All You Ever Wanted To Know About Vitamin D - Condensed

What Is Vitamin D And It’s Benefits

Vitamin D is a fat soluble vitamin grouping essential for the normal metabolism of calcium. Vitamin D3 can be synthesized by humans in our skin via exposure to ultraviolet-B (UVB) radiation from sunlight, or it can be obtained from diet; Vitamin D2 is synthesized in plants via UVB. When exposure to UVB is insufficient for the synthesis of adequate amounts D3 in the skin, adequate intake of vitamin D from diet is essential for good health.

Vitamin D itself is actually biologically inactive and must be metabolized to its biologically active forms after it is consumed through diet or synthesized in the epidermis of the skin. When Vitamin D enters the circulatory system it is transported to the liver where it is converted to a biologically active form and is utilized by the body.

Vitamin D is associated with more than 50 genes in tissues throughout the body as well as being essential for the maintenance of serum calcium (and phosphorous) levels which is vital for normal functioning of the nervous system as well as for bone growth and maintenance of bone density. Vitamin D also effects cell differentiation, specialization of cells for specific functions, which in general leads to the decrease in proliferation (even though cellular proliferation is necessary for wound healing and growth, uncontrolled proliferation of cells can lead to mutation and to diseases like cancer). The active form of vitamin D inhibits proliferation while stimulating the differentiations of cells. There is considerable research that Vitamin D is also a potent immune system modulator and has a variety of effects on immune system functions which may enhance the innate immunity and inhibit the development of autoimmunity.

Natural Sources Of Vitamin D

Vitamin D is associated with prevention of numerous diseases including Osteoporosis, colorectal cancer, breast cancer, and prostrate cancer, autoimmune diseases such as diabetes and multiple sclerosis and high blood pressure.

Good sources of Vitamin D include solar ultraviolet (UVB wavelengths of 290 to 315 nanometers) which can provide many people with all the vitamin D their body requires. For lighter skinned people as little as 10 minutes exposure per day can be sufficient (darker skinned people may require up to 3 hours of exposure to synthesize their daily vitamin D requirement). Of course there are also food sources:

• Salmon, pink, canned, 3 oz  = 530 IU or 13.3 mcg
• Sardines, canned, 3 oz =231 IU or 5.8 mcg
• Mackerel, canned, 3 oz = 213 IU or 5.3 mcg
• Quaker Nutrition for Women Instant Oatmeal, 1 packet = 154 IU or 3.0 mcg
• Cow’s milk, fortified with vitamin D, 8 oz = 98 IU or 2.5 mcg
• Soy milk, fortified with vitamin D, 8 oz = 100 IU or 2.5 mcg
• Orange juice, fortified with vitamin D, 8 oz = 100 IU or 2.5 mcg
• Cereal, fortified 1 cup = 40 -50 IU or 1.0 to 1.3 mcg
• Egg yolk, 1 large = 21 IU or .53 mcg

Adequate daily intake of vitamin D as recommended by the Institute of medicine is as follows:

The tolerable upper intake (UL) for vitamin D as published by the Institute of Medicine is:

Is Vitamin D Deficiency Possible

Deficiency of vitamin D has been linked to and has an adverse effect on insulin secretion and glucose tolerance, adequate levels of vitamin D are also thought to play a role in some forms of human hypertension as well as decreasing the risk of high blood pressure. The risk of osteoporosis is greater with deficiency in Vitamin D as well as rickets, osteomalacia (soft bones), muscle weakness/pain and hyperparathyroidism.

Deficiency risk can be caused by various factors, including:

• Exclusively breast fed infants as human breast milk falls short of required intake without supplementation (the American Academy of pediatrics recommends that all infants be given a vitamin D supplement of 400 IU per day)
• Dark skinned people synthesize less vitamin D on exposure to sunlight than those with light skin
• The elderly have a reduced capacity to synthesize vitamin D in the skin when exposed to UVB (plus elderly people in general have a tendency to stay indoors which exacerbates this problem)
• People who cover up and do not allow themselves to have sun exposure also run an increased risk of deficiency as well as sunscreen above SPF factor 8 reduces production of vitamin D by 95%
• Cystic fibrosis and cholestatic liver diseases impair the absorption of dietary vitamin D
• Inflammatory bowel diseases like Crohn’s appear to increase the risk of deficiency
• Obesity increases the risk of deficiency as the vitamin D that is synthesized in the skin or ingested is deposited into the fat stores and becomes less bioavailable

Is Supplementation Necessary

Normally you should be able to get most of your vitamin D requirements through diet and exposure to sunlight, however if you fall into one of the high risk groups (mentioned above), you may benefit from vitamin D supplementation.

Side Effects Of Vitamin D

Vitamin D has no side effects when getting your daily requirements through food, sunlight exposure or supplementation at normal levels. Supplementing at very high levels runs the risk of vitamin D toxicity.

Vitamin D toxicity, also known as hypervitaminosis D induces abnormally high serum calcium levels (hypercalcemia) which can result in bone loss, kidney stones and calcification of organs like the heart and kidneys if left untreated over a long period of time. Vitamin D toxicity has not been observed to be the result of over exposure to the sun. However certain medical conditions can also increase the risk of toxicity in response to vitamin D including primary hyperparathyroidism, sarcoidosis, tuberculosis and lymphoma. A physician should be consulted prior to supplementing vitamin D if a person has one of these ailments.

Final Thoughts

Most vitamin D supplements available over the counter include cholecalciferol (vitamin D3) which is more potent than vitamin D2. Vitamin D is recommended for supplementation by many researchers and especially for adults over 50 years of age.