Information on Nutrients
What constitutes a 'healthy diet'?
The plans in this website demonstrate that what's 'healthy' for one individual need not be 'healthy' for another. We are all different and have different daily routines and therefore have different nutritional requirements. However there are a few basic 'rules' that are common to everyone whatever we do and whoever we are. The main one being we need to eat a wide variety of different foods, not just to prevent boredom, but as no single food contains all the nutrients we need, we have to eat a mixture.
All plans on this site take into account complete nutrition and variety, so use them as a baseline in order to teach yourself what you should be eating to suit your job, sport or metabolic state, and you can be assured of not only adequate nutrition, but also of optimum nutrition. It may seem confusing with all the names of all the different nutrients, so to help you out, this section gives a brief run down of all the main nutrients, what each nutrient does in the body, and the relevance of each to your nutrition.
In addition to the information in this section on the different nutrients we require, you may wish to refer to our Information on Foods and Supplements section, where you can read about some less common foods and nutritional supplements referred to in the meal plan text that you may not be familiar with.
Carbohydrates traditionally form the bulk of many people's diets, and there are different types:
The simplest form of carbohydrate and the building blocks of complex carbs, sugars are single or double units known as saccharides. Monosaccharides, such as glucose, fructose and galactose are single unit sugars, while disaccharides, such as sucrose (table sugar - two glucose molecules) and lactose (milk sugar - glucose and galactose) are made up of two monosaccharides, joined together.
These are short chains of monosaccharides (about 3-20). They often pass through the small intestine into the colon, where they are digested by the so-called 'friendly bacteria', helping them to survive and multiply in the gut. For this reason, some oligosaccharides, e.g. FOS (fructo-oligosaccharides) are known as prebiotics. As oligosaccharides taste slightly sweet but are not absorbed, they are used as bulking agents in low calorie granulated sweeteners.
These are commonly known as complex carbohydrates and are large molecules of many hundreds of monosaccharides, joined with different bonds creating unique structures. Glycogen is a storage carbohydrate composed of many glucose molecules in the muscle and liver as an energy store, to be broken down when energy supplies are required. Starch is the plant equivalent of glycogen, and is a major nutrition source in people's diets.
There are numerous methods of classifying carbohydrates, depending on their structure or digestibility and absorption, the most well known is the glycaemic index or GI. The GI measures the reaction of the blood glucose levels to consuming a carb-containing food when compared with glucose, which has a GI of 100. Low GI foods, below about 55 cause glucose levels in the blood to rise only slowly and over a long time period, compared with high GI foods of over 70, which lead to a rapid but short lived rise in blood glucose.
In practical terms, a low GI food with its more sustained release of glucose into the blood will keep you feeling fuller for longer compared with a high GI food that will satisfy hunger only for a short time period. The situation is complicated by the fact that consuming different foods with one another will alter the GI. Thus, eating high GI white bread with butter will lower the overall blood glucose response, so lowering the glycaemic load. Fat and protein both act to slow the absorption of glucose from carb-containing foods, reducing the glycaemic load of the meal.
Please see our Glycaemic Index Tables for GI values of foods.
Another relevant method of classifying carbohydrates is by the insulin index or II. This describes the response of blood insulin to consuming all foods, not just one that contains carbohydrate. Some meats and other low carbohydrate foods evoke an insulin response without a glycaemic response.
High GI carbohydrate foods include all sugars, cakes, confectionary, white bread, white pasta and some breakfast cereals. Medium GI foods include wholemeal bread, some types of potato and some high fibre breakfast cereals. Low GI carb foods include sweet potatoes, small new potatoes, basmati rice, quinoa, granary bread and oats.
Uses of carbohydrate
Digestible carbohydrate, in whatever form is ultimately broken down into short chains or single units and absorbed into the bloodstream. Monosaccharides may then be converted to glucose and used immediately as an energy (ATP) source. Alternatively, they will be stored (associated with water) as glycogen in both the liver and muscle. This energy store can be quickly mobilised to supply the muscles and brain (which relies solely on glucose as its energy source).
