Here’s a big list of studies about the effects of vitamin D deficiency:
Vitamin D Treatment Improves Levels of Sexual Hormones, Metabolic Parameters and Erectile Function in Middle-Aged Vitamin D Deficient Men (2017)
Conclusion: In a 12-month study of 102 vitamin D-deficient middle-aged men, monthly high-dose vitamin D therapy raised their testosterone levels, improved erectile function, and reduced body fat.
Plasma Vitamin D Deficiency Is Associated With Poor Sleep Quality and Night-Time Eating at Mid-Pregnancy in Singapore (2017)
Conclusion: A study of 1,152 pregnant women found that those who were vitamin D-deficient had higher incidences of poor sleep quality compared to women with sufficient vitamin D levels.
Association of Metabolic Syndrome and 25-Hydroxyvitamin D with Cognitive Impairment Among Elderly Koreans (2016)
Conclusion: In a study of 2,940 elderly Koreans, those suffering from cognitive impairment had lower vitamin D levels compared to those with higher vitamin D levels.
Effect of Vitamin D3 on Self-Perceived Fatigue: A Double-Blind Randomized Placebo-Controlled Trial (2016)
Conclusion: A study of 120 vitamin D-deficient adults complaining of fatigue were enrolled in a 4-week-long double-blind placebo-controlled trial where they were either given a single dose of 100,000 IU of vitamin D or a placebo. The vitamin D group reported experiencing significantly improved energy levels compared to the placebo group and more members of the vitamin D group reported being cured entirely of fatigue symptoms. The study also found that those who experienced the biggest increases in their vitamin D levels also experienced the biggest improvements in their fatigue symptoms.
Vitamin D Supplementation for Premenstrual Syndrome-Related Mood Disorders in Adolescents with Severe Hypovitaminosis D (2016)
Conclusion: In a randomized control trial involving 158 vitamin D-deficient teenage girls and young women, the girls given high doses of vitamin D adequate for correcting their deficiencies experienced significantly less severe PMS over the four-month period compared to the placebo group.
Relationship Between Plasma 25-Hydroxyvitamin D and Leucocyte Telomere Length by Sex and Race in a US Study (2016)
Conclusion: In a study of 1,154 older adults, vitamin D-deficient white people were found to have shorter telomeres.
Conclusion: A study of 200 female Iranian nurses found that the nurses with lower vitamin D levels had worse fatigue scores.
Conclusion: A 61-year-old man was seeking treatment for severe fatigue and daytime sleepiness. It was found that he had low vitamin D levels and he was subsequently put on a vitamin D supplementation program. After two weeks the patient report improved energy levels and after three months of Vitamin D supplementation he reported that his fatigue was completely cured.
Vitamin D and Actigraphic Sleep Outcomes in Older Community-Dwelling Men: The MrOS Sleep Study (2015)
Conclusion: In a study of 3,048 elderly men, those with lower vitamin D levels were found to have lower sleep quality compared to men with higher vitamin D levels.
Vitamin D is Significantly Associated with Total Testosterone and Sex Hormone-Binding Globulin in Malaysian Men (2015)
Conclusion: A study of Malaysian men found that those with lower vitamin D levels also had lower testosterone levels.
Serum 25-Hydroxyvitamin D and Cognitive Decline: A Longitudinal Study Among Non-Demented Older Adults (2014)
Conclusion: A multi-year study of 527 non-demented elderly people found that those with lower vitamin D levels also demonstrated worse cognitive function compared to those with higher vitamin D levels.
Note: This article provides a technical overview of the prevalence and health effects of vitamin D deficiency in adolescents world-wide.
Relationship Between 25-Hydroxyvitamin D and Cognitive Function in Older Adults: The Health, Aging and Body Composition Study (2014)
Conclusion: In a 4-year study of 2,777 elderly people found that those with lower vitamin D levels had worse cognitive function and experienced a greater decline in cognitive function over the 4 years compared to those with higher vitamin D levels.
Suicidal Patients are Deficient in Vitamin D, Associated with a Pro-Inflammatory Status in the Blood (2014)
Conclusion: 59 suicide attempters were enrolled in a study and tested for their vitamin D status along with non-suicidal depressed people and non-depressed healthy control subjects. 58% of the suicide attempters were clinically deficient in vitamin D and had lower levels than than the non-suicidal depressed subjects and non-depressed, healthy control subjects.
