Patient information
Vitamin D deficiency
Vitamin D is made in your skin, eaten in your food, and spent on your bones. When one step on that route slows down, your level can drop, often without a single symptom. Here is how the route works and where it can break.
What it is
A vitamin that works like a gatekeeper for calcium
Vitamin D dissolves in oil, not water. Its main job is to help your gut take in calcium and phosphorus from food. It also quiets parathyroid hormone, the hormone that tells bone to break down.
With both in place, calcium and phosphate in your blood stay at normal levels and your bones stay firm.
- Made in skin
Sunlight on your skin starts the process.
- Found in food
A short list of foods carries it.
- Spent on bone
It keeps the calcium supply to your skeleton moving.
- Active in immune cells
Vitamin D helps regulate immune cell activity. Extra vitamin D has not consistently prevented infections.
- Present in the brain
Vitamin D receptors are present in the brain. A role in mood is being studied, but supplements have not reliably treated depression.
- At work in muscles
Vitamin D takes part in normal muscle function. Studies of extra vitamin D for strength have had mixed results.
- Hair, skin and nails
Vitamin D signaling is involved in skin and hair biology. Evidence that supplements improve hair or nails is limited.
Source one
Sunlight starts it. Your skin sets the pace.
How much vitamin D your skin makes depends on the season, the time of day, your age, your skin pigmentation and your health. Production is strongest at midday, when the sun is straight overhead.
Skin makes less as we get older. Skin with more pigmentation needs more sun to make the same amount. Sunscreen also limits production.
Because of the long-term risk of skin cancer, sun exposure is not recommended as a vitamin D source for anyone, children included. If your level is low, your physician decides what to do about it.
How much vitamin D skin makes over a day. This sketch shows the direction of each effect, not a measurement.
The route
Five stops between sunlight and bone
Vitamin D has to be made or eaten, switched on, absorbed and put to work. Any stop can become the weak point, and each weak point has its own usual causes.
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Made or eaten
Skin makes it in sunlight, and a few foods carry it.
Sunlight on skinFoodCan slow down here
- Too little in the diet, a particular risk for infants, children and older adults
- No dairy products in the diet
- Breast milk contains little vitamin D
- Little or ineffective sun on the skin, especially with more pigmented skin
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Switched on
Enzymes in the liver and kidneys turn it into its active form.
Can slow down here
- Chronic kidney disease
- Chronic liver disease
- Less common inherited or acquired conditions that affect those enzymes
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Absorbed
With it, your gut takes in calcium and phosphorus from food.
Can slow down here
- Celiac disease, Crohn's disease or cystic fibrosis
- Surgery that removes or bypasses part of the stomach or intestines, such as gastric bypass
- Older age, when absorption may be limited even with a good diet
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Held steady
Blood calcium and phosphate stay normal, and parathyroid hormone stays quiet.
When it falls short
- Blood calcium may dip
- Parathyroid hormone may rise and speed up bone breakdown
- Blood phosphate may fall
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Put to work
Bone gets the calcium and phosphate it needs to stay dense and strong.
When it falls short
- Lower bone density may follow
- Children's bones may soften (rickets)
- Adults' bones may soften (osteomalacia)
Low, and sometimes silent
Below normal is not the same as sick, and not always harmless
Doctors speak of insufficiency and deficiency. Both mean a level below normal. What differs is how much the body may feel it. Choose a level to see the difference.
Calcium and phosphate stay steady in your blood, and your bones get what they need.
Common, and by definition without visible signs or symptoms. It can still go along with weaker calcium absorption, lower bone density (osteopenia or osteoporosis), a mild dip in blood calcium, higher parathyroid hormone and a greater risk of falls and possibly fractures.
The most serious effects may include low blood calcium, low blood phosphate, rickets in childhood and osteomalacia in adults.
The tube is a picture of the idea. It does not show real thresholds, and only a physician can interpret your own result.
What it can mean for bone
Under a lens, healthy bone is a dense lattice. Lower density means fewer, thinner struts to carry weight, which is why identifying a low level matters.
Source two
The plate carries some of it
Few foods contain vitamin D naturally. Eating them helps, but diet alone does not settle the question for everyone.
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Fatty fish
One of the natural food sources of vitamin D.
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Cod liver oil
Contains vitamin D, and also a large amount of vitamin A. Too much vitamin A can bring side effects, including liver damage and bone fractures, so speak to a physician before adding it.
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Egg yolk
Contains vitamin D too, though to a lesser extent.
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Foods with vitamin D added
In some places, cereals and other products have it added.
Finding out
If you cannot feel it, you have to check it
Because a low level can be silent, how you feel is not a reliable guide. Our physicians can check your vitamin D level, look at why it may be low, and decide on treatment with you.
Hair fall in women and its common causes
If you are already thinking about wider testing, you can book a screen directly.
Worth raising with us if you
- Are an older adult
- Have a child or infant
- Avoid dairy products
- Spend little time in the sun
- Have more pigmented skin
- Have celiac disease, Crohn's disease or cystic fibrosis
- Have had stomach or intestinal surgery
- Live with kidney or liver disease
Questions
What patients ask us
What does vitamin D do in the body?
It helps the gut absorb calcium and phosphorus and keeps parathyroid hormone, which drives bone breakdown, in check. Together this keeps blood calcium and phosphate steady and supports bone health. It may also support muscle and immune function, although this needs more research.
Can I get enough vitamin D from sunshine alone?
Skin makes vitamin D in sunlight, but how much depends on season, time of day, age and skin pigmentation, and sunscreen limits it. Because of the long-term risk of skin cancer, sun exposure is not recommended as a vitamin D source for anyone, including children. Our physicians can advise you on what suits you.
Which foods contain vitamin D?
Fatty fish and cod liver oil contain vitamin D, and egg yolk contains less. Some cereals and other products have it added. Cod liver oil also holds a lot of vitamin A, and too much vitamin A can cause side effects such as liver damage and bone fractures, so speak to a physician before adding it.
Can my vitamin D be low even if I feel fine?
Yes. A level that is lower than normal often causes no visible signs or symptoms. It may still be linked with lower bone density and, in some people, a higher risk of falls and possibly fractures. A level check is the way to know.
Who is more likely to have low vitamin D?
Infants, children and older adults, people who avoid dairy products, and people with limited sun exposure, especially those with more pigmented skin. Conditions that affect absorption, such as celiac disease, Crohn's disease and cystic fibrosis, stomach or intestinal surgery such as gastric bypass, and chronic kidney or liver disease also raise the chance.
What can happen if vitamin D stays very low?
Deficiency may lead to low blood calcium, low blood phosphate, and softening of the bones, called rickets in children and osteomalacia in adults. Your physician will explain what applies to you and decide on treatment.
Talk to a physician
Let us check where your vitamin D stands
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This page is general information. It is not a diagnosis, and it does not replace advice from your physician.
Salam International Polyclinic · Building no. 2/710, Block no. 221, Way no.102, Madinat Sultan Qaboos, Muscat, Oman
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