The capacity for storing carbohydrate is limited when compared to the near limitless amounts of fat that can be stored in the body. Therefore, if excess carbohydrate is consumed beyond the body's needs, it will be transformed and stored as adipose tissue (i.e. fat). In most cases a reduced (but not zero) carb intake is advisable for fat loss.
Relevance of carbohydrate in exercise
Carbohydrates add calories (i.e. energy), they provide valuable vitamins, minerals and fibre, and they ensure that muscle recovery is swift and effective following training. The basis of an exercising person's diet should be low to moderate GI carbohydrates, to keep blood glucose and hence insulin levels stable. The pre-workout meal should contain sufficient amounts of low GI carbs to ensure the training is adequately fuelled. For hard exercising people, fast acting, high GI carbohydrate, immediately post training important to promote re-fuelling.
Fibre refers to the indigestible part of carbohydrates, consisting of non-starch polysaccharides (NSP) and other molecules such as oligosaccharides, inulin and pectin. Although, strictly a carbohydrate, we tend to classify dietary fibre on its own. Soluble forms of fibre may be used by the microflora in the colon for energy, helping to maintain adequate levels of 'friendly bacteria' and may also help control blood cholesterol levels. Insoluble fibre absorbs water and helps produce healthy bowel movements by creating large, soft stools that pass through the system more rapidly.
Sources of soluble fibre include oats, pulses (peas, beans and lentils) and some fruits. Sources of insoluble fibre include green vegetables and wholemeal and wholewheat products.
Protein molecules are long chains of constituent amino acids, joined together by 'peptide' bonds. There are 20 standard amino acids that can be joined to form proteins. The combination of different amino acids in the chain, along with the relative numbers of each in the protein will determine the overall structure of the protein and therefore its purpose. The 20 amino acids used in protein are listed below. Those in italics are deemed essential because they cannot be created in the body from other amino acids, therefore they must be obtained from the diet, or deficiency will result:
There are other, non-protein amino acids such as ornithine and taurine, which have their own particular biological functions. Indeed, many of the above standard amino acids also have non-protein functions in the body, as discussed below.
Uses of protein
- Structural – protein is incorporated into muscle tissue, and is needed for muscle growth. Other structural proteins include collagen, responsible for giving skin its structure and elasticity and keratin, present in hair and nails.
- Enzymes – these are molecules of protein responsible for performing or catalysing metabolic reactions. For example, amylase is an enzyme that catalyses the digestion of starch into smaller molecules in the mouth and in the upper intestine.
- Oxygen transport molecules – these facilitate the carriage of oxygen around the body in the bloodstream (haemoglobin) or in the muscles (myoglobin).
- Hormones – some hormones, such as growth hormone, insulin and glucagon are proteins. These play a key role in anabolism and metabolism.
- Immune system – some immune systems factors are made up of proteins.
Uses of amino acids
The majority of amino acids are incorporated into protein to fulfil the above functions, and some individual amino acids have particular roles in the body. These include:
- Glycine is used in the production of creatine (muscle function), haem (oxygen transport and the final part of respiration) and glutathione (antioxidant)
- Lysine is required to synthesise carnitine, an amino acid used to transport fat for oxidisation.
- Arginine is metabolised to form nitric oxide, which is involved in blood pressure control, neurotransmission and immune function.
- Tryptophan is used in the synthesis of the 'happy hormone' serotonin, which is why consuming tryptophan rich foods before bed such as milk or cottage cheese may help you sleep.
Many other amino acids have vital functions in the body. However, supplementing with these aminos will not necessarily result in, say, more creatine or more fat being oxidised, as they may just be surplus to requirements.
Biological value (BV) of protein is a measure of the percentage of protein ingested that is stored in the body. Whey protein has the highest biological value, with egg a close second. Further down the list is milk, followed by fish, beef, chicken, soy and pulses. This method of characterising protein has significant flaws, such as ignoring the amino acid profile of a protein (which effectively could have a high biological value but lack an essential amino acid).
When bulking, eat as much of your protein from lean food sources: grilled chicken and turkey, lean cuts of red meat, white fish, oily fish, tuna, low fat cottage cheese, pulses, egg whites, etc. However, for those with high protein requirements but not so big appetites, supplementary protein shakes can be a useful addition.
