Here’s a big list of studies about vitamin D and child development:

Linking Vitamin D Status, Executive Functioning and Self-Perceived Mental Health in Adolescents Through Multivariate Analysis: A Randomized Double-Blind Placebo Control Trial (2017)

Conclusion: A randomized double-blind placebo-controlled trial involving 50 Norwegian adolescents found that those given vitamin D supplements performed better on cognitive tests compared to the placebo group.


Diet, Sunlight, and 25-Hydroxy Vitamin D in Healthy Children and Adults. (2017)

Conclusion: 1970’s study of 110 white, British school children found that their vitamin D levels peaked at the end of summer, hit their nadir at the end of winter, and children who went on summer beach vacations had higher vitamin D levels months after.


Vitamin D and Dental Caries in Children (2015)

Conclusion: Vitamin D levels and dental caries history were measured in 1,017 Canadian children. “ Our findings suggest that optimal vitamin D concentrations (≥75 nmol/L) are associated with a 39% lower odds for dental caries and overall caries experienced in young school-aged children.” (Editor note: many vitamin D researchers now consider 75 nmol/L to be inadequate.)


Vitamin D Deficiency in Adolescents (2014)

Note: This article provides a technical overview of the prevalence and health effects of vitamin D deficiency in adolescents world-wide.


Prenatal Vitamin D and Dental Caries in Infants (2014)

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.


Vitamin D in Fetal Development: Findings From a Birth Cohort Study (2014)

Conclusion: This study examined 901 mother-child pairs to see what relationship existed between the mother’s vitamin D levels 18 weeks into a pregnancy and the health of the child later in life. The researchers found that maternal vitamin D-deficiency was “associated with impaired lung development in 6-year-old offspring, neurocognitive difficulties at age 10, increased risk of eating disorders in adolescence, and lower peak bone mass at 20 years.” The study also found associations between maternal vitamin D-deficiency and speech problems and autistic behavior later in life for the child.


Maternal Vitamin D Status and Infant Outcomes in Rural Vietnam: A Prospective Cohort Study (2014)

Conclusion: This study measured the vitamin D levels of 960 pregnant Vietnamese women at 8-months into their pregnancies, then six months later the cognitive, motor, and speech development of the babies was examined. Babies born from vitamin D-deficient mothers had reduced language development compared to babies born from mothers with higher vitamin D levels during pregnancy.


Vitamin D Status of Children with Severe Early Childhood Caries: A Case–Control Study (2013)

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.


Ultraviolet Sunlight Exposure During Adolescence and Adulthood and Breast Cancer Risk: A Population-based Case-Control Study Among Ontario Women (2011)

Conclusion: 3,101 breast cancer patients and 3,471 healthy, age-matched controls in Canada were evaluated for lifetime sun exposure habits and time spent outdoors. Researchers found that women who reported more lifetime sun exposure (21+ hours outside per week versus less than 6 hours per week) enjoyed a lower risk of breast cancer and that even increased sun exposure in adolescence alone carried a protective effect into adulthood, even if sun exposure decreased with age.


A Cross-Sectional Study of Vitamin D and Insulin Resistance in Children (2011)

Conclusion: A study of 85 Philadelphia children found that those with lower vitamin D levels have worse insulin resistance.


Vitamin D Status, Adiposity, and Lipids in Black American and Caucasian Children (2011)

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.


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.


Vitamin D Status and Muscle Function in Post-Menarchal Adolescent Girls (2009)

Conclusion: Adolescent girls with higher vitamin D levels are able to jump faster and higher compared to girls with lower vitamin D levels.


Low Vitamin D Status Has an Adverse Influence on Bone Mass, Bone Turnover, and Muscle Strength in Chinese Adolescent Girls (2009)

Conclusion: In a study of 301 young Chinese girls, those with the higher vitamin D levels demonstrated superior handgrip strength and had higher bone mass.


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.


Significant Vitamin D Deficiency In Youth With Type 1 Diabetes Mellitus (2009)

Note: Article covering a variety of studies documenting that kids with type-1 diabetes have much higher rates of vitamin D deficiency compared to non-diabetic kids.

Vitamin D Deficiency in a Healthy Group of Mothers and Newborn Infants (2007)

Conclusion: 40 mother-baby pairs were tested for vitamin D deficiency. 50% of the mothers and 65% of the babies were deficient. There is a strong correlation between maternal vitamin D levels and vitamin D levels of newborn infants.


