Macronutrients are nutrients that provide calories or energy. Nutrients are substances needed for a number of bodily functions such as growth and metabolism. We need macronutrients in large quantities, hence "macro" which means large.
There are three macronutrients:
The amount of calories provided by each differs as follows:
- Carbohydrate provides 4 calories per gram.
- Protein provides 4 calories per gram.
- Fat provides 9 calories per gram.
The only other substance that provides calories is alcohol (7 calories per gram) however alcohol is not classed as a macronutrient because we do not need it for survival.
Macronutrients are not the only things that we need for survival - water is of course essential, but we also need micronutrients. Micronutrients are nutrients that our bodies need in smaller amounts, and include vitamins and minerals.
Carbohydrates are the macronutrient that we need in the largest amounts. The recommended daily intake of between 45% - 65% of calories should come from carbohydrate.
Carbohydrate is needed because it:
- is the body’s main source of fuel.
- is easily used by the body for energy (all of the tissues and cells in our body can use glucose for energy).
- is needed for the central nervous system, the kidneys, the brain, the muscles (including the heart) to function properly.
- can be stored in the muscles and liver and later used for energy.
- is important in intestinal health and waste elimination.
Most living things - plant or animal - contain carbohydrates in some form. However some foods are a better source than others. Starches are a primary source of carbohydrate and include the following:
- Starchy vegetables e.g. all kinds of potatoes, yams, squashes, pumpkin, cassava root and Jerusalem artichokes.
- Mildly starchy vegetables e.g. carrots, cauliflower, beets, rutabaga and salsify.
- Cereal grains e.g. wheat, rye, barley, rice, millet, buckwheat and oats.
- Legumes e.g. peanuts, lentils, peas and beans.
- Fruits e.g. bananas, apples, melons, plums, grapes, cherries and fried fruits such as apricots and dates.
Fibre is a type of carbohydrate that our body cannot digest, instead it passes through the intestinal tract thereby helping to move waste out of the body. Diets high in fibre have been shown to decrease risks for heart disease, obesity, and they help lower cholesterol. Foods high in fibre include fruits, vegetables and whole grain products.
It is recommended that the average person consume at least 50 to 100 grams of carbohydrates per day.
The recommended daily intake of between 10% - 35% of calories should come from protein. Every cell in the human body contains protein - it is a major part of the skin, muscles, organs, and glands.
Protein is needed for:
- Tissue repair
- Immune function
- Making essential hormones and enzymes
- Energy when carbohydrate is not available
- Preserving lean muscle mass
Animal sources of protein include meats such as beef and pork, poultry, fish or shellfish, as well as cheese and milk. You don't need to eat meat alone to obtain protein though - vegetarians are able to get enough by eating a variety of plant proteins. Plant sources of protein include:
- Pinto beans, black beans, kidney beans, lentils and split peas
- Nuts and seeds, including almonds, hazelnuts, mixed nuts, peanuts, peanut butter, sunflower seeds, or walnuts (due to their high fat content, these should be consumed in relatively small amounts)
- Tofu, tempeh and other soy protein products
When proteins are digested they are broken down into their constituent parts, amino acids. Amino acids need to be eaten in large amounts for optimal health benefits. Some amino acids are essential which means that we need to get them from our diet, and others are non-essential which means that our body can make them. If you find it difficult to get enough protein into your daily diet then an amino acid supplement is easy and convenient.
Fats might evoke negative connotations, for example being the cause of weight gain, however some fat is essential for survival. A recommended daily intake of 20% - 35% of calories should come from fat. This is required for:
- Normal growth and development
- Energy (fat is the most concentrated source of energy)
- Absorbing fat-soluble vitamins A, D, E, K, as well as cartenoids
- Providing cushioning for the organs
- Maintaining cell membranes
- Providing taste, consistency, and stability to foods
Fat is made up of individual fatty acids - they are essentially the ‘building blocks’ of fat. Some of these fatty acids have vital functions in your body, and you have to get them from your diet as your body can’t make them. These are known as essential fatty acids and include Omega-3 and Omega-6. The essential fatty acids are important as they are used to make the outer layer (membrane) of the cells in your body and are also involved in the production of certain substances that control chemical reactions inside your cells.
It is extremely important to the right fat into your diet - there are in fact three main types of fat: saturated fat, unsaturated fat, and trans fat.
Saturated fat and trans fat have been shown to increase your risk for heart disease. Replacing saturated and trans fat in your diet with unsaturated fat has been shown decrease the risk of developing heart disease.
The average man should consume no more than 30g of saturated fat per day, and the average woman no more than 20g per day. A high amount of saturated fat is considered to be anything over 5g of saturated fat per 100g, whereas a low amount is considered to fall under 1.5g of saturated fat per 100g. The following are classed as foods high in saturated fat therefore your intake should be limited (better yet fatty meats should be avoided altogether):
- Fatty meat and meat products
- Dairy products such as butter, cheese and cream
- Cakes and biscuits
- Palm oil
Unsaturated fat, which includes monounsaturated and polyunsaturated fats, are the type of fats you need to aim to eat instead of saturated fats.
Good sources of unsaturated fats include:
- Sunflower, rapeseed, olive and vegetable oils, and spreads made from these oils (so long as they have not been hydrogenated)
- Nuts and seeds
- Oily fish, such as mackerel, salmon or trout – these are a particularly good source of omega-3
Putting this advice into practice, try the following:
- Watch your portion sizes – if you can't resist a bacon sarnie then just have one less rasher.
- If you love your cheese, grate it to make it go further.
- When you fancy a cake or biscuit, savour just the one!
- Try delicious smoked mackerel for breakfast instead of indulging in that greasy fry-up.
- Opt for lean meats such as chicken and turkey or try fish and keep red meat to a minimum.
- Choose tomato-based sauces over creamy or cheesy ones in pasta dishes and curries.
- Grill or bake your food rather than fry it.
- And if you get an attack of the munchies, snack on a handful of nuts, rather than heading straight for the biscuit tin.