Fats are essential to any diet although the form of fat influences its metabolic fate and relative 'healthiness'. While fat does not make you fat per se, consuming an excess of these naturally calorie dense macronutrients may lead to weight gain, as they contain 9kcal per gram making fats the most calorie dense macronutrient. However, in spite of their high energy value, their effect on appetite is poor, making it easy to consume excessive amounts without the usual feeling of satiety that accompanies eating a meal rich in complex carbohydrate or protein.
Types of fat
Fatty acids are chains that can vary in length from a few units long to over 20 units in length. Some are essential, while others can be made from other fatty acids in the diet.
Saturated fats have been associated with an increased risk of developing cardiovascular disease, when consumed in excess. They are mostly found in animal products, and although fashionably maligned, can be a useful source of energy in some diets, provided they are not eaten in excess.
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. They are found in olive and rapeseed oils.
Trans monounsaturated fatty acids are unsaturated but because of their structure, they behave more like a saturated fat. They are predominantly industrially produced during the creation of 'hydrogenated' fats, used in margarines and manufactured foods like cakes, pies and biscuits. They confer texture and shelf life benefits on manufactured foods. They have a worse effect on cardiovascular health than saturated fats. However, some trans fats are naturally present in meat and dairy products. Avoidance of industrially produced trans fats is possible by choosing products that do not contain hydrogenated vegetable oil.
Omega 3 and omega 6 fats
The omega 3 and omega 6 fatty acids are both types of polyunsaturated fats. Omega 3s are derived from the seed oils linseed, rapeseed and walnut oil, meat from grass-fed animals e.g. beef and green leafy vegetables. Omega 6 fatty acids are derived from other seed oils, such as sunflower, and soya oil. Both types of fatty acid are essential to humans, as they cannot be made in the body from other nutrients.
It is thought that the balance of intake between the omega 6 and omega 3 fatty acids is more important for health than the actual amounts consumed. Currently, far more omega 6s are consumed than omega 3, when they should ideally be consumed in a ratio of about 2:1 (omega 6:3).
The length of the fatty acid chain of omega 3s can vary. Very long chain omega 3s are known as EPA and DHA and are predominantly found in oily fish, fish oils and the algae eaten by the fish. It is thought that long chain omega 3s, derived from fish or marine algae have particular health benefits for cardiovascular health and brain development. These do not appear to be seen at equivalent intakes of omega 3s derived from seed oils, nuts and plant sources. It may be that at high levels of seed oil consumption, similar benefits are conferred and this is of particular importance to those who do not eat oily fish.
Studies have shown that fish oils may decrease blood pressure. They have been shown to decrease the level of blood lipids, improve the diameter of blood vessels and decrease inflammation within of the blood vessels. The retina and brain contain a lot of DHA. Some studies have shown that by supplementing with long chain omega 3s during pregnancy, the mental development of children may be improved. They may also play a role in the healthy development of the eye.
Functions of fats
- Storage – is often not a desired function! However, fat is a mode of energy storage as adipose tissue, visible in the form of external fat, located on the abdomen (common in men) or hips, bottom and thighs (common in women). Excess stored fat can increase risk of cardiovascular disease and cancer, decreasing mobility and therefore affecting fitness and affecting self esteem. Fat stored in the abdominal region is thought to be the worst in terms of the effects on health. Fat can also be internal, located around organs such as the liver or heart. This type of fat is a significant health risk.
- Cellular structure – the membrane of every cell is composed of a type of fat known as phospholipids, which allows the transfer of molecules from outside the cell to the inside and vice versa. This is also a water resistant barrier between the cell and its external environment.
- Hormones - such as the steroid hormones testosterone and oestrogen are made from fats.
Sources of fats in the diet
- Hard fats – the composition of these depends on the origin. Hard animal fats such as lard and suet contain a greater percentage of saturated fats. Butter contains milk fat and also a high proportion of saturated fats because it is hard at room temperature. Margarines and lower fat spreads have variable amounts of the different types of fat, some being high in poly- or monounsaturates. Some older spreads were made by hydrogenation producing trans fats so fortunately manufacturers have now begun to develop processes that do not result in the formation of trans fats.