High Prevalence of Vitamin D Insufficiency in Black and White Pregnant Women Residing in the Northern United States and Their Neonates (2007)

Conclusion: A study of pregnant women in Pittsburgh found that roughly 50% of them, and later their babies, were vitamin D insufficient.


Vitamin D Status and Parathyroid Hormone in Obese Children Before and After Weight Loss (2007)

Conclusion: Obese children were found to have lower vitamin D levels than non-obese children. In the obese children, losing weight resulted in an increase of their 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 recurrent wheezing.


A Prospective Analysis of Plasma 25-Hydroxyvitamin D Concentrations in White and Black Prepubertal Females in the Southeastern United States (2007)

Conclusion: This study of the vitamin D levels of young girls living in the southeastern U.S. found that 75% had levels below 32 ng/ml (experts recommend maintaining 50 ng/ml), 18% had levels below 20 ng/ml, the white girls had higher vitamin D levels than the black girls, and vitamin D levels fluctuate with the seasons. The study also found that younger girls have higher vitamin D levels than older girls, which may be due to the increased ability of younger people to cutaneously synthesize vitamin D.


Maternal Vitamin D Intake During Pregnancy and Early Childhood Wheezing (2007)

Conclusion: 2000 healthy pregnant women were enrolled in this study examining the effect of maternal vitamin D levels on the respiratory health of the child five years later. When the children were followed up with 5 years later, those born from mothers who had higher vitamin D levels during pregnancy were and had been suffering fewer wheezing and asthma symptoms compared to children born from mothers with lower vitamin D levels during pregnancy. “In summary, we report an inverse association between maternal vitamin D intake in pregnancy and risk of recurrent wheezing in 5-y-old children.”


Vitamin D From Dietary Intake and Sunlight Exposure and the Risk of Hormone-Receptor-Defined Breast Cancer (2007)

Conclusion: Canada study where researchers compared vitamin D intake and lifetime sun exposure habits between 759 breast cancer patients and 1,135 healthy, matched controls. The study found that women with a higher vitamin D intake and increased lifetime sun exposure enjoy a significantly lower risk of estrogen-receptor positive and progesterone-receptor positive breast cancers, and a slightly lower risk for estrogen and progesterone negative breast cancers. For sun exposure specifically, they found that increased frequency of outdoor activities and ever having an outdoor job between the ages of 10 and 29 was associated with lower breast cancer risk, suggesting that breast cancer could possibly be due to developmental defects caused by early life vitamin D deficiency. The study also found that women who reported exposing more naked skin to the sun enjoyed a lower breast cancer risk. Early life sunburns, while not good for skin cancer risk, are actually associated with lower breast cancer risk.


Effect of Vitamin D Replacement on Musculoskeletal Parameters in School Children: A Randomized Controlled Trial (2006)

Conclusion: For a one-year period, 179 girls ages 10-17 were given either a weekly placebo, low dose of vitamin D, or higher dose of vitamin D. After one year the girls given the higher dose of vitamin D showed the biggest increase in lean muscle mass and bone density, especially among the younger girls.


Prospective Study Of Maternal Intake Of Vitamin D During Pregnancy And Risk Of Wheezing Illnesses In Children At Age 2 Years (2006)

Conclusion: 1,306 mother-child pairs were analyzed and it was found that higher “maternal vitamin D intake was associated with lower childhood risks of any wheeze” or asthmatic symptoms in their child by age two.


Vitamin D Deficiency in Breastfed Infants in Iowa (2006)

Conclusion: 78% of unsupplemented babies in the study became vitamin D deficient during winter.


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.


Adolescent Girls in Maine Are At Risk for Vitamin D Insufficiency (2005)

Conclusion: Vitamin D deficiency was observed in 11 out of 23 young Maine girls who were part of a six-month study. The study also found that the mean vitamin D level dropped 28% during winter.


Vitamin D Deficiency and Whole-Body and Femur Bone Mass Relative to Weight in Healthy Newborns (2005)

Conclusion: In a study of 50 healthy mothers and their newborns, nearly half were classified as being vitamin D-deficient and newborns with lower vitamin D levels also were found to have lower bone density.


