Vitamin D Deficiency: Risk Factors, Causes, Signs, Treatments

Vitamin D and its deficiency

Vitamin D, a group of fat-soluble vitamins, is responsible for helping the body absorb calcium, magnesium, and phosphate, all of which are essential for the formation of healthy teeth and bones and maintaining good overall health. Today’s lifestyle and diet choices mean that many of us are at risk of having one or more vitamin deficiencies. This post is all about vitamin D deficiency.

Types of vitamin D

There are five types of vitamin D: D1, D2, D3, D4, and D5. Only D2 and D3 are the most significant to the body. They can be taken as supplements in one of these two forms:

  1. Ergocalciferol (Vitamin D2)
  2. Cholecalciferol (Vitamin D3)

Both vitamins, D2 and D3, have been believed to be the same since they were concluded as just vitamin D according to some historical studies of preventing rickets in children.

Plants synthesize vitamin D2. Human body cannot produce it. However, when the sunlight hits our bare skin, vitamin D3 is prepared in huge quantities in the skin. Vitamin D3 can be ingested from animal sources as well.

Factors lead to D deficiency

Several factors can lead to hypovitaminosis D or vitamin D deficiency. However, the most common factors include eating food without sufficient amount of vitamin D, failure to get proper exposure to the sunlight, which is the biggest and cheap source of vitamin D etc.

In addition to these factors, certain other conditions and disorders can also cause an acute vitamin D deficiency. These conditions are usually related to malfunctioning metabolism in liver, kidney or due to any other heredity disorder.

Vitamin D deficiency hinders the absorption of essential minerals for bones. Calcium cannot be absorbed easily without vitamin D, and chronic deficiency of vitamin D can cause rickets in children.

Rickets is a disease due to which bones of the children soften. In adults, vitamin D deficiency can cause problems in bone formation and building, or in medical terms, deficiency of vitamin D in adults can cause an aggravate osteomalacia and osteoporosis. Adults suffering from osteomalacia and osteoporosis become susceptible to bone fractures. Another symptom of vitamin D deficiency in adults is muscle weakness.

Normal Levels of Vitamin D

Blood concentration of the 25-hydroxyvitamin D is measured to diagnose vitamin D deficiency. The following concentration levels indicate acceptable standards for classification of the amount of vitamin D in the human body.

  • Deficiency: <20 ng/mL
  • Insufficient: 20–29 ng/mL
  • Normal: 30–100 ng/mL

People with a normal level of vitamin D should avoid vitamin D supplements because excessive intake of vitamin D can be detrimental to the human body.

If your test reveals that you’re still dangerously low after attempting any one or combination of the vitamin D deficiency treatments that your health specialist has suggested, simply change the way that you approaching the issue, try a different combination, and do not despair.

Table: Sources of vitamin D


Int Units

per serving


Value (%)

Cod liver oil, 1 tablespoon 1,360 340
Cooked Swordfish, 3 ounces 566 142
Cooked Salmon (sockeye), 3 ounces 447 112
Tuna fish, canned in water, drained,

3 ounces

154 39
Orange juice, vitamin D fortified, 1 cup 137 34
Milk, vitamin D-fortified, 1 cup 115-124 29-31
Yogurt, fortified with 20% of the DV

For vitamin D, 6 ounces

80 20
Fortified Margarine, 1 tablespoon 60 15
Sardines, canned in oil, drained,

2 sardines

46 12
Cooked beef liver, 3 ounces 42 11
Egg, 1 large 41 10
Ready-to-eat cereal, fortified with 10%

Of the DV for vitamin D, 0.75-1 cup

40 10
Swiss cheese, 1 ounce 6 2

Daily Values developed by the U.S. Food and Drug Administration

Signs and Symptoms of D Deficiency in Human

Sometimes vitamin D deficiency can have no apparent symptoms, and it can be totally asymptomatic. However, problems caused by the deficiency of vitamin D can lead to crippling diseases/conditions including osteomalacia, osteoporosis, rickets, etc.

