Health THE SUNSHINE VITAMIN Its crucial for bone health and muscle function, but many of us are deficient in vitamin D BY ANGIE JEFFERSON, REGISTERED DIETITIAN Summer 2023 was wetter than usual, which means weve missed out on sunny days that are essential for boosting winter stores of vitamin D. As vitamin D has a role in reducing inflammation and keeping the immune system healthy, we need to make up for missing stores. Vitamin D is, in fact, a hormone, and can be produced in the skin from sunlight. Clever stuff! But in the UK, this only happens from April to September, when the sun is high in the sky and if sunscreen hasnt been applied. Body stores of vitamin D increase during these months and then gradually fall, reaching their lowest around March. Just 10 minutes of outdoor sunshine on the face and forearms every day is enough to boost stores. But when sun is lacking, so is vitamin D. This matters as it has many roles in health, helping us absorb dietary calcium; allowing muscles to function normally; and supporting normal immune function. Food sources of vitamin D are limited. Only oily types of fish, liver, some mushrooms, eggs, and foods where its been added (such as some breakfast cereals and fat spreads) contain significant amounts. Its really challenging to get enough vitamin D from diet alone, and we typically only eat a quarter of the 10 micrograms recommended daily. The combination of limited dietary sources and unreliable weather mean that half the UK population have low vitamin D status, and one in six of us are deficient. The challenge is that poor vitamin D status is asymptomatic, meaning that you wont have noticeable signs or symptoms. At its extreme, prolonged vitamin D deficiency contributes to osteoporosis. Poor status can mean increased frequency of colds and infections, feeling fatigued, low mood and depression, muscle weakness and pain, and poor wound healing. All things we put down as part and parcel of getting older and living with arthritis. Vitamin D and arthritis Studies have found that people with rheumatoid arthritis (RA) have less vitamin D. What we dont know is whether low levels of vitamin D contribute to RA, or whether the condition causes poor vitamin D status. There is some evidence that vitamin D supplementation in people with low levels might reduce osteoarthritis pain, but more research is needed. Adults living in the UK are advised to consider taking a daily supplement of 10 micrograms of vitamin D, especially during the winter, so thats a good place to start. After the wet summer of 2023, making wise food choices and taking vitamin D is more important than ever. 12 versusarthritis.org PP12_Inspire_Winter 2023_Vitamin D.indd 12 14/11/2023 11:46