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Protein and satiety

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Protein and satiety

When starting your nutritional transformational journey it is important to understand your macros. There are three macros: protein, fat and carbs. In this post we will discuss the importance of protein. Let’s look into why protein is so important

Importance of protein

Proteins are always being built up and broken down within our cells. Imagine protein as the raw material, or the building blocks for our body. If we don’t eat enough protein our cells can’t do their job. Over time this can lead to problems such as hormonal imbalances, depressed immune function, poor recovery and more.

Protein is also a critical building block of bones, muscles, cartilage, skin, and blood. Hair and nails are mostly made of protein, while our body uses protein to build and repair tissues. We also use proteins to produce molecules such as

  • enzymes
  • hormones and cytokines
  • neurotransmitters
  • antibodies and immune system components
  • transport proteins
  • structural proteins
The word protein is derived from the ancient Greek protos, meaning first, primary or most important. Indeed, proteins are the body's building blocks!

Sufficient amounts of protein will lead to : 

Increased satiety. Protein increases satiety to a greater extent than carbohydrate or fat by increasing the production of certain hormones like peptide YY and GLP-1. It also reduces ghrelin, the hunger hormone, for several hours.

Increased thermogenesis. Protein increases the thermal effect in our body, which also influences satiety and energy expenditure.

Increased muscle mass. A moderately higher protein diet has anabolic effect to our muscles and favours the retention of lean muscle mass while improving metabolic profile. However, more protein won’t make you build exponentially more muscle beyond a certain threshold. Current research has seen that limit being around 0.8-1.0 grams of protein per pound of lean body mass. Higher protein intake during dieting promotes keeping the metabolic rate up.

Adequate protein intake prevents muscle loss or sarcopenia. It’s observed that muscle atrophy starts to occur even after the third decade of our life with a 30-50% decrease between ages of 40-80. This has to do with not enough resistance training and not enough protein intake.

Higher animal protein intake promotes bone health and reduces risk of hip fracture. Falling and breaking bones is actually one of the biggest concerns related with aging. A higher protein intake may be more important for the aging population amongst whom it’s been found that the RDA for protein may be inadequate for maintaining skeletal muscle

Summary

  • Many people think of protein only in the context of building muscle. However, this is far from the actual need of proteins.
  • Proteins are the building blocks of every cell in our body allowing them to create and repair everything that is required.

The protein and amino-acid connection

When we eat protein sources the body will break it down into compounds called amino-acids which are the raw material we need.  This is important since not all protein sources have the same (or all ) amino-acids. Once the raw material are available they will be combined back into proteins for the different body needs.

There are 21 amino-acids and are categorised as essential and non-essential.

  • 9 Essential amino-acids : The nine amino acids humans cannot synthesize are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, histidine
  • 6 conditionally essential amino acids :  This means their synthesis can be limited under special pathophysiological conditions. These six are arginine, cysteine, glutamine, proline and tyrosine. 
  • 6 non-essential amino acids : These can be synthesized in sufficient quantities in the body and are alanine, aprartic acid, asparagine, glutamic acide, serine and selenocysteine. 

 

How much protein should you get

Protein is probably the most important macronutrient because your entire body is made of its amino acid building blocks so we need to get sufficient amounts. 

The Recommended Daily Allowance for protein is 0.8 g/kg. That would be enough to cover your daily bare essentials for survival but, in my opinion, it’s definitely not optimal.

A diet is considered ’appropriate in protein’ when the daily protein consumption is higher than 15% of total energy intake. That would maybe give you about 1 g/kg of body weight but I’d say that’s not high at all.

For a diet to be considered ’optimal in protein’, it would have to consist of at least 20-25% of daily calories with around 1.5-2.0 g/kg of your ideal body weight.

  • The more lean muscle mass you have, the more protein you need to sustain that amount of muscle.
  • Being more active, in general, increases your protein demands because physical activity damages the muscle cells to a certain extent.
  • If you do resistance training, you need more protein to support that training with enough protein synthesis and mTOR activation.
  • If you primarily do endurance training, you need slightly less protein because endurance training doesn’t break down that much muscle tissue as resistance training does. 
  • As you age, your ability to maintain skeletal muscle decreases and thus you need more protein as well.

