Lauren Oster is a contributing writer based in New York City. She covers health and wellness, science and sustainability, lifestyle and culture, and travel. Her work appears in many publications including Smithsonian Magazine, New York Times Magazine, Health, Redbook, Refinery29, HGTV, Travel Channel, and more.
We get vitamin D from a great source: the sun. But it’s still possible to not get enough vitamin D—which can lead to negative health consequences. According to the National Library of Medicine, vitamin D deficiency can lead to a loss of bone density, which can contribute to osteoporosis and fractures (broken bones). Severe vitamin D deficiency can also lead to other diseases. And researchers are studying vitamin D for its possible connections to several medical conditions, including diabetes, high blood pressure, cancer, and autoimmune conditions such as multiple sclerosis.
The good news? It’s relatively easy to get enough vitamin D. Certain foods, including fatty fish, can help you increase your levels, as can sunlight. Specifically, 15 minutes of sunlight on your hands and face each day can do the trick, Donald Ford, MD, a family medicine doctor at Cleveland Clinic, told Health. (Also worth noting, if it’s raining one day, you can make up for it by spending 30 minutes in the sun the next.)
Here are 26 reasons you should consider spending more time outdoors if your doctor mentions that your vitamin D levels are low.
Obesity
Obese men, women, and children are 35% more likely to be vitamin D deficient than non-obese people, and 24% more likely to be D deficient than overweight people, according to a 2015 meta-analysis published in Obesity Reviews. According to a 2019 review in Cochrane Database of Systematic Reviews, the accumulation of vitamin D in the adipose tissue might explain why obese people have low vitamin D blood levels, since fat cells hold on to vitamins and don’t release them efficiently. Translation: Obesity could actually make vitamin D deficiency worse.
Diabetes
People with diabetes or prediabetes have lower vitamin D levels than those with normal blood sugar levels, according to a Spanish study published in 2015 in the Journal of Clinical Endocrinology & Metabolism. The link held for folks across the BMI spectrum. In fact, both lean and severely obese people with diabetes or prediabetes had significantly lower D than their nondiabetic counterparts. The study’s authors believe that vitamin D deficiency and obesity “interact synergistically” to increase the risk of diabetes and other metabolic disorders.
Heart Disease
Heart disease and vitamin D deficiency are known to go hand in hand. One 2022 study appearing in the European Heart Journal found evidence that vitamin D deficiency can increase blood pressure and the risk of cardiovascular disease.
However, experts say there isn’t evidence of a direct link between higher vitamin D levels and lowering cardiovascular risk. A 2019 meta-analysis published in JAMA Cardiology looked at more than 83, 000 participants and vitamin D supplementation. Study researchers found vitamin D supplementation was not associated with reduced risks of major adverse cardiovascular events, myocardial infarction, stroke, or cardiovascular disease mortality.
Lupus
Lupus, a chronic inflammatory disease in which the body’s immune system attacks its own organs and tissues, is frequently associated with vitamin D deficiency—in part because lupus patients are often advised to stay out of the sun (the source of 90% of our vitamin D), and may be prescribed corticosteroids, which are also linked to low levels of D, according to the Lupus Foundation of America.
A 2022 study in the British Medical Journal found that vitamin D supplementation for five years taken with, or without, fish oil (Omega 3 fatty acid) may help reduce autoimmune disease, such as lupus. Researchers found autoimmune disease was reduced by 22% in those who took the increased levels of vitamin D with or without fish oil.
Preterm Birth
In a 2015 study published in Obstetrics and Gynecology, more than 2,000 mothers-to-be, women with higher levels of 25-hydroxy vitamin D (an indicator of our bodies’ vitamin D stores, measurable with a blood test) had a lower risk of giving birth before 37 weeks. The authors suggested that D could be having a protective effect by reducing bacterial infection in the placenta, which can cause preterm birth.
In a 2014 study in American Journal of Epidemiology, researchers who examined data from the Collaborative Perinatal Project (a study of more than 42,000 women) reported that among nonwhite mothers, higher concentrations of 25-hydroxy D were associated with a reduced risk of birth before 35 weeks.
