Nutrition Glossary (cont.)

K (potassium): K is the symbol for potassium, the major positive ion (cation) found inside of cells. The chemical notation for potassium is K+.

The proper level of potassium is essential for normal cell function. An abnormal increase of potassium (hyperkalemia) or decrease of potassium (hypokalemia) can profoundly affect the nervous system and heart, and when extreme, can be fatal.

The normal blood potassium level is 3.5 - 5.0 milliEquivalents/liter (mEq/L), or in international units, 3.5 - 5.0 millimoles/liter (mmol/L).

Lactase: Enzyme that breaks down the milk sugar lactose.

Lactase deficiency: Lack of an enzyme called lactase in the small intestine that is needed to digest lactose, a component of milk and most other dairy products. Lactose is sometimes also used as an ingredient in other foods, so those with a lactase deficiency should check labels carefully.

Most people are born with the ability to make adequate amounts of lactase, but lactase production normally decreases with age, more so in some persons than others. There are significant differences relative to lactase production among ethnic groups.

Inadequate lactase production can cause difficulty digesting lactose-containing products, which include dairy products themselves and foods containing dairy products as ingredients.

The most common symptoms of lactase deficiency are diarrhea, bloating, and gas. The diagnosis may be made by a trial of a lactose-free diet or by special testing. In some cases, other diseases of the intestine may need to be excluded by further medical evaluation.

Lactobacillus acidophilus: The bacteria found in milk and fermented milk products, particularly yogurt with "live cultures" of L. acidophilus. L. acidophilus assists with the digestive process within the intestinal tract. It can be decimated by the use of antibiotics, and many health professionals urge people to use probiotics to counter this unfortunate side effect of antibiotic use.

Lactose intolerance: The inability to digest lactose, a sugar component of milk and most other dairy products. Lactose is sometimes also used as an ingredient in other foods, so those with a lactase deficiency should check labels carefully. The basis for this condition is lack of an enzyme in the small intestine called lactase. Lactase is essential to digest lactose. Without enough lactase, there is lactose intolerance.

Underproduction of lactase can cause difficulty digesting lactose- containing products, which include dairy products themselves and foods containing dairy products as ingredients.

The most common symptoms of lactose intolerance are diarrhea, bloating, and gas. The diagnosis may be made by a trial of a lactose- free diet or by special testing. In some cases, other diseases of the intestine may need to be excluded by further medical evaluation.

Most people are born with the ability to make adequate amounts of lactase but lactase production normally declines with age, more so in some persons than others, and there are also significant differences relative to lactase production among ethnic groups.

Lipid - A chemical compound characterized by the fact that it is insoluble in water. Both fat and cholesterol are members of the lipid family.

Lipoprotein: A complex of lipid and protein, the way lipids travel in the blood.

LDL cholesterol: Lipoproteins which are combinations of lipids (fats) and proteins are the form in which lipids are transported in the blood. The low-density lipoproteins transport cholesterol from the liver to the tissues of the body. LDL cholesterol is therefore considered the "bad" cholesterol.

Magnesium deficiency: Can occur due to inadequate intake or impaired intestinal absorption of magnesium. Low magnesium (hypomagnesemia) is often associated with low calcium (hypocalcemia) and potassium (hypokalemia) levels. Deficiency of magnesium causes increased irritability of the nervous system with tetany (spasms of the hands and feet, muscular twitching and cramps, spasm of the larynx, etc.). According to the National Academy of Sciences, the Recommended Dietary Allowances of magnesium are 420milligrams per day for men and 320 milligrams per day for women. The upper limit of magnesium as supplements is 350 milligrams daily, in addition to the magnesium from food and water.

Metabolism: The whole range of biochemical processes that occur within us (or any living organism). Metabolism consists both of anabolism and catabolism (the buildup and breakdown of substances, respectively).

Metabolic rate: The metabolic rate is the amount of energy liberated per unit of time. Our metabolic rate is represented by the work we do, heat from body metabolism, and stored energy, such as in the form of fat.

