Amino Acids to Zinc: A Glossary of Nutrition Terms
Reading nutrition labels is smart shopping. But what do the terms mean?
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Anxious about antioxidants? Perplexed by polysaccharides? This guide will help you navigate the world of nutrition and health.

Live Science talked with experts and consulted several publications to get definitions and explanations of many common terms used when discussing nutrition. 

Amino acids are organic compounds that combine with each other to form proteins, according to the National Institutes of Health (NIH). There are about 20 amino acids that regularly make proteins and they can be arranged in thousands of different ways. There are three types of amino acids: essential, non-essential and conditional.

Essential amino acids cannot be made by the body, out of the materials ordinarily available, at a speed that can meet the demands for normal growth; they must be provided preformed in the diet, according to the American Journal of Public Health (AJPH). There are nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. A food that contains all nine is considered a complete protein. 

Non-essential amino acids are amino acids that the body can produce. They include: alanine, asparagine, aspartic acid, and glutamic acid.

Conditional amino acids are amino acids that the body only requires at times of illness or stress. They are: arginine, cysteine, glutamine, tyrosine, glycine, ornithine, proline and serine.

Anti-inflammatory diets have become popular in recent years. According to Harvard Health Publications, many major diseases, including cancer, heart disease, diabetes, arthritis, depression, and Alzheimer's disease, have been linked to chronic inflammation. 

An anti-inflammatory component in food or drinks, such as omega-3 fatty acids, protects the body against the possible damage caused by inflammation, said Jimenez. Anti-inflammatory foods include leafy greens, fatty fish, nuts like almonds and walnuts, tomatoes and olive oil. [Related: Inflammation: Causes, Symptoms & Anti-Inflammatory Diet]

Antioxidants are molecules that interact with free radicals to stop the condition of oxidative stress, according to an article in the journal Pharmacognosy Review

"Antioxidants work in the body to prevent damage of our cells," said Paige Smathers, a Utah-based registered dietitian. Free radicals attack macromolecules, causing cell damage and disruption. They can attack all molecules in the body, including lipids, proteins and important acids. Without sufficient antioxidants to keep them in check, the cell disruption caused by free radicals can lead to oxidative stress. 

Vitamins E and C and beta-carotene are principle nutrient antioxidants. The body cannot produce them naturally; they must be supplied in the diet. According to the Mayo Clinic, good sources of antioxidants include berries, other fruits with skins, leafy green vegetables, sweet potatoes, nuts, pomegranate juice and even red wine and coffee, in moderation. 

Eight essential water-soluble vitamins are called the B-complex vitamins, according to the National Institutes of Health. They are: vitamin B1 (thiamine), vitamin B2 (riboflavin), vitamin B3 (niacin), vitamin B5 (pantothenic acid), vitamin B6 (pyridoxine), vitamin B7 (biotin), vitamin B9 (folic acid or folate) and vitamin B12. 

All B vitamins contribute to energy production by helping the body convert carbohydrates into glucose. They help the nervous system function, help metabolize fats and protein, and help keep the liver, eyes, skin and hair healthy. All B vitamins are water soluble, meaning they cannot be stored in the body and must be replenished through food or supplements. 

Beta-carotene is a pigment that gives plants their orange and yellow colors. It is a carotenoid and type of antioxidant associated with helping improve sun sensitivity, macular degeneration, metabolic syndrome and other conditions, according to the University of Maryland Medical Center. Carrots, sweet potatoes, tomatoes and other warm-colored fruits and vegetables, leafy greens and broccoli contain high amounts of beta-carotene. [Related: What Are Carotenoids?]

The body mass index is an estimation of a person's body fat that can be calculated using the person's height and weight. It can be used in screening for someone's weight category but cannot diagnose fatness or a weight problem. [Related: Understanding Weight: BMI & Body Fat

Calcium is a metallic element that is the most plentiful mineral found in the human body, according to the University of Maryland. According to the AJPH, it makes up 1.5 to 2 percent of the body weight of the mature human; 99 percent of body calcium is present in bones and teeth. 

"Calcium aids in bone loss prevention, as well as maintaining a healthy metabolism and alkaline environment in your body," said Tina Paymaster, a certified health and lifestyle coach based in New York.

A calorie is a unit of energy. In nutrition, calories may refer to the amount of energy your body needs to survive, or to the amount of energy that a food or drink provides (in reality, anything that contains energy contains calories, even if it is not a food). Different people require different amounts of calories. 