Conclusion: In an 8-year study of 1,658 elderly people, there was an increased rate of alzheimer’s disease and dementia among those with lower vitamin D levels compared to those with higher vitamin D levels.
Serum 25-Hydroxyvitamin D Concentrations and Depressive Symptoms Among Young Adult Men and Women (2014)
Conclusion: A study of 615 young adults found that those with lower vitamin D levels had worse depression scores.
Conclusion: In an 8-year study of 1,658 elderly people, there was an increased rate of alzheimer’s disease and dementia among those with lower vitamin D levels compared to those with higher vitamin D levels.
Serum Vitamin D Profile In Black African Men with Prostate Cancer at Tertiary Referral Facility in Sub-Saharan Africa (2014)
Conclusion: The vitamin D blood levels of 162 black African prostate cancer patients were analyzed. 88.9% of them were vitamin D-deficient.
Conclusion: 207 mother-infant pairs were evaluated for vitamin D levels and dental caries in the children. The mothers had their vitamin D levels tested during pregnancy and then the infants were evaluated 1-2 years later on. The vitamin D levels of the expecting mothers were very bad with 90% having levels below the recommended minimum, 32% of them having levels below 14 ng/ml, and only 12% having levels above 30 ng/ml. The mothers who were tested during winter had much lower levels than the mothers who were tested during summer. Enamel hypoplasia was found in 22% of the infants and 36% were found to have dental caries (which correlates closely with the percentage of mothers badly deficient in vitamin D). Mothers of infants with dental caries had much lower prenatal vitamin D levels.
Influence of Vitamin D Status on Respiratory Infection Incidence and Immune Function During 4 Months of Winter Training in Endurance Sport Athletes (2013)
Conclusion: In a 4-month winter study of 225 endurance athletes it was found that those with the lowest vitamin D levels suffered more upper respiratory tract infections compared to those with optimal vitamin D levels. Athletes with good vitamin D levels who did get sick also tended to recover faster than the deficient athletes.
Conclusion: 144 Canadian children with severe cases of dental cavities had their vitamin D levels tested and compared to 122 age-matched cavity-free control children. Children with dental cavities had “significantly lower” vitamin D levels compared to the cavity-free children. 86% of the children who took a vitamin D supplement belonged to the cavity-free group. Children with sub-optimal vitamin D levels were found to be twice as likely to have dental cavities.
Note: This article covers many studies providing strong evidence that a lack of UVB exposure / vitamin D is strongly associated with colon cancer, rectal cancer, breast cancer, gastric cancer, non-Hodgkin’s lymphoma, Hodgkin’s lymphoma, bladder cancer, ovarian cancer, pancreatic cancer, esophageal cancer, lung cancer, cervical cancer, renal cancer, vulvar cancer, gallbladder cancer, brain cancer, multiple myeloma, leukemia, prostate cancer, laryngeal cancer, thyroid cancer, melanoma, and pharyngeal cancer.
Conclusion: A study of 3,051 European men over the age of 40 from eight different locations found that testosterone levels were lower among the vitamin D-deficient men.
Effects of 25OHD Concentrations on Chances of Pregnancy and Pregnancy Outcomes: A Cohort Study in Healthy Danish Women (2012)
Conclusion: A study of 153 women trying to get pregnant found that those with lower vitamin D levels had a higher risk of miscarriage.
Conclusion: 995 esophageal cancer patients in Australia were analyzed along with 1471 population controls. The cancer patients reported having less sun exposure over their lifetimes and tended to live in less sunny areas than the controls.
Conclusion: 1,500 ovarian cancer patients and 1,459 healthy female controls in Australia were analyzed. The top third of all the women who reported having the most sun exposure over their lifetimes and who lived in the sunnier areas of Australia had the lowest risk for ovarian cancer. Those in the bottom third for lifetime sun exposure had the highest risk for ovarian cancer. “Women who spent their lives in areas with higher levels of ambient UVR [ultraviolet radiation] had a lower risk of developing epithelial ovarian cancer than those living in areas with lower levels of ambient UVR.”
Vitamin D and Cancer (2012)
Conclusion: “In clinical studies, an impact of vitamin D has been reported in different types of cancer. A low vitamin D activity is associated with an increased cancer risk and a more aggressive tumor growth, while high activity of this pathway induces antitumoral effects. In particular, serum circulating levels of 25(OH)D levels <20 ng/ml seems to expose to the risk of developing mammary and colorectal cancer.”
