Fat, carbohydrate, protein and fibre are known as ‘macronutrients’ because we need them in large amounts in our diets. These nutrients are responsible for providing us with energy as well as having a number of other specific functions. You’ll see these labelled on most food items. Although salt is a mineral, we consume it in relatively large amounts so it’s listed in the nutritional information on food labels along with the macronutrients.
We need fat in our diet. The reason that fats get such a bad rap is that many of us consume too much of the wrong types of fat. Fat is required for growth, development and cell function. There are two fatty acids which are essential and we need them to survive; these are linoleic acid (LA – an omega-6 fatty acid) and alpha-linolenic acid (ALNA – an omega-3). In addition, there are four semi-essential fatty acids that themselves have health benefits, and they can reduce the requirement for LA and ALNA. These are arachidonic acid (AA), gamma-linolenic acid (GLNA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). If you do not include sufficient of these four in your diet, then you need to make sure you’re including plenty of foods that contain LA and ALNA.
There are different types of fat:
Saturated fats - these have historically been associated with an increased risk of developing cardiovascular disease (CVD) when consumed in excess as too much can increase your total cholesterol level. However, more recent evidence has indicated that saturated fats may not be the culprits for CVD but it would still be wise to not over-consume them.
Monounsaturated fats - monounsaturated fats may help to lower the level of 'bad', i.e. LDL, cholesterol in our blood while keeping 'good', i.e. HDL, cholesterol high. Olive and rapeseed oils are rich in monounsaturates, and these fats are also found in small amounts in many nuts and seeds and their oils.
Polyunsaturated fats - there are two main sub-grounds of polyunsaturates: omega-3s found in the seeds and oils of flaxseed (linseed), rapeseed and walnuts as well as oily fish, and omega-6s derived from other seed oils, such as sunflower and soya oil. Both types of fatty acids are essential to humans, as they cannot be made in the body from other nutrients.
The balance of how much omega-3s and 6s is important for health. Most of us are consuming too many omega-6s and not enough omega-3s; ideally, we should aim to consume them in a ratio of at least 1:1-2 (omega 3:6)[1, 2].
EPA and DHA are the omega-3s that are predominantly found in oily fish, fish oils and the algae eaten by the fish. If you don’t consume oily fish, then you need to ensure you’re having a good intake of plant sources of omega-3s. You can read more about this here.
One principal reason why there is overconsumption of omega-6s is that many processed and junk foods are made from these oils which are tasty and cheap to use so they are added in large amounts. These oils are heavily processed and therefore the fats become oxidised – or rancid. These, in turn, are atherogenic or plaque-forming – the initial process involved in the pathology of CVD. We need to include some omega-6s in our diet, but make sure they’re from plant sources where the oil hasn’t been subject to oxidation.
trans fats - trans fatty acids are predominantly industrially produced during the creation of 'hydrogenated' fats, and they are used in margarines and manufactured foods like cakes, pies and biscuits. They confer texture and shelf-life benefits on manufactured foods. These are atherogenic and should be avoided as much as possible.
MCTs - medium-chain triglycerides (MCTs) are types of fat that are absorbed and metabolised more like carbohydrates than fats. Structurally speaking they are saturated fats, but they are processed in the body in a different way, and they provide a very energy-dense, efficient source of fuel. A great source of MCTs is coconut oil.
Read more about fats in our article Good Fats & Bad Fats.
Whilst not essential per se, carbohydrates are extremely useful as an efficient source of energy.
There are two groups of carbs: mono- or disaccharides, aka ‘simple’ carbs, and polysaccharides or ‘complex’ carbs, e.g. starch. Simple carbs include all sugary foods and are fast acting; in other words, the body gets them into the blood-stream quickly creating the ‘sugar rush’.
Many complex carbs are digested more slowly, but there are some that are still broken down quite quickly. Complex carbs include rice, oats, potatoes, couscous, quinoa, other cereals, etc. The Glycaemic Index (GI) is a guide to how slowly carb foods are digested and absorbed. Anything with a low GI is a slow carb, and anything with a high GI will be a fast carb.
Try to minimise your intake of high GI foods as they can cause a spike in the hormone insulin which regulates blood glucose levels. High levels of insulin have been associated with a number of health issues and is a significant factor in the cause of the so-called metabolic syndrome which, in turn, is associated with obesity, type 2 diabetes, CVD and polycystic ovary syndrome (PCOS).
Fibre is actually carbohydrate; it’s all the polysaccharides that humans can’t digest. There are two main groups: insoluble and soluble. Cereals, seeds and vegetables are rich in insoluble fibres – these are great for a healthy digestive system and help fill you up and stop you snacking.
Soluble fibre is found in pulses (peas, beans and lentils), oats and fruit. Not only do these help maintain a healthy digestive system, but they also can help reduce the risk of CVD by binding cholesterol in the gut, stopping it being re-absorbed. Oats are rich in a particularly effective soluble fibre called beta-glucan.
We should all be including plenty of fibre at each meal, and many fibrous foods are also rich in vitamins and minerals. In addition, it’s vital to consume plenty of water to get the most out of your high fibre intake as fibre acts like a sponge.
Protein is essential for the structure of many tissues including muscle, skin and tendons, as well as being a constituent of substances involved in biological processes in the body like enzymes, hormones and antibodies to fight infection.
There are 20 principle amino acids in nature and humans need to include 9 of them in our diet. The 9 essential amino acids are:
All these amino acids have to be included in significant amounts each day. However, one amino acid that needs a particular mention is leucine. This is because it is the amino acid that ‘switches on’ protein synthesis[4, 5]. An enzyme called mTor is the key enzyme that initiates protein synthesis in tissues, and when the level of leucine reaches a certain amount, mTor is switched on and protein synthesis commences. If there’s too little leucine present, then protein synthesis is not ‘switched on’. The amount of leucine that we need to consume in order to keep protein synthesis seems to be over 2.5g per meal three times per day[6, 7] and must be in combination with other amino acids.
Although it’s hard in the Western diet to have an insufficient amount of daily protein, it’s not uncommon for each meal to be too low in protein. Since most proteins are between 5% and 10% leucine, this means that protein synthesis will not be triggered to its fullest degree and not all the protein will be used for anabolic functions. Instead, it will be used for energy and, if there’s sufficient energy, it will be stored as body fat.
Read more in our article Guide to Protein Quality, Digestion and Absorption.
Salt is sodium chloride. Both sodium and chloride are essential electrolytes that we need to consume every day. The problem is most of us are consuming too much as salt is added as a preservative and flavour enhancer to many snack and convenience foods. Sodium is found naturally in many foods, and around 90% of the sodium most people consume is in the form of salt.
Salt can be beneficial for helping hydration, which is why isotonic drinks contain sodium and other electrolytes. If you’re an active person, then include at least 2.5g salt per day, but no more than 6g per day.
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