The late 19th and early 20th centuries were the golden era of vitamin research. The Hollywood version of this enlightened age is that brilliant epidemiologists, chemists, and physicians from across the globe made brilliant discoveries that miraculously eradicated the pestilences afflicting humanity. Suffering from scurvy? Here comes vitamin C to the rescue! Plagued by pellagra? You just need niacin!
While these and other vitamin breakthroughs did indeed save lives and profoundly impacted the future of nutritional health, the process of discovery was neither swift nor glamorous. There were many false starts, failed experiments, boned-headed theories, and, perhaps unsurprisingly, a lack of cooperation among researchers.
In fact, the rush to make medical history created some awkward moments. In 1913, two groups of researchers, Elmer McCollum and Marguerite Davis at the University of Wisconsin and Lafayette Mendel and Thomas Burr Osborn at Yale, independently discovered what would come to be known as Vitamin A. Once they caught wind of each other’s work, the race was on to be the first to publish the findings in a research journal.
McCollum and Davis submitted their paper three weeks before Osborne and Mendel to claim the title of “The Scientists Who Discovered Vitamin A” even though both studies were published in the same issue of the Journal of Biological Chemistry.
Regardless of who received the credit, the key to this vitamin discovery was studying the role of fats in diets. As a result, vitamin A was found to be fat-soluble and eventually vitamins D, E and K were discovered to be as well.
- Fat-soluble vitamins are absorbed by fat globules and stored in the body in fat tissue and the liver
- Fat-soluble vitamins leave the body slowly
- Since the body maintains stores of these vitamins, most people do not need supplements
- Mega doses of fat-soluble vitamins can be detrimental to health
- Health issues can occur from low levels of fat-soluble vitamins, especially in developing nations
- The fat-soluble vitamins are vitamin A, vitamin K, vitamin D, and vitamin E
- Overview: Vitamin A is a group of organic compounds that support the immune system, vision, and general cellular growth and maintenance. Some of the vitamin A compounds are retinol, retinal, retinoic acid, and the carotenoids –especially alpha and beta-carotene. As an antioxidant, vitamin A inhibits the chemical reactions in molecules that produce free radicals. Free radicals are atoms or molecules that have unpaired electrons and are highly chemically reactive with other substances, including other free radicals. As by-products of natural metabolic processes, free radicals are biologically inevitable, but they can still be harmful. High levels of free radicals can damage cells, cell membranes and even DNA which has been linked to cancer and other health problems.
- Best Food Sources: Most dietary vitamin A is obtained through retinol, also known as active vitamin A, and through beta-carotene. In a beautiful instance of natural symmetry, retinol is available from animal-derived sources while beta-carotene is almost exclusively found in fruits and vegetables. Foods high in retinol include: cod liver oil, butter, eggs, liver, cheese, and milk. There are also synthetic source of retinol that are used in supplements. Animals, including humans, create retinol in the intestinal mucosa by breaking down beta-carotene obtained from plant sources. Carotene, as the name might suggest, is what give carrots their orange color. It shouldn’t be a surprise that other foods high in beta-carotene are often orange as well including: sweet potatoes, cantaloupe, and mangoes. Leafy greens are also good sources of beta-carotene especially kale, spinach, mustard greens, and collard greens.
- Recommended Dietary Allowance: Daily intake guidelines for vitamin A are measured in micrograms.
- Infants up 6 months need between 400 ug and 600 ug
- Infants 7 to 12 months need between 500 ug and 600 ug
- Children1 to 3 years need between 300 ug and 600 ug
- Children 4 to 8 years need between 400 ug and 900 ug
- Males 9 to 13 years need between 600 ug and 1700ug
- Males14 to 18 years need between 900 ug and 2800 ug
- Males 19 and above need between 900 ug and 3000 ug
- Females 9 to 13 years need between 600 ug and 1700 ug
- Females 14 to 18 years need between 700 ug and 2800 ug
- Females 19 and up need between 700 ug and 3000 ug
- Pregnant women need between 750 ug and 3000 ug
- Lactating women need between 1200 ug and 3000 ug
- Deficiencies: Vitamin A deficiency can impair vision and is a leading cause of childhood blindness among children according to the United Nations. Deficiency can also lead to diarrhea, malabsorption of other nutrients and even death. One of the primary causes of vitamin A deficiency is weaning children from breastmilk too soon.
- Side Effects and Dangers: Toxicity from vitamin A can only occur from excessive intake of retinol, not from beta-carotene. High levels of vitamin A can have serious side effects including: nausea, hair loss, blurry vision, abdominal pain, weight loss, and anemia.
- Overview: Vitamin D is a group of compounds known as secosteroids that are important in aiding the body’s absorption of vital nutrients including calcium, magnesium, iron, zinc, and phosphate. The two most important compounds in the D group are vitamin D3 and Vitamin D2. Vitamin D is primarily obtained through dermal synthesis via the skin’s exposure to the sun. Before the body can use vitamin D it must be converted by enzymes in the liver and kidney.
- Best Food Sources: Very few foods are high in vitamin D, and the best source is ultimately the sun. To absorb vitamin D, the skin needs to be exposed to sunlight; it is not absorbed through clothing. Mushrooms, fish, including fish oil, and alfalfa are reasonable sources of vitamin D, but most other food sources, such as milk and grains, have vitamin D added as a supplement.