- Oils - vegetable oils, from plant seeds (linseed, rapeseed, sunflower seed, etc) or from the fruit (avocado, olive and most nuts) have variable fatty acid composition. Many are good sources of omega 6 fatty acids and monounsaturated fatty acids. Linseed oil is a good source of omega 3 fatty acid. Notably, palm oil and coconut oil are rich in medium chain saturated fatty acids.
- Milk and dairy products – The fats present will depend upon whether the product is made from skimmed, semi-skimmed or full fat milk. Unfortunately most milk fat is unhealthy homogenised fat.
- Eggs – provide a significant source of fat (mainly saturated and monounsaturated fatty acids) and cholesterol, most of which is housed in the yolk.
- Fish oils – lean, white fish store their fat in their liver (e.g. cod) whereas oily fish will store it in the flesh (e.g. mackerel, salmon). Fish oils are a great source of omega 3 fatty acids.
- Meat – the proportion of the different types of fatty acid in muscle meat will vary depending upon the species and the cut of meat. Leaner cuts will have a greater proportion of unsaturated fatty acids compared to saturated and are therefore healthier than those cuts with visible fat or 'marbled' effect.
Micronutrients are elements or small molecules essential for life but are only required in very small quantities, i.e. dietary minerals and vitamins. Always aim to get micronutrients into the body by eating a wide variety of foods. Supplements should only be used in cases of high requirements or clinical deficiency.
Sodium, potassium and chloride ions are essential to the regulation of water balance within the body. Deficiency of sodium, chloride and water, as seen with vomiting, diarrhoea, kidney failure, excessive sweating or loss via burns or dialysis can lead to characteristic symptoms of dehydration, i.e. physical exhaustion, reduced blood pressure and cold extremities.
Treatment of mild cases is best achieved by administration of sodium chloride and other salts orally with water being retained in parallel. For hard exercise, replacement of electrolytes by use of one of the many proprietary sports drinks is usually sufficient.
Excessive intakes of sodium chloride are common in the Western world, as salt is a frequent addition to processed foods to add flavour. Therefore, people's palates have changed to favour saltier tasting foods. The result of diets high in salt, even when these do not elevate levels high enough to impact salt content within the body, is often high blood pressure, which can put strain on the heart and lead to heart attacks and strokes.
These are minerals found in larger amounts in the body. Deficiency of calcium, phosphorous and magnesium can lead to bone wasting diseases such as osteoporosis, where the bone composition remains the same but the volume decreases, rendering the sufferer more prone to fractures. However, the causes of osteoporosis are multiple and not due to diet alone.
There is 1kg of calcium in the adult skeleton and this calcium is in constant flux between the skeleton, kidney and intestine via the blood, and the balance is maintained by hormones. Calcium is also required for muscle contraction and healthy teeth. It is primarily found in dairy products but is also present at significant levels in dark green vegetables, seeds (where it is highly bioavailable) oily fish with edible bones (e.g. canned sardines and salmon) and pulses.
85% of the phosphorus is within the skeleton, although it plays a vital role in the formation of DNA, ATP and the phospholipids that make up cell membranes. The skeletal form of phosphorus is calcium phosphate and provides stiffness and structure to the bone.
The skeleton contains up to 60% of total body magnesium. Magnesium is also essential for muscle contraction, formation of DNA and is a catalyst for many reactions such as the release of energy from ATP. Deficiency of magnesium has been linked to muscle spasms, cardiovascular disease, high blood pressure and diabetes. Magnesium can be found in dark green vegetables, nuts, seeds and some whole grains.
Iron has vital functions in the body, as a carrier for oxygen (as part of haemoglobin in blood cells and myoglobin in muscle tissue) from the lungs, as a transporter in the ATP generation pathway and as an integral part of many enzyme controlled pathways.