Multiple Sclerosis
In 2013, an international team of researchers examined data from 465 people with early-stage MS, an often-disabling autoimmune disease that affects the central nervous system. As published in JAMA Neurology, researchers reported that higher levels of 25-hydroxy D measured at the onset of symptoms (and then 6, 12, and 24 months later) predicted a slower rate of disease progression. Subjects with higher levels of D had a slower increase in brain lesion volume, fewer new lesions, lower brain volume loss, and lower disability levels than those with low levels of D.
PMS
High dose vitamin D supplementation was found to reduce the prevalence of PMS and dysmenorrhea (severe and frequent menstrual cramps and pain during your period according to Johns Hopkins Medicine) in a 2017 study published in Gynecological Endocrinology. Vitamin D also had positive effects on the physical and psychological symptoms of PMS.
Non-steroidal anti-inflammatory drugs like ibuprofen and naproxen are still the first line of therapy for PMS symptoms, but researchers believe vitamin D supplements are a promising alternative.
Inflammatory Bowel Disease
Vitamin and mineral deficiencies, including D deficiency, are extremely common for people with gastrointestinal health issues that affect their body’s ability to absorb nutrients. Patients with active ulcerative colitis, a type of inflammatory bowel disease (IBD), especially those who take corticosteroids, are often deficient in D, a 2013 tudy in Digestive Diseases and Sciences suggested. In addition, some researchers believe deficiency could have a role not only in increasing the risk of developing IBD but in determining the severity of a person’s symptoms, as a 2013 study in Alimentary Pharmacology and Therapeutics found.
Alopecia and Hair Loss
Women with female pattern hair loss had significantly lower levels of vitamin D than those without hair loss, a 2013 study in Skin Pharmacology and Physiology found. The vitamin is crucial for hair cycling and helps push hair from its resting phase to the growing phase. Turkish researchers found that patients with alopecia areata, an autoimmune disease that attacks follicles and can cause hair loss all over the body, had significantly lower levels of 25-hydroxy vitamin D than folks without the condition, according to a 2014 study in British Journal of Dermatology. Researchers also noted, the lower their D levels, the more severe their disease.
Insulin Resistance
Insulin resistance, which leads to glucose buildup in the blood and type 2 diabetes and prediabetes, has been linked to vitamin D deficiency for quite some time. A 2019 study in Nutrients concluded that vitamin D deficiency is one of the factors accelerating insulin resistance formation. However, researchers noted that it is not fully recognized how vitamin D may reduce the risk of metabolic disorders development (such as type 2 diabetes).
In addition, researchers in Iran found that vitamin D supplements had no effect on insulin sensitivity in pre-diabetic patients, as published in a 2013 study in the Journal of Research in Medical Science.
Eczema
Vitamin D is known to have a regulatory influence on both the immune system and skin barrier function, both critical in the development of eczema. Research suggests a link between vitamin D and eczema, specifically lower serum vitamin D levels associated with increased incidence and severity of eczema symptoms, according to a 2015 study in Journal of Clinical Medicine.
Supplementing with vitamin D in pill form can improve winter-related eczema, one 2014 study published in the Journal of Allergy and Clinical Immunology found.
Tooth Decay in Infants and Toddlers
Vitamin D is crucial both to our dental health and the formation of our teeth in the first place—yet another reason taking prenatal vitamins is so important. A 2014 study in Pediatrics measured the blood levels of vitamin D in pregnant women, then checked the teeth of their babies at 1 year old. Researchers found that mothers of children with weak enamel and tooth decay had significantly lower vitamin D levels during pregnancy compared to moms of children with healthy teeth.
Gum Disease and Tooth Loss
Because vitamin D helps your body absorb calcium, it’s essential for healthy teeth and gums, says the National Library of Medicine.
When vitamin D levels are unregulated, it weakens your teeth, making you susceptible to cavities, fractures, and decay. A 2020 study in the journal Oral Diseases looked at over 4200 US adults and found that vitamin D levels are significantly associated with the occurrence of cavities.
