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An enzyme is a protein that speeds up the rate at which a particular chemical reaction takes place and the best known examples are digestive enzymes. The human body produces 22 digestive enzymes, which are divided into three main groups: proteases help us break down dietary proteins; amylases digest carbohydrates; and lipases break down fats.
Many other enzymes with a similar action are found in fruit, vegetables and fungi, including cellulases that digest fibre.
Digestion starts in the mouth, where biting and chewing breaks down food into suitable portions for swallowing. Saliva moistens food and contains salivary enzymes, such as amylase, which starts breaking down starch, and lipase, which starts breaking down fats.
As food reaches the stomach, the gastric lining produces hydrochloric acid and two digestive enzymes: pepsin, which breaks down proteins into chains of amino acids called peptides, and lipase, which continues breaking down fat.
Once food leaves the stomach and enters the duodenum (the first part of the small intestine), it mixes with bile. Bile contains salts that act like detergents by turning fat into tiny globules, so that it can be further digested by lipase. Bile is made in the liver, stored in the gallbladder and released into the duodenum when you eat.
At the same time, the pancreas releases even more powerful digestive enzymes: trypsin makes quick work of breaking down protein; a pancreatic lipase acts on fats; and more amylase breaks down starch into smaller units containing two glucose molecules (disaccharides) or three glucose molecules (trisaccharides).
The action of all these digestive enzymes should mean that, by the time food leaves the duodenum and enters the rest of the small intestine, the building blocks of food - sugars, amino acids and fatty acids - are ready to be absorbed into the bloodstream.
We each produce different levels of enzymes depending on our genes, diet, lifestyle, gender and age. When these enzymes are all made in the correct quantities digestion occurs flawlessly, but as we get older, most people tend to produce fewer intestinal enzymes.
People who suffer from digestive disorders, such as Crohn's disease, ulcerative colitis and coeliac disease, may also lack sufficient enzymes.
As we age, the stomach lining becomes less active, often as a result of inflammation (atrophic gastritis). In addition to producing less stomach acid - a condition known as hypochlorhydria - the output of digestive enzymes also decreases. Atrophic gastritis affects as many as 19 per cent of people in their 50s, 24 per cent of those in their 60s, 32 per cent of those in their 70s and 40 per cent of those aged 80 plus - an overall prevalence of 31.5 per cent of those aged 60 or more.1
Other common age-related problems that affect digestion include reduced production of bile (known as bile insufficiency) and a reduced output of pancreatic secretions (known as pancreatic insufficiency).
This is why multivitamins aimed at people aged 50+ or 70+ have different, usually increased, levels of certain micronutrients.
A lack of digestive enzymes has been linked to health issues such as bloating, wind, indigestion, heartburn and irritable bowel syndrome.
Digestive enzymes found in modern supplements are mainly derived from plants such as fungi, which use these enzymes to decompose substances, for example wood, to obtain their nutrition.
Some enzymes produced by probiotic bacteria also help to digest foods, especially protein; for example, these enzymes are what convert milk to yoghurt. Although taking a probiotic supplement may help to relieve some digestive symptoms, a digestive enzyme supplement can provide a more powerful effect.
A digestive enzyme supplement can improve your digestion of fats, carbohydrates and proteins, while those containing lactase can also help you digest lactose (milk sugar). Some supplements also contain cellulases, which digest cellulose and can help to overcome common digestive symptoms such as bloating.
The efficacy of digestive enzymes is measured by activity units, which reflect the potency of the enzymes. Good-quality digestive enzyme supplements will use the standard FCC (Food Chemical Codex) units of measurement, which is the national standard for establishing plant enzymes' activity levels.
Each activity unit is determined by a different test method, which calculates how each enzyme performs under specific conditions. This is why each enzyme is assigned its own FCC activity unit. When determining the potency of each individual activity unit, those with the highest number are the most active.
Alpha amylase works to break down long chains of carbohydrate molecules called polysaccharides, specifically amylose which is a component of starch. Alpha amylase and glucoamylase work synergistically to break down starch, so they should always be taken in combination.
Alpha galactosidase aids with the breakdown of carbohydrate-rich foods linked with protein or fats (known as glycoproteins or glycolipids). Such foods include legumes, whole grains and some vegetables, particularly cruciferous vegetables. These foods are difficult to break down in the digestive tract. Food particles that are not sufficiently digested may be fermented by the gut bacteria resulting in the production of excess gas. Alpha galactosidase has been shown to ease intestinal gas production and discomfort.2
Proteases help to digest dietary proteins into smaller fragments called amino acids. Proteins are made up of more than 20 amino acids, each with a different, complex structure that makes them hard to break down.
There are multiple protease enzymes, each acting optimally at a different pH level. Protease enzymes will often be labelled with a number, such as 'protease (4.5)'. The number relates to the optimal pH of that specific digestive enzyme. It is best to have a range of proteases, as the pH will vary along the digestive tract.
Lipase is essential for the digestion of fats, breaking them down into fatty acid and glycerol molecules.
Lactase is responsible for digesting lactose milk sugar into galactose and glucose. It is produced naturally in the digestive tract of infants, but as production declines in adulthood, many adults aren't able to digest lactose effectively. This can result in lactose intolerance, where the undigested lactose is fermented by gut bacteria causing symptoms of abdominal pain, bloating, diarrhoea and gas.
Cellulase works to break down cellulose, a plant fibre found in fruit and vegetables. Cellulose is the major component found in plant cell walls and is extremely strong and tough. Humans cannot produce cellulase naturally and instead rely on the fermentation of cellulose by gut bacteria found in the large intestine.
Bromelain and papain aid with the breakdown of proteins. Papain originates from the papaya fruit, and bromelain is the digestive enzyme derived from pineapple stems.
Digestive enzymes are normally taken at the beginning of a meal to help improve food-related problems. If taking the enzymes for indigestion, don’t take an antacid or indigestion remedy within two hours of taking the digestive enzymes, as this may reduce their effectiveness.
If your symptoms do not improve within two weeks of taking digestive enzyme supplements, stop taking them and seek medical advice.
Dr Sarah Brewer is Healthspan's Medical Director and holds degrees in Natural Sciences, Surgery and Medicine from the University of Cambridge. Having worked as a GP and hospital doctor, Dr Sarah now holds an MSc in Nutritional Medicine from the University of Surrey and specialises in nutrition. She is also an award-winning writer and author.
Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.