Macronutrients carbohydrates, protein and fats provide calories, according to Smathers. Minerals, vitamins and water do not. One gram of carbohydrates yields four calories; one gram of protein yields four calories; and one gram of fat yields nine calories. 

"Empty calories" are devoid of nutritional value. They are the calories from solid fats — fats that are solid at room temperature, such as butter, beef fat and shortening — and added sugars — sugars and syrups that are added to foods or beverages during processing, such as sodas, pastries, cheese, pizza, ice cream and meats — according to the U.S. Department of Agriculture.

Carbohydrates are the sugars, starches and fibers found in fruits, grains, vegetables and milk products. "Carbohydrates are one of the three main ways our body obtains energy or calories," said Smathers. There are three classes of carbohydrates: monosaccharides, disaccharides, and polysaccharides. 

In recent years, low-carb diets have become popular but Smathers emphasized that carbs should not be feared. "Carbohydrates are important for brain function including mood, memory, etc. as well as a quick energy source," she said. 

Carbohydrates can be classified as complex or simple, depends on the chemical structure of the food and how quickly the sugar in the food is digested and absorbed, according to the NIH. Simple carbohydrates have just one or two sugars, while complex carbohydrates have three or more sugars. Examples of simple carbs include fruits, most vegetables, milk, soda and candy. Examples of complex carbs include legumes, whole grains and starchy vegetables. Smathers asserted that it is "best to focus on getting primarily complex carbs in your diet, including whole grains and vegetables." [Related: What Are Carbohydrates?

Carotenoids are a type of phytonutrient. They are pigments responsible for yellow, red and orange colors found in plants. Commonly encountered carotenoids are alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, zeaxanthin, and lypocene, according to the Linus Pauling Institute at Oregon State University

Carotenoids also function as anti-inflammatories. They may be able to "help both rheumatoid arthritis and osteoarthritis," said Flores. While all types of carotenoids have antioxidant capabilities, each has its own unique benefits. [Related: What Are Carotenoids?

Cholesterol is a waxy, fat-like substance in all of the body's cells, according to the National Institutes of Health. Cholesterol is essential for some body functions, including making hormones, and the body produces what it needs. Excess cholesterol comes from high-cholesterol foods. 

There are good and bad types of cholesterol, though both are necessary in healthy amounts. LDL (low-density lipoprotein) cholesterol is considered bad because it builds up in the arteries. HDL (high-density lipoprotein) cholesterol is considered good because it is removed from the body via the liver. 

When someone has "high cholesterol," he or she is usually referring to having high levels of cholesterol in his or her blood. This is associated with coronary heart disease. See reference article. [Related: Cholesterol Levels: High, Low, Good & Bad]

Dietary fiber is an indigestible carbohydrate that aids in improving digestion by increasing stool bulk and regularity, Smathers said. "It also helps you feel full when you eat and aids in getting a feeling of satiety from fewer calories."

Smathers recommends getting fiber from whole grains, beans, fruits and vegetables.

Victoria Jarzabkowski, a nutritionist with the Fitness Institute of Texas at the University of Texas at Austin, added, "Fiber can help lower cholesterol because the fiber binds with cholesterol in the blood. After it binds, we excrete it." [Related: What Is Fiber?]

Electrolytes are minerals in the blood and other body fluids that carry an electric charge. They are "necessary for optimum body function, and too few can cause cramps, as many athletes know," said Jarzabkowski. "Electrolytes are lost through sweat." 

She listed sodium and potassium as two important electrolytes. Since water does not contain electrolytes, they must be replenished through foods or other drinks. 

Enzymes are complex proteins that cause chemical changes. They are found in all parts of the body and necessary for all body functions, according to the National Institutes of Health. Best known for aiding digestion by breaking down food, enzymes also help purify blood, cause blood clots and more. 

Fats, also called lipids or fatty acids, are macronutrients. Like carbohydrates and proteins, they contain calories. "We need fat to be full at our meals and to provide our cells with the lipids they need to maintain their cell structure," Smathers said. "Fat intake is important on the cellular health level, as well as to help us feel full and satisfied."

"There are some fatty acids that human bodies do not produce on their own, called essential fatty acids, including omega 3 and omega 6 fatty acids," Smathers continued. "There are other types of fatty acids that are unsaturated or saturated." Unsaturated fats are considered healthy and do not increase LDL cholesterol, while saturated fats are more dangerous and can increase LDL cholesterol.

