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Vitamins

Vitamin Quick Select:

A | B1 | B2 | B9 | B12 | C | D | E | K

Before delving into the fascinating list of vitamins below, it is important to review a few simple facts and definitions…

Vitamins are organic compounds used by our bodies for normal growth, nutrition, and biochemical function. We need to obtain vitamins from our diet or other sources because we cannot generate them ourselves.

As human beings, our bodies use 13 different vitamins. Four are fat-soluble (A, D, E, and K), and nine are water-soluble (8 different B vitamins, and C). So, what does it mean if a vitamin is fat-soluble? Water-soluble?

Simply defined, fat-soluble refers to those vitamins that are dissolved in fats and oils. After digestion/absorption through the intestines, they are dissolved into and stored in fatty tissues throughout the body. As they are less easily removed from the body, toxicity (side effects) may occur from hypervitaminosis (too much of one particular vitamin in our body).

Water-soluble vitamins are readily excreted (expelled as waste) through the kidneys. Since they are not stored in the tissues toxicity is quite rare; for the same reason, daily intake is more important.

Many vitamins have antioxidant properties.

So, what are antioxidants?

Simply put, antioxidants block oxidation.

Oxidation refers to a biochemical reaction that normally occurs in our bodies. Unfortunately, oxidation reactions produce free radicals (molecules that damage our own cells).

Antioxidants protect our bodies by scavenging (chomping up) the free radicals and limiting oxidation.

The naming of vitamins skips from E to K. Vitamins that correspond to letters F through J have been reclassified over time, disregarded, or renamed because of their relationship to vitamin B (which has become a complex of vitamins). The German scientists who isolated and described vitamin K (in addition to naming it as such) did so because the vitamin is intimately involved in the Koagulation of blood following wounding. At the time, most (but not all) of the letters from F through to J were already designated, so the use of the letter K was considered quite reasonable.

Vitamin A is a fat-soluble vitamin that we obtain from both plant and animal sources. Plant sources include carrots, leafy green vegetables, and most yellow fruits. These foods provide beta-carotene, which is converted to Vitamin A after ingestion. Animal sources include eggs, butter, whole milk, enriched margarine, liver, and oily salt-water fish.

Vitamin A is needed for night vision, bone development, testicular and ovarian function, and maintenance of our bodies’ mucosal and epithelial surfaces (the “inner” membranes). Vitamin A is an anti-oxidant and free radical scavenger.

Deficiency of Vitamin A leads to night blindness and xeropthalmia (dry eyes). People suffering from pneumonia or chronic kidney disease may pass Vitamin A through their system without complete metabolism.

Vitamin A supplementation is used to treat vitamin deficiency. It has also proven to decrease the size and secretion of sweat glands; hence, a derivative (isotretinoin – formerly branded Accutane) is used to treat acne.

As Vitamin A is fat soluble, toxicity may occur (though usually with ingestion of greater than 100,000 IU per day). Signs of toxicity include nausea, jaundice, irritability, blurry vision, headaches, hair loss, muscle and abdominal pain and weakness, drowsiness, and altered mental status.


Vitamin B1 is also known as thiamine (“thio-vitamine” actually derived from Greek as “sulfur-containing vitamin”). It is a water-soluble vitamin synthesized in bacteria, fungi, and plants with dietary sources found in yeast, cereal, legumes, peas, nuts, pork, and beef.

Thiamine is needed for proper function of our nervous, cardiovascular, and musculoskeletal systems.

Thiamine deficiency occurs from malnutrition (often with alcoholism) or diets rich in foods that prevent its metabolism (raw freshwater fish, raw shellfish, betel nuts). Mild deficiency may lead to headache, nausea, poor balance, malaise, and myalgia (muscle pain). Severe deficiency may lead to Beriberi (nerve dysfunction, confusion, congestive heart failure) or Wernicke’s encephalopathy (a neurologic disorder associated with alcoholism, characterized by paralysis of eye movements, abnormal stance and gait, and markedly deranged mental function). Wernicke’s encephalopathy may progress to Korsakoff’s psychosis (characterized by malaise, amnesia, and severe impairment of neurologic function), which is potentially irreversible.