Conclusion: A study of 3,325 elderly Americans found that those with lower vitamin D levels performed worse on cognitive tests compared to those with higher vitamin D levels.
Conclusion: 237 children had their BMI and vitamin D levels measured. 98% of the black and 90% of the white kids had low vitamin D levels.The study also found that the FATTER kids had lower vitamin D levels than leaner kids. Vitamin D-deficiency is known to be both a contributing factor TO and a symptom OF obesity. Vitamin D levels rose slightly in the summer.
Conclusion: In a year-long study of 41 NCAA division 1 athletes, it was found that those with lower vitamin D levels suffered more illnesses compared to athletes with higher vitamin D levels.
Prevalence of Serum Vitamin D Deficiency and Insufficiency in Cancer: Review of the Epidemiological Literature (2011)
Conclusion: “This review confirms a high prevalence of vitamin D deficiency in multiple cancer sites.”
Conclusion: A study of 340 black adults with type-2 diabetes found that those with the highest percentage of body fat also had the lowest vitamin D levels and the highest amount of carotid artery and aorta plaque. There is a correlation between high body fat and low vitamin D levels and a correlation between low vitamin D levels and increased risk for atherosclerosis.
A 16-Week Randomized Clinical Trial of 2000 International Units Daily Vitamin D3 Supplementation in Black Youth: 25-Hydroxyvitamin D, Adiposity, and Arterial Stiffness (2010)
Conclusion: A 4-month study of 44 black teenagers found that 95% had low vitamin D levels and that supplementing with 2,000 IU of vitamin D daily was effective for reducing arterial stiffness and increasing vitamin D levels. The study also found that the vitamin D levels of the obese subjects rose less than the leaner subjects. Although 2,000 IU daily was effective in raising levels, only 56% achieved sufficient levels after the four months.
Increased UVA Exposures and Decreased Cutaneous Vitamin D3 Levels May Be Responsible for the Increasing Incidence of Melanoma (2009)
Conclusion: Low vitamin D levels resulting from a lack of direct, midday sun exposure increase the risk of developing melanoma skin cancer
Prevalence and Associations of 25-Hydroxyvitamin D Deficiency in US Children: NHANES 2001-2004 (2009)
Conclusion: A 3-year study of 9,757 U.S. children and young people found that: 61% had low vitamin D levels, those who spent more time watching/using TVs and computers had lower vitamin D levels, obese children had lower vitamin D levels, and those with lower vitamin D levels had higher blood pressure.
Conclusion: A study of 3,577 U.S. adolescents found that those with higher vitamin D levels had lower blood pressure compared to those with lower vitamin D levels.
Maternal Vitamin D Deficiency Is Associated with Bacterial Vaginosis in the First Trimester of Pregnancy (2009)
Conclusion: In a prospective study involving 469 pregnant women, those who were vitamin D deficient had more than double the rates of bacterial vaginosis compared to the women with adequate vitamin D levels.
Conclusion: 253 women who had recently given birth were analyzed. Those with lower vitamin D levels had a higher rate of cesarean sections compared to mothers with higher vitamin D levels. “Vitamin D deficiency was associated with increased odds of primary cesarean section.”
Conclusion: A 10-year study of 18,225 men found that those with low and intermediate levels of vitamin D were at an elevated risk for heart attacks. Those who had heart problems had lower vitamin D levels.
Independent Association of Low Serum 25-Hydroxyvitamin D and 1,25-Dihydroxyvitamin D Levels with All-Cause and Cardiovascular Mortality (2008)
Conclusion: In an 8-year study of 3,258 elderly people, those with the lowest vitamin D levels had the highest mortality rate, with the majority of deaths resulting from cardiovascular causes.
Serum 25-Hydroxyvitamin D Levels and the Prevalence of Peripheral Arterial Disease: Results from NHANES 2001 to 2004 (2008)
Conclusion: A study of 4,839 adults found that those with lower vitamin D levels had higher rates of peripheral arterial disease.
Prevalence of Cardiovascular Risk Factors and the Serum Levels of 25-Hydroxyvitamin D in the United States: Data from the Third National Health and Nutrition Examination Survey (2007)
Conclusion: A study of 15,000 adults found that those with high blood pressure had lower vitamin D levels.
