Which disease causes vitamin D deficiency?

Which disease causes vitamin D deficiency? The question has two answers, and that is exactly where the confusion sits. A prolonged deficiency can itself lead to disease: rickets in children, osteomalacia in adults. In the other direction, several diseases cause a deficiency, including coeliac disease, Crohn's disease and chronic kidney damage.

Most pages cover only one of those two directions. Both are below.

Which diseases result from a vitamin D deficiency?

A severe, prolonged deficiency disrupts how you absorb calcium and phosphate from food. Bone tissue then stops mineralising properly. In children that is called rickets. In adults the same mineralisation problem is called osteomalacia.

Rickets causes soft bones, delayed growth and sometimes bowed legs. Osteomalacia causes dull bone pain and muscle weakness, mostly around the hips and thighs. An international consensus group describes both as a direct consequence of vitamin D or calcium deficiency (Munns et al., 2016. PMID 26745253).

Osteoporosis is more nuanced. A deficiency contributes to it, but bone loss has many more causes: age, hormones, heredity and physical activity. A low vitamin D value is one factor there, not the explanation.

Which diseases cause a vitamin D deficiency?

This is the direction that rarely gets explained. Vitamin D is fat-soluble. Anything that disrupts fat absorption in the gut, or conversion in the liver and kidney, lowers your value. In these conditions a deficiency is not coincidence but an expected consequence.

After bariatric surgery the 25-OH value drops structurally, according to a systematic review with meta-analysis (Giustina et al., 2023. PMID 37665480). That is precisely why this group is monitored for life.

Medication matters too. Some anti-epileptics and long-term corticosteroid use speed up the breakdown of vitamin D in the liver.

What a vitamin D deficiency does not cause

Here I will take a position. Many health sites state that a deficiency causes cancer, cardiovascular disease or depression. That is phrased far too firmly. Those associations come from observational research, where a low value is often a consequence of illness rather than its cause.

The largest trial on this is called VITAL. It gave 25,871 participants vitamin D or a placebo for just over five years. Supplementation did not lower the incidence of cancer or cardiovascular events (Manson et al., 2019. PMID 30415629).

That does not make vitamin D unimportant. It makes that specific claim wrong.

Who is most at risk of a deficiency?

Besides the diseases above, some groups see deficiency more often without anything being wrong with the gut or kidney. For them it comes down to sunlight, skin tone or age.

• People with darker skin, because more pigment slows production in the skin
• Older adults, since skin makes vitamin D less efficiently over the years
• Anyone who spends little time outdoors or keeps the body largely covered
• Pregnant women and women over 50
• People with obesity, because vitamin D accumulates in fat tissue

The Dutch health institute RIVM advises several of these groups to supplement daily regardless of their blood value. How much is sensible is covered in our article on how much vitamin D per day.

How do you know whether you really have a deficiency?

Only through a blood test. Complaints such as fatigue and muscle pain are too general to navigate by, because they fit dozens of other causes. The value measured is 25-OH vitamin D, expressed in nmol per litre.

The Dutch Health Council uses 30 nmol/L as the lower limit for people up to 70, and 50 nmol/L above that age. Below that threshold it counts as a deficiency.

Imagine two people with the same November complaint, both tired and stiff, except one measures 68 nmol/L and the other 18 nmol/L. Without measurement those two stories look identical. With measurement the gap is wide, and only in the second is vitamin D a plausible explanation.

You can have the value measured separately with the vitamin D test, or first read the background on the marker page for vitamin D (25-OH). To look wider than vitamin D alone, our overview of vitamin deficiency and which vitamins to test helps.

Frequently asked questions

Is English disease the same as rickets?

Yes. English disease is the Dutch common name for rickets, the bone condition that develops in children through severe vitamin D or calcium deficiency. The name dates from the nineteenth century, when the condition was common in English industrial cities with little sunlight.

Can a vitamin D deficiency cause hair loss?

An association has been described for certain forms of hair loss, but the evidence is limited. Hair loss usually has other causes, such as iron deficiency, thyroid problems, stress or heredity.

How long does it take to correct a deficiency?

That varies per person and per dose. The value usually rises noticeably within eight to twelve weeks. My advice is not to retest sooner, because you would be reading a value still on its way up. Your doctor decides whether and when a recheck is useful.

What is the difference between symptoms and finding the cause?

Symptoms tell you that something is going on, not what. More on connecting complaints to values is in vitamin D deficiency: symptoms, causes and how to test it.

References

• Munns CF, et al. Global Consensus Recommendations on Prevention and Management of Nutritional Rickets. Journal of Clinical Endocrinology & Metabolism. 2016. PMID 26745253. PubMed
• Manson JE, et al. Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. New England Journal of Medicine. 2019. PMID 30415629. PubMed
• Giustina A, et al. Vitamin D status and supplementation before and after Bariatric Surgery. Reviews in Endocrine and Metabolic Disorders. 2023. PMID 37665480. PubMed