The "basal metabolic rate" (BMR) is the metabolic rate determined at rest 12 to 14 hours after the last meal. In healthy humans the BMR is approximately 2000 kcal/day. (The metabolic rate is actually lowest during sleep.)

The metabolic rate is affected by recent food ingestion, muscle exertion, environmental temperature, height, weight, body surface area, age, sex, emotional state, body temperature, pregnancy, menstruation, level of thyroid hormones, and "stress" hormones (epinephrine and norepinephrine).

Mitochondria: The mitochondria are normal energy- producing structures within cells. They are located in the cell's cytoplasm outside the nucleus.

The mitochondria are responsible for energy production. They consist of two sets of membranes, a smooth continuous outer coat and an inner membrane arranged in tubules or in folds that form plate- like double membranes (cristae). The mitochondria are in fact the principal energy source of the cell (thanks to the cytochrome enzymes of terminal electron transport and the enzymes of the citric acid cycle, fatty acid oxidation, and oxidative phosphorylation). The mitochondria convert nutrients into energy as well as doing many other specialized tasks.

Each mitochondrion has a chromosome that is made of DNA but is otherwise quite different from the better known chromosomes in the nucleus. The mitochondrial chromosome is much smaller. It is round (whereas the chromosomes in the nucleus are shaped like rods). There are many copies of the mitochondrial chromosome in every cell (whereas there is normally only one set of chromosomes in the nucleus).

No matter whether we are male or female, we inherit our mitochondrial chromosome from our mother. In other words, the mitochondrial chromosome is transmitted in a matrilinear manner. We have Eve to thank for our mitochondrial chromosome.

Niacin for high cholesterol: Niacin or nicotinic acid, one of the water-soluble B vitamins, improves all lipoproteins when given in doses well above the vitamin requirement. Nicotinic acid lowers the total cholesterol, "bad" LDL-cholesterol, and triglyceride levels, while raising the "good" HDL-cholesterol level.

There are two types of nicotinic acid: immediate release and timed release. Most experts recommend starting with the immediate-release form; discuss with your doctor which type is best for you.

Nicotinic acid is inexpensive and widely accessible to patients without a prescription but must not be used for cholesterol lowering without the monitoring of a physician because of the potential side effects. (Nicotinamide, another form of the vitamin niacin, does not lower cholesterol levels and should not be used in the place of nicotinic acid.)

All patients taking nicotinic acid to lower serum cholesterol should be closely monitored by their doctor to avoid complications from this medication. Self-medication with nicotinic acid should definitely be avoided because of the possibility of missing a serious side effect if not under a doctor's care.

Patients on nicotinic acid are usually started on low daily doses and gradually increased to an average daily dose of 1.5 to 3 grams per day.

Nicotinic acid reduces LDL-cholesterol levels by 10 to 20 percent, reduces triglycerides by 20 to 50 percent, and raises HDL-cholesterol by 15 to 35 percent.

A common and troublesome side effect of nicotinic acid is flushing or hot flashes, which are the result of the widening of blood vessels. Most patients develop a tolerance to flushing, and in some patients, it can be decreased by taking the drug during or after meals or by the use of aspirin or other similar medications prescribed by your doctor. The effect of high blood pressure medicines may also be increased while you are on niacin. If you are taking high blood pressure medication, it is important to set up a blood pressure monitoring system while you are getting used to your new niacin regimen. A variety of gastrointestinal symptoms including nausea, indigestion, gas, vomiting, diarrhea, and the activation of peptic ulcers have been seen with the use of nicotinic acid.

Three other major adverse effects include liver problems, gout, and high blood sugar. Risk of these three complications increases as the dose of nicotinic acid is increased. Your doctor will probably not prescribe this medicine for you if you have diabetes, because of the effect on your blood sugar.

Niacin deficiency: Deficiency of niacin, one of the B-complex vitamins, causes pellagra.

