vitamin d

Vitamin D May Protect Against Respiratory Infections

Vitamin D supplements may help reduce people’s risk of developing acute respiratory infections, particularly among those with vitamin D deficiency, suggests a new meta-analysis published online February 15 in the BMJ.

However, some experts caution that these findings should not alter clinical practice, as the absolute benefit is relatively small.

“Vitamin D supplementation resulted in a statistically significant reduction in the proportion of participants experiencing at least one acute respiratory tract infection,” write Adrian R. Martineau, MD, PhD, from the Queen Mary University of London, United Kingdom, and colleagues.

“Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.”

According to the authors, acute respiratory infections are a substantial cause of illness and death, and in 2013, they accounted for one tenth of ambulatory and emergency department visits in the United States and approximately 2.65 million deaths worldwide.

Although some observational studies have linked patients’ low vitamin D levels with greater susceptibility to acute respiratory infections, including colds and influenza, clinical trials investigating the protective effect of vitamin D supplementation have produced conflicting results.

Dr Martineau and colleagues therefore conducted a systematic review and individual participant data meta-analysis of randomized controlled trials involving vitamin D supplementation. The individual participant data meta-analysis could potentially identify factors to help explain the discrepancy in results among previous studies, the authors say.

Their analysis included data on 10,933 participants (aged 0 – 95 years) from 25 randomized controlled trials.

Overall, they found that vitamin D supplementation was associated with a 12% reduction in the proportion of participants who experienced at least one acute respiratory infection (adjusted odds ratio, 0.88; 95% confidence interval [CI], 0.81 – 0.96; P for heterogeneity < .001) compared with no supplementation.

They also conducted subgroup analyses to explore reasons for the variable results in previous studies.

These analyses showed a protective effect of vitamin D supplementation in participants who received daily or weekly vitamin D supplements without additional large bolus doses (adjusted odds ratio, 0.81; CI, 0.72 to 0.91), but not in those who received one or more large bolus doses (adjusted odds ratio, 0.97; CI, 0.86 to 1.10; P for interaction = .05).

In addition, the protective effect was greater in participants with severe vitamin D deficiency (baseline blood 25-hydroxyvitamin D levels <25 nmol/L; adjusted odds ratio, 0.30; 95% CI, 0.17 – 0.53) than among those with baseline 25-hydroxyvitamin D levels at least 25 nmol/L (adjusted odds ratio, 0.75; 95% CI, 0.60 – 0.95; P for interaction = .006).

Vitamin D supplementation was also safe, the authors say, and did not affect the proportion of participants who experienced at least one serious adverse event of any cause (adjusted odds ratio, 0.98; CI, 0.80 – 1.20; P = .83).

“Our results add to the body of evidence supporting the introduction of public health measures such as food fortification to improve vitamin D status, particularly in settings where profound vitamin D deficiency is common,” Dr Martineau and colleagues conclude.

However, in an accompanying editorial, Mark J. Bolland, MD, PhD, from the University of Auckland, New Zealand, and Alison Avenell, MD, from the University of Aberdeen, United Kingdom, question whether these findings represent a significant new development or a hypothesis that needs to be tested in adequately powered randomized controlled trials.

Although the study showed that vitamin D supplementation resulted in a 12% reduction in the odds of an acute respiratory infection, the editorialists stress that these findings should be regarded cautiously.

In particular, because the primary result involves only a 2% absolute risk reduction in the proportion of participants who experienced at least one acute respiratory tract infection, the editorialists do not think the general population would consider this sufficient justification to take vitamin D supplements.

Dr Bolland and Dr Avenell therefore conclude that the results should not change clinical practice.

“We think that they should be viewed as hypothesis generating only, requiring confirmation in well designed, adequately powered, randomised controlled trials,” they conclude.

This study was funded by the National Institute for Health Research. Dr Bolland has received funding from the Health Research Council of New Zealand. Both editorialists have published randomized controlled trials and systematic reviews in the field of vitamin D. The authors and editorialists have disclosed no other relevant financial relationships.


Low Vitamin D Linked to Frequent Headaches

Men who have low levels of vitamin D may increase the risk of frequent headaches, a new study from Finland suggests.

The study analyzed information from about 2,600 Finnish men ages 42 to 60 who gave blood samples and answered questions about the frequency of their headaches. The men were originally part of a study on risk factors for heart disease, and were assessed in the years 1984 to 1989.

