What Is Protein?
Proteins are made up of strings of amino acids. The shape of a protein depends on what amino acids are used as building blocks for the protein, and the sequence that these amino acids are assembled in. DNA stored in the nucleus of our cells holds the instructions on how to assemble these strings of amino acids to produce specific proteins. Chemical bonds between the amino acids not only hold the strings together but also cause the string of amino acids to fold into very specific shapes. The shape of the protein allows it to interact with other molecules in very specific ways. There are a lot of different proteins that make up our body but, for now, we are looking at the proteins that make up skeletal muscle.
Why Is Protein Important?
Skeletal muscle, the muscle that we use to move and perform our daily activities, makes up around 45% of our total body mass. Muscle protein makes up around 20% of total skeletal muscle mass; that’s roughly 7kg of protein stored in skeletal muscle. As we age, we start to lose muscle mass. This loss of muscle mass, called sarcopenia, starts to happen around age 40. Research has shown that in the general population, we lose between 0.5% and 1% of our muscle mass per year. This could lead to a reduction of lean muscle mass from around 45% at age 40 down to around 25% at age 80.
The loss of muscle can increase our risk of falls, leading to injury, and when combined with osteoporosis could contribute to bone fractures. Skeletal muscle can remove blood glucose from the bloodstream to be used as energy or to be stored as glycogen. So, having greater muscle mass can help reduce our risk of insulin resistance or type 2 diabetes. The loss of muscle mass has also been shown to significantly reduce our quality of life by impacting our ability to perform daily tasks and leisure activities. So there seems to be a pretty strong case for trying to maintain a good level of muscle mass for as long as we can.
Slowing the Loss of Muscle As We Age
So, muscle is made of protein! If we get enough protein in our diet, we should be able to maintain a good level of muscle mass, right? Maybe we can even gain some extra muscle? Well, as usual, things are never that easy. To get the most benefit out of the protein in your diet you need to include some resistance exercise in your weekly schedule.
There’s plenty of research that shows that we don’t have to lose muscle as quickly as some of us do. The loss of muscle doesn’t seem to be related to changes in the way we build and break down protein at a base level. Though aging does seem to slightly interfere with our ability to increase protein synthesis through exercise or food intake, this slight interference doesn’t mean that we can’t build or maintain muscle. Resistance exercise combined with the right protein intake has been shown to improve our ability to increase muscle mass, particularly in untrained people. Studies have shown that protein intake in conjunction with resistance exercise helps to maintain or increase muscle mass as we age, even in those aged 85 and older. A study comparing 20-year-old males to 75-year-old males found that both groups had similar levels of muscle protein synthesis when exercise was followed by good nutrition which included protein.
How Much Protein Do We Need and Should We Eat?
If you are involved in resistance exercise, having 25 to 35 grams of protein at each meal will help you get the most benefit from all your hard work. That 25 to 35 grams is the protein content of the food, not how many grams of a particular food you need to eat. For example, a 100g steak has about 31g of protein, and a cup of milk (250g) has around 9g.
What Foods Are Good Sources of Protein?
Without going into too much biochemistry, there are 20 amino acids used to make all the proteins in our body. Nine of these are essential, meaning that we need to get them from our diet; the other 11 can be produced in our body. These essential amino acids are found in animal-based foods like red meat, poultry, fish and dairy. For people who eat these foods, it’s just a matter of quantities and choosing lean options. If you don’t eat animal-based foods, then you’ll need to think a bit more about your mix of foods. Grains and legumes contain some of the essential amino acids, so you need to get the right mix of these types of foods. If you would like to know more about that, let me know. That could be a topic for a future article.
What About Protein Powders and Drinks?
Milk is high in essential amino acids and particularly the branched-chain amino acid Leucine. Leucine not only provides a building block for protein but stimulates protein production in our muscle cells. Whey protein isolate, derived from milk, is high in all the essential amino acids, including Leucine; that’s why it makes such a great post-workout protein drink. Studies show that protein intake soon after resistance exercise can increase production of muscle protein. Consuming a good quality source of protein within the first 2 hours after exercise has been shown to increase the synthesis of muscle protein. This is where a good protein drink can be beneficial.
The production of muscle protein doesn’t just stop after the first 2 hours. Some studies have shown protein synthesis to remain high for 24 to 48 hours after resistance exercise. With this in mind, you can see why including high-quality protein with every meal is really important, and most of it won’t have to come from protein powders.
The take-home message is that exercise and good nutrition are integral to maintaining health and quality of life as we age.
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