Four of the essential vitamins are fat soluble. That means that they dissolve in fat, not water, and are stored in fatty tissue and in the liver. Because they can be stored for long periods of time, people consuming a well-balanced diet do not need to supplement them. In fact, because these vitamins hang around, they are more prone to toxicity than the water-soluble vitamins.
A normal amount of fat in the diet is necessary to metabolize these fat-soluble vitamins. They are absorbed through the large intestine, and there must be some fat present for successful absorption. After absorption, these vitamins are stored in the liver until needed.
Also known as retinol, vitamin A is primarily found in animal foods, including dairy products, fish, liver, and egg yolks. It has a pro-vitamin, called beta carotene, which is found in vegetables with orange pigment, like carrots, sweet potatoes, and apricots, as well as some dark, leafy greens including spinach and kale.
As you may have guessed by its pseudonym, beta carotene, and its presence in carrots, vitamin A is important for the health of your eyes. It is vital for night vision and the adjustments the eye regularly makes to various light levels.
Vitamin A also helps keep skin healthy, promotes healthy bone and tooth growth, and is vital for proper cell division and reproduction. It also strengthens and moistens mucous membranes, which helps resist infections.
A pro-vitamin is not a vitamin that has renounced its amateur status. Also known as a vitamin precursor, pro-vitamins are organic compounds that, once ingested, the body converts into a vitamin.
Deficiencies are rare, but symptoms may include night blindness and seriously dry and itchy skin, as well as slow tooth and bone growth.
Signs of vitamin A toxicity include dry itchy skin, nausea, and headache. Excessive beta carotene has been known to turn skin a pale orange.
Because it is naturally synthesized by sunlight on your skin, vitamin D is sometimes called the sunshine vitamin. Ten minutes in the sun is enough to give you your daily dose.
During the Industrial Revolution, when people began spending more time indoors, and the skies were clouded by pollutants, rickets was rampant. Rickets is a disease in which bones do not harden properly and become soft and painful. Scientists suspected a dietary deficiency along the same lines as scurvy, and it was soon found that cod liver oil eliminated the disease. It was also noted that long doses of sunshine were restorative.
Will sunblock prevent vitamin D absorption?
Proper use of sunblock, with a sun protection factor (SPF) of 15, will deflect or absorb all but 7 percent of the UVB rays that synthesize vitamin D (and cause skin cancer). But most people fail to apply sunblock properly. You need at least an ounce, or about two tablespoons, and it should be applied 15 to 20 minutes before going outdoors so that it has ample time to penetrate. Most people apply it too late, and too sparingly, cutting its effectiveness in half. Chances are you’re still getting your vitamin D.
Vitamin D’s main function is to control the absorption of calcium, which promotes the hardening of bones and teeth. Deficiency in vitamin D leads to rickets in children, and a similar affliction in adults, osteomalacia. It might also be a contributor to osteoporosis.
These conditions occur when bone mineralization is impaired, keeping bones from hardening properly. As a result, they become soft, weak, painful, and fragile. People living with minimal sunshine, in areas with lots of cloud or fog cover, spending much of their time indoors, or covered with sunblock, are likely candidates for vitamin D deficiency.
Because of this, vitamin D has been added to many products, most notably milk. Small amounts occur naturally in a few foods, including sardines, herring, and cod liver oil.
Toxicity of vitamin D in mild forms leads to nausea, irritability, and weight loss. Severe cases result in mental and physical growth retardation, calcium in the blood, and kidney damage.
This vitamin is a powerful antioxidant. Additionally it works to protect vitamins A and C and red and white blood cells, promotes iron metabolism, and helps maintain nervous system tissue.
Some past studies suggest that vitamin E can slow the development of heart disease, but current wisdom notes that diets high in all antioxidants lower risks of cancer and disease. You’ll find vitamin E in seeds, whole grains, and nuts.
Antioxidants can slow, prevent, and reverse damage done by oxidation. Oxidation is an electron transfer process (the loss of electrons by a molecule, atom, or ion), which can produce free radicals. Free radicals damage body cells and tissues.
Deficiency in vitamin E is rare, but toxicity can occur. Symptoms include nausea and gastrointestinal disorders.
This vitamin is sometimes called the band-aid vitamin because its primary function is in the clotting of blood. In fact, the K comes from the Danish word koagulation. Vitamin K also helps hold calcium in your bones. It is naturally produced by bacteria in the intestines, but it can also be found in dark, leafy green vegetables, like turnip greens, spinach, broccoli, and cabbage.
Deficiency results in excessive bleeding. Because vitamin K is formed by bacteria in the intestines, bacteria-killing antibiotics can be problematic. Also, because it is fat soluble, people that have difficulties digesting fat may become deficient.