Flavonoids are phytonutrients with antioxidant behaviors. They are compounds in fruits and vegetables that are responsible for pigments. In addition to their antioxidant behavior, flavonoids also modulate cell-signaling behavior, which can be beneficial. Studies have shown that they may help reduce the risk of Parkinson's disease, cardiovascular disease and stroke. Flavonoids are the largest family of polyphenols, a large class of phytonutrient. [Related: What Are Flavonoids?]  

Free radicals are molecules with an odd number of electrons. As they search for another electron to make up a pair, they can cause damage to surrounding cells. This can cause a chain reaction as more cells are damaged or killed. The free radical theory of aging holds that free radical damage is the primary cause of the aging process, but this theory is unproven, according to Current Aging Science

Tina Paymaster, a certified health and lifestyle coach based in New York, noted that free radical damage might also lead to "serious diseases such as cancer."

Antioxidants neutralize free radicals' electronic charge, thereby stopping them and their damaging behavior. When the body has too many free radicals damaging cells, a condition known as oxidative stress occurs. 

Free radicals can be caused by inflammation, cigarette smoke, environmental pollutants, radiation, certain drugs, industrial solvents and more, according to the journal Pharmacognosy Review

"Fructose is the naturally occurring sugar found in fruits, root vegetables and honey," said Jimenez. While fructose in fruit is generally not considered harmful, fructose in the form of high fructose corn syrup can be problematic.

According to the American Journal of Clinical Nutrition, "Fructose is an intermediary in the metabolism of glucose, but there is no biological need for dietary fructose." Liver cells break down fructose, resulting in triglycerides (a form of fat), uric acid and free radicals. In excess, these can be harmful. 

According to Harvard Medical School, when people consumed most of their fructose through fruits and vegetables, they averaged 15 grams per day. Today, when most Americans consume fructose through high fructose corn syrup, they ingest an average of 55 grams per day.

Glucose is a type of sugar and the body's primary source of energy. It is "the byproduct of digestion," said Jimenez. "What we eat is eventually converted to glucose via digestion." 

Carbohydrates are the primary source of glucose; they are turned into glucose before fat or protein. Simple carbs are turned into glucose faster than complex carbs. Glucose provides energy with the help of insulin.

Glucose in the bloodstream on its way to cells is commonly referred to "blood glucose" or "blood sugar." It is normal for blood glucose levels to fluctuate throughout the day, reaching their highest levels after eating. But in general, the body regulates the level of blood glucose.

Iron is a metallic chemical element that occurs in the hemoglobin of red blood cells, is stored in tissues in the form of ferritin and is an essential part of important respiratory enzymes. "Iron helps in the formation of hemoglobin, which is the main carrier of oxygen to cells of the body," said Paymaster. "It is also important for muscle and brain health." A deficiency in iron can cause anemia. 

Minerals are micronutrients the body needs to complete certain functions, according to Jimenez. They are chemical elements required for life. In humans, "they have a role in virtually every process of the body." 

There are two kinds of minerals: trace minerals and macrominerals. The body needs macrominerals in larger amounts than trace minerals. Macrominerals are magnesium, sodium, calcium, chloride, phosphorus and sulfur. Trace minerals are iron, zinc, selenium, cobalt, fluoride, iodine, molybdenum and manganese. 

Monosaccharides are the simplest form of carbohydrate. Chemically, they contain only one sugar unit and are easily and quickly digested. Examples of monosaccharides include glucose, sucrose and galactose, according to the George Mataljan Foundation's World's Healthiest Foods website. They are found in ripe fruits, honey and high fructose corn syrup. 

Monounsaturated fats are considered healthy. They are unsaturated, which means they are liquid at room temperature, said Jimenez. Examples are canola, peanut or olive oil. Chemically, monounsaturated fats have one carbon bond in the fat molecule (called a double bond). Saturated fats have no double bonds because they are saturated with hydrogen molecules. 

"[Monounsaturated fats] are known to have a heart protective role," said Jimenez, but she cautioned that "moderation is important because fat has more than double the calories than carbs."

"Phytonutrients," also called phytochemicals, simply means "plant nutrients" or "plant chemicals." It refers to all nontraditional substances in plants that provide specific health benefits — "nontraditional" means everything except vitamins, minerals, proteins, carbohydrates and fats. All of the qualities of good food — how it looks, smells, tastes — are the result of a food's phytonutrients, according to Elson M. Haas, author of "Staying Healthy With Nutrition: The Complete Guide to Diet & Nutritional Medicine" (Celestial Arts, 2006). [Related: What Are Phytonutrients?]