Incidental Finding of Vitamin-D Deficient Rickets in an Otherwise Healthy Infant: A Reappraisal of Current Vitamin-D Supplementation Guidelines (2005)

Conclusion: Most babies require vitamin D-supplementation. However, the dose recommended in this article has long since been found to be inadequate.


Vitamin D Requirements During Lactation: High-Dose Maternal Supplementation as Therapy to Prevent Hypovitaminosis D for Both the Mother and the Nursing Infant (2004)

Conclusion: This randomized control trial found that breastfeeding mothers need at least 4,000 IU of vitamin D daily to ensure their breastfeeding infants are getting enough vitamin D.


Assessment of Dietary Vitamin D Requirements During Pregnancy and Lactation (2004)

Conclusion: Vitamin D-deficient mothers have vitamin D-deficient breast milk, putting their newborns at a high risk of vitamin D deficiency.


Prevalence of vitamin D deficiency among healthy adolescents (2004)

Conclusion: In a study of 307 Boston teenagers, it was found that 42% had vitamin D blood levels 20 ng/ml or below, 24% had levels of 15 ng/ml or below, and 4.6% were severely deficient with levels of 8 ng/ml or below. The study also found vitamin D levels to be 24% lower in the winter compared to summer.


Nutritional Rickets Among Children in the United States: Review of Cases Reported Between 1986 and 2003 (2004)

Conclusion: This meta-analysis of 22 studies on the prevalence of rickets in American children found that 83% of kids with rickets were black and over 90% were breastfed without any supplementary vitamin D source. People with darker skin types, especially those residing in more northern latitudes, are almost universally are found to have the lowest vitamin D levels and make up a disproportionately higher amount of vitamin D-deficiency diseases and symptoms due to their high melanin content acting as a natural sunscreen blocking the UVB necessary for vitamin D production.This analysis also found that most of the rickets cases were diagnosed in the winter and spring, when population vitamin D levels are the lowest. Five of the studies analyzed that reported cases of white children developing rickets were all from extreme northern states Washington, Minnesota, New York, Connecticut, and New Hampshire, where it is physically impossible for anyone to synthesize vitamin D from sunlight for roughly half of the entire year from autumn to spring.


A Systematic Review and Meta-Analysis of Northern Hemisphere Season of Birth Studies in Schizophrenia (2003)

Conclusion: Schizophrenics tend to be born more in winter and spring compared to other seasons, when vitamin D-creating UVB radiation is less available. They also tend to be born more in latitudes farther away from the equator, which get less UVB radiation.


Low Maternal Vitamin D as a Risk Factor for Schizophrenia: A Pilot Study Using Banked Sera (2003)

Conclusion: “Low levels of maternal vitamin D may be associated with an increased risk of schizophrenia.”


Association of Low 25-Hydroxyvitamin D Concentrations with Elevated Parathyroid Hormone Concentrations and Low Cortical Bone Density in Early Pubertal and Prepubertal Finnish Girls (2003)

Conclusion: A study of 193 young Finnish girls found that those with vitamin D-deficiency had lower bone density.


Vitamin D and Attainment of Peak Bone Mass Among Peripubertal Finnish Girls: A 3-y Prospective Study (2002)

Conclusion: A 3-year study of 171 young, healthy Finnish girls found that the girls with lower vitamin D levels also had weaker bones.


Effects of Vitamin D Metabolites on Intestinal Calcium Absorption and Bone Turnover in Elderly Women (2002)

Conclusion: A study of vitamin D and bone mineral density levels in young Finnish girls found that those with lower vitamin D levels also had lower bone density.


Wintertime Vitamin D Deficiency in Male Adolescents: Effect on Parathyroid Function and Response to Vitamin D3 Supplements (2001)

Conclusion: A study of French male teenagers found that the majority of the test subjects were very deficient in vitamin D.


Nutritional Rickets in African American Breast-Fed Infants (2000)

Conclusion: 30 cases of infant and childhood nutritional rickets in North Carolina were analyzed. 100% of the patients were dark-skinned, had been breast-fed an average of 12 months, and did not receive vitamin D supplements prior to their rickets diagnoses. Dark-skinned people tend to have disproportionately lower vitamin D levels due to the melanin in their skin blocking UVB solar radiation necessary for vitamin D synthesis. Babies who are breastfed by vitamin D-deficient mothers without receiving vitamin D supplements tend to develop even more severe vitamin D deficiencies than their mothers.