Additionally, a 2020 study published in the Journal of Periodontal Researchfound lower vitamin D levels are linked with an increased risk of periodontitis, possibly because of its connection to the immune system. Vitamin D seems to positively impact inflammation and mineralization effects on the tissue surrounding your teeth.
Alzheimer’s and Dementia
Studies have linked low vitamin D to abnormalities in brain structure, cognitive decline, and dementia. In a 2015 study in JAMA Neurology, which measured vitamin D and cognitive function each year in an ethnically diverse group of elderly patients (about half of whom had some form of cognitive impairment at the start of the study), lower levels of D were associated with accelerated cognitive decline.
A 2021 review in Nutrients concluded that, though there is certainty that vitamin D is involved in normal brain function and that low vitamin D concentrations can occur in patients with dementia, there is no clear evidence that supplementation with vitamin D can prevent or modify the course of cognitive decline and dementia.
UTIs
Vitamin D helps prevent infection by helping our bodies produce natural antibiotics. A 2014 study in Archives of Disease in Childhood found that D deficiency is a risk factor for urinary tract infections in children, especially girls. It’s a bit too soon to call vitamin D the new cranberry juice, but low levels are associated with UTIs for adults, too. A 2013 International Journal of Infectious Disease study of women who suffered from recurrent UTIs found that they had lower levels of vitamin D than women who didn’t.
Female Incontinence
Since vitamin D is critical for muscle strength, according to the National Library of Medicine, deficiency can contribute to weakness in the pelvic floor—that is, the hammock of muscles that supports the bladder, vagina, uterus, and rectum. According to a 2019 meta-analysis in the published in the Journal of Mid-Life Health, vitamin D levels in women with pelvic floor disorder (PFD)—which includes includes pelvic organ prolapse, urinary incontinence, and fecal incontinence—were significantly lower than healthy women. Study authors wrote that additional studies regarding the association between vitamin D and PFD are needed.
Asthma
According to a large 2014 study published in Allergy that tracked more than 21,000 adults with asthma, while people with asthma were no more likely to have low D than those in the general population, asthmatics who did have a vitamin D deficiency were 25% more likely to experience acute attacks and to need to see a doctor more frequently for their asthma. The study’s authors say that their findings support the importance of vitamin D level screenings for patients with severe asthma—and that supplements could be necessary for those falling short.
Schizophrenia
There’s a strong link between vitamin D deficiency and this mental health disorder: In a 2014 review of 19 studies published in The Journal of Clinical Endocrinology & Metabolism, researchers found that 65% of schizophrenia patients had low levels of vitamin D, and people with vitamin D deficiency were more than twice as likely to have schizophrenia. That correlation doesn’t necessarily mean that deficiency causes schizophrenia. In fact, experts hypothesize that the reverse may be true, with schizophrenia causing people to make lifestyle and diet choices that lead to deficiency.
Depression
Female college students who had low levels of vitamin D were more likely to have clinically significant symptoms of depression, according to a 2015 study published in Psychiatry Research. A larger 2018 meta-analysis of more than 31,000 research subjects, published in the British Journal of Psychiatry, found a correlation as well. There’s hope that vitamin D supplements might help: A very small study presented to the Endocrine Society in 2012 found three women with moderate to severe depression experienced improvement in their symptoms after they received treatment for vitamin D deficiency.
A 2020 review published in Depression and Anxiety found that people experiencing negative emotions who received vitamin D supplements noticed an improvement in symptoms. Authors wrote that patients with major depressive disorder and individuals with vitamin D deficiency were most likely to benefit from supplementation.
Colorectal Cancer
Previous studies have suggested a link between vitamin D and colorectal cancer risk but were inconclusive, according to the American Cancer Society.
A 2018 study in the Journal of the National Cancer Institute by an international group of researchers from organizations including the American Cancer Society found that higher levels of vitamin D in the blood was associated with a lower risk for getting colorectal cancer.
Breast Cancer
Some evidence has suggested a link between higher levels of vitamin D and a lowered risk of breast cancer: One 2013 meta-analysis published in Medicine, for example, found that a small increase in vitamin D levels could reduce risk for postmenopausal women by 12%.