Nearly 70 percent of the men in the study had blood vitamin D levels below 20 nanograms per milliliter (50 nanomoles per liter), which is generally considered the threshold for vitamin D deficiency. Low vitamin D levels are a particular concern in Finland and other Nordic countries, because these countries are farther north and have less exposure to sunlight, which the body needs to make vitamin D, the researchers said. [9 Good Sources of Disease-Fighter Vitamin D]

On average, men with frequent headaches — occurring at least once a week — had vitamin D levels of 15.3 ng/ml (38.3 nmol/L), compared to 17.6 ng/ml (43.9 nmol/L) among those men without frequent headaches. (In the United States, vitamin D levels are usually reported in ng/ml, while in other parts of the world, they are reported in nmol/L.)

Men with the lowest vitamin D levels (below 11.6 ng/ml or 28.9 nmol/L) were about twice as likely to have frequent headaches, compared to men with the highest vitamin D levels (above 22 ng/ml or 55 nmol/L.)

The study adds to a growing body of evidence linking low vitamin D levelsto an increased risk of certain diseases and conditions, including headaches. The new study is one of the largest to look at the link between vitamin D and headaches, the researchers said.

However, the study was conducted at a single point in time, so the researchers cannot tell which came first, the low vitamin D levels or headaches, the scientists said. It’s possible that people with frequent headaches may be less likely to spend time outside, and so they have less exposure to sunlight, the researchers said. However, this explanation may be less likely in Finland, where people overall have less exposure to sunlight, the researchers said.

In addition, because the study involved only men, it’s not clear if the findings also apply to women, the scientists said.

Future studies are needed to see if vitamin D supplements may prevent or treat frequent headaches, the researchers said. The study was published online yesterday (Jan. 3) in the journal Scientific Reports.

Original article on Live Science.

Tanning may limit skin’s ability to produce vitamin D: Study

MONDAY, April 4, 2016 — While the sun helps the body make vitamin D, a new study says that too much exposure might actually lower the levels of the essential vitamin.

Tan skin may provide some protection against the sun’s harmful UV rays, but this increase in pigment blocks vitamin D synthesis and limits the skin’s ability to produce vitamin D, according researchers in Brazil.

“Our findings suggest that skin tanning, which is a natural protection against the harmful effects of UV irradiation, limits the progressive rise in serum vitamin D towards optimal concentrations,” said study author Dr. Francisco Bandeira, of the University of Pernambuco Medical School in Recife, Brazil.

For the study, researchers examined nearly 1,000 males and females from Recife who were between 13 and 82 years old. All had significant daily sun exposure and none routinely used sunscreen or took vitamin D supplements.

Using the Fitzpatrick skin phototype scale, which is a numerical measure of skin color and type used by dermatologists, the researchers assessed the response of different skin types to UV light. Generally, higher scores indicate darker skin tones and the tendency to tan, not burn.

The participants’ sun index was also calculated by multiplying the number of hours of sun exposure they got on a weekly basis by the fraction of exposed skin.

The researchers compared the participants’ sun index scores and skin type with their blood level of vitamin D. Most of the participants with very high daily exposure to the sun had lower-than-normal serum vitamin D levels.

Overall, 72 percent of the participants were deficient in vitamin D. Those lacking this nutrient tended to be older and have lower sun index values, the study found.

“Our research showed that, in a large sample of individuals living in a tropical region located 8 degrees south of the equator with very high rates of sun exposure and extremely high UV irradiation, most people had serum vitamin D below 30 ng/ml [nanograms per milliliter], the cutoff for normal,” Bandeira said in a news release from the Endocrine Society.

The findings were presented Saturday at the annual meeting of the Endocrine Society, in Boston. Studies presented at meetings are usually considered preliminary until published in a peer-reviewed medical journal.

Vitamin D boosts heart function in study

MONDAY, April 4, 2016 — Regular doses of vitamin D3 may improve heart function in heart failure patients, a new British study suggests.

“These findings could make a significant difference to the care of heart failure patients,” said study leader Dr. Klaus Witte, from the University of Leeds School of Medicine. “It is the first evidence that vitamin D3 can improve heart function of people with heart muscle weakness — known as heart failure.”

The study included more than 160 patients who had pacemakers and/or were receiving blood pressure drugs known as ACE inhibitors or beta blockers.

The study participants took either vitamin D or inactive placebo pills once a day for a year.

The researchers explained that they avoided using a calcium-based vitamin D supplement, because calcium can cause other problems for heart failure patients.

Heart pumping function improved from 26 percent to 34 percent in patients who took vitamin D, while there was no change among those who took the placebo pills, the investigators found.

The study was presented Monday at the annual meeting of the American College of Cardiology in Chicago. Research presented at medical meetings is typically considered preliminary until published in a peer-reviewed journal.

