Studies about worldwide, pandemic vitamin D deficiency:
A Randomized Controlled Trial of Vitamin D Supplementation on Perinatal Depression: In Iranian Pregnant Mothers (2016)
Conclusion: This randomized control trial study split 169 pregnant Iranian women in their third trimester into two groups. One group received a placebo, the other received 2,000 IU of vitamin D3 daily for the duration of their pregnancy. Compared to the placebo group, the mothers receiving vitamin D had higher vitamin D levels and lower depression scores during the last month of pregnancy and the two months after childbirth. “The present trial showed that consuming 2000 IU vitamin D3 daily during late pregnancy was effective in decreasing perinatal depression levels.” Alarmingly, this study also found that 72% of the mothers were suffering from vitamin D-deficiency at baseline.
Note: much research has shown that 2,000 IU of vitamin D3 is inadequate for adults who don’t get much unprotected sun exposure. One wonders how much better the depression scores would have been with 5,000 IU of vitamin D daily.
Conclusion: A study of 2,313 athletes all over the world found that 56% of them had low vitamin D levels. Indoor sports athletes had worse levels than outdoor sports athletes.
Role of Vitamin D Deficiency and Lack of Sun Exposure in the Incidence of Premenopausal Breast Cancer: A Case Control Study in Sabzevar, Iran (2014)
Conclusion: Sun exposure habits and vitamin D levels were evaluated and compared in 60 premenopausal breast cancer patients and 116 matched, healthy controls in northern Iran. Researchers found that 95% of women in both groups were vitamin D-deficient, but women who reported ever consuming any vitamin D supplements were less likely to develop breast cancer. 98% of the women reported receiving ZERO sun exposure due to how Iranian women dress, which has them completely covered up all the time. Iranian women are also known to start developing breast cancer a decade earlier compared to women in other countries. Could their sun-starved way of dressing be killing them?
Conclusion: A meta-analysis of 195 different population vitamin D status studies involving 168,000 participants from 44 different countries found that 88% had inadequate levels.
Note: This article provides a technical overview of the prevalence and health effects of vitamin D deficiency in adolescents world-wide.
Assessment of Vitamin D Concentration in Non-Supplemented Professional Athletes and Healthy Adults During the Winter Months in the UK: Implications for Skeletal Muscle Function (2012)
Conclusion: A study of athletes in the UK found that 62% had low vitamin D levels. 8 weeks of ingesting 5,000 IU of vitamin D daily significantly improved sprinting and vertical jump performance compared to the placebo group.
Seasonal Variation in Vitamin D Status in Professional Soccer Players of the English Premier League (2012)
Conclusion: A study of English soccer players found that their vitamin D levels dropped during Fall and Winter.
Conclusion: This study of 19 endurance runners living in Baton Rouge, Louisiana found that despite being outdoor athletes training in the lower latitude southeastern U.S., 42% of them had inadequate vitamin D levels below 32 ng/ml. You can train outdoors all you want, but if you’re using sun protection (sunscreen and clothes) and running in the mornings or evenings (when there is no UVB available to make vitamin D), you can still end up suffering from low vitamin D levels.
“Since the quantity of UV-B photons in midday sunlight is sufficient to stimulate endogenous vitamin D synthesis throughout the year in the southern part of the United States (latitudes <35°), insufficient status in our runners was most likely explained by training time in relation to peak sun exposure. Most likely our athletes – similar to the aforementioned middle eastern sportsmen – avoided training near solar noon and trained in the early morning or early evening when vitamin D is not likely to be synthesized even at latitudes close to the equator. It is also possible that our group of runners were habitual sunscreen users, which is known to inhibit endogenous vitamin D synthesis.”
Conclusion: This study analyzed the vitamin D levels of 1,111 healthy people in Isfahan, Iran. 50.8% were deficient, with 26.9% being severely deficient. Women were especially found to have low vitamin D levels due to the increased amount of clothing they’re required to wear under Islamic law. “Exposure to sun is limited due to the type of clothing required by current law.”
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.
Pretreatment Serum Concentration of 25-Hydroxyvitamin D and Breast Cancer Prognostic Characteristics: A Case-Control and a Case-Series Study (2011)
Conclusion: Vitamin D levels were measured and compared for 579 breast cancer patients and 574 healthy age-matched controls. Researchers found that the breast cancer patients had lower vitamin D levels. They also found that for every 10 ng/ml increase in vitamin D blood levels the women enjoyed a 64% lower risk for developing triple-negative breast cancer.
