Vitamin D is a group of five fat-soluble secosteroids:
Vitamin D1 (Mixture of molecular compounds of ergocalciferol with lumisterol, 1:1)
Vitamin D2 (Ergocalciferol made from ergosterol)
Vitamin D3 (Cholecalciferol made from 7-dehydrocholesterol in the skin)
Vitamin D4 (22-dihydroergocalciferol)
Vitamin D5 (Sitocalciferol made from 7-dehydrositosterol)
These secostetoids are responsible for the intestinal absorption of calcium which assists in bone growth and the integrity of bone and promotes strong teeth. It must be pointed out that, although vitamin D is necessary to absorb calcium, vitamin K2 which is produced by the bacteria in the intestines from vitamin K1, is also essential to transport calcium into the bones.
Copper, together with zinc improves the absorption of vitamin D which aids in the absorption of calcium. Alcohol and some medications cause the expulsion of zinc so it is advisable to consume more zinc rich foods if on medications or if alcohol is consumed regularly.
Vitamin D helps to regulate the amount of phosphorus and magnesium in the body and helps to maintain a healthy heart and nervous system. In some recent studies it has also shown great promise in assisting with the treatment of psoriasis and the maintenance of the immune system and thyroid function as well as normal blood clotting. It also acts as a co-factor in the utilisation of amino acids.
Vitamin D protects against vascular disease via several different mechanisms, including reducing chronic inflammatory reactions that contribute to the pathology of the disease. Vitamin D also improves blood circulation throughout the body, which is essential for the heart to function properly. This helps reduce the risk of heart attacks, heart failure, strokes and other problems.
Women who have sufficient levels of vitamin D are less likely to develop uterine fibroids.
Consuming foods rich in vitamin D also protects the pancreas by its ability to block the proliferation of cancerous cells.
Maintaining adequate levels of vitamin D can help breathing and helps to protect against tuberculosis (TB).
Deficiency of vitamin D
More than 75% of the world's population are deficient in vitamin D and unaware of it. However, this figure may be much higher as testing vitamin D levels is not done on a regular basis, if at all, in most people. Vitamin D is produced by cholesterol in the skin when it is exposed to sunshine. It is then stored in the liver for between 30-60 days. From October there is often not enough to last through until the sun reaches its optimal strength again around April leading to a deficiency unless extra vitamin D-rich foods are consumed.
A poorly functioning liver will affect vitamin D levels and excessive alcohol and some medications can contribute to this.
Healthy kidneys are rich with vitamin D receptors and play a major role in turning vitamin D into its active form. This helps balance calcium and phosphorus in the body by controlling absorption of these minerals from the food consumed and regulates the parathyroid hormone.
Gastrointestinal conditions such as Crohn’s, celiac and non-celiac gluten sensitivity and inflammatory bowel disease can lead to a deficiency of vitamin D.
Deficiency can lead to softening of the bone and muscle cramps, twitching and convulsions and in children it causes rickets resulting in bent legs. In adults, the shortage causes loss of minerals from the bones, (osteomalacia) where the bones are sore, tender and the muscles are weak with the possibility of deafness and tooth decay developing. In older people, osteoporosis may appear when protein is also lost from the bone and lower back pain can be caused by vitamin D deficiency.
Low vitamin D levels can also cause dry eye syndrome and increase the risk for age-related macular degeneration (AMD) as it has an important role in the protection of the eyes.
Deficiency in vitamin D is associated with increased autoimmunity as well as an increased susceptibility to infection and depression. Vitamin D can have a beneficial impact on all autoimmune diseases particularly multiple sclerosis (MS) and a lack of it can worsen these conditions. MS is a chronic, neurodegenerative disease of the nerves in the brain and spinal column, caused through a demyelization process. It a disease with few treatment options.
A lower maternal intake of vitamin D during pregnancy in women whose prospective child was at risk of developing autoimmune diabetes mellitus is associated with a statistically increased risk of the child developing pancreatic autoimmunity. Low vitamin D levels during pregnancy can also be responsible for autism developing in the unborn child.
Excessive sweating of the head can be a key symptom of rickets, a form of vitamin D3 deficiency that affects bone development in children.
It has been shown that low vitamin D levels are also associated with increased cardiovascular mortality. Maintaining a 25-hydroxy vitamin D blood level of 50 – 80 ng/mL can eliminate this risk.
Low levels of vitamin D can also increase the excretion of amino acids in the urine which can affect the maintenance of all body cells and hormone and neurotransmitter production.
Vitamin D regulates the concentration of minerals in the body which then helps to regulate fluid balance which, in turn, regulates the body temperature. Low vitamin D levels leads to fat accumulation which then lowers the metabolism and can cause tiredness and chronic fatigue.
Vitamin D also acts as a natural antibiotic working against all types of microbes (bacteria, fungi, parasites and viruses). It has shown, in scientific studies, to be more affective at preventing influenza than vaccines and anti-viral medications. Vitamin D levels can easily become deficient, especially during the winter months, as the body only stores it for up to 60 days thus making an individual susceptible to infections from November to April. It is during this period that blood tests should be done, especially if an individual keeps getting infections, colds, coughs and influenza, and extra vitamin D rich foods should be consumed.
