I have a severe case of post-Christmas blues! One of the key things driving this is the state of my arms after a bit of a sedentary time over the holidays. As a result, one of my new year’s intentions is to get better muscle tone and finally rid myself of the post-45 ‘tuck shop arm’ sag. Bring on the protein!
It can be very confusing trying to work out exactly how much protein you need as you age, and the world is populated with food Nazis at every corner – all with completely opposing views. In our book, Fast Living, Slow Ageing, we’ve taken a fairly pragmatic approach as you’ll read further on. You can also adopt a diet which has a sensible amount of protein and I’m personally a great fan of Barry Sears and his Zone Diet (he recommends 40% of all calories should come from protein). I lost 13kg on the zone diet. I want to say upfront though that I’m not a nutritionist – we consulted a range of experts to put the following together as a basic guide.
Firstly, a little bit about protein
Proteins are the structures our body builds – from the hair on our heads to the nails on our toes. Over half of our body’s dry weight is protein. Although there are countless different proteins in every cell of our body, at their core proteins are composed of the same twenty bricks. These bricks are called amino acids. Every protein is made up of chains of amino acids linked together in differing amounts and different combinations determined by our genetic code. The body can also use amino acids building blocks for other purposes, like the synthesis of hormones and as a fuel source for energy metabolism.
The body can make eleven of the twenty amino acids we need to make a protein. The others must be obtained from the food we eat. If any of these nine essential amino acids is lacking in our diet, the body must break down another protein to obtain them. This chapter will examine the different kinds of dietary protein and its role in slowing aging.
What protein should we eat?
When we eat any protein, it is rapidly dismantled by our digestive system. So when we consider the value of any protein in our diet, we are really talking about:
- The other nutrients that are ingested at the same time (such as fats, vitamins and fiber). For example, a steak is packed with animal fats as well as protein. By comparison, lentils contain less than 5% fat, as well as the bonus of fiber, vitamins and minerals.
- Its composition of essential amino acids. For example, most animal sources of protein (e.g. meat, milk, eggs) have the complete complement of all the essential amino acids. Most plant proteins lack at least one amino acid. However, there is little danger of deficiency in a vegetarian diet, as most involve eating a broad range of plant foods (known as protein combining or complementing). For example, a meal containing rice as well as legumes provides all the essential amino acids found in a typical meat dish. Some special vegetable sources provide a full range of amino acids (so called complete proteins), including soy products, quinoa, spirulina, buckwheat and amaranth.
- Its biological value. This measures the amount of any dietary protein that ends up being used by the body. Some proteins, like egg white and whey, are almost completely utilized. This is why these are the main ingredients of most protein supplements used by body builders and people with increased protein requirements. Methods of food preparation also impact on the biological value of proteins. For example, prolonged cooking or processing in the presence of fats can destroy some amino acids, reducing their biological value as well as generating toxins and carcinogens.
How much protein should we eat?
Adults need between 45 to 80 grams of protein a day. We regularly consume twice this much. In general, if we are getting enough calories, we are almost always getting enough protein. Most animal products are between 20% and 30% protein. For example, a 100g piece of steak will contain about 29g of protein and a piece of fish about 22g. Legumes contain approximately 15% protein with soy and nuts containing about 20%.
Higher protein intakes may be helpful for those undertaking an exercise program, in pregnant women and those with increased protein turnover (e.g. recovering from surgery or illness, cancer, burns). In particular, there is some advantage in consuming extra protein around the time of exercise, when muscles are at their most needy.