A Moment for Science

As a Registered Dietitian, I am all about the science behind food and nutrition. While some of you may gloss over at the word “amino acid” or “gluconeogenesis,” I still think it’s important to arm you with the facts so you can better understand where my nutrition recommendations come from

The human genome contains about 23,000 protein-coding genes, and proteins make up as much as half of the dry mass of the adult human body, with fat being the other major component. These proteins are synthesized using amino acids as the building blocks that are linked in a particular sequence. Obviously, we need to consume proteins and their constituent amino acids in order to build our own proteins, but amino acids are used for more than just making proteins in the body. For example, our bodies use parts of amino acids to synthesize neurotransmitters, hormones, and even the nitrogenous bases in DNA and RNA. Most of the 20 amino acids can also be used as gluconeogenic precursors to help maintain blood glucose concentrations during periods of fasting or low carbohydrate intake. The only two amino acids that cannot be used for gluconeogenesis (the metabolic pathway converting amino acids into energy) are leucine and lysine, which are referred to as totally (or exclusively) "ketogenic." Protein isn’t just for building those muscles!

Proteins are unique among the macronutrients in that they contain the atom nitrogen. The presence of nitrogen in amino acids requires an important set of reactions, including transamination and deamination reactions. Once the nitrogen has been removed from amino acids, the remaining carbon skeleton can have multiple fates including being oxidized for energy or used to synthesize glucose in the liver.

Importance of Protein in the Diet

Protein is a vital macronutrient and plays a crucial role in maintaining overall health and well-being. Its importance in the diet is multifaceted, as it serves various essential functions in the body. Proteins are the building blocks of tissues, including muscles, skin, bones, and organs. When we consume protein, our bodies break it down into amino acids, which are used to repair and regenerate tissues in the body.

Protein is essential for maintaining and building muscle mass. It provides the necessary amino acids for muscle protein synthesis, which is critical for muscle growth and repair, especially during physical activity and exercise.

Many enzymes and hormones in the body are made up of proteins. Enzymes are essential for facilitating various chemical reactions, while hormones play a vital role in regulating processes like metabolism, growth, and stress response.

Some proteins in the immune system, such as antibodies, help defend the body against infections and pathogens. A well-balanced protein intake is crucial for maintaining a strong immune system.

Proteins are involved in transporting essential molecules, such as oxygen in the blood (hemoglobin) and lipids (lipoproteins). They also act as carriers for various nutrients and molecules throughout the body.

While carbohydrates and fats are the primary sources of energy for the body, protein can be used as an energy source when carbohydrate and fat stores are insufficient. However, protein's primary role is not energy production, and its breakdown for energy can lead to muscle loss if adequate calories are not consumed. We don’t want to be using protein as energy!

Protein-rich foods can help promote feelings of fullness and satiety, which may aid in weight management by reducing overall calorie intake and curbing hunger.

Certain proteins, such as collagen and keratin, serve as structural components in the body. Collagen is essential for skin elasticity, joint health, and bone strength, while keratin is a major component of hair and nails. Proteins play a significant role in maintaining healthy hair and skin, as they are essential for the growth and repair of these tissues.

How Much Protein Do I Need?

It is essential to consume adequate amounts of protein daily to meet the body's needs. The recommended daily intake varies based on factors such as age, gender, activity level, and overall health status. This is where it can be beneficial to work with an RD who understands your unique needs. For example, some endurance athletes may need close to 2.5 grams per kilograms of bodyweight to meet their protein needs, while someone who is less active may be okay consuming about 1.0 grams per kilograms of bodyweight. This could be the difference between consuming about 170 grams of protein per day or 70 grams of protein per day for someone who weighs 150 pounds.

Good Sources of Protein in the Diet

There are numerous good sources of protein, both animal-based and plant-based. Animal-based proteins are considered complete proteins, meaning they contain all essential amino acids, which are amino acids we must consume from food. They are also generally more bioavailable than plant-based proteins, so you need to consume less volume of an animal-based protein than a plant-based protein to get the same amount of protein. I like to use the term “condi-meat” with my clients when discussing incorporation of high quality animal protein in their diet. It does not need to be the star of the meal so treat it more as a side. Including a variety of plant protein sources in your diet ensures that you get a wide range of essential amino acids and other nutrients. Combining different plant-based protein sources, such as beans and rice or hummus and whole-grain pita, can provide a complete profile of essential amino acids. This is particularly important for individuals following vegetarian or vegan diets.