There are two types of iron in the diet – haem and non haem, each with a different mode of absorption from the intestine. Haem iron is present in meat and meat products, non-haem iron is found in plant based products such as dark green vegetables, dried fruit, etc. Haem iron is more easily absorbed whereas non-haem iron is influenced by the iron status of the individual. In addition, iron's absorption is facilitated by vitamin C and meat products and inhibited by calcium, soy protein and phytates from raw bran.
Deficiency of iron can lead to anaemia, from dietary inadequacy, infection or tumours causing loss of blood. Symptoms include reduced endurance in relation to physical activity, as oxidative metabolism (and ultimately ATP generation) is impaired. Memory and learning may be affected, along with compromises to the immune system. Pregnancy is also a common time in which iron deficiency anaemia may occur due to the increased demands on the body.
Zinc is an essential mineral, required for normal growth. It is a constituent of certain enzymes, acts to stabilise cell membranes and is involved in DNA synthesis, protein digestion and synthesis, carbohydrate metabolism, oxygen transport and protection against free radical damage. Zinc deficiency is difficult to characterise but seems to cause reduced growth rates and reduced immune capacity. Good sources of zinc are dark red meats with a low fat content and unrefined (whole) grains. However, its absorption is hindered by phytates in wholegrain cereals and other vegetables. Animal protein enhances zinc absorption.
There are a number of other minerals required in our diet, but in minute quantities, and they are relatively easy to obtain sufficient amounts from food, with deficiency symptoms being very rare. Chromium is thought to enhance insulin sensitivity and has therefore been marketed as a tool for diabetics and as a weight loss aid, but its usefulness is unfounded despite what marketing would have you believe. Other trace elements include molybdenum, vanadium, copper, manganese, fluoride (which we obtain from toothpastes as well as diet), iodine and selenium.
Fat soluble vitamins
Fat soluble vitamins are less likely to be lost on cooking than water soluble ones but are more likely to build up to toxic levels as they are not excreted from the body in the urine.
Vitamin A has two major forms: animal based retinol, found in liver, dairy products and oily fish; and the plant derived β-carotene, found in orange and dark green vegetables and palm oil (the latter has lower potency than retinol). Vitamin A is absorbed in the small intestine and mainly stored in the liver.
Vitamin A is involved in night vision due to its role in retina formation. Other major functions are in cell differentiation and the immune system's responses to infection. In addition to its vitamin A activity, β-carotene is also a potent anti-oxidant as are other carotenoids.
Deficiency is characterised by night blindness, and may also increase the risk of infections, especially in children. Vitamin A excess is possible and symptoms include nausea, vomiting, headaches, muscular in coordination, blurred vision and vertigo.
Vitamin D is primarily synthesised in the skin on exposure to UV light, although it is found in oily fish, eggs and fortified margarine. It has a hormone like action, controlling the absorption of calcium from the intestine and the flux of calcium between the bones and the circulatory system. Vitamin D also plays a role in the immune system. Deficiency is seen in Muslim women who practice Purdah and do not expose their skin to sunlight; the condition here is called osteomalacia and is characterised by bone pain. Deficiency in children is rickets, where the growth and mineralization of the bone is poor, leading to skeletal deformity.
Vitamin E is a powerful antioxidant that helps to protect against oxidative damage from metabolic reactions in the body and exercise, compounded by smoking, poor diets and polluted atmospheres. Vitamin E plays a role in protecting fats from free radical damage. Vitamin E is also required in DNA synthesis, the immune response and has anti-inflammatory effects.
Studies relate intake of adequate amounts of vitamin E with a reduced risk of intestinal, breast and lung cancer and coronary heart disease. Vitamin E deficiency has several symptoms, related to cell membrane damage, which causes the leakage of cell contents such as enzymes, into the plasma.
For sources of vitamin E click here
Vitamin K is found in plant foods especially leafy green vegetables and vegetable oils. It is thought to play a role in healthy bone development, as deficiency may lead to bone disease. Its deficiency is also responsible for a haemorrhagic disease in newborn infants.
Water soluble vitamins
These are more likely to be lost on cooking (leaching into the cooking water) or damaged in food processing. Care must be taken to eat foods in as raw a state as possible, to obtain sufficient levels.
