than animal or dairy protein, is linked with better mental status and fewer physical function impairments. 

It’s also a better protein choice for the environment. According to a 2023 study published in Scientific Reports, plant and fish proteins had the best individual and environmental outcomes while meat proteins scored lower in nutrition, higher in health risks and had a worse environmental effect because of the greenhouse gas emissions created in production.

Here are some popular forms of plant protein:

• Beans
• Chickpeas
• Lentils
• Nut butter
• Nuts and seeds
• Soymilk
• Tofu
• Tempeh
• Veggie patties
• Quinoa

With these foods, you’re also getting fiber, vitamins and minerals along with protein.

Nuts are good sources of healthy fats and fiber. Plant protein sources like greens and broccoli are rich in antioxidants, vitamin K and vitamin C among others. Beans are chock-full of fiber, protein, iron and resistant starch, a form of starch that improves gut health because it doesn’t raise glucose. They also contain polyphenols, which act as antioxidants and may protect against some cancers, cardiovascular diseases, diabetes and neurodegenerative diseases.

Regardless of the type of protein, it's important to understand how much protein you're getting. Many misunderstand this and take the number of grams at face value, says Dr. Gregory Katz, an assistant professor of medicine at the NYU Grossman School of Medicine. Instead, think about the grams of protein as a percentage of calories. Foods that are higher in protein relative to the total number of calories will be more satiating.

What does protein do for your body?

When we eat protein, our body breaks it down into amino acids, which we absorb and use to produce energy or build structures like muscle. This fuels "every chemical reaction in our body," Katz says.

There are 20 amino acids and our body can naturally produce all but nine of them. The ones that we can't produce on our own are called "essential amino acids."

The Dietary Guidelines for Americans recommend adults consume 0.8 grams of protein per kilogram of body weight. For someone who weighs 170 pounds, that’s about 60 grams. Older adults or anyone recovering from illness or surgery should aim for closer to 1.2 grams per kilogram, according to Gentile.

But while most Americans eat enough daily protein to function, Katz isn't convinced we're eating enough to prevent age-related muscle loss.

"Higher protein diets tend to be better at preserving muscle, especially when that's coupled with some degree of physical activity," Katz says, adding that you should look for a source of protein in every meal. Aiming for close to 30-40 grams per meal can prevent frailty.

Are plant proteins complete proteins?

Soy and quinoa are complete plant proteins, meaning they contain all of the essential amino acids. Most other plant proteins are not. But though it's necessary to get all of the amino acids in your diet, it's not necessary to consume them all at the same time.

Getting in a variety of protein and fiber sources, fruits and vegetables will help you to get all of those essential amino acids in.

"If you're eating a balanced diet, it's almost impossible not to," Katz says.

You don't need to go and buy fancy supplements either, though Katz says protein powder without sugar or additives can have a place in a healthy diet: "There's a lot of money to be made by making this stuff feel onerous and feel like it's really difficult. But for most people, I think just keeping it simple is probably the best way to think about it."

Healthiest beans?Boost your daily protein and fiber with these

What foods are high in protein?

Aside from beans, legumes, nuts and seeds – heroes of the plant protein category – Gentile suggests trying these high-protein foods:

• Lean meat: This is the healthiest meat to choose if you’re going for animal protein, experts previously told USA TODAY. Chicken is a popular choice, though any meat labeled at least 90% lean meat is a healthy choice. 
• Fish:Eating fish is one of the easiest ways to increase your intake of omega-3 fatty acids, essential nutrients that 68% of adults don’t consume enough of.
• Tofu: This plant protein warrants another emphasis. Tofu, made of soybeans, is a complete protein and endlessly versatile. Try pressing it and crisping it up in a pan or air fryer or use it in a miso soup.

Nuts, flax seeds, hemp seeds and chia seeds also contain trace amounts of protein, Gentile says, and can be good additions to toast, soups, salads and smoothies.

Discover more health tips for your daily diet: 

• Healthiest fruit: This one has cognitive and cardiovascular benefits
• Healthiest vegetable: Check out these great nutrient-dense options
• Healthiest nut: Add these two daily for cognitive benefits and more
• Healthiest deli meat:Guide for your next sandwich, plus during pregnancy
• Healthiest eggs:Best preparations for protein gain, weight loss

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