Summary

  • Protein can’t be stored, as carbs and fats are, for later use. We need sufficient amount of protein daily.
  • Aim for more that 1g/kg of ideal body weight on a daily basis and depending on the level of exercise you are doing.

Best sources of protein


As we discussed not all protein sources are equal, and we can broadly separate the sources into two categories. 

Animal protein : All meat sources have a complete protein profile, where plant sources need to be combined to make-up for all essential amino-acids. Best source of protein, due to the amounts of protein they contain and also of other minerals and vitamins, are free-range eggs and grass-fed beef. Then comes lamb, pork and chicken.

Plant protein : Plant proteins need to be combined in order to get the full amino-acid profile. For example combining legumes (e.g. beans) with rice will give you the protein you need. 

Gram for gram, animal sources have more protein so they are said to be more nutrient dense. This means you need to eat less from that food to get everything you need, which is important as low nutrient density can lead to over-eating. Another consideration is that plant sources have anti-nutrients, like phytic acid, which can block absorption of minerals and make it more difficult to absorb the protein. 

That’s why you need to be eating protein on a consistent basis and you can’t survive without it for too long. The body doesn’t have a backup vault for protein that could be used for protein synthesis long-term.

Other considerations

Protein is the only macronutrient that can’t be stored inside the body long-term.

Carbohydrates can be stored as liver and muscle glycogen. Extra carbs will be converted into triglycerides and get stored as body fat. Fat and extra carb can be stored in an infinite amount as body fat in the adipose tissue. 

Protein intake will be used for elevating muscle protein synthesis and activating mTOR which will help to maintain your current lean muscle mass. To activate these pathways, you need only a certain amount of protein and more won’t have a dose-increasing effect. You can’t really store protein inside the body beyond a certain necessary limit. To store protein as energy it has to be converted into glucose through gluconeogenesis first.

There is a limited amount of transporter cells and receptors in the small intestine which restrict how many amino acids can be moved into the blood. Hence the theory that our body can only absorb a certain amount of protein in one meal.

  • There are many other factors that determine protein absorption such as the pH levels of the gut, the permeability of the intestinal lining, protein sensitivity, and the presence of hormones related to gastric emptying.
  • If eating fewer meals with higher amounts of protein, our body will adjust to the amount of protein we eat. Intestines will contract according to the speed at which it can digest food. If they can’t handle any more protein, then they won’t waste this precious resource away but will simply slow down gastric emptying. After a few moments when you’ve digested the protein you’ve already consumed, the intestines will then move the remaining protein down the line so to say and continue absorption. 
  • Triggering muscle protein synthesis is mostly regulated through leucine, which is the main anabolic amino acid. It requires about 2-3 grams of leucine to activate muscle protein synthesis and generally, you can get that amount of leucine from 20-30 grams of a complete protein. Best source of leucine are eggs.
  • When you’re doing intermittent fasting and you’re eating a ketogenic diet, then the protein you eat will be used primarily for protein synthesis instead of gluconeogenesis because there’s not much need for glucose-derived energy. Hence, you’ll end up assimilating your protein from food better instead of burning it off as sugar.

Even considering the above, the magic amount of protein seems to be about 30 grams but still consider that muscle protein synthesis may continue for 24 to 48 hours post-workout.

What does that amount look like? Here are a few examples…

  • 1 cup cottage cheese (28 grams protein).
  • 20gr of Greek yogurt plus a handful of nuts (25g).
  • A palm size portion of steak, fish and/or poultry (28g).
  • 3 whole eggs (27g).

Key Takeaways

  • Protein is the body’s most important building block!
  • Sufficient amount of protein is required for optimal health and you probably need more than the RDA.
  • All animal protein provides the essential amino-acids whereas plant protein needs to be combined.
  • Protein is a satiety factor regulating ghrelin, and is important for suppressing hunger.

Further reading