RICHMOND HILL, Ontario — Many vulnerable segments of the population, including children, pregnant women, seniors and those with pre-diabetes, would benefit from vitamin D supplementation, according to an extensive scientific study published last month.
The authors of the study, “Vitamin D for Disease Prevention: An Endocrine Society Clinical Practice Guideline,” briefly discussed food fortification, including wheat flour fortification, as a possible way to reach individuals who would benefit from increased vitamin D intake.
The 30-page study was released in June. Journal of Clinical Endocrinology and MetabolismThe paper’s authors were led by endocrinologist Marie B. DeMay of Massachusetts General Hospital in Boston and Harvard Medical School, and contributors included representatives of many other U.S. states and institutions, as well as researchers from Brazil, Ireland, the Netherlands and New Zealand.
For more than a decade, the question of whether and how much to increase dietary intake of vitamin D has swirled in the scientific community. In 2010, the Institute of Medicine of the National Academies recommended raising the daily intake of vitamin D from 200 IU to 600 IU, and the upper tolerable limit from 2,000 IU to 4,000 IU.
In 2012, the North American Flour Mills Association began technical studies on vitamin D fortification of flour and submitted a draft petition to the Food and Drug Administration to allow for the addition of 80 IU of vitamin D per 30 grams of whole wheat and fortified flour. This effort did not move forward. Other industry efforts include Lallemand’s launch of yeast with naturally high vitamin D content in the 2000s and, more recently, the FDA’s approval of a petition by Kellogg Company to allow for the fortification of cereals and grain-based bars in 2023.
During this period, promising research findings suggesting that vitamin D might be beneficial were mixed with data showing that it provided little to no benefit for most people, dashing hopes that vitamin D would be a panacea for conditions ranging from cancer to depression.
In the article Scientific American “When scientists tried to administer vitamin D as a means to prevent or treat these problems, the miracle supplement failed miserably,” concludes author Christy Aschwanden, who published a book earlier this year chronicling the rise and fall of vitamin D mania.
While it may not be a miracle drug, Aschwanden said research has found that vitamin D has many benefits.
Because vitamin D intake has been linked to preventing or reducing the risk of many diseases, the group of scientists involved in the study, led by DeMay, posed a set of questions about the use of vitamin D to reduce disease risk and about vitamin D testing. Scientific studies on the vitamin were evaluated using the agreed-upon questions as a guide.
In describing their study, the authors noted that studies have demonstrated associations between vitamin D and “a variety of common diseases, including musculoskeletal, metabolic, cardiovascular, malignant, autoimmune, and infectious diseases.” Although a causal relationship between serum 25(OH)D (the main circulating form of vitamin D) concentrations and many diseases has not been definitively established, these associations have led to widespread vitamin D supplementation in the general population and increased laboratory testing for 25(OH)D. The benefit-risk ratio of increased vitamin D use is unclear, and the role of optimal vitamin D intake and 25(OH)D testing for disease prevention remains unclear.
In assessing the research on vitamin D, the researchers prioritized studies conducted as randomized, placebo-controlled trials in the general population, which are not always available. The paper suggests that substantial further scientific research is needed to more precisely understand the need for vitamin D in the diet.
“The Committee recommends empiric vitamin D supplementation for children and adolescents aged 1 to 18 years for the potential prevention of nutritional rickets and reduced risk of respiratory infections; for people aged 75 years and older for the potential reduced risk of mortality; for pregnant women for the potential reduced risk of preeclampsia, intrauterine death, preterm birth, small-for-gestational age, and neonatal mortality; and for individuals with high-risk prediabetes for the potential to reduce progression to diabetes,” the researchers concluded.
Additionally, the committee said people over 50 who need vitamin D should receive it daily, rather than in high doses.
Because most natural foods are not rich sources of vitamin D, supplementation should consist of “a combination of fortified foods and vitamin D-containing supplements,” the researchers say.
Children: From bone health to immunity
Addressing the different population groups they studied separately, the researchers said that many children around the world are vitamin D deficient. The prevalence is significantly higher in Northern Europe, they said.
The importance of vitamin D in preventing rickets, a bone disease in children, has been known for decades, but researchers say the disease is now on the rise in high-income countries.