  1. Osteomalacia weakens the bones of the adults. Muscles near to the bones also become weak. People suffering from osteomalacia feel pain while walking and moving because of fragile bones.
  2. Bone density decreases because of osteoporosis. Ultimately, bones become fragile.
  3. Because bones become weak, the risk of bone fracture increases.
  4. In children, rickets soften and deform their bones. Craniotabes or softening of the skull of the children is usually the earlier sign of the vitamin D deficiency.
  5. Pains in muscle
  6. Light-headedness
  7. Periodontitis or inflammation of gums and bones that support tooth
  8. Pre-eclampsia: There has been a correlation between pre-eclampsia during pregnancy and vitamin D deficiency. However, what factors lead to this correlation are still to be understood. If the mother suffers from vitamin D deficiency, this could have several repercussions for the baby. The baby may be born with impaired bones or bones of the baby may become fragile over a period of time.
  9. Depression: Hypovitaminosis D can also cause depression. Researchers have discovered that depression and D deficiency are related to each other.

It’s indeed a overwhelming list and lends to difficulty in identifying exactly how vitamin D deficiency is causing such a disastrous biological breakdown. It’s thought that because this vitamin is one of the only ones that’s naturally produced in the body, and the resultant substance known as cholecalciferol is much like a hormone in behavior, perhaps that’s why depletion is so devastating to the system and immunology.

What Causes D Deficiency

Decreased exposure of skin to the sunlight doesn’t let the body to absorb sufficient amount of UV rays to make vitamin D. Sunscreens and melanin can absorb and restrict the supply of UV rays, reducing the formation of vitamin D. Increasing the rate of metabolism of vitamin D, certain medicines can also cause vitamin D deficiency. Digestive disorders because of liver and kidney malfunctioning are also responsible for vitamin D deficiency.

Due to liver disease, formation of the 25-hydroxyvitamin either reduce or completely stopped. Using 25-hydroxyvitamin, kidneys form the 1, 25-hydroxyvitamin which is the active form of vitamin D in the human body. Therefore, if the kidney doesn’t function properly due to any diseases, it’s very likely to cause a D deficiency.

Sometimes, our body cannot absorb vitamin D from digested food. Absorption of vitamin D fails because of intestinal conditions, i.e. celiac disease, cancer etc. Vitamin D helps the body to absorb calcium from the digested food. An excessive amount of unabsorbed calcium can cause osteoclasts, breaking down bone matrix. Converse to insufficient absorption of calcium, hypocalcemia is a perilous condition in which less than normal calcium is found in blood plasma. Hypocalcemia invokes the hyperparathyroidism. The body tries to restore the amount of calcium in the blood plasma by hyperparathyroidism. In hyperparathyroidism causes the bones to lose calcium and the calcium is taken up the kidneys and added to the blood plasma. Prolonged hyperparathyroidism increases the risks for adults of osteoporosis and of rickets for children.

Find more information here.

Risk Factors of Vitamin D deficiency

The people who cannot get sufficient exposure to the sunlight are most likely to be affected by the vitamin D deficiency. Therefore, cloudy climate, excessive use of sunscreens, and avoidance of sun exposure increase the risk of vitamin D deficiency.

  • Elderly people are more susceptible to developing D deficiency

Due to a combination of various risk factors, elderly people are more susceptible to developing D deficiency. Older people may prefer to eat less diet containing little vitamin D. They may have a sedentary lifestyle with little or no activity at all, decreasing their exposure to the sunlight. Furthermore, their skin becomes hardened and callus. It becomes difficult for the body to absorb sunlight through callus and hardened skin.

Check this article about vitamin D deficiency in children.
  • Malnutrition is a key factor in developing D deficiency

Over the years, the number of people suffering from both rickets and osteomalacia has considerably decreased. However, a large proportion of immigrant community especially women still suffers from vitamin D deficiency.

Although melanin can absorb UV rays from sun, skin color and less exposure to the sunlight don’t significantly increase the risk of vitamin D deficiency. In such conditions, poor diet lacking vitamin D can be real cause of vitamin D deficiency. Therefore, people eating foods containing meat, fish, eggs, and low intakes of cereal as well as living in countries with the sunny weather during most of the months of the years develop vitamin D deficiency due to deficiency of calcium in their diets.