The B vitamins
The greatest source of thiamin is in unrefined grains or starchy roots and tubers. However, industrial processing such as polishing of the rice grain removes the thiamin. Other sources include liver, kidney, pork, nuts and pulses as well as fortified breakfast cereals.
Thiamine is involved in the metabolism of carbohydrate, so it plays an important role in energy generation. Thiamin deficiency causes a condition known as beriberi, common in countries where refined rice is the staple. Symptoms are related to both the cardiovascular and nervous systems such as oedema, irregular heart beat, enlarged heart, vasodilation plus muscle weakness and neural degeneration. Thiamin deficiency is also seen in chronic alcoholism, resulting in Wernicke-Korsakoff syndrome, which causes neural damage that can eventually lead to psychosis and memory loss, if left untreated.
Found in dairy products, meat, fish and some green vegetables, riboflavin plays a role in the metabolism of other nutrients. Clinical deficiency in children causes growth retardation, skin rashes around mucous membranes as they meet the skin, e.g. at the nostrils.
Niacin is found in food in the form of nicotinic acid and the provitamin tryptophan (an amino acid). It is found in meat in both forms and also in cereals as niacytin (which has a lower bioavailability). Niacin is required as a cofactor in the metabolism of carbohydrate to produce energy. Deficiency results in pellagra, which is associated with diets high in maize or millet and is characterised by dermatitis and gastrointestinal lesions and discomfort. Diarrhoea and mental disturbance may also be observed.
Folate (Folic acid)
While folate is widely distributed across many food sources, there is no one particularly good source (except liver). Fresh vegetables provide folate but high levels must be consumed and cooking losses minimised. Adequate folate status in women is essential pre-conception and during the first 12 weeks of foetal development to prevent neural tube defects, which may otherwise result in spina bifida. Folate also plays a role in DNA synthesis and in the regulation of plasma homocysteine, which, if allowed to reach high levels, can contribute to cardiovascular disorders.
Deficiency, even at mild levels, leads to a large increase in the incidence of neural tube defects in newborns and also to increases in homocysteine levels and changes to the blood, due to the compromised DNA synthesis. This last effect can lead to a type of anaemia, which is also associated with vitamin B12 deficiency. Deficiency may be due to dietary inadequacy, reduced absorption, the demands of pregnancy, use of anticonvulsant drugs and chronic alcohol abuse. Prevention of neural tube defects should be taken by supplementing with 400μg a day, before conception.
Deficiency of this vitamin leads to a form of anaemia that cannot be distinguished from that seen in folate deficiency but with the added symptom of neurological degeneration. Causes of deficiency may be dietary insufficiency, malabsorption and the use of certain drugs. Vitamin B12 is found only in foods of animal origin i.e. meat and dairy products. Vegetarians and especially vegans should manipulate their diet to ensure adequate status.
Ascorbic Acid (Vitamin C)
Dietary sources of vitamin C include fresh fruit and vegetables, especially spinach, tomatoes, broccoli, potatoes, strawberries, oranges and other citrus fruit. Vitamin C is sensitive to ageing of the produce and also to the cooking process. Vitamin C is actively absorbed by the intestine and circulates to all cells, with excess being excreted by the kidney, in the urine. It is an antioxidant and plays roles in the synthesis of collagen (a structural protein in the skin, maintaining elasticity) and carnitine (the molecule responsible for transporting fats for oxidation). It may also play a role in the immune system, although the effects on reducing the length of or even preventing the common cold are still equivocal.
The deficiency disease scurvy is well characterised, with symptoms including poor wound healing and swollen gums, bone pain and weakness and haemorrhaging through the skin. This may result in chronic dietary insufficiency or in malabsorption syndromes and alcoholism. Smokers and those under stress may be more at risk of vitamin C deficiency.
There are other molecules found in our foods, mainly in plants, known as anutrients or phytonutrients which purported health benefits. However they are not classic nutrients as they are not required for life and do not exhibit any deficiency symptoms. Examples of these include phenolic compounds like the flavonoids found in tea and red wine which may play a role as antioxidants in cancer prevention. Research is still in its infancy in this area and there are a large number of phytonutrients discovered and no doubt more still undiscovered.