Conclusion: This meta-analysis reviewed 11 different studies investigating vitamin D status and breast cancer risk and concluded that women with vitamin D levels in the optimal range (above 47 ng /ml) enjoy a 50% lower risk of breast cancer compared to those with only 10 ng/ml or less. They also concluded that breast cancer risk drops approximately 10% for every 10 ng/ml vitamin D blood level increase.
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.
Conclusion: A study of 98 young adult athletes and dancers found that 73% had insufficient vitamin D levels. Outdoor sports athletes had better levels than indoor sports athletes.
Conclusion: The vitamin D levels of 929 newborns in New Zealand were tested. 73% had low vitamin D levels. The babies born during winter time had the lowest vitamin D levels.
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.
Demographic Differences and Trends of Vitamin D Insufficiency in the US Population, 1988–2004 (2009)
Conclusion: In this study of 32,252 members of the U.S. general population, using data collected from the 1988-1994 Third National Health and Nutrition Examination Survey and 2001-2004 National Health and Nutrition Examination Survey, the Average vitamin D level of hispanics was significantly lower than that of non-hispanic whites, and the average vitamin D level of non-hispanic blacks was even lower. The prevalence of severe vitamin D-deficiency was exponentially higher for blacks compared to whites and hispanics. The study also found that men have slightly higher vitamin D levels than women (who also have a higher rates of severe deficiency) and that younger people have slightly higher vitamin D levels than older people. Although this study shows the glaring racial disparities in the U.S. population’s vitamin D levels, most alarming is that it also found a large decrease in vitamin D levels for all demographics in the time between the two surveys with 77% of all subjects being found to have inadequate vitamin D levels in the second survey. The lower vitamin D levels of darker-skinned people are attributed to their increased amount melanin in their skin, which acts as a natural sunscreen limiting cutaneous vitamin D synthesis from UVB exposure.
Conclusion: The vitamin D levels of 93 middle-eastern male sports athletes in Qatar were analyzed. 91% had levels below 20 ng/ml. Vitamin D experts nowadays recommend levels of at least 50 ng/ml.
Reduced Prediagnostic 25-Hydroxyvitamin D Levels in Women with Breast Cancer: A Nested Case-Control Study (2009)
Conclusion: Scientists evaluated the pre-diagnosis vitamin D levels of 142 breast cancer patients and 420 closely-matched healthy controls. What they found was that the breast cancer patients had lower vitamin D levels. Those with the highest pre-diagnosis vitamin D level group enjoyed a 48% lower risk of breast cancer.
Conclusion: 40% of 146 Boston infants and toddlers were found to be vitamin D deficient.
Conclusion: 18 teenage female gymnasts in Australia were tested for their vitamin D status. 15 (83%) had inadequate levels.
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.
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.
Conclusion: 78% of unsupplemented babies in the study became vitamin D deficient during winter.
Note: Extremely comprehensive study on worldwide population vitamin D levels.
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: 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.
Conclusion: The vitamin D deficiency rates in North America are becoming more alarming as new research is influencing a rise in vitamin D level standards.
Conclusion: Even in South Florida vitamin D deficiency is a problem. 40% of 99 tested residents were deficient.
Conclusion: The vitamin D levels of 370 adolescent girls living in the north eastern U.S. were analyzed. The average vitamin D level of all the girls was only a low 21 ng/ml, 17% were found to be severely deficient, and 54% had levels below 20 ng/ml. The average level of the black girls was only 17 ng/ml, with non-black girls having a higher average level of 28 ng/ml (which is still bad). The vitamin D levels were higher in the spring and summer and lower in the fall and winter.
Conclusion: This study of the vitamin D levels of 15,390 American adults found that the men had higher vitamin D levels than the women, white people have higher vitamin D levels than hispanics and blacks (due to increased melanin blocking the UVB necessary for vitamin D synthesis), and although white males had the best vitamin D levels, 34% still tested low. The study also found that elderly people have lower levels compared to younger adults (as we age we slowly lose our ability to cutaneously synthesize vitamin D).
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.
Conclusion: The vitamin D levels of 1,210 random Tehran residents were tested. The majority of them were deficient.
Conclusion: This study measured the vitamin D levels of 35 medical residents before and after winter. 74% of them had low vitamin D levels in the spring following winter versus only 26% in the fall following summer. 20% had low levels for both testing periods and 51% had low levels for at least one of the testing periods. Once again the deficiency rates in this 2004 study are actually much worse because the definition of vitamin D inadequacy here is only <20 ng/ml, which has since been updated by vitamin D experts to <50 ng/ml. The conclusion of the researchers is that the medical residents have such bad levels because they work long hours indoors and don’t get much sun exposure.
