Vitamin D

Vitamin D helps regulate the amount of calcium and phosphate in the body, which are needed to keep bones, teeth and muscles healthy. A lack of it can cause rickets in children and, in adults, bone pain from a condition called osteomalacia (NHS).

Where does vitamin D come from?

Most of it is made in the skin from direct sunlight outdoors. In the UK, from about late March or early April to the end of September, most people can make all the vitamin D they need this way. Between October and early March the sun isn’t strong enough. A small number of foods contain it too: oily fish, red meat, egg yolks and fortified foods such as some breakfast cereals (NHS).

Because it depends on sun on your skin outdoors, a summer spent mostly indoors at a desk gives you fewer chances to make it.

What does the NHS advise about vitamin D?

The NHS guidance is (NHS):

• Autumn and winter. Everyone, including pregnant and breastfeeding women, should consider a daily supplement of 10 micrograms.
• All year. The Department of Health and Social Care recommends 10 micrograms a day throughout the year for adults who are not often outdoors (for example, frail or housebound), who live in a care home or similar institution, or who usually cover most of their skin outdoors. People with dark skin, for example of African, African-Caribbean or south Asian background, should also consider it all year.
• Not more than 100 micrograms (4,000 IU) a day. Taking too much for a long time can cause too much calcium to build up (hypercalcaemia), which can weaken bones and damage the kidneys and heart. If a doctor has advised a different dose, follow their advice.

Does vitamin D help back pain?

Low vitamin D and back pain often turn up together, but taking vitamin D hasn’t been shown to ease back pain.

• Studies that compare people. A review of 29 observational studies found that people with low back pain were more likely to be vitamin D deficient. The link with how bad the pain was was inconsistent, and with no long-term studies included, the review couldn’t show which came first (Zadro et al., 2017).
• Following people over time. In 135,934 UK Biobank participants, links between vitamin D and low back pain disappeared once other factors were accounted for, and neither vitamin D status nor supplements predicted new low back pain over a median of 8.5 years (Sha et al., 2024).
• Trials of supplements. A review of 8 trials found very low-quality evidence that vitamin D was no better than placebo or other treatments for low back pain (Zadro et al., 2018). A 2024 meta-analysis of 10 randomised trials found no significant reduction in pain scores, whatever people’s starting levels (Lee et al., 2024). Across chronic pain conditions more broadly, a Cochrane review of 10 trials found no consistent benefit and judged a large effect unlikely (Straube et al., 2015).

For what does help most back pain, see non-specific low back pain and lower back pain from sitting.

Vitamin D, bones and fractures

Correcting a real deficiency is not the same as adding more to normal levels. In a trial of 25,871 generally healthy adults who were not selected for deficiency, low bone mass or osteoporosis, 2,000 IU a day for a median of 5.3 years did not lower the risk of fractures compared with placebo (LeBoff et al., 2022). A meta-analysis of 81 trials found no effect on fractures or falls and no clinically meaningful change in bone density (Bolland et al., 2018). For people who do have osteoporosis, the NHS notes that a doctor may prescribe vitamin D to take all year round (NHS).

When to see a doctor

In adults, osteomalacia can cause pain in the back, shoulders, ribs, pelvis or legs, weak muscles that make stairs or getting out of a chair hard, muscle cramps or twitching, and bones that break more easily. See a GP if you think you might have it; they can check your vitamin D and calcium levels with blood tests (NHS).