Hundreds of people are being admitted to hospital with vitamin D deficiency at the Mid Yorkshire NHS Trust.
Vitamin D deficiency cases at the trust, which runs Dewsbury and District Hospital, have soared over the last three years, with 1,115 diagnoses in the 12 months to March 2018, data from NHS Digital shows.
Public Health England (PHE) has encouraged people to consider taking a vitamin D supplement during the winter months, after a surge in diagnoses at hospitals.
Vitamin D helps the body to regulate calcium and phosphate levels, which are needed to maintain healthy bones, muscles and teeth.
A lack of it can lead to bone deformities in children or painful musculoskeletal conditions such as osteomalacia in adults.
Sunlight is the main source of vitamin D, but a small amount can be obtained through dietary sources.
The NHS says vitamin D is only found naturally in a small number of foods, such as oily fish, egg yolks, and liver.
It is also found in fortified foods such as low-fat spreads, cereals and fortified milk.
Professor Louis Levy, head of nutrition science at PHE, said: “Vitamin D is essential for healthy bones and most of us get enough from sunshine and a healthy balanced diet during summer and spring.
“During autumn and winter, those not consuming foods naturally containing or fortified with vitamin D should consider a 10 microgram supplement.”