Thiamine supplementation is used to treat deficiency and the diseases mentioned above.


Vitamin B2 is also known as riboflavin. It is a water-soluble vitamin found in milk, enriched breads and cereals, meat (specifically liver and kidney), eggs, nuts, green vegetables and brewer’s yeast.

Deficiency of riboflavin alone is quite rare, but can occur in combination with other B-complex vitamins if intake is inadequate. Medications that might impair your ability to absorb B-complex vitamins include probenecid, phenothiazine, and some oral contraceptives.

We obtain pyridoxine, or Vitamin B6, from cereal grains, legumes, vegetables, liver, and eggs. It is a water-soluble vitamin that we need for the metabolism of fats, proteins, and carbohydrates. It is also essential for the formation of red blood cells, and proper central nervous system function.

Deficiency of pyridoxine alone is rare, but may demonstrate as skin inflammation. Oral supplementation will reverse this condition.


Vitamin B9 is most commonly known as folic acid. We obtain our folic acid from both plant and animal sources including liver, kidneys, enriched yeast, and leafy, green vegetables.

Folic acid is a water-soluble vitamin essential for proper DNA synthesis in our bodies. Without enough folic acid, improper DNA synthesis leads to abnormal cell division. Red blood cell production is impaired by the abnormal cell division, and immature cells are produced. These immature red blood cells are larger than normal red blood cells, and usually do not carry oxygen effectively. This disease process is referred to megaloblastic (larger cells) anemia (not enough red blood cells to carry oxygen efficiently), and presents with fatigue, weakness, heart palpitations, diarrhea, and glossitis (red, swollen, painful tongue). It is reversed with proper supplementation. This form of anemia is the same as with Vitamin B12 deficiency.

Folic acid is also essential for proper growth of the neural tube in embryos. The neural tube develops into the brain and spinal cord. Women who supplement with folic acid prior to pregnancy and during the first trimester have demonstrated to reduce the incidence of neural tube defects in their children. In 1998, the FDA mandated that all food manufacturers fortify enriched grain products with folic acid to prevent these devastating births defects.

Folic acid also helps to protect our blood vessels. Deficiency of folic acid leads to higher levels of homocysteine in our blood. Elevated levels of homocysteine have proven to be an independent risk factor for the development of atherosclerosis (hardening of the arteries).

The most common causes for deficiency include poor dietary intake (usually associated with alcoholism), increased demand from pregnancy/lactation, and impaired metabolism form diseases such as celiac sprue or certain anti-seizure medications.

Oral supplementation is the mainstay for treatment, but an intravenous form is available for extreme cases.


Vitamin B12 is also known as cyanocobalomin. We obtain Vitamin B12 from fish, shellfish, meats, and dairy products. It is a water-soluble vitamin.

Deficiency of Vitamin B12 in healthy adults is quite rare, but strict vegetarians and vegans as well as patients with malabsorption (inefficient digestion) are at higher risk. Proper digestion of Vitamin B12 begins with gastric (stomach) production of a substance called intrinsic factor. Intrinsic factor binds to the Vitamin B12 from our diet, and the combination is absorbed in the terminal ileum (the end of our small intestine). For this reason, diseases of the stomach (improper production of intrinsic factor) or terminal ileum (improper absorption) may lead to deficiency.

Severe deficiency may lead to megaloblastic (larger cells) anemia (not enough red blood cells to carry oxygen efficiently), intestinal problems, and even irreversible nerve damage. The megaloblastic anemia is this same as with folic acid deficiency. Vitamin B12 is essential for red blood cell growth, protein synthesis, maintenance of myelin (the protective sheath around our peripheral nerves) and the integrity of axons (the long part of our nerves that allow for conduction of the signals) as well. Pernicious anemia is an autoimmune disease (our bodies produce cells that impair the production of intrinsic factor by our stomach) that causes deficiency as well.

