Here’s a list of common nutrition terms that are often used in relation to a healthy lifestyle and balanced diet, and which are used in this book.
Kilojoules
Kilojoules, or calories, measure the energy-generating capacity of our food. Put simply, they show us the amount of energy that foods provide us with – one calorie has the same value as 4.186 kilojoules. The energy content of foods depends on their ratio of carbohydrates, fats and proteins. Carbohydrates have 16 kilojoules per gram, protein 17 kilojoules per gram, fat 37 kilojoules per gram and alcohol 27 kilojoules per gram. Your body needs kilojoules for energy, but too many in your diet and not enough movement to burn them off can lead to weight gain. Different body types and lifestyles require different amounts of kilojoules per day; for example, I had to greatly reduce my intake when I stopped training and no longer needed the same amount of energy. On average, an adult female has a daily requirement of 9000 kilojoules and an adult male requires 11,000 kilojoules.
Carbohydrates
Carbohydrates are the body’s preferred fuel source as they are quickly converted to glucose, the body’s main form of energy. (Other energy sources are fat and protein, but their conversion to energy is less efficient.) The average adult should aim to consume 310 g of carbohydrates a day, or in other words, sixty per cent of their energy intake should come from carbohydrates. When I am training and competing, I have a very high amount of carbohydrates in my diet as I literally burn them all off in the pool.
There are two main types of carbohydrates: ‘simple’ and ‘complex’, relating to what they are made up of and how quickly they are absorbed and raise glucose levels in the blood. Simple carbohydrates are sugars that are converted into energy quickly, but which also burn out just as fast. Examples are sugar itself, as well as soft drinks, honey and some fruit. Complex carbohydrates are starches that take longer to be digested and absorbed, and therefore give a slower release of energy. Their slower digestion also means they are less likely to cause an overproduction of glucose, which in turn is less likely to be stored as fat. Complex carbohydrates include grains and legumes, rice, bread and potatoes. The best complex carbohydrates are those that are unrefined and contain fibre, such as wholemeal bread or brown rice, as they are the slowest to be digested and absorbed, so they provide sustained energy, and they also come with more nutrients.
Glycemic Index and Glycemic Load
The Glycemic Index is a ranking from zero to 100 (and sometimes above) given to foods to describe how quickly the carbohydrate they contain is digested and absorbed into the blood. The scale doesn’t simply go from complex carbohydrates at the bottom through to simple carbohydrates at the top, as some complex carbohydrates have a medium or high GI, such as white bread, white rice and potatoes.
GI is an extremely important consideration for those with diabetes, as by eating low-GI foods, the body is able to control its blood glucose and insulin levels. Low-GI foods take longer to digest, which means they keep you feeling fuller for longer. Low-GI foods include wholegrain cereals, breads and pastas; beans and lentils; seeds and nuts; milk and yoghurt; vegetables such as broccoli, avocado and salad greens; and fruit such as apples, cherries, oranges, pears and plums.
High-GI foods include a lot of the white, refined stuff with ‘empty’ calories, such as white bread, white rice and breakfast cereals such as Rice Bubbles or cornflakes, and dates, watermelon and soft drinks.
However, to make matters slightly more confusing, it has been revealed that GI doesn’t give the full picture – as it doesn’t take into account the quantity of carbohydrate in foods, only the quality of the carbohydrate. Glycemic Load (GL) is based on GI as well as the amount of carbohydrate, and gives you a more accurate idea of how foods affect your body. It paints foods such as watermelon (with a high GI but a small amount of carbohydrate) in a much better light. How you combine food in meals is another factor that should be considered – as foods high in GI and GL combined with foods low in these things, such as high-fibre vegetables, also changes the effect on blood sugar.
Eating low GI and GL foods for slow energy release is really important for endurance sports. Considering the GI and GL value of foods can give an athlete a definite edge, as sometimes high GI and GL foods are needed for an energy burst, whereas in long hours of continuous exercise, low GI and GL foods are required.
Protein
Protein is the base of our muscles, skin and cells as well as our hormones, antibodies and enzymes. It is used to build and repair muscles, making it an especially important part of any athlete’s diet. Protein can also provide the body with energy in the absence of adequate carbohydrates, but it does this slowly and in smaller amounts.
The protein we eat is digested to release amino acids, and while the body makes some of its own amino acids, there are others that must be supplied through food. Meat including fish is a well known source of protein (100 g of lean beef contains around 23 g of protein; 100 g of fish has 27 g), but other excellent sources include eggs and dairy products, beans, lentils, soy products, seeds and nuts. The recommended daily intake of protein is 46 g for women and 64 g for men, but this varies with an individual’s weight. Like fibre, eating protein makes us feel full.
Fibre
Dietary fibre is extremely important for a healthy digestive system – even though it is actually indigestible. There are two types of fibre – insoluble and soluble. Insoluble fibre passes through the body relatively unchanged, adding bulk to the contents of our intestines and producing a laxative effect. Soluble fibre absorbs water and softens bowel movements, and is fermented by friendly bacteria in the large intestine to produce short-chain fatty acids that stabilise blood-glucose levels and can help to reduce low-density lipoprotein (LDL or ‘bad’) cholesterol. It is recommended that we eat 30 g of fibre a day to reduce such things as constipation and the risk of bowel cancer. Fibre is found in plant-based foods, which often have a combination of both soluble and insoluble fibre. Sources of insoluble fibre include wholegrain bread and cereals, bran, legumes and the skin of fruits and vegetables, while sources of soluble fibre include fruit and vegetables, oats, barley, legumes and seeds.
