Understanding the complex world of nutrition can be overwhelming - from BMI, NRV, BCAAs and the many other acronyms, to the intricacies of the human digestive system. This challenge grows when you consider the many contrasting opinions and streams of misinformation.
However, having clarity on these major concepts can help you navigate this field and develop your own healthy eating habits. This glossary aims to help you achieve this.
Allergen
An allergen is a substance that causes an abnormally vigorous immune (allergic) reaction in a susceptible person, in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Allergens exist in many forms, including pollen, various medicines, and certain foods - such as nuts, soy, wheat, eggs and cows' milk. Allergies are different to food intolerances/sensitivities.
Amino acids
Amino acids (AAs) are the building blocks that make up proteins. There are 20 different amino acids that combine in different sequences to make all the proteins required for metabolism and growth. AAs also play non-protein roles. For example, the AA tryptophan is a precursor of the neurotransmitter serotonin. Of the 20 AAs used by humans, 9 are essential in adults - meaning they must be obtained from the food we eat.
Antinutrient
Antinutrients are compounds that interfere with the absorption of nutrients. These include lectins, phytates, oxalates, and gluten. With some diets, and in some people, antinutrients may be problematic. The effects of antinutrients can be minimised with soaking, sprouting, fermenting, and with certain cooking styles.
Antioxidants
Antioxidants are chemical substances that help protect cells against damage from reactive compounds known as free radicals. Free radicals are produced during normal essential metabolic processes in the human body or come from external sources such as exposure to X-rays, cigarette smoking, air pollutants, and industrial chemicals. The body makes its own antioxidants, but also makes extensive use of dietary antioxidants, such as vitamins A, C, and E, and phytonutrients such as carotenoids and flavonoids.
BCAAs
Branched Chain Amino Acids (BCAAs) are three essential amino acids: leucine, isoleucine, and valine. BCAAs are important to ingest on a daily basis and can be found in sufficient quantities in many protein sources, such as meat and eggs. For people with low dietary protein intake however, BCAA supplementation can promote muscle protein synthesis and increase muscle growth over time.
BMI
The body mass index (BMI) is a standardized ratio of weight to height, calculated by dividing weight in kilograms (kg) by height in metres squared (m2). It's an indirect measure of body fat that is often used as a general indicator of health. However, it doesn't take into account important details about age, sex, bone structure, and fat distribution.
Calorie
The calorie is a unit of energy widely used in nutrition. One calorie is formally defined as the amount of energy required to raise one cubic centimeter of water by one degree centigrade. What we commonly think of a calorie is actually a kilocalorie(kcal), which equals 1000 calories (cal). Measuring calories is useful for determining the energy content of those foods. However, it must not be considered as a measure of the health of any given food item, since there is no consideration for what the food is and how it affects the body.
Carbohydrates
Carbohydrates are a type of macronutrient, and come in 2 main forms – simple and complex. Simple carbohydrates, also known as simple sugars, include lactose in milk and fructose in fruits. Complex carbohydrates, known as starches, can be found in foods such as rice and potatoes. Carbohydrates can be stored in your liver and muscles as glycogen. When required, these can be broken down into simple sugars and used by cells for energy production. Excess sugar is stored as triglyceride in adipose (fat) tissue.
Coeliac
Coeliac disease is a type of autoimmune disease (a condition where your immune system attacks your own tissues). It occurs in genetically predisposed people where the ingestion of gluten leads to damage in the small intestine, limiting its ability to absorb nutrients. Since gluten is found in cereals, including wheat, barley and rye, the current recommended treatment is to avoid these in the diet. It is estimated to affect 1 in 100 people in the UK. Coeliac disease differs from non-coeliac gluten sensitivity.
Cholesterol
Cholesterol is a type of lipid found in the body. It is an essential part of cell membranes, a precursor to some hormones and is used to produce vitamin D. However, having too much cholesterol in the blood can increase the risk of heart disease.
Diabetes
Diabetes (mellitus) is a disease that occurs when your blood glucose, also called blood sugar, is too high. There are 2 main types of diabetes, both of which involve insulin. Type 1 is where the body's immune system attacks and destroys the cells of the pancreas that produce insulin. Type 2 is where the body doesn't produce enough insulin, or the body's cells do not react to insulin. Type 2 diabetes is more common than type 1. In the UK, around 90% of all adults with diabetes have been diagnosed with type 2. Although diabetes has no cure, lifestyle and dietary changes can be made to manage diabetes and stay healthy.