Potassium is an essential mineral electrolyte that helps nerves and muscles communicate. It also brings nutrients to cells and removes waste from them. "High potassium intakes are also associated with a reduced risk of stroke, lower blood pressure, lower risk of death from heart disease, protection against loss of muscle mass, preservation of bone mineral density and reduction in the formation of kidney stones," said Megan Ware, an Orlando-based registered dietitian and nutritionist. Good sources of potassium include Swiss chard, sweet potatoes, kale and lima beans. According to Ware, only 2 percent of U.S. adults meet the daily 4,700 mg recommendation for potassium. 

Often referred to as the "building blocks of life," proteins are large molecules essential for body structure and function, according to the National Institutes of Health. Protein makes up about 20 percent of body weight, and muscles, skin and bone all contain large amounts of it. Enzymes, hormones and antibodies are all proteins. "Protein is a macronutrient that is part of every part of your body. It is also a nutrient that gives you energy," said Jimenez.

Saturated fats are fat molecules that are saturated with hydrogen molecules. "They are solid at room temperature," said Jimenez, who cited lard as an example. Other examples include cheese, butter, fatty meats and poultry with skin, many fried foods and palm oil. Jimenez pointed out that saturated fats are known to promote heart diseases, raise bad cholesterol, and contain lots of calories. She recommended a "small intake . . . about 7 percent of total daily calories)." 

Sodium is a mineral electrolyte that is essential for cell membrane maintenance, absorption and transport of glucose, water and amino acids, and maintaining a healthy blood pressure, according to the Linus Pauling Institute at Oregon State University

Excess sodium, however, can increase blood pressure by causing too much fluid to stay in the body and put more strain on the heart. Diseases associated with too much sodium include stroke, heart disease, stomach cancer and kidney disease, according to the American Heart Association. Most excess sodium comes from processed or restaurant foods, not from sprinkling salt on homemade foods. The AHA recommends consuming 1,500 mg of sodium daily. 

"Sucrose is another term for table sugar," said Jimenez. It comes from sugar cane or sugar beets. Like fructose and glucose, sucrose is a simple carbohydrate. According to Jimenez, it is made up of both fructose and glucose and when it is ingested, the body splits sucrose into those two components for processing and use.

There are many types of sugar, including fructose, sucrose and glucose, according to Jimenez. There are naturally occurring sugars, such as fructose from fruit and lactose from milk. There are also added sugars, such as high fructose corn syrup or sugar added to coffee. No added sugar is necessary for a healthy diet, according to the Harvard School of Public Health

According to the National Institutes of Health, sugar contains calories but no nutrients. Nevertheless, fruits, which contain naturally occurring sugars, are nutrient-dense foods that are part of a healthy diet. 

According to Jimenez, trans fats, also called trans fatty acids, are sometimes found naturally in meats or dairy, but usually in small amounts. More often, she said, they are "produced by the food industry for the purpose to increase shelf life of the product." This is done by adding hydrogen to liquid vegetable oils to make the oils more solid. These are called partially hydrogenated oils. Jimenez said that they are often found in "convenient foods" like frozen pizzas. 

Other common sources of trans fats include baked goods, crackers, refrigerated dough, margarine and coffee creamer. Fast food restaurants often use them in deep fryers because partially hydrogenated oil does not have to be changed as often as regular oil.

"Trans fats are not recommended at all because of the link to heart diseases," warned Jimenez. In fact, they are often considered the worst type of fat. According to the Mayo Clinic, they both lower your good cholesterol and increase your bad cholesterol. In 2013, the FDA decreed that partially hydrogenated oils were no longer considered safe. There is currently a three-year adjustment period in place so that food manufacturers can change their practices or seek approval. 

Unsaturated fats are liquid at room temperature. There are three types of unsaturated fats: monounsaturated fats, polyunsaturated fats and Omega-3 fatty acids. According to the Mayo Clinic, these can all provide health benefits. They are called "unsaturated" because they have at least one carbon bond (called a double bond) in the fat molecule. Saturated fats have no double bonds because they are saturated with hydrogen molecules. 

Vitamin A is a fat-soluble vitamin that is good for healthy vision, skin, bones and other tissues in the body. Through retinol, vitamin A helps support skin health and vision, according to Paymaster. "Vitamin A is required for sebum production to keep hair moisturized," added Ware. [Related: Vitamin A: Sources & Benefits

Also known as thiamin, vitamin B1 "is involved in energy production," said Flores. It helps convert carbohydrates into energy. [Related: What Is Thiamine (Vitamin B1)?