  • Overweight people are more prone to having a D deficiency

Unlike vitamin C, vitamin D is not a water-soluble vitamin. Our body can store excessive vitamin D in fat. Therefore, people with more amount of fat should be able to store more amount of vitamin D. However, people who are overweight or obese on their body mass index (BMI) are more prone to having a D deficiency. The relationship between weight and vitamin D deficiency is still to be understood.

  • Restricted sun exposure boosts vitamin D deficiency

Excessive use of sunscreens, especially the use of sunscreen having protection factor more than 8, can inhibit the absorption of sunlight and ultimately inhibit the production of vitamin D. Clothing is more preferable option to save oneself from UVR exposure and not to affect the formation of vitamin D. However, one should be circumspect of the fact that such clothing which prevents the exposure of sunlight for a long period of time can also contribute towards vitamin D deficiency.

Urbanization and modern lifestyle have also restricted the exposure of sunlight to the people. More and more people have to spend time working indoors. Elder people also don’t get enough exposures due to hospitalization, weakness, and being housebound.

  • Human skin color is a risk factor too

Light color skin can absorb more amount of sunshine because fair complexion skin contains little amount of melanin. Melanin is a pigment, which is present in skin and hairs. This can reduce the absorption of sunlight. Therefore, people with dark color require more time to spend in sunlight as compared to white people.

  • Malabsorption can also cause the D deficiency

Celiac diseases, insufficiency of exocrine pancreatic, inflammatory, short bowel syndrome, and other problems causing malfunctioning of absorption of vitamin D can also cause the vitamin D deficiency.

D Deficiency Treatments

Since 2016, the recommended dose of vitamin D is 400, 600, and 800 IU/day for children, adults, and elderly people respectively. According to the Canadian Pediatric Society, both pregnant and breastfeeding women should take 2000 IU/day, breastfeed babies should receive 400 IU/day through supplements. The Society also recommends 800 IU/day during the months from October to April for the babies who live in the north of 55 N. Women who don’t have any periods for 12 months are highly likely to have the vitamin D deficiency.

The treatment to correct the D deficiency depends on the level of deficiency. During the initial stages of the treatment, high dosages are administrated until normal or required level of vitamin D in the blood serum is achieved. Thereafter, normal dosage is maintained. The higher dosage is usually given either on daily basis or on weekly basis in the form of single doses or one large dose. If the concentration of the 25 (OH) D serums is low, the higher dosage is administrated so that an acceptable level of vitamin D can be achieved quickly.

The medical community has yet to develop a consensus for optimum practices on vitamin E therapy. Some studies indicate that both D2 and D3 are equally effective in maintaining the status of 25 (OH) D statuses; however, some researchers have also found that D3 raises 25 (OH) D blood level efficiently as compared to Vitamin D2.


Be sure to map out your levels of vitamin D deficiency before trying any treatments, and get your levels checked after a couple of months on your new regime to make sure that you have increased your levels to a healthy amount. While exploring your vitamin D deficiency treatments, it is important to keep checking your levels even if you feel great, just to be certain.

Relationship between D Deficiency and Cancer

Researchers have relentlessly investigated the causal relationship between vitamin D deficiency and other symptoms such as cancer and non-alcoholic diseases of the liver. Few researchers have discovered that there is a relationship between hypovitaminosis and worse outcomes for certain types of cancers.  However, these findings are insufficient to for recommending not taking of vitamin D for people with cancer. Vitamin D has no effect on cancer. Some researchers have found that vitamin D3 is useful in reducing the risk of death from cancer. However, these results are still not credible and widely acknowledged.

Relationship between D Deficiency and Other Diseases

Vitamin D deficiency can also catalyze the non-alcoholic fatty liver diseases. Consistent with this, some researchers have discovered that lower levels of vitamin D can severally affect the immunity, making human susceptible to a wide range of diseases such as cardiovascular, type 1 and 2 diabetes, and some cancers.



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