Medications such as proton pump inhibitors (antacids) may interfere with Vitamin B12 absorption by impairing stomach acid secretion. The acid in our stomach helps to release B12 from the food we eat.

For patients with stomach or intestinal causes for deficiency, Vitamin B12 is available in sublingual, nasal, intramuscular, and intravenous forms in addition to oral. Intranasal supplementation is not as effective as intramuscular – it requires weekly dosing as opposed to monthly.


Vitamin C, also know as ascorbic acid, is a water-soluble vitamin. We obtain most of our vitamin C from fruits and vegetables. Excellent sources include oranges, green peppers, watermelon, papaya, grapefruit, cantaloupe, strawberries, blackcurrants, kiwi, mango, broccoli, tomatoes, Brussels sprouts, cauliflower, cabbage, and citrus juices. Remember that vitamin C is quite sensitive to light, air, and heat; up to 25% of vitamin C may be lost by boiling, freezing/unthawing, or canning fruits and vegetables. Cooking fruits and vegetables for over 10 to 15 minutes may even reduce up to 50% of vitamin C!

Vitamin C is essential for proper collagen synthesis. Collagen is the main protein of our connective tissue. In other words, collagen is the supporting structure of our skin, bones, tendons, and ligaments; also, collagen is important for normal wound healing.

The disease classically associated with vitamin C deficiency is Scurvy. Scurvy was most common in sailors – as fruits and vegetables will perish after prolonged periods of time (at sea). Supplies of vitamin C on board became limited, and improper collagen synthesis led to weak blood vessel walls. Sailors would develop dark spots on their skin, spongy and often bleeding gums.

Today, with prevalent sources of natural vitamin C and supplementation, deficiency is quite rare. Pasteurization will destroy its content in milk, so infants fed purely by bottle will need vitamin C from other sources.

Vitamin C may promote resistance to infection. It is an anti-oxidant, and it plays a role in the generation of other anti-oxidants (i.e., glutathione, a-tocopherol). Vitamin C also helps to activate white blood cells and regulate our bodies’ inflammatory processes. Though vitamin C has been promoted for the treatment of infection, cancer, heart disease, diabetes, etc., clinical use for any diseases other than Scurvy has not yet proven definitive benefit.


Vitamin D exists in two primary forms: Vitamin D2 (ergocalciferol) is produced by plants, and Vitamin D3 (cholecalciferol) is made by our skin after exposure to ultraviolet-B sunlight. All Vitamin D is fat-soluble.

Our liver and kidneys process vitamin D to its active form (1,25-hydroxycholecalciferol) after we obtain Vitamin D2 from food, or vitamin D3 from sunlight.

Dietary sources for Vitamin D2 include fish (catfish, salmon, mackerel, sardines, tuna, eel), eggs, fortified milk, and cod liver oil with lesser amounts in beef liver, cheese, and egg yolks. Mushrooms are the only vegan source of Vitamin D2. At least ten minutes of ultraviolet-B sun exposure per day is needed for adequate skin production of vitamin D3.

Deficiency may occur when dietary intake is insufficient, with malabsorption (the intestinal tract is bypassed or diseased), kidney disease (prevents conversion to the active form), chronic steroid use, or when exposure to sunlight is limited. The NIH has not established recommended daily intake due to lack of sufficient data; however, it is generally recommended that adults get at least 400 IU daily.

The main function of Vitamin D is to regulate our blood levels of calcium and phosphorous. It helps to “mineralize” (add calcium crystals for strength) bone, so deficiency may lead to bone softening or thinning. Supplementation will prevent/treat osteomalacia in adults and rickets in children. Vitamin D may help to prevent high blood pressure, limit heart disease, enhance immune function, and may even protect against some forms of cancer, particularly pancreatic and colon. It is important to note that appropriate calcium and magnesium levels are necessary for Vitamin D therapy, and should be supplemented if needed.