Pellagra was known as the "disease of the four D's" -- dermatitis, diarrhea, dementia and death. The disease is specifically characterized by:

  • Dermatitis: A rash on areas of the skin exposed to light or trauma and ulcerations within the mouth
  • Diarrhea
  • Dementia: Mental disorientation, confusion, delusions and depression
  • Death, if untreated.

Pellagra, once a puzzle, was solved by Joseph Goldberger (1874-1929). Serving in the Public Health Service, Dr. Goldberger proposed that pellagra was due to a nutritional deficiency and in 1915 began experiments with Mississippi prison inmates (who "volunteered" in return for full pardons). Dr. Goldberger fed them a poor diet he believed caused pellagra and within months, many developed the disease. Their symptoms of pellagra were reversed when meat, fresh vegetables and milk were added to their diet.

Niacin, Dr. Goldberger subsequently showed, was the principle that had this remarkable effect. A readily-available B vitamin, niacin cures pellagra and prevents it.

The name "pellagra" comes from the Italian "pelle", skin + "agra", rough = rough skin, referring to the skin problems in pellagra.

Nicotinic acid: Deficiency of nicotinic acid (also known as niacin), one of the B-complex vitamins, causes pellagra.

Pellagra was known as the "disease of the four D's" -- dermatitis, diarrhea, dementia and death. The disease is specifically characterized by:

  • Dermatitis: A rash on areas of the skin exposed to light or trauma and ulcerations within the mouth
  • Diarrhea
  • Dementia: Mental disorientation, confusion, delusions and depression
  • Death, if untreated.

Pellagra, once a puzzle, was solved by Joseph Goldberger (1874-1929). Serving in the Public Health Service, Dr. Goldberger proposed that pellagra was due to a nutritional deficiency and in 1915 began experiments with Mississippi prison inmates (who "volunteered" in return for full pardons). Dr. Goldberger fed them a poor diet he believed caused pellagra and within months, many developed the disease. Their symptoms of pellagra were reversed when meat, fresh vegetables and milk were added to their diet.

Niacin, Dr. Goldberger subsequently showed, was the principle that had this remarkable effect. A readily-available B vitamin, niacin cures pellagra and prevents it.

The name "pellagra" comes from the Italian "pelle", skin + "agra", rough = rough skin, referring to the skin problems in pellagra.

Nutraceuticals: A food or part of a food that allegedly provides medicinal or health benefits, including the prevention and treatment of disease A nutraceutical may be a naturally nutrient-rich or medicinally active food, such as garlic or soybeans, or it may be a specific component of a food, such as the omega-3 fish oil that can be derived from salmon and other cold-water fish.

Nutrition: 1) The science or practice of taking in and utilizing foods. 2) A nourishing substance, such as nutritional solutions delivered to hospitalized patients via an IV or IG tube.

Nutritionist: 1) In a hospital or nursing home, a person who plans and/or formulates special meals for patients. It can also simply be a euphemism for a cook who works in a medical facility but who does not have extensive training in special nutritional needs. 2) In clinical practice, a specialist in nutrition. Nutritionists can help patients with special needs, allergies, health problems, or a desire for increased energy or weight change devise healthy diets. Some nutritionists in private practice are well-trained, degreed, and licensed. Depending on state law, however, a person using the title may not be trained or licensed at all.

Phytochemical/Phytonutrient: The active health-protecting compounds that are found as components of plants.

Currently, the terms "phytochemical" and "phytonutrient" are being used interchangeably to describe those plant compounds which are thought to have health-protecting qualities.

The antioxidant, immune boosting and other health promoting properties of active compounds in plants are being investigated. Phytonutrients or phytochemicals that are being studied presently include (and are not limited to) terpenes, carotenoids, limonoids, and phytosterols.

Protein: One of the three nutrients that are used as energy sources (calories) by the body. (The other energy sources are in the form of fats and carbohydrates. Proteins are essential components of the muscle, skin, and bones of animals. Proteins and carbohydrates each provide 4 calories of energy per gram, while fats provide 9 calories per gram.