Digestion
Digestion is the breakdown of large food molecules into smaller nutrients so that they can be absorbed into the blood through the small intestine. Proteins, for example, are broken down into amino acids, and carbohydrates are broken down into simple sugars. There are two ways our digestive system breaks down food; mechanically (by chewing, for example) and chemically (with stomach acid, for example). Following digestion and absorption, the nutrients in the blood are taken up by cells and used for energy, growth and repair, known as assimilation.
Electrolytes
Electrolytes are minerals that affect fluid balance in the body and are necessary for our nerves and muscles to function. Electrolytes include potassium, sodium, calcium, and magnesium. Sports drinks often contain electrolytes to replace those lost through sweat. Minerals in this form are more easily absorbed since they are dissolved in water, unlike minerals found in foods, which are bound to other elements and therefore less bioavailable. Electrolyte replacement is not needed during short bursts of exercise, but may be beneficial for activity lasting longer than 60 minutes, especially in a hot environment.
DRV
Dietary Reference Values (DRVs), also called Nutrient Reference Values, comprise of a series of estimates of the amount of energy and nutrients needed by different groups of healthy people in the UK population. Individual nutritional requirements vary from person to person, but averages can be taken from populations. These averages are used to calculate the DRVs, and are useful in identifying nutritional status on a population level. This means they are not specific recommendations or targets for individuals DRVs.
Elimination diet
An elimination diet is a style of eating that can help relieve symptoms of people who suffer from frequent digestive problems with an unknown cause. The process involves eliminating certain foods for a period of time, usually 3-4 weeks, then slowly reintroducing specific foods and monitoring your symptoms for possible reactions.You may even find your tolerance levels towards certain problematic foods through this method. This self-experimentation method of identifying problematic foods is an effective approach which can offer many benefits to personal health.
Fatty acids
Fatty acids are an important type of lipid in the body and play key structural and functional roles. Like amino acids in protein, fatty acids make up triglycerides - the major type of ‘fat’ molecule in the body. Fatty acids are categorised by their chemical structure, by the length of their chain (short, medium and long chain fatty acids), or by the number of double bonds in the chain (saturated, monounsaturated and polyunsaturated fatty acids).
Fibre
Dietary fibre is a type of complex carbohydrate that cannot be digested by humans. It comes from the thick cell walls of plants, and is found in high amounts in foods such as fruits, vegetables, and wholegrains. Dietary fibre is a noncaloric macronutrient and is not absorbed. However, it plays a key role in digestion and is associated with a lower risk of heart disease, stroke, type 2 diabetes and bowel cancer. Resistant starch, whilst technically not a fibre, has similar effects on the body.
Food Security
Food security is a measure of the availability of food and an individuals' ability to access it. Food security occurs when all people, at all times, have physical, social, and economic access to sufficient, safe, and nutritious food for an active and healthy life, and importantly in ways the planet can sustain into the future. Food insecurity is significant and growing in the UK, with levels among the worst in Europe, especially for children. Globally, 2 billion people are moderately or severely food insecure, yet at the same time, no region is exempt from the epidemic of obesity.
Fortification
Food fortification is the process of adding micronutrients to food. It can be voluntarily carried out by food manufacturers, or be mandatory by governments as a public health policy which aims to reduce the number of people with dietary deficiencies within a population. For example, the UK’s Bread and Flour Regulations specify that calcium, iron, thiamine (Vitamin B1) and niacin (Vitamin B3) must be added to all white and brown flour.
Glucose
Glucose is a simple carbohydrate and the primary source of energy for cells of the body, especially the brain. This simple sugar is predominantly made from the breakdown of carbohydrates, but can also be made from proteins and fats. It is carried around the body by the blood. Insulin plays a key role in allowing cells to take up glucose from the blood.
Gluten
Gluten is a protein found in wheat, rye, and barley. It can be found in a large variety of foods including soups, salad dressings, processed foods and natural flavorings. It is the gluten that gives dough its sticky cohesiveness which is important in manufacturing many products such as bread. It can also be in products such as vitamin and nutrient supplements, lip balms, and certain medicines. Gluten is problematic when ingested by people with coeliac disease or non-celiac gluten sensitivity.
Heavy metals
Heavy metals are minerals such as mercury and lead, named due to their relatively high atomic weight. Many heavy metals are toxic or poisonous at low concentrations. Heavy metals can damage and alter the functioning of organs such as the brain, kidney, lungs, liver, and blood. Heavy metal toxicity can have both acute and chronic effects. There are dietary guidelines in place for the consumption of certain foods, such as shark, swordfish and tuna, due to their high mercury content.
IBD
Inflammatory bowel disease (IBD) is an umbrella term used to describe disorders that involve chronic inflammation of your digestive tract. The two most common forms of IBD include ulcerative colitis and Crohn's disease. Ulcerative colitis only affects the colon (large intestine), while Crohn's disease can affect any part of the digestive system. The exact cause of IBD remains unknown, but there are known risk factors which include age, family history, and a history of certain medications.