As vitamin D is fat-soluble, toxicity may occur. Fortunately, it is extremely rare with doses less than 10,000 IU daily, and cannot occur from sun exposure. The earliest signs of Vitamin D toxicity are usually from elevated calcium levels and include loss of appetite, nausea, vomiting, weakness, confusion, or even kidney stones.


“Vitamin E” represents a group of eight different chemicals, called tocopherols. We obtain a-tocopherol, the most active form, from vegetable oils, wheat germ, cereal, fruits, green vegetables, meat, eggs, and some fish. Vitamin E is fat-soluble.

Vitamin E is very prevalent in the average human diet, so deficiency is quite rare. It is mostly seen in patients who suffer from disorders of the gastrointestinal tract that prevent proper digestion (i.e. cystic fibrosis, Crohn’s, Celiac, and Whipple’s disease).

The main function of vitamin E in our bodies is as an antioxidant.

Vitamin E has been investigated for the treatment and prevention of heart disease, vascular disease, and prostate cancer. Its topical form has been used in attempt to heal minor burns and sunburns as well. These applications are considered off-label. Some studies, however, have demonstrated slowing of the progression of Alzheimer’s disease when vitamin E is combined with donepezil.


In 1935, German scientists named vitamin K (phytonadione) as “Koagulationsvitamin,” which translates to “clotting vitamin.” It is fat-soluble, and refers to a set of chemical compounds that share similar actions in the body. Vitamin K is necessary for normal function of many of the proteins in our body that help blood clotting.

Dietary sources of vitamin K include green vegetables such as broccoli, Brussels sprouts, collard greens, lettuce, and spinach. Other sources include plant oils such as soybean and canola. It is absorbed by the small intestine, and requires bile salts and pancreatic enzymes for digestion.

Warfarin (Coumadin) is a medication that is used to treat diseases that may lead to abnormal blood clotting. Abnormal blood clotting may cause DVT (deep vein thrombosis), pulmonary embolism (blood clot that has traveled through veins, and lodged in the lungs), heart attack, stroke, and many other serious medical conditions. Warfarin blocks the actions of vitamin K, thus impairing our body’s ability to clot. Please note that many foods and medications will interact with Warfarin. These interactions could lead to abnormal blood clotting, or even hemorrhage (severe bleeding). If you are taking Warfarin, be sure to address this with your provider.


Just for kicks:

Fruit – The ripened ovary of a flowering plant that contains the seeds, sometimes fused with other parts of the plant. Fruits can be dry or fleshy. Berries, nuts, grains, pods, and drupes are fruits. Fruits that consist of ripened ovaries alone, such as the tomato and pea pod, are called true fruits. Fruits that consist of ripened ovaries and other parts such as the receptacle (the part at the top of the stem that bears the organs of a flower) or bracts (modified leaves), as in the apple, are called accessory fruits or false fruits.

Vegetable – Simply, the part of a plant that is grown primarily for food (the leaf of spinach, the root of a carrot, the flower of broccoli, and the stalk of celery are all vegetables). In everyday, nonscientific speech we make the distinction between sweet plant parts (fruits) and non-sweet plant parts (vegetables). This is why we speak of peppers, cucumbers, and squash as vegetables – because they have seeds, they are fruits in the eyes of a botanist!

Legume – Any of a large number of plants with a seed pod. Legumes live in a symbiotic relationship with bacteria in structures called nodules on their roots. These bacteria are able to convert nitrogen from the air into compounds that the plants can use. Beans, peas, clover, alfalfa, locust trees, and acacia trees are all legumes.

Vitamin Quick Select:

A | B1 | B2 | B9 | B12 | C | D | E | K