RDAs (Recommended Dietary Allowances): a set of estimated nutrient allowances established by the National Academy of Sciences. It is updated periodically to reflect current scientific knowledge.

RDIs (Reference Daily Intakes): a set of dietary references based on the Recommended Dietary Allowances for essential vitamins and minerals and, in selected groups, protein. The name "RDI" replaces the term "U.S. RDA."

Unlike DRVs, which are a new concept, many consumers may already have a good idea of what the RDIs are. Since the RDIs (the former U.S. RDAs used by FDA) have been around for almost 20 years as the established estimated values for vitamins, minerals and protein.

Selenium: An essential mineral that is a component of a key antioxidant enzyme, glutathione reductase, in tissue respiration. Deficiency of selenium causes Keshan disease, a fatal form of cardiomyopathy (disease of the heart muscle) first observed in Keshan province in China and since found elsewhere. According to the National Academy of Sciences, the Recommended Dietary Allowances of selenium are 70 milligrams per day for men and 55 milligrams per day for women. Food sources of selenium include seafood, some meats such as kidney and liver, and some grains and seeds. Too much selenium may cause reversible changes in the hair (balding) and nails, garlic odor to the breath, intestinal distress, weakness and slower mentation (slowed mental functioning).

Selenium Deficiency: Deficiency of the essential mineral selenium causes Keshan disease, a fatal form of cardiomyopathy (disease of the heart muscle) first observed in Keshan province in China and since found elsewhere. According to the National Academy of Sciences, the Recommended Dietary Allowances of selenium are 70 milligrams per day for men and 55 milligrams per day for women. Food sources of selenium include sea foods, some meats such as kidney and liver, and some grains and seeds.

Serving Size: 1. The portion of food used as a reference on the nutrition label of that food.
2. The recommended portion of food to be eaten. The National Cancer Institute defines a serving as:

  • One medium-sized fruit (such as apples, oranges, bananas, pears)
  • 1/2 cup of raw, cooked, canned or frozen fruits or vegetables
  • 3/4 cup (6 oz.) of 100% fruit or vegetable juice
  • 1/2 cup cut-up fruit
  • 1/2 cup cooked or canned legumes (such as beans and peas)
  • 1 cup of raw, leafy vegetables (such as lettuce and spinach)
  • 1/4 cup dried fruit (such as raisins, apricots, mango)

Sodium: The major positive ion (cation) in fluid outside of cells. The chemical notation for sodium is Na+. When combined with chloride, the resulting substance is table salt.

Excess sodium (such as from fast food hamburger and fries) is excreted in the urine. Too much or too little sodium can cause cells to malfunction, and extremes can be fatal.

Normal blood sodium level is 135 - 145 milliEquivalents/liter (mEq/L), or in international units, 135 - 145 millimoles/liter (mmol/L).

Trans fatty acids: These are byproducts of partial hydrogenation, a process in which some of the missing hydrogen atoms are put back into polyunsaturated. Some of the hydrogenated fatty acids take on a "straighter" structure: these are the trans fatty acids. "Hydrogenated vegetable oils," such as vegetable shortening and margarine, are solid at room temperature because straightening fatty acids allows them to pack more tightly.

Triglyceride: A fatty substance that is composed of three fatty acids each of which is attached to a glycerol molecule. Like cholesterol, triglyceride in the blood either comes from the diet or the liver. Also, like cholesterol, triglyceride cannot dissolve and circulate in the blood without combining with a lipoprotein are a form of fat that is transported through the blood to the body tissues.

Whether elevated triglyceride levels in the blood lead to atherosclerosis and heart attacks is controversial. While most doctors now believe that an abnormally high triglyceride level is a risk factor for arteriosclerosis, it is difficult to conclusively prove that raised triglyceride by itself can cause atherosclerosis. However, it is increasingly recognized that elevated triglyceride is often associated with other conditions that increase the risk of atherosclerosis including obesity, low levels of HDL- cholesterol, insulin resistance and poorly controlled diabetes mellitus, and small, dense LDL cholesterol particles.