In addition to its general B vitamin goodness, vitamin B2, or riboflavin, acts as an antioxidant helping to fight free radicals. It also helps the body utilize vitamin B6 and folate (vitamin B9) as well as produce red blood cells, according to the University of Maryland Medical Center. [Related: Vitamin B2 (Riboflavin): Sources & Benefits

Vitamin B3, or niacin, helps with the healthy functioning of the digestive system, nerves and skin. According to the University of Maryland Medical Center, niacin helps produce sex- and stress-related hormones, improves circulation and reduces inflammation. It is associated with lowering cholesterol. According to the National Institutes of Health, one to three doses of niacin daily is a popular treatment for those suffering from high LDL (bad) cholesterol and low HDL (good) cholesterol. [Related: Niacin (Vitamin B3): Benefits & Side Effects

Pantothenic acid, or vitamin B5, is essential for manufacturing red blood cells, according to the University of Maryland Medical Center. It also helps produce sex and stress hormones (sometimes it is called the "anti-stress" vitamin), synthesize cholesterol, utilize other vitamins and keep the digestive tract healthy. [Related: What Is Vitamin B5 (Pantothenic Acid)?

Vitamin B6 helps with brain development and function, producing neurotransmitters, serotonin, norepinephrine and melatonin, according to the University of Maryland Medical Center. It also helps regulate homocysteine. [Related: Vitamin B6: Sources & Benefits]

Biotin helps metabolize carbohydrates, amino acids and fats. It can help to strengthen nails and hair, according to the University of Maryland Medical Center. Because of its benefits to hair, it is sometimes called Vitamin H. [Related: What Is Biotin?

Folic acid, also called folate or vitamin B9, is important for women of childbearing age to consume daily, said Laura Flores, a nutritionist based in San Diego. Folate can decrease the risk of neural-tube defects in fetuses, so it is essential that mothers-to-be get enough of it. Flores said that it is also helpful in "lowering [high] levels of homocysteine, a cardiovascular risk factor." [Related: What Is Folic Acid?

Though it is part of the B complex group, vitamin B12 is quite different than other B vitamins. For starters, the body can store several years' worth of it in the liver. It can also be difficult to absorb from plant sources. According to World's Healthiest Foods, it is essential for proper brain functioning and cognitive development. It helps with the production of DNA and RNA, works with folate to develop red blood cells and use iron, and helps control homocysteine levels. It is common for older adults to be deficient in Vitamin B12. [Related: Vitamin B12: Deficiency & Supplements]

Vitamin C, also called ascorbic acid, is important to many functions in the body. "Vitamin C is important for immune health and joint health, helps to keep the body hydrated and also increases your metabolism," said Paymaster. Ware added that it helps with the "building and maintenance of collagen, which provides structure to skin and hair." Vitamin C is a popular remedy for the common cold, but research is mixed on whether it helps or prevents the sniffles. [Related: Vitamin C: Sources & Benefits]

Vitamin D is a fat-soluble vitamin that is present in few foods and added to others, like fortified milk. The body makes it when it is exposed to sunlight. Vitamin D is essential to maintaining strong bones; it works with calcium to keep them healthy. Lack of Vitamin D in children can lead to weak bones or Rickets disease. It is also a component in immune system function and cell growth and has been linked to cancer prevention, according to the University of Maryland Medical Center. [Related: Vitamin D: Facts and Effects]

Vitamin E is a fat-soluble vitamin that functions as an antioxidant. It aids in immune system function, the development of red blood cells and widens blood vessels to prevent clotting. It has been linked to cancer, heart disease and stroke prevention but that connection is not fully established according to the National Institutes of Health. [Related: Vitamin E: Sources, Benefits & Risks]

"Vitamin K is important for heart health, blot clotting, bone health, cancer prevention and diabetes prevention," said Paymaster. It is sometimes called the clotting vitamin. [Related: Vitamin K: Sources & Benefits

Zinc is a trace mineral essential for body functioning. According to the Mayo Clinic, zinc is effective for treating ADHD, diarrhea, stomach ulcers, acne, some forms of herpes and sickle cell anemia. It is a popular cold remedy, though scientific results remain unclear about its effectiveness in this area. Good sources of zinc include beef, lamb, shellfish and sesame seeds, according to World's Healthiest Foods.  

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