In my opinion, protein intake is the second most important factor you can actively control to further the progression towards your specific goal (second to altering your caloric balance).
But WHY is protein so important?
Compared to carbs and fats, dietary protein is the most satiating macronutrient. If your goal is weight loss, increasing your protein intake can lead you to feeling fuller, which could help you consume less calories throughout the day. Protein also has a higher thermic effect of food. This means your body needs to use more calories to digest protein. In fact, your body needs to burn 20-35% of the calories consumed from protein simply to process it. Comparing this to the 5-15% needed from carbs and fats, you’re seeing a pretty solid return on investment for eating higher protein meals. The last point I’ll touch on for WHY protein is important (but this certainty is not an exhaustive list) is that protein is essential for building muscle. Proteins are made up of 20 amino acids. Our bodies can produce 11 of these, leaving 9 that we must get from our diet (known as essential amino acids). All essential amino acids are important, but studies show that leucine is the main signal for muscle protein synthesis (MPS). MPS is the repairing and rebuilding of muscle tissue that has been broken down from activities such as resistance training. Without consuming dietary protein, it would be virtually impossible for your body to go through the MPS required for you to reach your goals.
So WHERE do we get protein from?
Protein can come from two sources, plants and animals. Unfortunately, not all grams of protein are created equal. Plant protein generally contains less essential amino acids (EAAs), making it less likely for your body to go through sufficient MPS. Some plant-based proteins like buckwheat, quinoa, and soy contain all nine EAAs, but most plants only contain some. If you get the majority of your protein from plant-based food, eating a variety of beans, grains, nuts, and vegetables will help you get all EAAs through your diet without supplementation. Attached is an image of recommended protein sources for different restricted diets!
HOW MUCH protein should we eat?
Depending on your lifestyle, this answer will be a little different. If you are someone that isn’t super active and doesn’t resistance train, a great baseline to shoot for is 120g of protein per day. However, if you are someone that resistance trains, your protein intake will need to be higher to properly go through MPS and rebuild the muscles you have broken down. Research suggests that 0.8g-1.25g per pound of body weight per day is optimal for MPS. In my own training, I aim for the higher end to minimize my chance of leaving potential benefits on the table. However, if you’re a 150 person and aiming for 150-190g of protein sounds difficult, start at 120g and make it a goal each day or week to add 5-10g. Eventually it WILL become habitual. If most or all of your protein comes from plants, these optimal numbers will also look different for you. Studies show that similar MPS responses from animal protein can be had by people that eat 1.5-2 times that amount in plant protein. For example, similar MPS responses can be generated by eating 35g of casein (dairy protein) and 60g of wheat protein. So if your diet is heavy in plant protein, try to eat more of it! (Also, if you’ve heard that eating too much protein is bad for your kidneys, that’s not true. People with healthy kidneys will not damage their bodies from protein consumption.)
WHEN should we eat protein?
The majority of the literature on protein timing suggests that 30-50g of quality protein per meal with 3-5 meals evenly spread throughout the day is likely to lead to maximal MPS. This supports the underlying theory that there is a cap on how much protein your body can use to rebuild muscle at a given time. If you eat a low-protein breakfast, you are not likely to reap the maximal MPS rewards by loading up your subsequent meals with protein to play catch up. For serious lifters and competitors, it may be beneficial to eat a high-protein meal before bed, as there is likely 8-10 hours before your next feeding window.