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What Causes Low Vitamin D Levels?

We Bet You Didn't Know What Causes Low Vitamin D Levels

Vitamin D is useful for our body in many ways. Although our body can prepare vitamin D on its own, its levels are found to be low in some people. Let's find out the probable causes behind vitamin D deficiency.
Bidisha Mukherjee
Last Updated: Mar 14, 2018
Did You Know?
When our body is exposed to a 20-minute period of sun exposure, it is able to make almost 10,000 units of Vitamin D. That's almost 50 times more than the daily recommended intake of 200mg.

Vitamin D is essential for the normal functioning of our body. It increases the ability of the body to absorb calcium, which makes our bones stronger. Thus, it delays the onset of osteoporosis in older adults. It also helps in prevention of several other diseases that include cancer, diabetes and multiple sclerosis. Our body can prepare this fat-soluble vitamin on its own with the help of sunlight. Thus, we can say that the main source of vitamin D in our body is the sun and hence this vitamin is also known as sunshine vitamin. Apart from sun, foods like milk, orange juice, cereals are available which are fortified with vitamin D and can be used to make up for its deficiency.
Low vitamin D levels can be found in people of all age group including small babies and the elderly. Some of the most common symptoms of low vitamin D are fatigue, muscle pain, joint pain, weight gain, headache, constipation or diarrhea, high blood pressure, etc. There are several factors that can contribute to this problem. Following are some of the prevalent causes of low vitamin D in the human body.
● Lack of Exposure to Sunlight
The inner layer of the skin produces vitamin D using sunlight. If one does not have enough sun exposure, he or she may develop vitamin D deficiency. For instance, absence of sunlight in certain geographical locations like in the northern hemisphere make the people living there prone to this problem.
● Diseases and Disorders
Those who have lupus have extremely sensitive skin and cannot tolerate sunlight for a long time. They develop vitamin D deficiency as they prefer to stay out of direct sunlight. In Crohn's disease or colitis, an inflammation is caused in the inner lining of the intestine and colon that results in diarrhea. In this condition, large quantities of vitamins are excreted and leads to lowering in levels of vitamin D. Some diseases have an adverse impact on the body's natural ability to synthesize vitamin D. Liver disorder or kidney disorder can lead to a similar condition. In some rare occurrences, the levels decrease because of some hereditary diseases like cystic fibrosis which impairs fat absorption capacity of the body.
● Hyperparathyroidism
Hyperparathyroidism is a disorder that is characterized by excessive production of parathyroid hormone (PTH) by the parathyroid glands, which are glands that regulate the levels of calcium, phosphorus, and vitamin D in blood, as well as the bones. If a person suffers from primary hyperparathyroidism due to a parathyroid tumor, the PTH causes the blood calcium levels to increase. The body may then lower the vitamin D levels to bring down the levels of calcium in the blood. People who suffer from kidney disease could also suffer from a vitamin D deficiency and secondary hyperthyroidism. Failing kidneys are unable to convert vitamin D into calcitriol, which is the active form of vitamin D. They are also unable to flush out phosphorus. This affects the calcium levels, thereby causing secondary hyperparathyroidism.
● Deficiency of Vitamin D in Diet
There are only a few food substances that contain naturally occurring vitamin D. Some dietary sources of vitamin D are beef liver, fleshy part of the fish, egg yolk, fish oils and cheese. Therefore, vegetarians are at a greater risk of having vitamin D deficiency due to low dietary intake of vitamin D rich foods. Breast feeding infants may have this problem as vitamin D content in human milk is very low.
● Dark Skin
Dark skin is a result of the pigment melanin which is produced by melanocytes that are present in the epidermis layer of the skin. These pigment hinder the absorption of sunlight which in turn reduces the body's ability to produce vitamin D. Hence we can say dark skin color could also cause the levels to drop specially in case of older people.
● Old Age
Elderly people may face a deficiency of this vitamin as their thin, aging skin need more time to prepare vitamin D. If they are not exposed to sun for longer duration, the level of vitamin D decreases in their body. Function of other parts of the body also slows down in older people. Kidney of elderly people become less capable of converting vitamin D to its active form which may further result in deficiency.
● Other Causes
Exposure to toxic substances, harmful chemicals, side effects of certain medicines can also give rise to such condition that the level of vitamin D goes below the normal level. High body fat is also responsible for low-level of vitamin D. As vitamin D is fat-soluble, its absorption process often gets affected in absence of sufficient amount of fat in the body. Obesity is another factor that causes deficiency of vitamin D. It can happen even if both sun exposure and intake of vitamin D are appropriate. The reason behind this is that the vitamin D in the body becomes unusable as it is stored in excessive body fat.
Low levels of vitamin D badly affect the bones of our body. In children, it can lead to a disease called rickets. This results in slow bodily growth and deformation of long bones like the leg bones. In adults, low vitamin D levels can cause thinning of bones and the condition is referred to as osteomalacia. It causes fragility of bones and weakens the muscles so much that one can suffer from severe muscle pain. Another disease caused due to low levels of vitamin D is osteoporosis. This is more commonly found in adult women. In this condition, bone density decreases significantly and makes them fragile.
The normal level of vitamin D in blood is 50 nmol/L and more. When a blood test reveals that the vitamin D level has gone below 25 nmol/L, it is considered as deficiency. The main aim of the treatment is to restore normal level of vitamin D in the body. For this, dietary supplement of vitamin D is prescribed. The dosage of the supplement and the duration of the treatment largely depends on the severity of the condition. A mild deficiency can be treated with low dose of supplement which has to be continued for 6-12 weeks. In more severe cases, higher doses of supplements are needed which may be administered either orally or through injections for several months. Vitamin D enriched foods are good for this condition along with a healthy diet that consists of plenty of fresh fruits and vegetables. Doctors often recommend fortified milk for children who are suffering from rickets. People with low vitamin D levels are advised by the physicians to spend more time under the sun.
This article highlighted the causes that can trigger low vitamin D levels in the body. It also clarifies who are at a risk of getting it. This piece of information will help you to prevent occurrence of the condition. However, if you are already diagnosed with low vitamin D, then do not panic. Just undergo treatment under the supervision of your physician and continue with it as per his or her instructions.