Vitamins are extremely important for proper functioning of various body systems. Vitamin D3 plays a very crucial role in proper functioning of bones and joints. Deficiency of this vitamin is quite common but can be identified and managed easily. Read on to know more about its functions, causes of deficiency, symptoms and management.
Function: Vitamin D3 is essential for the absorption of calcium from the food that is consumed. A decrease in the amount of vitamin D3 leads to poor calcium absorption, resulting in thin, soft, brittle bones.
Some of the possible causes of vitamin D3 deficiency (and ways to manage them) are listed below:
- Reduced intake:People with a strict vegan diet may be consuming reduced amounts of this important chemical. Most natural food sources are animal based including fish, fish oils, fortified milk, egg yolks and beef liver.
- Limited sun exposure:People who spend a lot of time indoors are likely to have this deficiency. People who wear sunscreen constantly, wear long robes for religious reasons, live in the polar areas; upper/lower hemispheres are all prone to vitamin D3 deficiency.
- Darker complexion:The body’s ability to make vitamin D3 when exposed to the sun is reduced if there is more melanin in the skin.
- Obesity:Vitamin D is extracted from the blood by fat cells and people with BMI of more than 30 have a vitamin deficiency.
Symptoms: While some people may go completely asymptomatic with this condition, others could develop significant symptoms.
- Bone pain and aches: When there is less calcium getting incorporated into the bones, pains and aches leading to fatigue are common.
- Depression: The areas of the brain that regulate mood contain vitamin D receptors, and low levels of this vitamin can lead to depression. They are also at higher risk of developing cognitive conditions like schizophrenia, Alzheimer’s and dementia.
- Gut problems:Vitamin D is fat soluble and in people with stomach conditions like Crohn’s or IBD, the gut functioning is altered and so vitamin D absorption is reduced.
- Increased risk of heart disease: Both the risk of developing heart disease and the severity of the disease went up considerably when there is vitamin D deficiency. This is given their role in controlling inflammation and improving immune function.
- Lesser chances of surviving cancer: In patients with colorectal cancer, lymphoma, and breast cancer, increasing vitamin D levels improved cancer prognosis by 4%. The chances of developing prostate cancer also increased in patients with vitamin D3 deficiency.
Management: Providing the required amounts of vitamin D3 through diet and supplements is the best way to manage this. Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources. Small amounts of vitamin D are found in beef liver, cheese, and egg yolks. Vitamin D in these foods is primarily in the form of vitamin D3 and its metabolite 25(OH)D3. Some mushrooms provide vitamin D2 in variable amounts. Mushrooms with enhanced levels of vitamin D2 from being exposed to ultraviolet light under controlled conditions are also available.
Health Risks from Excessive Vitamin D
Vitamin D toxicity can cause non-specific symptoms such as anorexia, weight loss, polyuria and heart arrhythmias. More seriously, it can also raise blood levels of calcium which leads to vascular and tissue calcification, with subsequent damage to the heart, blood vessels, and kidneys. The use of supplements of both calcium (1,000 mg/day) and vitamin D (400 IU) by postmenopausal women was associated with a 17% increase in the risk of kidney stones over 7 years in the Women’s Health Initiative. A serum 25(OH)D concentration consistently >500 nmol/L (>200 ng/mL) is considered to be potentially toxic.
Excessive sun exposure does not result in vitamin D toxicity because the sustained heat on the skin is thought to photo-degrade pre-vitamin D3 and vitamin D3 as it is formed. In addition, thermal activation of pre-vitamin D3 in the skin gives rise to various non-vitamin D forms that limit formation of vitamin D3 itself. Some vitamin D3 is also converted to non-active forms. Intakes of vitamin D from food that are high enough to cause toxicity are very unlikely. Toxicity is much more likely to occur from high intakes of dietary supplements containing vitamin D.
Long-term intakes above the UL(Upper Limit) increase the risk of adverse health effects. Most reports suggest a toxicity threshold for vitamin D of 10,000 to 40,000 IU/day and serum 25(OH)D levels of 500–600 nmol/L (200–240 ng/mL). While symptoms of toxicity are unlikely at daily intakes below 10,000 IU/day, the FNB pointed to emerging science from national survey data, observational studies, and clinical trials suggesting that even lower vitamin D intakes and serum 25(OH)D levels might have adverse health effects over time. The FNB concluded that serum 25(OH)D levels above approximately 125–150 nmol/L (50–60 ng/mL) should be avoided, as even lower serum levels (approximately 75–120 nmol/L or 30–48 ng/mL) are associated with increases in all-cause mortality, greater risk of cancer at some sites like the pancreas, greater risk of cardiovascular events, and more falls and fractures among the elderly.
The FNB committee cited research which found that vitamin D intakes of 5,000 IU/day achieved serum 25(OH)D concentrations between 100–150 nmol/L (40–60 ng/mL), but no greater. Applying an uncertainty factor of 20% to this intake value gave a UL of 4,000 IU which the FNB applied to children aged 9 and older and adults, with corresponding lower amounts for younger children.
Interactions with Medications
Vitamin D supplements have the potential to interact with several types of medications. A few examples are provided below. Individuals taking these medications on a regular basis should discuss vitamin D intakes with their healthcare providers.
Corticosteroid medications such as prednisone, often prescribed to reduce inflammation, can reduce calcium absorption and impair vitamin D metabolism. These effects can further contribute to the loss of bone and the development of osteoporosis associated with their long-term use.
Both the weight-loss drug orlistat and the cholesterol-lowering drug cholestyramine can reduce the absorption of vitamin D and other fat-soluble vitamins. Both phenobarbital and phenytoin, used to prevent and control epileptic seizures, increase the hepatic metabolism of vitamin D to inactive compounds and reduce calcium absorption.
N.B. Harini M.Sc(Clinical Nutrition)., RD., Certified Diabetes Educator.