The researchers suggested that the improvement seen in some of the patients who took vitamin D might reduce their need for an implantable cardioverter defibrillator (ICD). An ICD is a device that detects dangerous heart rhythm problems and delivers a shock to restore a normal heartbeat.

“ICDs are expensive and involve an operation. If we can avoid an ICD implant in just a few patients, then that is a boost to patients and [health systems] as a whole,” Witte said in a university news release.

Heart failure affects about 23 million people worldwide, the study authors said.

More information

The American Academy of Family Physicians has more about heart failure.

Vitamin D, Calcium a Bust for Preventing Colorectal Polyps

Taking vitamin D, calcium, or a combination of the two supplements, failed to prevent the recurrence of precancerous colorectal polyps in a large, randomized, placebo-controlled trial that followed patients for up to 5 years.

The negative findings came as a surprise because they contradict years of previous observational and animal studies suggesting a protective role for the supplements in preventing precancerous polyps, researcher John Baron, MD, of the University of North Carolina, Chapel Hill, and colleagues wrote in the Oct. 15 issue of New England Journal of Medicine.

They also contradict findings from several smaller randomized trials, including one by Baron and colleagues published in 1999, which showed calcium supplementation significantly lowered recurrent colorectal polyp risk.

‘Calcium Data Especially Surprising’

The newly published study is among the first randomized trials to examine vitamin D’s role in the prevention of polyp recurrence and the largest to examine calcium’s role, Baron said.

“We were especially surprised by the calcium data,” Baron told MedPage Today. “We plan to look at this trial and our previous trial to see if we can explain the difference in findings.”

The study included 2,259 people between the ages of 45 and 75 with at least one colorectal adenoma removed within 120 days of enrollment who also had no evidence of polyps on follow-up colonoscopy.

Participants were assigned to one of four regimens daily: 1,000 IU of vitamin D3, 1,200 mg of calcium as carbonate, both agents, or placebo. Women could elect to be randomly assigned to receive either calcium or calcium plus vitamin D or placebo.

Follow-up colonoscopy was performed 3 to 5 years after baseline examination and randomization, according to the endoscopist’s recommendation.

Participants randomized to receive vitamin D had a mean net increase in serum 25-hydroxyvitamin D levels of 7.83 ng per milliliter, relative to those in the placebo arm of the study.

A total of 43% of participants had one or more adenomas identified during follow-up colonoscopy. The adjusted risk ratios for recurrent adenomas were 0.99 (95% CI 0.85-1.09) for vitamin D versus no vitamin D, 0.95 (95% CI 0.85-1.06) for calcium versus no calcium, and 0.93 (95% CI 0.80-1.08) for both supplements versus neither.

Similar findings were shown in a subanalysis of patients with advanced adenomas and in those with low baseline serum 25-hydroxyvitamin D levels.

1,000 IU of Vitamin D Isn’t Protective

Study strengths included its large size, rigorous design, and a high adherence rate among participants.

“We can say with some confidence that at this (1,000 IU) dose, which is a very commonly used dose now, vitamin D does not affect colorectal carcinogenesis,” Baron said. “The calcium story is somewhat more complicated given the strength of the previous evidence.”

Baron added that it is not clear if larger doses of vitamin D or increasing the duration of supplementation would protect against colorectal polyp recurrence and colorectal cancer.

“We started designing this trial around 15 years ago, and at the time there was some concern about toxicity at the dose we used,” he said. “Today 1,000 IU is considered a relatively moderate dose of vitamin D.”

A 2014 meta-analysis of randomized controlled trials examining the impact of vitamin D supplementation on various outcomes including ischemic heart disease, stroke, cancer, and hip fracture showed no evidence of protection with supplementation, with or without calcium, against any of these outcomes.

In an email exchange with MedPage Today, the meta-analysis’ lead author Mark J. Bolland, PhD, of the University of Auckland, Auckland, New Zealand, noted that earlier trials have failed to show vitamin D supplementation to protect against cancer.

“This (latest trial) was a large, well-conducted, randomized, placebo-controlled study carried out by experienced researchers that was specifically designed to test whether calcium or vitamin D supplements can prevent colorectal adenomas,” he said.


Joshua Miller, professor in the Department of Pathology and Laboratory Medicine at the time when the research was conducted and now professor and chair of the Department of Nutritional Sciences at Rutgers University said, “Independent of race or ethnicity, baseline cognitive abilities and a host of other risk factors, vitamin D insufficiency was associated with significantly faster declines in both episodic memory and executive function performance. But on average, people with low vitamin D declined two to three times as fast as those with adequate vitamin D.”