The authors also reviewed evidence that vitamin D may help prevent respiratory infections in children, noting that such illnesses are highly common, with pneumonia “the most common cause of infectious death in the first 5 years of life.”
The researchers were also interested in the role that vitamin D, possibly over the long term, plays in immunity.
“Early childhood is a window of opportunity for training the immune system,” the study states, “so vitamin D deficiency in early life may affect vulnerability to disease throughout life.”
Based on this study, the group concluded that vitamin D supplementation would be beneficial for most people and that any undesirable effects “are likely to be minor for all.”
“Additional studies suggest that universal vitamin D supplementation through wheat flour fortification would be cost-saving, but targeted supplementation of children would be cost-effective,” the study states.
Benefits for healthy adults are unclear
However, the researchers said that in adults under 50 years of age, controlled trials had not found any benefit of vitamin D supplementation in preventing respiratory infections.
As people age, their vitamin D status may decline for a variety of reasons, including reduced intake of dairy and fish, weight gain, reduced exposure to sunlight and reduced biosynthetic capacity, the researchers said. This decline is “most pronounced in those aged 75 years and older,” they added.
The most powerful effect of supplementation in adults aged 50 to 74 appears to be reducing the risk of fractures.
“The period between ages 50 and 74 corresponds to the bone loss, decline in muscle function, and increased risk of falls associated with menopause and normal aging, all of which contribute to increased fracture risk,” the authors wrote. “Importantly, several studies suggest that these risks can be mitigated by vitamin D and calcium.”
A review of studies showed that taking vitamin D supplements slightly reduces fracture risk. For a variety of other adverse effects that have been extensively studied, studies have found no benefit from vitamin D supplements. These include cancer, cardiovascular disease, and kidney stones. While questions remain about whether the studies should be considered conclusive, the researchers do not recommend comprehensive supplementation for adults aged 18-74 beyond those recommended by the Institute of Medicine.
Surveys targeting older adults have mixed reviews
While recommending vitamin D supplements for adults aged 75 and older, the authors cautioned that it is unclear whether supplements reduce the risk of falls, fractures, or respiratory disease in older adults, but they cited data showing that supplementation “is likely to be associated with a small reduction in all-cause mortality” in this group.
Research shows that vitamin D is important for pregnant women for a number of reasons, including the fetus’s reliance on maternal circulating vitamin D for placental metabolism and transfer of vitamin D metabolites. Low levels of vitamin D have been associated with several life-threatening neonatal conditions, including cardiomyopathy.
The researchers said eight studies suggest that taking vitamin D may reduce the risk of preeclampsia. Vitamin D may also slightly reduce the risk of stillbirth and neonatal death, and may also lower the risk of preterm birth, low birth weight, and gestational diabetes.
How much vitamin D is needed during pregnancy and when is not fully understood, the authors note.
“Thus, preconception and pregnancy-specific vitamin D recommendations are not universal, and there is no consensus on the dose of vitamin D or 25(OH)D levels needed to maintain a healthy pregnancy,” the researchers said.
Hard evidence for prediabetes
The study highlighted the importance of addressing prediabetes and the role that vitamin D plays.
“More than one in three U.S. adults aged 18 and older have prediabetes, yet only about 20 percent of them have been informed by a health professional that they have prediabetes,” the study states.
“Intensive lifestyle changes focused on weight loss and increased physical activity” are often emphasized and are effective in reducing the risk of developing diabetes in this population, the authors note.
“However, these lifestyle changes are difficult to maintain in the long term,” they added.
According to the researchers, several studies conducted over the past decade have addressed the role of vitamin D in “slowing the progression” to diabetes in adults with prediabetes. For their analysis, the group looked at 15 randomized controlled trials.
Studies have shown that subjects who took vitamin D had a 15% reduction in the incidence of new-onset diabetes compared to subjects who took a placebo. In other studies, subjects who took vitamin D had lower blood sugar levels compared to subjects who took a placebo.
Based on their review of the studies, the authors concluded that vitamin D may have a modest benefit for people with prediabetes, but that “potential undesirable effects are probably trivial.”