IBS
Irritable bowel syndrome (IBS) is a common condition that affects the digestive system. Classified as a syndrome, which is defined as a group of symptoms, IBS causes symptoms like stomach cramps, bloating, diarrhoea and constipation. IBS can cause a great deal of discomfort and it can severely affect your quality of life. Unlike inflammatory bowel disease, IBS is a functional disorder, which means there is some type of disturbance in gut function, but this does not cause inflammation. The exact cause is unknown – it's been linked to things like food passing through your gut too quickly or too slowly, oversensitive nerves in your gut, stress and a family history of IBS. There's no cure, but diet changes and medicines can often help control the symptoms.
Intermittent Fasting
Intermittent fasting (IF) is an umbrella term for various meal timing schedules that cycle between voluntary fasting and non-fasting over a given period. IF is not a diet; it's a pattern of eating. It is not designed to change what you eat - it is designed to change when you eat. Common IF frameworks include time-restricted feeding, in which the person eats within a predetermined feeding window, or a weekly fast such as the 5:2 method in which caloric intake is reduced for two days a week.
Sensitivity/ intolerance
A food intolerance is difficulty digesting certain foods and having an unpleasant physical reaction to them. Physical reactions to certain foods are common, but most are caused by a food intolerance rather than a food allergy. A food intolerance can cause some of the same signs and symptoms as a food allergy, so people often confuse the two. However, food intolerance symptoms are generally less serious and often limited to digestive problems. Whilst it is often unclear why a person is sensitive to certain foods, one common cause is the absence of an enzyme needed to fully digest a food. Lactose intolerance is a common example of this.
Insulin
Insulin is a hormone produced in the pancreas in response to increased blood glucose levels. The primary role of this hormone is to transport glucose from the bloodstream into cells of the body. In individuals with diabetes mellitus, insulin signalling has been limited in some way, and so the effects of insulin are reduced, meaning blood sugar remains high.
Lipids
Lipids are a general class of compounds that are insoluble in water. Cholesterol, fatty acids, triglycerides (fats), and certain vitamins are all members of the lipid family. Lipids are critical for all life on earth. The wide variety in their structure gives them a wide variety of functions; from being the building blocks of cell membranes and hormones, to organ protection and energy storage.
Macronutrients
Macronutrients are the nutrients that form the major portion of the human diet. This includes the energy providing carbohydrates, fats, and protein, but also the noncaloric macronutrients water and dietary fibre. All other nutrients are consumed in smaller amounts, and are labelled as micronutrients.
Metabolism
Metabolism describes all the biochemical processes that go on continuously inside your body to keep you alive and your organs functioning normally. Metabolic reactions may be categorized as catabolic – the breaking down of large molecules (for example, proteins into amino acids) - or anabolic – the synthesis of large molecules (amino acids into proteins). These chemical processes require energy. The minimum amount of energy your body requires to carry out these chemical processes is called the basal metabolic rate (BMR). Your BMR accounts for anything between 40% and 70% of your body's daily energy requirements, depending on your age and lifestyle.
Microbiota
The microbiota, or microbiome, refers to the collection of microbes - bacteria, viruses, and fungi - that inhabits the human body. Different species live on different parts of the body; there is an oral microbiota of the mouth, a microbiota of the skin that has many subcategories (the armpits, nose, feet, etc.), and a gut microbiota. The colon (large intestine) alone contains 10 bacteria. Although bacteria are often associated with infections, many of the bacteria that colonize the surface and insides of our bodies are essential for life. We are dependent on these bacteria to help digest our food, produce certain vitamins, regulate our immune system, and keep us healthy by protecting us against disease-causing bacteria.
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Micronutrients
Micronutrients are nutrients required by the body in small amounts, and include vitamins and minerals. Adequate intake of all micronutrients is necessary for optimal growth, development and maintenance of health, as each vitamin and mineral has a specific role in your body. Unlike macronutrient undernourishment, the health impacts of micronutrient deficiency are not always acutely visible; it is therefore sometimes termed ‘hidden hunger’. The World Health Organization estimates that more than two billion people suffer from micronutrient deficiency globally.
Minerals
Minerals are elements found in our planet’s soil and water, and are a type of micronutrient in our diets. There are at least 15 different minerals that our bodies need, which we normally get from the food and water we consume. There are two types of essential minerals; major and trace. Major minerals include calcium, potassium, and magnesium, and are needed in large quantities. Trace minerals, as the name suggests, are only needed in small amounts, and include iron, zinc, manganese, and selenium. Minerals serve many important functions in regulating health.
