- The link between the sun and cancer is typically not seen as a positive one because of the connection with skin cancer. UV-B radiation from the sun is said to be the most important environmental risk factor for nonmelanoma skin cancer. Because the sun is the primary source of vitamin D, researchers are looking to see what role it plays in skin cancer. Some believe that enough sun exposure to keep your vitamin D levels up, while protecting your skin from damage, is beneficial to skin cancer survival. There has also been research to show the protective effect that vitamin D has with the development of other cancers, including colon, breast, and prostate cancer.
- In 1941, U.S. pathologist Frank Apperly published geographic data that demonstrated for the first time an inverse correlation between levels of UV-B radiation in North America and mortality rates from cancers. This study suggested that more exposure to UV-B radiation led to fewer deaths from cancers. Since this was published, other studies have suggested that there may be an association between an increased risk of dying of various malignancies (for example, colon, breast, ovarian, melanoma, and prostate cancer) and living far from the equator.
- The anti-inflammatory properties of vitamin D may also be able to assist with lowering pain levels in cancer patients when deficiencies are corrected.
It’s been shown that vitamin D plays a crucial role in brain development, brain function regulation, and a healthy nervous system. Vitamin D deficiency has been found to be common in patients with Parkinson’sdisease, Alzheimer’sdisease, schizophrenia, depression, anxiety disorders, dementia, and older adults with cognitive decline. A meta-analysis reported a 2.4-times greater risk of cognitive impairment in people with low vitamin D levels versus those with adequate levels. It’s been suggested that maintaining adequate levels of vitamin D levels throughout life may help to prevent age-related neurological disorders.
A summit with the leading experts, including physicians and scientists, from across the world convened in 2013 to review the research in this area and to come up with clear guidelines for the medical and scientific communities. There was a unanimous agreement that low vitamin D levels and/or the insufficient utilization of vitamin D can be considered a risk factor for cognitive decline and dementia in general and supplementation was needed to correct these levels. A review of vitamin D levels in 170 women, 65-77 years of age, over 10 years found that adequate vitamin D levels may be protective against declines in cognitive flexibility and psychomotor speed components of executive function.
The association between lack of sunlight and depressive disorders was first noted 2,000 years ago. There are numerous studies showing low levels of vitamin D are associated with major depression and the symptoms of depression. In a study of over 6,000 people over the age of 50, those with lower vitamin D levels reported more depressive symptoms (for example, felt sad, felt lonely, couldn’t get going). Those with the lowest vitamin D levels reported the greatest degree of depressive symptoms. Only small-scale studies have shown success in improving these symptoms by correcting the deficiency. Much more research is needed in this area to find out how best to treat it.
Cardiovascular disease (heart disease)
- Vitamin D deficiency is associated with increases in hypertension (high blood pressure), hyperlipidemia, peripheral vascular disease, coronary artery disease, myocardial infarction, heart failure, and stroke. The anti-inflammatory effects of vitamin D may be the reason for this, and studies are ongoing to examine this relationship.
- A review of six studies that included over 6,400 people found that patients with peripheral arterial disease (PAD) had lower levels of vitamin D and that vitamin D insufficiency may contribute to the development of more advanced PAD. Further research needs to be done to confirm the cause and effect.
What are vitamin D deficiency symptoms and signs? What are health risks of vitamin D deficiency?
- It’s possible that maintaining adequate vitamin D levels could lessen the length and severity of upper respiratory infections and possibly even prevent them from occurring in some people. A review of 12 studies, including 2,279 children, found that children with lower respiratory infections (LRTI) had significantly lower vitamin D levels compared with controls. There was also a relationship between the how low the level went and the incidence and severity of LRTI. The role of vitamin D in reducing the risk of hospital-acquired infections, such as pneumonia, bacteraemia, urinary tract infections, and surgical site infections is also being investigated.
- Many of the health benefits associated with vitamin D may come from its role in decreasing inflammation. Research has shown a decrease in levels of C-reactive protein, a marker of inflammation, with increased levels of vitamin D.
Inflammatory bowel disease (IBD)
- When there is an inability to properly absorb nutrients in the GI tract, there is a higher risk for nutritional deficiencies. Vitamin D’s role goes beyond this in that the level of deficiency may impact the severity of IBD, and maintaining adequate levels may keep you in remission longer. There has even been evidence showing larger numbers of cases of IBD in northern latitudes suggesting it has a role in prevention, as well.
- A study including over 500 adults found that vitamin D deficiency was linked to greater fat mass, but only in those with elevated parathyroid hormone (PTH), suggesting the cause may lie in controlling that level.
- Vitamin D enhances the absorption of dietary calcium by 30%-40% and phosphorus by 80%. Without it, only 10%-15% of calcium and 60% of phosphorus is absorbed. Vitamin D promotes calcium absorption in the gut and maintains blood calcium levels to enable normal mineralization of bone and prevent abnormally low blood calcium levels that can then lead to tetany.
- Vitamin D insufficiency leads to secondary hyperparathyroidism that causes increased bone loss, osteopenia, osteomalacia, osteoporosis, and increased fracture risk. Furthermore, moderate elevations of parathyroid hormones (PTH) may promote insulin resistance, weight gain, hypertension (high blood pressure), and left ventricular hypertrophy.
- Fall prevention is a public health goal for the elderly. Each year, one in three people 65 years and older experiences at least one fall, with 5.6% resulting in a fracture, and vitamin D can play a role in preventing this. There are vitamin D receptors in human muscle that have a direct effect on muscle strength. A severe vitamin D deficiency can cause myopathy, which can cause muscle weakness and pain. Vitamin D supplementation can reverse this and improve balance. Supplementing 700-1,000 IU/day of vitamin D3 has been shown to possibly reduce falls by 19%-26%. Vitamin D3 at a dosage of greater than 800 IU/day given with calcium has been shown to reduce the risk of fractures by 10%-15%.
- Another advantage to correcting a vitamin D deficiency has been seen in decreasing knee and hip pain. A longitudinal population-based cohort study of 769 randomly selected older adults aged 50-80 years found that moderate vitamin D deficiency predicts the incidence or worsening of knee pain over five years and possibly hip pain over 2.4 years.
Type 2 diabetes risk reduction
- Research has shown that those with blood vitamin D levels over 25 ng/mL had a 43% reduced risk of developing type 2 diabetes compared with those with levels under 14 ng/mL. Adequate vitamin D levels have been associated with improved blood sugar levels and decreased insulin resistance in some studies.
Adequate vitamin D levels have also been linked with improvements in kidney function, erectile dysfunction, sleep apnea, diabetic retinopathy, and decreased manic episodes in bipolar patients. There is ongoing research to determine links with vitamin D deficiency and the increase in the prevalence of asthma and allergies, autism, preterm birth, gestational diabetes, and preeclampsia.