Nicknamed the 'sunshine vitamin' because your body makes it from sunlight, vitamin D is essential for overall health. However, even in sunny Australia, you might not be getting enough, says Pamela Allardice.
Bone densityVitamin D (which is technically not a vitamin, but a hormone which your body produces in response to UVB rays) builds a strong skeleton and teeth by ensuring your bone cells absorb calcium. Without vitamin D, your body cannot absorb calcium from food or supplements, no matter how much you consume. Vitamin D is critical in preventing osteoporosis, a disease which causes brittle bones. Studies show supplements of calcium and vitamin D slow bone loss and reduce the incidence of fractures in men and women.
Immune functionSome of the most exciting work in nutritional science is being undertaken in the area of disease prevention, and vitamin D certainly shines here. Numerous studies indicate that getting enough D decreases your risk of developing many ailments, including type 1 diabetes, depression, and heart, muscle, and kidney disorders. It also improves the body’s disease-fighting capacity. Studies show that the production of germ-killing compounds and antimicrobial peptides - which defend the body against bacteria, viruses, and fungi - is increased in skin exposed to sunlight.
Cancer preventionVitamin D is a vital weapon in the fight against cancer, with high levels being associated with lower incidences of colon, prostate, and ovarian cancers, and especially breast cancer. In one study of over 3,900 women, researchers discovered that those participants who spent the most time in the sun halved their likelihood of getting breast cancer; low blood levels of vitamin D are also correlated with a higher breast cancer risk. In one small study, vitamin D actually seemed to arrest progression of breast cancer; in another, women with low vitamin D levels when diagnosed with breast cancer had double the risk of their cancer spreading. Vitamin D may even offer hope for one of the most difficult-to-treat cancers: pancreatic cancer. A Harvard University study indicates that taking D supplements could reduce risk.
Getting enoughMost people aren’t getting enough vitamin D, especially if they spend days office-bound, wear sunscreen, have dark skin (which filters out sunlight), or are over 45 (the body’s ability to manufacture vitamin D declines with age). Two Australian studies have highlighted low levels in one in three women in summer, rising to one in two in winter, and almost half of nursing home patients have a deficiency. Balancing skin-cancer protection with careful sun exposure – 15 minutes on your arms and legs, preferably not between 10 a.m. and 2 p.m. – is enough to produce your daily requirement of vitamin D. Cold-water fish (e.g. salmon, tuna) and fish liver oil are good food sources, followed by beef liver, cheese, and egg yolks. Fortified milk, juice, dairy products and cereals can boost levels, as can supplements – look for products containing vitamin D3 (cholecalciferol), which is considered to be more bioavailable than vitamin D2 (ergocalciferol).