Miller said that till now, there have been no serious researches to find out if taking vitamin D could slow down or prevent memory loss, but he suggested measuring your vitamin D level to see whether you need more vitamin D.

Low vitamin D levels are common in older age and this is linked to speedy decline in episodic memory and executive function. Recent research suggests that lower levels of vitamin D are directly proportional to a sudden decline in cognitive abilities in older adults. The lower levels of vitamin D then causes Alzheimer’s disease and dementia. The study done by researchers at the Rutgers University explained that deficiency of vitamin D in the body can be boosted with supplements.

Half of the participants were Caucasian and 50 percent were African-American or Hispanic. Research results are suggestive of the fact that 50 percent of Americans above 65 have low levels of vitamin D. It was also seen that African origin people have the highest chance to be deficient on Vitamin D.

Previous studies suggest a direct relation between low levels of vitamin D in the blood and symptoms of depression. The study, however, hasn’t yet shown clearly whether low vitamin D levels cause depression, or whether low vitamin D levels develop because someone is depressed.

The research was done in almost 400 racially and ethnically different men and women in Northern California participating in longitudinal research at the Alzheimer’s Disease Center in Sacramento, Calif.

Vitamin D’s effect on mental health extends beyond depression, as per the findings of earlier studies. Schizophrenia has also been linked with abnormal levels of vitamin D. John McGrath of the University of Queensland in Australia(link is external) studied 424 Danish newborns who developed schizophrenia. He concluded that infants born in winter or spring seasons, when birth mothers have decreased levels of vitamin D, are at an increased risk of developing schizophrenia.

It was seen that over this level, the risk of adverse health effects shoots up, with very high doses (10,000 IU/day or more) leading to significant damage to kidneys and other tissues. The study also revealed that people who are African-American or Hispanic had lower levels of vitamin D than white people. Vitamin D is crucial for its role in maintaining bone health and can be found mostly by sun exposure as well as egg yolks, cheese and fish oil.

Vitamin D may not benefit postmenopausal bone health

(Reuters Health) – High doses of vitamin D may not help strengthen bones in postmenopausal women, a study suggests.

Vitamin D helps the body use calcium, and calcium in turn helps support bone health. After a year on high-dose vitamin D supplements, women were absorbing slightly more calcium from their intestines into their blood compared to women who took low doses of vitamin D or a dummy pill.

But that didn’t seem to matter, because all three regimens produced similar results in terms of bone mineral density, muscle mass and the women’s risk for falling.

“We conclude that there is no reason to take more than the recommended daily allowance for vitamin D,” lead author Dr. Karen Hansen of the University of Wisconsin in Madison said by email.

Falls are a leading cause of fatal and nonfatal injuries among the elderly, according to the U.S. Centers for Disease Control and Prevention.

For older women, this risk of fall-related injuries is compounded by osteoporosis, or thinning bones, which occurs when production of the hormone estrogen declines after menopause.

For most adult women, the recommended daily intake of vitamin D is 600 IU (international units), or 800 IU after age 70, according to the U.S. National Institutes of Health. While few foods provide vitamin D, it can be found in beef liver, canned salmon or sardines, cheese and egg yolks as well as fortified milk and orange juice.

Even though doctors agree vitamin D is essential for bone health, many physicians continue to debate the appropriate role and dose of vitamin D supplements as well as the optimal concentrations of this nutrient in the blood.

Hansen and colleagues examined the impact of vitamin D supplements on 230 women who were at least five years past menopause but no older than 75, and without osteoporosis at the start of the study.

All of them had blood levels of vitamin D that put them at risk for deficiency.

During the study, the women were randomly assigned to take either 800 IU or 50,000 IU of vitamin D, or a dummy pill, once every 15 days for about a year.

Total fractional calcium absorption (TFCA) from the gut increased 1 percent among women on the higher dose of vitamin D, but declined 2 percent with the lower dose and 1.3 percent with the placebo, the researchers report in JAMA Internal Medicine.

While it’s possible that treatment for more than a year might result in a bigger benefit from taking vitamin D, the results suggest that this supplement may be no better than a placebo, Dr. Deborah Grady, deputy editor of the journal, noted in an editorial.

To prevent or slow the progression of osteoporosis, women can stay active, particularly with weight-bearing exercises, Dr. Rita Redberg, editor-in-chief of JAMA Internal Medicine, said by email. Workouts targeting balance such as yoga or pilates may also help prevent falls, she said.

“There were no clinical benefits seen in either low dose or high dose vitamin D for bone health,” Redberg said by email. “I would recommend not starting vitamin D supplementation, or stopping Vitamin D if you have started.”