Use of Cod Liver Oil During Pregnancy Associated with Lower Risk of Type 1 Diabetes in the Offspring (2000)

Conclusion: Norway study examining 85 type-1 diabetic subjects and 1,071 non-diabetic controls found that mothers supplementing with dietary vitamin D during pregnancy resulted in their offspring enjoying a lower risk for developing type-1 diabetes.


Vitamin D Intake is Low and Hypovitaminosis D Common in Healthy 9- to 15-Year-Old Finnish Girls (1999)

Conclusion: This one-year study followed 186 young caucasian Finnish girls aged 9-15, tracking their dietary habits, physical activity habits, measured their vitamin D levels multiples times throughout the year, and tested the effectiveness of supplementing with 400 IU of vitamin D daily for preventing deficiency. The vitamin D level of the group at the beginning of the study in winter was a horribly low 13.5 ng/ml.The group vitamin D level rose significantly during summer to 25 ng/ml, which is still inadequate (and in spite of taking 400 IU per day). At the 12-month testing in the next winter, after taking 400 IU of vitamin D most days, the vitamin D level of the group had barely increased and was still at the deficient level. The findings of this study are: vitamin D levels rise in the summer, vitamin D levels fall in the winter, and not only is 400 IU of vitamin D incapable of preventing vitamin D-deficiency in young girls, this dose barely increases vitamin D levels in young girls at all. Also, even during summer they failed to achieve adequate vitamin D levels. This is probably due to Finland’s very high latitude.


Height Depends on Month of Birth (1998)

Conclusion: This study found a correlation between the height people reach by the age of 18 and their birth month. Might this have something to do with the seasonal availability of  solar-generated vitamin D during fetal development, infancy, or early childhood?


Mild Mental Retardation in Black and White Children in Metropolitan Atlanta: A Case-Control Study (1995)

Conclusion: This study of 893 children in Atlanta, Georgia, U.S. (330 mildly retarded kids and 563 normal controls) found that the rate of mental retardation in black children is nearly double that of white children. Although this study did not explore vitamin D as a factor, it is proven and well-documented that vitamin D is a crucial factor in brain development in utero and during childhood and there is also an overwhelming amount of evidence that blacks disproportionately suffer from vitamin D-deficiency and vitamin D-deficiency-related diseases and disorders due to the high amount of melanin in their skin partially or totally preventing cutaneous vitamin D synthesis from sunlight. It is also well-documented that people with mental disabilities and mental disorders tend to have lower vitamin D levels or have been born from and breastfed by mothers with poor vitamin D levels, and that vitamin D plays a very large role in producing optimal cognitive performance throughout life.
Also see: Health Studies Regarding Skin Color, Vitamin D, and Racial Health Disparities


Seasonality of Hip Fracture and Haemorrhagic Diseases of the Newborn (1993)

Conclusion: Hip fracture rates for newborns reach their peak January-February and occur least July-August. These rates are in correlation with seasonal vitamin D level changes. Adequate vitamin D is essential for bone strength.


Vitamin D Deficiency, Hypocalcemia, and Increased Skeletal Muscle Degradation in Rats. (1983)

Conclusion: This study took two groups of rat pups and raised one on a vitamin D-deficient diet and raised the other group on a vitamin D-supplemented diet. The pups raised on the vitamin D-deficient diet gained weight at a significantly lower rate compared to the supplemented group and had lower muscle mass.The vitamin D-deficient group eventually developed hypocalcemia, at which point their growth rate declined even more. Later, the vitamin D-deficient rats were given vitamin D, leading to an increase in muscle mass and weight gain.


Mean Annual Hours of Sunshine and the Incidence of Dental Caries (1939)

Conclusion: This study measured the dental cavity incidence among 94,337 white pre-teen boys through the United States. Boys living in the sunniest areas of America had the fewest cases of dental decay and boys living in the least sunny areas of America had the highest rate of dental decay. Boys living in very sunny areas such as San Diego, California had half the dental decay rates of boys living in the least sunny areas like Portland, Oregon.


The Influence of a Cereal-Free Diet Rich in Vitamin D and Calcium on Dental Caries in Children (1932)

Note: This article covers multiple studies that have found children who get more vitamin D have healthier teeth.


Sunlight for Babies – U.S. Department of Labor, Children’s Bureau (1931)

Note: Great article guide from 1931 on the importance of sensible sunbathing for babies.


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