Dietician, Christine Peters, shares some secrets about how PROTEIN affects our diet!
Proteins are made up of amino acids, the building blocks of all tissues in our body. As well as being essential for growth and repair of body tissue, they are used to make hormones, enzymes, antibodies and neurotransmitters, and help transport substances around the body. Both the quality of the proteins you eat (determined by the balance of these amino acids) and the quantities of proteins you eat are important.
Generally, it is recommended that protein make up 15% of our total energy intake, but we are often not given enough guidance to the quality of protein. For example, the average baby only receives about 1% of its total energy intake as protein and manages to double its birth weight in six months. This is because the quality of protein is good and easily absorbed. Assuming that you actually take in 15% protein daily, 10% should be good quality (about 35g). This is an optimal intake for most adults, unless pregnant, breastfeeding, recovering from surgery or undertaking large amounts of exercise or heavy manual work. For us runners, the amount and quality of our protein intake is vital in ensuring we stay fit, healthy and strong.
PROTEIN REQUIREMENTS AND ENDURANCE EXERCISE
The amount of protein you need increases or decreases when exercising, according to the amount needed to fuel muscles, and the amount needed to account for any extra muscle that is laid down. As an athlete generally consumes more calories, this extra protein needed during endurance sports is generally covered, so there is no need for athletes to supplement with powders and supplements.
Most athletes’ total protein needs are met with 1g protein per kilogram of body-weight e.g. 60g for a 60kg athlete. However, if an athlete’s daily training sessions are lengthy and intense (burning up a significant amount of their protein fuel), they will require an increased protein intake. The protein requirements of different athletes are summed up in this table:
|General sports activity||1g of protein per kg body weight|
|Endurance training athletes (aim for high end of range for very strenuous and prolonged activity)||1.2g to 1.6g of protein for every kg you weigh|
|Adolescents and growing athletes||2g of protein for every kg you weigh|
|Pregnant athletes||Extra 10g of protein per day in trimesters two and three|
|Breastfeeding athletes||Extra 20g of protein per day|
Most South African diets cover these recommendations (12% to 15% total energy intake as protein) however, low-energy consumers may find that 15% to 20% of their total energy budget is needed as protein. For example, people who are watching their weight and are only eating limited amounts, may need to consume a slightly bigger percentage of their total intake as protein.
In the sporting world, many people tend to think that consuming large amounts of protein will lead to bigger muscles and enhanced muscle function. However, any excess protein that is not used is broken down and its waste products are excreted via the kidneys in urine. This means that a high protein diet will put strain on the kidneys and can even leech calcium off your bones, increasing the risk of osteoporosis. In fact, there isn’t enough evidence to prove that massive amounts of protein in any form are advantageous to athletes. Also, concentrated amounts of amino acid solutions found in protein can cause cramping and diarrhoea due to the large amounts of water that are drawn into the intestines.
GOOD PROTEIN, BAD PROTEIN
Protein choices should always be made with other nutritional goals in mind. Animal proteins supply the body with essential amino acids which are easily absorbed, as well as other nutrients such as calcium (dairy products) and iron (meat and shellfish). But, many animal proteins are also naturally high in saturated fat and cholesterol. The best choice is to choose proteins with a low fat content, such as low fat or fat free milk, chicken without skin, lean beef or boiled eggs. Vegetable proteins, on the other end of the scale, tend to be high in carbohydrates, such as is found in soya products like soya sausages, cutlets, burgers.
Complete Versus Incomplete Proteins
Some foods provide a good balance of essential amino acids and are generally regarded as superior sources of protein. Generally, animal proteins are seen as more ‘complete’ in terms of their amino acids, than vegetable proteins. But, people who don’t eat many animal proteins can obtain essential amino acids from a variety of plant foods such as vegetables, fruit and grains. Grains, nuts and legumes are great sources of plant protein but they all lack a different essential amino acid. When these complementary proteins are eaten together, all the essential amino acids can be obtained from them. Not sure how to combine these? Try rice and beans, rice and peas, peanuts or peanut butter and bread, or samp and beans.
YOU DON’T EAT MEAT?
There are a lot of concerns surrounding vegetarians and vegans. Vegans have to make a concerted effort to eat sufficient amounts of high quality protein and are at risk of having insufficient amounts of calcium, iron and vitamin B12. It is recommended that true vegetarians consult a dietician to ensure they get a good balance of essential nutrients. Lacto-vegetarians (dairy consuming vegetarians) and ovolacto-vegetarians (egg and dairy consuming vegetarians) can easily meet the recommended intakes of these ‘lacking’ nutrients.
PROTEIN, PROTEIN EVERYWHERE
This table can be used a guideline to help you assess which proteins will help you meet your daily nutritional requirements.
The following foods have approximately 10g protein:
Low-fat animal proteins
- Grilled fish (50g cooked weight)
- Tuna, salmon or pilchards (50g)
- Lean beef or lamb (35g cooked weight)
- Turkey or chicken (40g cooked weight)
- Game biltong (15g)
- Lean beef biltong (25g)
- Eggs (2 small)
- Cottage cheese (70g)
- Reduced fat cheese (30g)
- Low fat yoghurt (200g carton)
- Low fat milk (300ml)
- Liquid meal supplements (150ml)
- Wholewheat bread (4 slices)
- All bran flakes (2 cups)
- Cooked pasta (1 ? cups)
- Cooked brown rice (3 cups)
- Cooked lentils (2/3 cup)
- Baked beans (4/5 cup)
- Cooked soya beans (? cup)
- Nuts (50g)
- Raw tofu (120g)
- Peanut butter (3 tablespoons)
Source: Langenhoven M, Kruger M, Grouws E, Faber M. MRC Food composition Tables, 3rd Edition. Parow: Medical Research Council. 1991.