Conclusion: In a study of 275 pregnant women, mothers with lower vitamin D levels were much more likely to develop preeclampsia and, in addition to many other potential health problems arising from preeclampsia, newborns from preeclamptic mothers tended to have insufficient vitamin D levels.
Conclusion: “Our prospective analysis suggests that lower plasma 25(OH)D levels are associated with a higher risk of incident hypertension.”
Serum 25-Hydroxyvitamin D, Ethnicity, and Blood Pressure in the Third National Health and Nutrition Examination Survey (2007)
Conclusion: A study of 12,644 adults found that those with lower vitamin D levels had higher blood pressure compared to those with higher vitamin D levels.
Maternal Intake of Vitamin D During Pregnancy and Risk of Recurrent Wheeze in Children At 3 y of Age (2007)
Conclusion: 1194 mother-child pairs in Massachusetts were analyzed. It was found three years later that the children from mothers with the highest vitamin D intake during pregnancy had the lowest risk of developing a recurrent wheeze.
Vitamin D Deficiency is Associated with Low Mood and Worse Cognitive Performance in Older Adults (2006)
Conclusion: A study of 80 older adults found that 58% had inadequate vitamin D levels and those with lower levels had worse scores on depression and cognitive function tests.
Estimation of Optimal Serum Concentrations of 25-Hydroxyvitamin D For Multiple Health Outcomes (2006)
Conclusion: People with lower vitamin D levels have a higher risk of developing colorectal cancer.
Vitamin D Status Among Patients with Hip Fracture and Elderly Control Subjects in Yekaterinburg, Russia (2006)
Conclusion: 63 elderly people with hip fractures were analyzed. They had lower average vitamin D levels and vitamin D deficiencies were more common in comparison to a control group of independently living elderly people.
Serum 25-hydroxyvitamin D concentrations in girls aged 4–8 y living in the southeastern United States (2006)
Conclusion: This study of 168 young girls living in the southeastern U.S. found that those with lower vitamin D levels had a lower bone mineral content, white girls have higher vitamin D levels than black girls (due to the increased melanin preventing vitamin D synthesis), their vitamin D levels dropped in the winter, and their levels increased in the summer. These girls also were found to have higher vitamin D levels compared to girls living at higher latitudes. Despite the black girls having lower pre-vitamin D levels, they had a higher bone density than the white girls. This adds support to findings of people of darker-skinned races possibly have differing vitamin D endocrine systems.
Note: This is an in-depth article from world-leading vitamin D expert Michael Holick on the international prevalence of vitamin D deficiency, its causes (lack of afternoon sun exposure, overuse of sunscreen, increased body fat, people living far away from the equator, ignorance of the importance of sun exposure and vitamin D for health, misinformation about the proper dosage for vitamin D supplementation, increased skin pigmentation, and a decrease in the capacity to cutaneously synthesize vitamin D as we age), and the short and long-term negative health consequences of vitamin D deficiency (increased cancer risk, increased autoimmune disorder risk, increased skeletal disease and fracture risk, increased risk of devastating falls in the elderly, increased risk of cardiovascular disease, and decreased neuromuscular function).
Conclusion: A study of 44 elderly first-time stroke victims found that 77% of the stroke victims had low vitamin D levels and lower vitamin D levels compared to healthy elderly subjects.
Prevalence of Vitamin D Deficiency in Patients Attending an Outpatient Cancer Care Clinic in Boston (2004)
Conclusion: This study compared the vitamin D blood levels of 56 middle-aged Boston cancer patients and 50 age-matched health control. 48% of the cancer patients were clinically deficient in vitamin D versus only 12% of the healthy controls. More alarming was that those who were deficient were deficient during summer when people’s vitamin D levels tend to be the highest.
Conclusion: Older women with lower vitamin D levels have a higher colorectal cancer risk.
Prevalence of Severe Hypovitaminosis D in Patients With Persistent, Nonspecific Musculoskeletal Pain (2003)
Conclusion: Of 150 patients seeking treatment for chronic musculoskeletal pain, 93% were found to be vitamin D-deficient.
Conclusion: A study of 54 congestive heart failure patients found that the patients had lower vitamin D levels compared to control subjects.
