1. Contraindications
1.1. Vit D intake isn't associated with a risk of kidney stone formation when taken in typical amounts
2. Deficiencies
2.1. Rickets, osteomalacia (rickets in adults), bone pain, muscle weakness and poor bone density
2.2. The elderly & other people who don't go out in the sun and people who cover up for cultural reasons all have a far higher risk of vitamin D deficiency.
2.3. Those with dark skins synthesise less vit D and need 3-5 times longer in the sun the make the same amount as a european.
2.4. reduced liver and/or kidney function have a higher risk as both organs play a role in conversion to its active form
2.5. Obesity is a risk factor for vitamin D deficiency as vitamin D is stored away in fat tissue rather than being released into circulation for use.
2.6. Sunscreen prevents the synthesis of vitamin D - e.g. a sunscreen with an SPF of 8, reduces vitamin D production by 95%.
3. CVD
3.1. Vitamin receptors have been found in cardiac cells, vascular smooth muscle cells and endothelial cells.
3.2. Vitamin D suppresses renin gene expression and therefore diminishes production of angiotensin 2 so lowering blood pressure
4. Found in...
4.1. Vitamin D3 is found in oily fish such as salmon, mackerel,sardines,cod liver oil, eggs, liver and milk
4.2. Sunshine - 30 mins of full body sun exposure by fair skinned people will produce 30,00iu of vitamin D
4.3. In the uk Vitamin D can only be made via sunlight for March to October
5. Interactions
5.1. Ca - vitamin D works with PTH to regulate plasma Ca levels
5.2. Vitamin D controls Ca absorption, excretion and bone mineralization
5.3. Absorption of Ca is greatly increased in the intestines with there too Vitamin D
5.4. Vit D also enhances Ca uptake in the muscle, which is vital to muscle contraction and relaxation.
5.5. Phosphorous absorption in the gut is enhanced by up to 80%
6. Immunity
6.1. All immune cells have significant quantities of vitamin D receptors and deficiency of vitamin D is associated with an increased risk of infection and an increased risk of auto-immune disease
6.2. Vitamin D is considered immunomodulatory as it increases innate immunity and promotes a more tolerant adaptive immunity.
6.3. Vitamin D stimulates the maturation of Natural Killer (NK) cells and a deficiency contributes to a reduction of NK cells activity
6.4. It has been shown that immune cells, such as macrophages and dendritic cells are able to locally convert 25-hydroxyvitamin D into the active form of vitamin D.
6.5. vitamin D receptor are present on leukocytes, T-helper cells and monocytes and vitamin D3 has been shown to inhibit production of inflammatory markers such as IFN-γ, IL-2, and IL-5 by T-helper 1 lymphocytes
6.5.1. Also differentiation of immune stem cells into monocytes and macrophages takes place in the presence of adequate levels of vitamin D
7. Metabolism
7.1. 1. Skin - the action of sunlight on the skin changes a cholesterol derivative precursor 7 dehydrocholesterol into vitamin D3
7.2. 2. The liver converts vitamin D3 into 25-hydroxyvitamin D3
7.3. 3. The kidneys convert vitamin D to its active form 1,25-dihydroxyvitamin D3, which is released into the blood for other tissues to use.
7.4. Parathyroid hormone (PTH) increases the conversion of vitamin D to active form.
7.5. The enzyme that converts vitamin D to its active form is present in the kidneys and in many other cells.
7.6. The action of sunlight on the skin changes a cholesterol derivative precursor - 7 dehydrocholesterol into vitamin D3. This then travels to the liver to convert the vitamin D3 into 25-hydroxyvitamin D3. The kidneys then convert the 25-hydroxyvitamin D3 to its active form 1,25-dihydroxyvitamin D3, which is released into the blood for tissues to use.
8. RNI
8.1. A safe intake of 8.5-10mcg per day for all infants from birth to 1 year
8.2. A safe intake of 10mcg per day for children aged 1-4 years
8.3. An RNI of 10mcg of vitamin D per day for pregnant and lactating women and population groups at increased risk of vitamin D deficiency
8.4. A reference nutrient intake (RNI) of 10mcg (400iu) of vitamin D per day, throughout the year, for everyone in the general population aged 4 and over.
9. Roles
9.1. Receptors for vitamin D are found throughout the body
9.2. Bones
9.2.1. Vitamin D is essential for skeletal growth and bone health and maintaining bone mass density, calcium metabolism and immune function.
10. Skin Health
10.1. Acne - vitamin D may have a regulatory effect on sebum producing cells & therefore may be helpful in acne.
10.2. Psoriasis - vitamin D is produced by keratinocytes and regulates keratinocyte differentiation.
11. Therapeutics
11.1. Bone mineralisation
11.1.1. Adequate levels of the active form of vitamin D is required for intestinal Ca absorption which promotes Ca absorption in bones.
11.1.2. Severe vitamin D deficiency leads to osteomalacia, whereas less severe deficiency increases the risk of osteoporosis and bone fractures.
11.1.3. On the other hand, high vitamin D levels together with low dietary Ca intake will increase bone resorption and decrease bone mineralization in order to maintain normal serum Ca levels.
11.2. Cancer
11.2.1. Vitamin D may prevent malignancy by down-regulating cancer cell growth and inducing apoptosis
11.2.2. Vitamin D typically promotes cell differentiation and inhibits proliferation
11.3. Depression
11.3.1. lower concentrations of circulating vitamin D are associated with increased likelihood of having depressive symptoms.
11.3.2. Vitamin D receptors and vitamin D activating enzyme 1a-hydroxylase are present in the human brain
11.4. Inflammation
11.4.1. Vitamin D has anti-inflammatory properties as it has beneficial effects on Th1 cell mediated inflammatory conditions.
11.4.2. Vitamin D inhibits synthesis of IL-6 by monocytes, which is the primary stimulant of CRP production in the liver
11.4.3. Vitamin D receptor is present on leukocytes, T-helper cells and monocytes and vitamin D3 has been shown to inhibit production of inflammatory markers such as IFN-γ, IL-2 & IL-5 by T-helper 1 lymphocytes
11.5. Asthma
11.5.1. Vitamin D Supplementation has been shown to inhibit the influx of inflammatory cytokines in the lung, while increasing the secretion of anti-inflammatory IL10 by T-reg cells
11.6. Acne
11.6.1. viramin D may have a regulatory effect on sebum producing cells so could help with acne
11.6.2. Vit D is produced by keratinocytes so can regulate differentiation