Nutrition
Nutrition is the science that investigates the nutrients and other substances in food and their relationship to maintenance, growth, reproduction, health and disease of an organism. A nutritious, balanced diet gives your body energy to perform daily activities, helps you to maintain a healthy body weight, and can lower your risk for certain diseases such as diabetes and heart disease. The study of nutrition considers everything from physiology and microbiology to human behaviour and social inequality.
Obesity
Obesity is defined as abnormal or excessive fat accumulation that presents a risk to health. A crude population measure of obesity is BMI. A person with a BMI of 30 or more is generally considered obese and a person with a BMI equal to or more than 25 is considered overweight. Overweight and obesity are major risk factors for a number of chronic diseases, including diabetes, cardiovascular disease and cancer. It's a common problem in the UK that's estimated to affect around 1 in every 4 adults.
Phytonutrients
Phytonutrients, also called phytochemicals, are compounds produced by plants. Phytonutrient-rich foods include colourful fruits and vegetables, legumes, nuts, tea, whole grains and many herbs and spices. They have the capacity to alter biochemical reactions and consequently affect our health. One group of phytonutrients is the polyphenols, which constitute the most abundant antioxidants in the human diet. Food processing can both reduce and increase the potency of phytochemicals.
Protein
Protein is a macronutrient and a key component of a healthy diet. Proteins are made up of amino acids. All of the antibodies, enzymes, and many of the hormones in the body, are proteins. They allow for the transport of nutrients, oxygen, and waste throughout the body. They provide the structure and contracting capability of muscles. They also provide collagen to connective tissues of the body and to the tissues of the skin, hair, and nails. You get proteins in your diet from meat, dairy products, nuts, and certain grains and beans. You need to consume protein every day, because your body doesn't store it the way it stores fats or carbohydrates.
PUFAs
Polyunsaturated fatty acids (PUFAs) are a type of fatty acid with more than one double bond in the fatty-acid chain. PUFAs are of two kinds: omega-3 or omega-6. The human body is capable of producing all the fatty acids it needs, except for two: linoleic acid (LA) - an omega-6 fatty acid, and alpha-linolenic acid (ALA) - an omega-3 fatty acid. These are termed ‘essential’ fatty acids as they cannot be made by the body and we need to obtain them from our diet. Foods such as nuts, seeds and oily fish are high in PUFAs.
RI
Reference Intake (RI) values are a type of DRV that show you show you the maximum amount of calories and nutrients you should eat on average in a day. RIs are not targets for people to consume. Instead, they act as a guideline or benchmark to help people make healthy dietary choices and balance daily intake. RI values replaced Guideline Daily Amounts, which used to appear on food labels. RI values have been set by European law and are based on an average sized woman doing an average amount of physical activity.
Resistant starch
Resistant starch is a type of carbohydrate that cannot be digested in the small intestine. As a result it is classified as a type of fibre. Resistant starch passes through the small intestine intact and is then fermented by bacteria in the large intestine, producing short chain fatty acids which serve as an energy source for cells of the colon. Foods that increase the amount of SCFAs in the colon are thought to be beneficial to health by helping to prevent the development of abnormal cells in the gut. Resistant starch is naturally present in some foods such as bananas, potatoes, grains, pulses and seeds and is also produced or modified commercially and incorporated into some food products.
Supplementation
Dietary supplementation is the term used to describe the provision of relatively large doses of nutrients, usually in the form of pills, capsules, or powders to improve health or achieve certain goals. Supplements may provide benefits in situations where insufficient amounts of nutrients are being consumed, for example, in certain diets, in people who have undergone bariatric surgery, or in people with certain medical conditions. Some of the most commonly taken supplements in the UK include multivitamins, vitamins D and C, calcium, fish oil, and protein. Over £400 million is spent on supplements in the UK every year.
Triglyceride
A triglyceride is a type of lipid composed of three fatty acids attached to a molecule of glycerol. Much like cholesterol, triglycerides are obtained by the diet and can be produced in the liver. When there is an excess of triglycerides in your blood they are stored in specialised cells called adipocytes. These cells make up adipose tissue, and play important protective and insulatory roles. The fatty acids in these cells also act as a store of energy, which can be released when needed. Long-term build up of fatty acids and resultant growth of adipose tissue can lead to obesity and increase risk of cardiovascular disease.
Vitamins
Vitamins are essential micronutrients needed by the body for health and development, and they must be obtained by the diet daily. The exceptions to this rule are vitamin D, which is made in the skin when exposed to sunlight, and vitamin K, which can be synthesised by gut bacteria in small amounts. Vitamins have diverse biochemical functions. Due to the important roles vitamins play, they are commonly used to fortify foods.