Low Vitamin D and High Parathyroid Hormone Levels as Determinants of Loss of Muscle Strength and Muscle Mass (Sarcopenia): The Longitudinal Aging Study Amsterdam (2003)
Conclusion: In a three-year study of 1,008 elderly people, those with lower vitamin D levels demonstrated weaker grip strength and lower muscle mass compared to those with higher vitamin D levels.
Calcium, Vitamin D, Milk Consumption, and Hip Fractures: A Prospective Study Among Postmenopausal Women (2003)
Conclusion: “An adequate vitamin D intake is associated with a lower risk of osteoporotic hip fractures in postmenopausal women.”
Conclusion: Vitamin D deficiency during pregnancy causes alterations in the brain development of rat pups.
The Effect of Vitamin D3 on Insulin Secretion and Peripheral Insulin Sensitivity in Type 2 Diabetic Patients (2003)
Conclusion: In a control trial experiment involving ten vitamin D-deficient type-2 diabetic women and 17 same-age, same-weight, non-diabetic females, taking just 1300 IU of vitamin D daily was found to be effective for increasing vitamin D levels by 75% and decreasing insulin resistance by 21%. “ We suggest vitamin D3 deficiency may at least partly contribute to the impairment of insulin secretion and probably of insulin action. Our results suggest that vitamin D3 supplementation could be an element in the complex treatment of type 2 diabetes.”
Vitamin D Deficiency and Secondary Hyperparathyroidism Are Common Complications in Patients with Peripheral Arterial Disease (2002)
Conclusion: A study of 161 patients with peripheral arterial disease found that they had significantly lower vitamin D levels compared to healthy controls.
Conclusion: Vitamin D levels, arm strength, and leg strength were tested in 269 elderly people over a 6-month period. Women with low vitamin D levels were found to have significantly weaker arm and leg strength.
Neuromuscular and Psychomotor Function in Elderly Subjects who Fall and the Relationship with Vitamin D Status (2002)
Conclusion: Vitamin D-deficient elderly people were found to have “slower functional performance, weaker quadriceps, slower reaction times, and worse stability” compared to those with higher levels.
Conclusion: “Low vitamin D levels were associated with a 5-fold increased risk for progression to tuberculosis” in a study of Pakistan tuberculosis cases.
Effects of a Short-Term Vitamin D(3) and Calcium Supplementation on Blood Pressure and Parathyroid Hormone Levels in Elderly Women (2001)
Conclusion: A study of 148 vitamin D-deficient elderly women found that supplementing with 1200mg of calcium and 800 IU of vitamin D daily was effective for measurably lowering blood pressure.
Vitamin D Status, Trunk Muscle Strength, Body Sway, Falls, and Fractures Among 237 Postmenopausal Women with Osteoporosis (2001)
Conclusion: Among osteoporotic postmenopausal women, those with lower vitamin D levels have an increased risk of falling and suffering fall-related fractures.
Conclusion: Tuberculosis rates were higher among people with lower vitamin D levels in this study.
Conclusion: Men with lower vitamin D levels have an increased risk of developing prostate cancer.
Conclusion: Osteomalacia patients experienced improved physical performance following three months of vitamin D treatment. Another study was performed on 55 vitamin D-deficient veiled Arab women living in Denmark who were experiencing reduced muscle function due to hypovitaminosis D myopathy. They were put on high-dose vitamin D treatment for 6 months and showed improved muscle function after 3 months and 6 months compared to a control group.
Conclusion: This documents five case studies where patients with severe myopathy (reduced muscle function) bad enough to need wheelchairs were found to have low vitamin D levels. After undergoing 4-6 weeks of high-dose vitamin D therapy, four of the five patients achieved full mobility and muscle strength restoration, with the fifth also enjoying improved mobility.
Vitamin D is Related to Blood Pressure and Other Cardiovascular Risk Factors in Middle-Aged Men (1995)
Conclusion: A study of 34 middle-aged men found that those with higher vitamin D levels had lower blood pressure.
Maternal Consumption of a Low Vitamin D Diet Retards Metabolic and Contractile Development in the Neonatal Rat Heart (1995)
Conclusion: In a randomized control trial with rats, low maternal intake of vitamin D resulted in offspring with smaller hearts compared to offspring from mothers with higher vitamin D intake.
Conclusion: Lower vertebral bone mass is correlated with low vitamin D levels in postmenopausal women.