Other studies, on the other hand, have found that blood levels of vitamin D have no link with breast cancer. A randomized trial, the ongoing VITAL study, studies effects of higher doses of vitamin D on both heart disease and cancer. Findings released in a 2018 VITAL update noted that supplemental vitamin D did not reduce the occurrence of breast, prostate, or colorectal cancers.
A 2017 review in the journal Breast Cancer found that “most of the vitamin D studies support the inverse association between vitamin D level and breast cancer risk.” Authors wrote that the studies showed that vitamin D deficiency is associated with increased breast cancer risk. Nonetheless, they wrote there is an “urgent need for better designed and randomized clinical trials that will address the association of vitamin D level with breast cancer risk, breast cancer development, recurrence, and survival at different breast cancer stages.”
Pancreatic Cancer
People with the highest vitamin D levels were 35% less likely to develop pancreatic cancer than those with the lowest levels, according to a 20-year study of nearly 120,000 people conducted by researchers from Brigham and Women’s Hospital in Massachusetts. And in exciting news for this deadly form of cancer, researchers are currently studying how a modified form of vitamin D may help “deactivate” a certain type of cell that feeds pancreatic tumor growth, making tumors more vulnerable to treatment with chemotherapy.
Prostate Cancer
Low levels of vitamin D were associated with more advanced, aggressive prostate tumors in biopsy patients in a 2014 study in Clinical Cancer Research. Among African American men, low vitamin D was also associated with a higher risk of developing prostate cancer in the first place.
And a 2019 review of 22 studies published in Hormone and Metabolic Research found an association between vitamin D levels and PSA (PSA is a protein produced by both cancerous and noncancerous tissue in the prostate) levels in response to vitamin D supplementation—19% of those enrolled had at least a 50% reduction in PSA by the end of treatment. However, the review did not find differences in other outcomes, such as death or cancer growth. The authors wrote, “Although before-after studies showed that vitamin D increases the PSA response proportion, it does not seem that patients with prostate cancer benefit from high dose vitamin D supplementation and it should not be recommended for the treatment.”
Osteoporosis
Our bodies rely on vitamin D to help absorb calcium and grow bones that stay dense and strong throughout our lives. According to the National Library of Medicine, vitamin D deficiency can lead to a loss of bone density, which can contribute to osteoporosis and fractures (broken bones). In fact, approximately one in two women over age 50 will break a bone because of osteoporosis, according to the Bone Health and Osteoporosis Foundation.
Accordingly, the National Osteoporosis Foundation recommends an intake of 400 to 800 IU of vitamin D per day for adults under the age of 50, and 800 to 1,000 IU for those over the age of 50 (the risk of osteoporosis increases with age).
Rickets
Rickets, or the softening and weakening of bones in children, can be inherited from a parent or related to a prolonged vitamin D deficiency (this is called nutritional rickets), according to the American Academy of Family Physicians. Children who are 3 to 36 months old are at highest risk because their bones are growing so fast. In the late 19th century, doctors realized that vitamin-D-rich cod liver oil helped to prevent and treat rickets in children; manufacturers added vitamin D to milk for the first time in the 1930s, and rickets has since become rare in the United States, according to the American Academy of Pediatrics. When nutritional rickets is diagnosed, supplementation with calcium and vitamin D corrects most bone damage within a few months, sometimes within a few days. The American Academy of Pediatrics recommends that all infants, children, and adolescents receive a minimum daily intake of 400 IU of vitamin D.
Childhood Language Impairment
Women who had low levels of vitamin D at 18 weeks pregnancy had nearly double the risk of having a child with signs of language impairment at ages 5 and 10 compared to women with higher levels, according to a 2012 study published in Pediatrics. The results don’t prove that vitamin D causes those difficulties, but they do highlight its importance in fetal brain development; it’s possible that prenatal vitamin D supplementation may reduce the risk of developmental language problems in children. Medically reviewed by Jonathan Purtell, MS
This article was 1st seen in Health