Here are some examples of animal-based protein sources:

1. Lean meats like chicken, turkey, and pork

2. Red meat

3. Eggs

4. Dairy products like Greek yogurt, cottage cheese, milk, and cheese.

5. Fish and seafood like salmon, which is also an excellent source of protein and healthy omega-3 fatty acids.

6. Bone broth which is a nutrient-rich liquid made by simmering bones, connective tissues, and vegetables, which is a good source of collagen and protein.

And here are some examples of plant-based protein sources:

1. Legumes like lentils, chickpeas, black beans, kidney beans, and other beans, which are rich in protein and fiber

2. Soy based products like tofu, edamame, and tempeh that provide a substantial amount of protein and are versatile in cooking

3. Quinoa, a pseudo-grain that contains all nine essential amino acids, making it a complete protein

4. Nuts and seeds like almonds, peanuts, cashews, chia seeds, flaxseeds, hemp seeds, and sunflower seeds

5. Whole grains like brown rice, oats, barley, and wheat contain some protein along with other essential nutrients

6. Plant-based protein powders which are typically made from pea protein, rice protein, and hemp protein powders

   
   

Is animal protein or plant protein better?

This is a loaded question, but my initial response is typically “it depends.” For example, my response to this question is going to depend on your past medical history, your current symptoms, your nutrition and health goals, your access to food, and personal taste preferences. In general, no protein is superior to the other, they are just different! As discussed above, animal proteins are complete proteins that are easily absorbed in the body, but they lack fiber and other beneficial nutrients like phytonutrients that plant based proteins contain. Therefore, both animal and plant proteins can be beneficial for our health.

Another way to look at choosing animal protein or plant protein is in terms of nutrient and energy density. When you consume animal protein, such as meat, poultry, fish, or dairy products, your digestive system begins breaking down the protein molecules into smaller peptides and individual amino acids. This process starts in the stomach, where gastric juices and enzymes begin breaking down the protein structures. As the partially digested proteins move into the small intestine, pancreatic enzymes further break them down into amino acids.

Once the proteins are broken down into amino acids, they are absorbed by the cells lining the small intestine and then enter the bloodstream. From there, these amino acids are transported to various tissues and organs in the body, where they are used for functions such as muscle repair and growth, enzyme production, hormone synthesis, immune system support, and other essential processes. A similar process is undertaken when you consume plant proteins, but our bodies don’t absorb or digest the fiber from plants so the vitamins and minerals in them are not as bioavailable as they are in animal foods.

It’s also important to consider that plants do not contain some vitamins that we must obtain from our diet, such as vitamin B12. Vitamin B12, which plays an important role in energy production, nervous system health, and red blood cell formation, is only found in animal protein. Therefore, if you are vegan, it’s imperative you supplement with vitamin B12 or you will develop a vitamin B12 deficiency. The active of form of vitamin A, retinol, is only found in animal foods. The inactive form of vitamin A, beta-carotene, is found in plant foods, but our bodies must convert beta-carotene to the active form retinol in order for our bodies to use it. Some people may have difficulties or limitations in converting beta-carotene into active vitamin A in their bodies. The conversion of beta-carotene into active vitamin A (retinol) occurs in the small intestine and requires the presence of specific enzymes. However, the efficiency of this conversion can vary among individuals due to several factors, including genetics, dietary habits, and health status.

I like to think of plants as our fiber, energy, and antioxidant sources which help fuel our microbiomes, metabolisms, and immune systems and then animals as the glue that keeps our bodies together. We need both to function.

Even the Blue Zones, which are glorified for their longevity and eating plant based, occasionally include animal foods like eggs, fish, poultry, and red meat as part of their diet. You also have to eat a large volume of food on a vegan diet in order to meet your nutrient needs, which was not feasible in prior centuries. It’s only because technology has advanced that’s allowed veganism to be feasible, but it’s that very technology that is presenting problems to our health and the environment. Okay, now I’m getting into some sensitive topics so I’ll get us back on track to the original question. Can you tell the science of nutrition and our food system is really complex??

In summary, animal versus plant-based proteins are not superior to one another, they are just different. As a food and nutrition expert, I believe we as humans need both for optimal health. This does not mean I won’t be supportive of a patient or client who wishes to follow a vegan diet, it just means we will have to be extra diligent to make sure you meet your overall nutrient needs through adequate portion sizes, optimized supplement protocols, and introducing enough variety in your diet.