Vitamins: The word "vitamin" was coined in 1911 by the Warsaw-born biochemist Casimir Funk (1884-1967). At the Lister Institute in London, Funk isolated a substance that prevented nerve inflammation (neuritis) in chickens raised on a diet deficient in that substance. He named the substance "vitamine" because he believed it was necessary to life and it was a chemical amine. The "e" at the end was later removed when it was recognized that vitamins need not be amines.

The letters (A, B, C and so on) were assigned to the vitamins in the order of their discovery. The one exception was vitamin K which was assigned its "K" from "Koagulation" by the Danish researcher Henrik Dam.

  • Vitamin A: Retinol. Carotene compounds responsible for transmitting light sensation in the retina of the eye. Deficiency leads to night blindness.
  • Beta carotene: An antioxidant which protects cells against oxidation damage that can lead to cancer. Beta carotene is converted, as needed, to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can temporarily yellow the skin, a condition called carotenemia, commonly seen in infants fed largely mashed carrots.
  • Vitamin B1: Thiamin, acts as a coenzyme in body metabolism. Deficiency leads to beriberi, a disease of the heart and nervous system.
  • Vitamin B2: Riboflavin, essential for the reactions of coenzymes. Deficiency causes inflammation of the lining of the mouth and skin.
  • Vitamin B3: Niacin, an essential part of coenzymes of body metabolism. Deficiency causes inflammation of the skin, vagina, rectum and mouth, as well as mental slowing.
  • Vitamin B6: Pyridoxine, a cofactor for enzymes. Deficiency leads to inflammation of the skin and mouth, nausea, vomiting, dizziness, weakness and anemia.
  • Folate (folic acid): Folic acid is an important factor in nucleic acid synthesis (the genetic material). Folate deficiency leads to megaloblastic anemia.
  • Vitamin B12: An essential factor in nucleic acid synthesis (the genetic material of all cells). Deficiency leads to megaloblastic anemia, as can be seen in pernicious anemia.
  • Vitamin C: Ascorbic acid, important in the synthesis of collagen, the framework protein for tissues of the body. Deficiency leads to scurvy, characterized by fragile capillaries, poor wound healing, and bone deformity in children.
  • Vitamin D: A steroid vitamin which promotes absorption and metabolism of calcium and phosphorus. Under normal conditions of sunlight exposure, no dietary supplementation is necessary because sunlight promotes adequate vitamin D synthesis in the skin. Deficiency can lead to osteomalacia in adults and bone deformity (rickets) in children.
  • Vitamin E: Deficiency can lead to anemia.
  • Vitamin K: An essential factor in the formation of blood clotting factors. Deficiency can lead to abnormal bleeding.

Zinc deficiency: According to the National Academy of Sciences, the Recommended Dietary Allowances of zinc are 12 milligrams per day for women and 10 milligrams per day for men. Food sources of zinc include meat including liver, eggs, seafood, nuts and cereal.

Deficiency of zinc is associated with short stature, anemia, increased pigmentation of skin (hyperpigmentation), enlarged liver and spleen (hepatosplenomegaly), impaired gonadal function (hypogonadism), impaired wound healing, and immune deficiency.

In a genetic disease called acrodermatitis enteropathica, there is impaired zinc uptake from the intestine. The condition is characterized by the simultaneous presence of dermatitis (skin inflammation) and diarrhea. The skin on the cheeks, elbows and knees and the tissues about the mouth and anus are inflamed. There is balding of the scalp, eyebrows and eyelashes. Wound healing is delayed. In addition, there are recurrent bacterial and fungal infections due to immune deficiency. The key laboratory finding is an abnormally low blood zinc level reflecting the impaired zinc uptake. Treatment with zinc is curative.


Last Editorial Review: 9/9/2004



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