A quarter of all toddlers in the UK are lacking vitamin D, according to new research. Despite a recommendation that all children under five should take vitamin D supplements, 74% of parents know nothing about the guidelines. And more than half of health professionals are also unaware of them.
Vitamin D deficiency is on the rise because people have become aware of the risks of skin cancer caused by exposure to the suns harmful rays and either use sunscreens or cover up and avoid the sun completely. Sunscreens with a sun protection factor (SPF) of 8 or more appear to block vitamin D-producing UV rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin or reapply sunscreen regularly. Therefore, skin likely synthesises some vitamin D even when it is protected by sunscreen as typically applied. Those with dark skin have less ability to produce vitamin D as over 90% of the sun rays cannot penetrate
the skin This is also applicable to those that maintain a deep suntan over a period of time.
Ten to fifteen minutes of midday sunshine on bare skin can provide all the body needs. It is not the same as sunbathing; the skin simply needs to be exposed to sunlight a few days a week. UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. Over exposure of the suns rays can be dangerous for the skin but no exposure at all can be equally detrimental to the health.
Ultraviolet B (UVB) rays in sunlight convert cholesterol in the skin into vitamin D. During the winter months (October-April) when it is too cold to expose the skin to the sun and in the northern hemisphere there is not enough UVB rays from the sun anyway, it is advisable to raise the weekly intake of vitamin D rich foods. Complete cloud cover reduces UV energy by 50%; shade (including that produced by severe pollution) reduces it by 60%.
The optimum level of vitamin D in the blood should be 50-70 ng/ml and up to 100 ng/ml to treat cancer and heart disease.
It is very important to have a blood test to determine vitamin D levels especially if any of the following health issues are present:
NOTE: Just a 10 percent rise in body mass index (BMI) causes a four percent drop in concentrations of vitamin D in the body.
There are more than 900 genes that vitamin D is now known to switch on and off - and in doing so alters the body’s vulnerability to disease. The large number of genes involved explains how so many quite different diseases can be caused by insufficient sunshine.
After the age of 50 the body becomes less proficient at converting the sun's rays to vitamin D and the kidneys become less efficient at making this process take place. It is important to check levels every six months over the age of 50, especially between October to April.
It is difficult for vegetarians to gain sufficient vitamin D as there are few plant foods that provide it. However certain mushrooms listed below and hemp seeds are two ways of gaining extra in their diet.
Highest sources of vitamin D per serving listed
Krill oil - 1 teaspoon: 1000 IU
Eel - 85 g or 3 oz: 792 IU
Maitake mushrooms - 70 g: 786 IU
Rainbow trout - 85 g or 3 oz: 540 IU
Cod liver oil - 1 teaspoon: 440 IU
Mackerel - 85 g or 3 oz: 400 IU
Salmon - 85 g or 3 oz: 400 IU
Halibut - 85 g or 3 oz: 196 IU
Tuna - 85 g or 3 oz: 228 IU
Sardines - 85 g or 3 oz: 164 IU
Chanterelle mushrooms - 85 g or 3 oz: 155 IU
Raw milk - 1 glass or 8 oz: 98 IU
Egg yolk - 1 large: 41 IU
Caviar - 28g or 1 oz: 33 IU
Hemp seeds - 100 g or 3.5 oz: 22 IU
Portabella mushrooms - 85 g or 3 oz: 6 IU
NOTE: One IU is the biological equivalent of 0.3 μg or 0.3 micrograms. The recommended daily allowance of vitamin D is 600 IU for ages 19 to 70 and 800 IU for ages 71 and over but this may be far below what should be taken and is dependent upon the amount of sunshine an individual's skin is exposed to on a regular basis. Farmed fish such as salmon are often deficient in vitamin D.
Supplements must be vitamin D3 and not D2 and check that aspartame has not been added to chewable forms. Krill oil capsules (1000 mg per day) can be beneficial as they provide vitamin D and other nutrients like omega-3 fatty acids and antioxidants. Vitamin D is fat-soluble meaning it must be consumed with some oil therefore capsules of vitamin D3 in oil will make it more effective than the dry chewable forms.
According to recent findings, the benefit of vitamin D, where bone strength is concerned, is greatly enhanced when combined with vitamin K2. Vitamin D improves bone health by helping the body absorb calcium. However, it is vitamin K2 that directs calcium to the skeleton, to prevent it from being deposited in the wrong areas. Vitamin K2 (menaquinones) only occurs in foods of animal origin or foods altered by bacterial fermentation.
Vitamin K2 is produced by the intestinal bacteria so the addition of fermented foods such as natto which is a fermented soya product is useful as it helps to provide extra beneficial bacteria to the gut. Other sources are gouda and brie cheeses and other products from grass-fed cows such as butter, milk and yoghurt, plus egg yolks and chicken breast or livers and other organ meats. Brine pickles and sauerkraut are also rich sources of vitamin K2. See Prebiotic and Probiotic Foods.
Overdose of vitamin D
If supplements of 40,000 IU are taken per day for a couple of months or longer, or a very large one-time dose is ingested, the liver produces too much of a chemical called 25(OH)D which causes a condition called hypercalcaemia which is high levels of calcium in the blood and muscles and can lead to irreversible kidney damage. The symptoms of hypercalcaemia include:
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