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 young Finnish girls found that 46% were vitamin D deficient.
Prevalence of Hypovitaminosis D in Elderly Women in Italy: Clinical Consequences and Risk Factors (2003)
Conclusion: 76% of elderly Italian women were found to be vitamin D deficient.
Conclusion: 95% of studied Italian centenarians had undetectable vitamin D levels.
Conclusion: This study of 1,619 elderly women living in nursing home facilities found that 22% of them women receiving low-level care had a severe vitamin D deficiency of <10 ng/ml and a shocking 45% of the women in high-level care were deficient below 10 ng/ml. The study also found that with each doubling of vitamin D levels, the risk of falling among the women dropped by 20%.
Conclusion: This study analyzed the vitamin D levels of 165 health adults at the end of winter and then analyzed the vitamin D levels of 142 adults at the end of summer. The winter group had a higher rate of vitamin D insufficiency compared to the summer group.
Conclusion: 60 Canadian adult men and 128 Canadian adult women living in Calgary had their vitamin D blood levels measured four times in one year during each season. 97% of them were found to have inadequate vitamin D levels in at least one of the four testings, with 34% being severely deficient in at least one of the four testings. The vitamin D levels were highest in the spring and summer and lowest in the fall and winter.
Hypovitaminosis D Prevalence and Determinants Among African American and White Women of Reproductive Age: Third National Health and Nutrition Examination Survey, 1988–1994 (2002)
Conclusion: The vitamin D levels of 1,546 black women and 1,426 white women in America were analyzed. The average vitamin D level of the black women was only 18 ng/ml, the rate of deficiency was 42%, and the rate of severe deficiency was 12%. White women had a much higher average vitamin D level of 33 ng/ml, the rate of deficiency was 10x less than black women at only 4%, and the rate of severe deficiency was more than 20x less at only 0.5%. One thing to mention is that the definition of vitamin D deficiency/insufficiency in this study was only <15 ng/ml, but most of the world’s leading vitamin D experts now consider anything below to 50 ng/ml to be insufficient. So this means that the rate of insufficiency was actually much, much greater than stated. Either way, this study does demonstrate the great vitamin D disparity between whites and blacks. The black women had 10x the rate of deficiency and an average level less than half of the white women.
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 horrifically deficient in vitamin D.
Conclusion: Vitamin D levels for pre-teen and teenage students at three different private schools in Lebanon were checked at the end of summer and at the end of winter. 65% were deficient at the end of winter, 40% were deficient at the end of summer.
Vitamin D Deficiency and Bone Health in Healthy Adults in Finland: Could This Be a Concern in Other Parts of Europe? (2001)
Conclusion: The vitamin D levels of 328 middle-aged southern Finnish people were analyzed (202 women, 128 men) following the winter of 1998. Overall 86% of women and 56% of men were found to have insufficient levels, with 28% of women and 26% of men being severely deficient. Researchers concluded that this is primarily the result of Finland’s high 60 degree Northern latitude which provides inadequate sunlight for maintaining adequate vitamin D levels year-round or at all. The researchers also concluded that this is also a problem for all parts of Europe except southern Europe.
Conclusion: This is an overview of many population vitamin D level studies conducted throughout Europe. Some of the study findings: 16% of elderly Dutch people were severely deficient, 38% of all Italian women were deficient during winter, 12% of all Italian women were still deficient during summer, one French study found that 100% of the adolescents tested were deficient, as much as 78% of dark skinned immigrants in Europe have been found to be severely deficient, and as much as 83% of Greek women have been found to have low levels during winter. The researchers conclude that all Europeans are at a high risk for vitamin D-deficiency due to all of Europe being located at a high latitude that does not receive adequate sunshine year-round. Although being located higher North and getting less sun, Scandinavia scored better for vitamin D sufficiency due to their higher consumption of vitamin D-rich fish.
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.
Conclusion: Due to most of Europe being located at high latitudes far away from the equator and much of Europe’s food supply not being vitamin D-fortified, Europeans are at a high risk of developing vitamin D deficiencies – as found in the investigations of individual European countries.
Conclusion: 57% of 290 studied general hospital patients were found to be vitamin D deficient.
Conclusion: The vitamin D levels of 155 elderly residents at three different Toronto nursing homes were observed. 60% were found to be deficient at the end of winter.