Sugar
Sugar is a simple carbohydrate that can be added to food or which naturally occurs in it. Some of the different types of sugar include table sugar (sucrose), sugar found in fruit (fructose), and sugar found in dairy foods (lactose). A small amount of sugar in the diet is okay – people generally assume that table sugar (sucrose) has a high GI, but in fact it has a moderate one of 65. But too much isn’t good for you and, like all carbohydrates, if sugar isn’t used as energy by the body, it is stored as fat. Food with naturally occurring sugar is always preferable to food with added sugar such as lollies and soft drinks (a 375 ml soft-drink can contains up to ten teaspoons of sugar!).
Salt
Salt is composed of the minerals sodium and chloride, which naturally occur in animal products, plant foods and water and are essential nutrients in our diets. Sodium balances the amount of fluid in the body’s tissues and blood, and helps with nerve and muscle function. However, excess sodium has adverse effects and today people commonly exceed the amount of sodium their bodies require, leading to high blood pressure, increasing the risk of strokes and heart disease, and also causing water retention. The Heart Foundation of Australia recommends a maximum sodium intake of 2300 mg (approximately 6 g or 11.2 teaspoons of salt) a day for Australian’s with normal blood pressure. Processed foods such as breakfast cereals, snack foods and tinned vegetables are generally very high in salt and contribute to seventy-five per cent of the salt intake in the average diet.
Fats
Fats don’t entirely deserve a bad wrap, as some are beneficial. Believe it or not, fat is actually classed as a nutrient and helps the body to absorb vitamins A, D, E and K. The good fats are monounsaturated and polyunsaturated fats. Monounsaturated fats are found in canola and olive oil, avocados and nuts. Polyunsaturated fats include Omega-3, which is found in oily fish such as salmon and sardines, as well as linseeds, walnuts, soy products and green leafy vegetables. It lowers LDL cholesterol and blood pressure and reduces the risk of heart disease. Omega-6 is another beneficial polyunsaturated fat found in nuts, seeds and plant-based oils such as soybean, corn and sunflower oil. However, it is over-consumed in the modern Western diet (i.e. cooking oil used in processed foods, and margarine) and has detrimental effects, even countering the benefits of Omega-3 and leading to conditions such as heart disease. So, most people today need to concentrate on their Omega-3 intake and reduce their Omega-6 intake.
Other fats to limit in your diet are saturated and trans fats. Saturated fats are found in animal products – fatty meats, processed meats and dairy products – and in some plant sources such as palm and coconut oil. Trans fats do occur naturally, but are also manufactured for use in margarine, shortening and factory-baked goods. Both of these fats behave similarly in our bodies and can increase the levels of LDL cholesterol and lead to heart disease.
Vitamins and minerals
Vitamins are organic compounds that our bodies use for a variety of metabolic processes. Minerals are inorganic elements that are also just as necessary for health and wellbeing.
It’s always best to get your vitamin and mineral needs from a varied diet, and supplements shouldn’t be considered a substitute for balanced eating. Studies have shown that vitamins and minerals can be dangerous taken in large doses and ‘out of context’ – without the related compounds they occur with in foods. Here are just a few of the vitamins and minerals our bodies require and some of the foods they occur in:
Calcium is a vitamin that promotes healthy bones and teeth and works with vitamin K in clotting blood when we are wounded. Good sources of calcium include dairy products, broccoli, green beans, almonds, orange juice, salmon and sardines.
Folate is a B vitamin used for growing and repairing red blood cells. Good sources include asparagus, broccoli, spinach, legumes, mushrooms, oranges, bananas, strawberries and tuna.
Vitamin A promotes health in bones, teeth, skin and mucous membranes, and is an antioxidant. Great sources include many orange fruits and vegetables such as mangoes, apricots, carrots, pumpkin and sweet potatoes, along with spinach, broccoli and tuna.
Vitamin C is used in collagen production, boosts our immune system, and is an antioxidant. Oranges are a well-known source of vitamin C, but others are grapefruit, berries, kiwi fruit, capsicums, tomatoes, cabbage and broccoli.
Vitamin D is involved in calcium absorption as well as general bone and teeth health. The best source of vitamin D is sunlight, but it is also found in eggs, tuna and salmon.
Vitamin E is important for good circulation and healthy skin, and is an antioxidant. Good sources of vitamin E include oils, nuts, seeds, broccoli and mangoes.
Iron is a mineral used for carrying oxygen in the blood. Great sources are red meat, oysters, leafy greens, soy products, dried fruit and sesame and pumpkin seeds. However, iron from animal sources is better absorbed by our bodies. Vitamin C assists in iron absorption.
Magnesium is a mineral involved in the production of energy and the function of enzymes. Great sources of magnesium are nuts and seeds, grains, seafood, spinach, broccoli and bananas.
Potassium is a mineral that helps in the functioning of nerves and muscles and in controlling blood pressure. Good sources are meat, milk, avocados, spinach, tomatoes, pumpkin, mushrooms and bananas.
Zinc is a mineral that supports the immune system, helps with wound healing and is an antioxidant. It is found in meat, fish, oysters, dairy products, wheatgerm and legumes.
Antioxidants Antioxidants are compounds found in certain foods that help to fight off the damaging effects of chemicals called free radicals. Free radicals come about when oxidation occurs in the body, and can be accelerated by environmental factors such as pollution, smoking, stress and overexposure to sunlight. The body can’t cope with an overload of free radicals, and they can eventually lead to serious conditions such as heart disease and cancer, which is why antioxidant-rich food should feature in our diets. Antioxidants neutralise cell damage and keep the body healthy. Just some of the great antioxidants include vitamins C and E and beta-carotene, which is a precursor to vitamin A and found in the same foods; flavonoids (found in green tea, red wine, citrus fruit and pomegranates); and lycopene (found in tomatoes and pink grapefruit).