Or take ageing. One paper looking at the link between vitamin D and life expectancy found that vitamin D3 can help with protein homeostasis — the process by which proteins are regulated within cells to maintain their health. But other studies have been less conclusive. One meta-analysis concluded that more research is needed to clarify the effect of vitamin D on mortality. The link between cardiovascular disease and vitamin D also has yet been properly established : the link could mean that heart disease is causing low vitamin D levels, not the other way around.
Ian Reid, professor in medicine at the University of Auckland, believes that diseases cause low vitamin D levels, as being unwell often leads to spending less time outdoors exposed to sunlight, rather than vice versa. Some experts believe people who are unwell have low vitamin D levels because they spend less time outdoors, not that their low levels cause health problems Credit: Getty Images. Researchers have found that higher vitamin D levels are associated with a lower risk of colorectal cancer — it plays a role in stemming the formation of new blood vessels and stimulating better communication between cells.
Vitamin D also has been found to help maintain normal levels of calcium in the colon, which slows growth of non-cancerous but high-risk cells. Other studies, including of the link between vitamin D and liver cancer, breast cancer and prostate cancer , suggest there is good reason to think that low vitamin D plays a part in the spread of cancer cells.
But taking supplements would then, surely, help stave off cancer — and a recent meta-analysis failed to find that supplementation reduced cancer risk. Another oft-discussed condition is seasonal affective disorder SAD , a mood disorder caused by the seasonal drop in exposure to sunlight.
The link between light exposure and SAD is long-established. But again, a direct link to vitamin D has been difficult to prove. Evidence suggests there may be a relationship since vitamin D is associated with levels of both serotonin, important for mood regulation, and melatonin, which regulates our sleep. Low levels of either hormone could contribute to SAD symptoms. Researchers have yet to carry out a definitive randomised control trial, however, and the exact mechanism by which vitamin D bolsters the hormones is unknown.
Research has found that vitamin D plays a wider role in our mental health, from depression to schizophrenia, as well as in brain development, but how it plays a role also remains unclear. More conclusive research around this is currently underway.
Even so, most experts generally agree that even vitamin D supplements can benefit those who have very low levels. Martineau says his research found that those with low levels of vitamin D tend to see the most benefits of supplementation preventing respiratory infections, whereas the effects are a lot more modest when levels are moderately low. Reid says his studies have also shown benefits in those with low levels.
The trouble is that it can be difficult to predict who is at a highest risk of suffering from low vitamin D. Then there is the question of exactly what level of supplementation people need. But with supplements offering doses as high as Suma Uday, co-author of the paper and PhD doctoral researcher at the university, says these deficiencies occur because infant vitamin D supplementation programs are poorly implemented in the UK and not monitored.
Disclaimer All content within this column is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional.
The BBC is not responsible or liable for any diagnosis made by a user based on the content of this site. The BBC is not liable for the contents of any external internet sites listed, nor does it endorse any commercial product or service mentioned or advised on any of the sites. Those are the basic facts, but some questions might remain: How should you get vitamin D?
How much should you get and when should you worry about your levels? In light of these common questions, our Yale Medicine doctors help clear up some confusion about vitamin D, separating fact from fiction. Vitamin D is stored in fat. Modest increases above the RDA are not likely to cause harm. The child, who developed high blood calcium hypercalcemia , had to be hospitalized and treated with several types of medications to get the calcium levels down to normal levels.
You can now get 50, IU tablets over the counter. There are patients with specific issues who might need a prescription for high levels of vitamin D, but for most people, that amount will raise your vitamin D level too high.
Babies should be getting smaller amounts in their first year of life, between and IU. Most people should be fine. Testing is important only for certain populations: for people who are institutionalized; for patients with a gastrointestinal disorder like inflammatory bowel disease or osteoporosis ; those who have had weight loss surgery; those on anti-convulsant medications; and children who are immobilized and not outside and active.
Breast milk doesn't have much vitamin D in it. That's what spurred a recommendation from the American Academy of Pediatrics that every breastfed infant be given vitamin D if they're being given liquid multivitamin drops, they're getting enough of it. There are claims that one needs to get a certain amount of sun exposure every day in order to produce enough vitamin D to be healthy. The majority of people can get their vitamin D from nutritional supplements and from vitamin D-fortified foods.
Don't go doubling your D intake just yet, though. Taking a dose of vitamin D at 50, IU for weight loss has yet to be proven effective. Before talking to your doctor, check yourself for signs of vitamin D deficiency. According to a study published in May in Psychiatry Research , depression is a common symptom of deficiency. In addition, a June article in Archives of Women's Health's suggests an increased likelihood of postpartum depression, which further supports the link between insufficient vitamin D and depression.
Additional symptoms, according to University Health News , include:. The sun is a great source, as are several foods, such as salmon. If you're struggling with deficiency levels though, the vitamin D in salmon won't be enough.
The National Institutes of Health suggests that the best source of vitamin D is a quality supplement. To decide which supplement is best for you, take your time and do some research. Vitamins can have undesired side effects, and vitamin manufacturers sometimes stretch the reality of their claims.
Even those that are effective still may not be right for you. For instance, the Alive! Women's Energy brand produces side effects from its high dosage of iron, which can upset sensitive stomachs. The National Institutes of Health states that the more depleted you are, the longer it takes for changes to occur. You should start feeling better once the vitamin D kicks in, but you should still have your levels checked every two to three months.
Remember it's always easier to avoid deficiency than it is to rebuild your system. So pay attention to what your body is telling you. By Danica Benninghoven Updated May 8,
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