- Recommended Dietary Allowance: The dietary intake guidelines assume no vitamin D is obtained through synthesis, only from food or supplements. One reason for this is that health agencies are reluctant to recommend exposure to sunlight due to concerns over skin cancer and a lack of reliable data. Daily intake guidelines are measured in International Units (IU).
- Infants up to 12 months need 400 IU
- Male and females between 1 and 70 need 600 IU
- Male and females 71 and older need 800 IU
- Pregnant and lactating women need 600 IU
- Deficiencies: The biggest danger of extreme vitamin D deficiency is bone damage and impaired bone mineralization which can lead to conditions such as rickets where bones are weak and deformed, and osteomalacia which is characterized by softening of the bones. Vitamin D deficiency is especially a concern in developing nations. Low-level deficiencies can contribute to drowsiness, irritability and depression. Because of the lack of sources of vitamin D and reduced exposure to sunlight, it is fairly common for people to have borderline deficiencies.
- Side Effects and Dangers: It is very rare to have vitamin D toxicity. You would need to take 40 times the daily dose for an extended period to even be at risk. Toxicity can lead to excessive levels of calcium and the bloodstream and eventually kidney failure, heart problems, and coma.
- Overview: Vitamin E is also an antioxidant that plays an important role in the elimination of free radicals as well as improving skin and hair health, balancing hormone levels, and improving vision. There are also indications that vitamin E helps the immune system. Studies have found that vitamin E’s potent antioxidant abilities can modulate immune system function. T cells play a crucial role in the body’s immune response by targeting specific antigens that enter the body. Vitamin E helps T cells target antigens effectively by differentiating mature T cells, which have a specific antigen target, and immature T cells which are not associated with a specific target.
- Best Food Sources: Vitamin E is abundant in oils, seeds, nuts and many vegetables. Some of the best sources of vitamin E include almonds, avocados, sunflower seeds and oil, leafy greens, and sweet potatoes.
- Recommended Dietary Allowance: Estimated Average Requirements for dietary intake of Vitamin E are based on milligrams. Daily intake guidelines are:
- Infants from birth to 6 months need 4 milligrams per day
- Infants between 7 and 12 months need 5 milligrams per day
- Children between 1 and 3 years of age need 6 milligrams per day
- Children between 4 and 8 years of age need 7 milligrams per day
- Children between 9 and 13 years of age need 11 milligrams per day
- Teens between 14 and 18 years of age need 15 milligrams per day
- Adults also need 15 milligrams per day
- Pregnant women do not require any additional intake beyond 15 milligrams per day
- Breastfeeding mothers, however, require 19 milligrams per day
- Deficiencies: Vitamin E deficiencies are fairly rare, but when they do occur they can lead to symptoms including anemia, impaired immune response, acute damage to the retina, and neurological and neuromuscular impairments including poor reflexes, loss of spatial orientation and vibratory sensation as well as motor speech impairments.
- Side Effects and Dangers: Because vitamin E is such a powerful antioxidant it can actually lower the body’s absorption of iron leading to anemia in some cases. Taking large amounts of vitamin E through supplements can have some many negative health effects. These include headaches, dizziness, stomach cramps and diarrhea. Nosebleeds, bleeding gums, and easy bruising can also occur. Hair loss and dry brittle hair have also been associated with excess levels of vitamin E.
- Overview: Vitamin K is a group of fat-soluble compounds that the body uses for the synthesis of proteins which are vital for functions such as calcium binding and blood coagulation. Vitamin K is also associated with reducing the risk of cardiovascular disease. Also known as phylloquinone, vitamin K is derived from plants. Some of the compounds in the vitamin K group are produce by bacteria in gut flora.
- Best Food Sources: Vegetables, especially leafy greens, are the best food sources of vitamin K. Some of the foods richest in vitamin K include kale, spinach, collards, broccoli, Brussels sprouts, cabbage, and asparagus.
- Recommended Dietary Allowance: Estimated Average Requirements for dietary intake of vitamin K are based on micrograms. Daily intake guidelines are:
- Infants up to 12 months need 2 ug
- Children between 1 and 18 need between 30 and 75 ug with the level increasing with age
- Men ages 18 and up need 120 ug
- Women ages 18 and up need 90ug
- Pregnant and lactating women need 90 ug as well
- Deficiencies: Primary vitamin K deficiency is fairly rare, but some medical professionals believe that newborn babies are at risk and an injection of vitamin K has been part of the birthing procedure in Western countries since 1944. There is some concern that administering a shot at birth introduces the potential for infection and that the pain inflicted on newborns can be traumatizing. Doses can be administered orally instead, and breastfeeding should be encouraged so mothers transfer vitamin K through their breastmilk. Some adults are at increased risk for vitamin K deficiencies, especially if they have liver disease, cystic fibrosis, or inflammatory bowel disease. Symptoms of a deficiency include anemia, bruising, excessive bleeding including heavy menstrual periods for women.
- Side Effects and Dangers: There is no known toxicity associated with vitamin K in its natural form, but it possible to have an allergic reaction to supplements. There is one synthetic form of vitamin K known as menadione that has been shown to be toxic at high doses leading to hemolytic anemia and cytotoxicity in liver cells.
Some Words of Caution
This information is not intended to be a substitute for professional medical diagnosis, treatment or advice. If you have questions about a vitamin deficiency or supplementation it is recommended you work with a qualified medical professional.