Study: Vitamin D And The Innate Immune System

 

 

 

# 6306

 

 

The theory that reduced levels of Vitamin D might lead to an increased likelihood of contracting viral infections – while not proven or universally accepted – has seen a fair amount of support in the medical field over the past few years.

 

While I don’t actively promote Vitamin D in this column, I have blogged on several flu-related Vitamin D studies over the years, Including:

 

Study: Vitamin D And Flu-Like Illnesses

Scientists To Study Vitamin D And The Flu

Vitamin D To Ward Off Flu?

 

Although intriguing, these studies have yet to settle the debate over Vitamin D’s benefits in warding off viral infections.  

 

 

In 2010, the IOM released a 999 page report on Vitamin D (see IOM Report On Vitamin D) finding - that while essential for promoting good bone health - insufficient evidence for its effects on other disease processes exists at this time.

 

The IOM granted that further studies were warranted, but found that those to date they have yielded conflicting and mixed results.

 

Which brings us to a new study, published in the May edition of the Journal of Leukocyte Biology that suggests that lower levels of Vitamin D – particularly in the elderly – may lead to autoimmune diseases and viral infections.

 

What these researchers found was a decrease in serum 25-hydroxy vitamin D in healthy adults as they aged, and a negative correlation between serum 25OHD levels and MFI (mean fluorescence intensity) expression of TLR7 on B cells, T cells, and monocytes.

 

TLR7 is one of a number of toll-like receptors, which are proteins that play an integral role in the innate (or non-specific) immune system. 

 

Our innate immune system  not only fights infections, it also buys time for our Adaptive Immune System to learn to recognize and fight specific pathogens.

 

First some excerpts from the press release, then a link to the abstract.

 

Vitamin D supplements may protect against viral infections during the winter

New research published in the Journal of Leukocyte Biology suggests that the older population could benefit from vitamin D supplementation in autumn and winter to protect against viral infections

Vitamin D may be known as the sunshine vitamin, but a new research report appearing in the Journal of Leukocyte Biology shows that it is more than that. According to the report, insufficient levels of vitamin D are related to a deficiency in our innate immune defenses that protect us from infections, neoplasias or autoimmune diseases. Since vitamin D levels decrease during autumn and winter when days are shorter and sunlight is relatively weak, this may explain why people are more prone to viral infection during these times. It also suggests that vitamin D supplementation, especially in older populations, could strengthen people's innate immunity against viral infections.

(Continue . . . )

Age and low levels of circulating vitamin D are associated with impaired innate immune function

Lorena Alvarez-Rodriguez, Marcos Lopez-Hoyos, Maite Garcia-Unzueta, Jose Antonio Amado, Pedro Muñoz Cacho and Victor Manuel Martinez-Taboada

 

 

This study adds incrementally to our knowledge, and suggests a mechanism by which low Vitamin D levels might impair immunity.

 

Not exactly proof that Vitamin D is protective against viral infections.

 

But it is another piece of data to consider.

IOM Report On Vitamin D

 

 

# 5100

 

 

The IOM (Institute of Medicine) released a lengthy report today giving their recommendations regarding the Dietary Reference Intakes (DRI) of what a lot of doctors have touted as practically a miracle supplement;  Vitamin D.

 

The IOM’s Food and Nutrition Board substantially increased their daily recommendations for Vitamin D, but they fell well short of endorsing the high daily doses that have become in vogue over the past decade.

 

Given the popularity of this supplement, particularly  among alternative and complementary medicine practitioners, I expect we’ll see a fair amount of controversy and discourse over these findings.

 

The entire 999 page report is available online for free, or may be ordered as PDF files, or as a hardback from the National Academies Press.

 

Luckily, for those of us with time only to deal with the condensed version, we have some alternatives.

 

First Dick Knox of NPR, has a story called:

 

Medical Panel: Don't Go Overboard On Vitamin D

by Richard Knox

 

 

We’ve also a press release from the IOM.

 

Nov. 30, 2010

FOR IMMEDIATE RELEASE

IOM Report Sets New Dietary Intake Levels for Calcium and Vitamin D To Maintain Health and Avoid Risks Associated With Excess

WASHINGTON — Most Americans and Canadians up to age 70 need no more than 600 international units (IUs) of vitamin D per day to maintain health, and those 71 and older may need as much as 800 IUs, says a new report from the Institute of Medicine. The amount of calcium needed ranges, based on age, from 700 to 1,300 milligrams per day, according to the report, which updates the nutritional reference values known as Dietary Reference Intakes (DRIs) for these interrelated nutrients.

 

The report's recommendations take into account nearly 1,000 published studies as well as testimony from scientists and stakeholders. A large amount of evidence, which formed the basis of the new intake values, confirms the roles of calcium and vitamin D in promoting skeletal growth and maintenance and the amounts needed to avoid poor bone health. The committee that wrote the report also reviewed hundreds of studies and reports on other possible health effects of vitamin D, such as protection against cancer, heart disease, autoimmune diseases, and diabetes. While these studies point to possibilities that warrant further investigation, they have yielded conflicting and mixed results and do not offer the evidence needed to confirm that vitamin D has these effects. Rigorous trials that yield consistent results are vital for reaching conclusions, as past experiences have shown. Vitamin E, for example, was believed to protect against heart disease before further studies disproved it.

 

"There is abundant science to confidently state how much vitamin D and calcium people need," said committee chair Catharine Ross, professor and Dorothy Foehr Huck Chair, department of nutritional sciences, Pennsylvania State University, University Park. "We scrutinized the evidence, looking for indications of beneficial effects at all levels of intake. Amounts higher than those specified in this report are not necessary to maintain bone health."

(Continue . . .)

 

 

The IOM has also released a relatively short Report Brief, which may be accessed at the following link.

Report Brief

Released: 11/30/2010

Download: PDF

Dietary Reference Intakes for Calcium and Vitamin D

Calcium and vitamin D are two essential nutrients long known for their role in bone health. Over the last ten years, the public has heard conflicting messages about other benefits of these nutrients—especially vitamin D—and also about how much calcium and vitamin D they need to be healthy.

 

To help clarify this issue, the U. S. and Canadian governments asked the Institute of Medicine (IOM) to assess the current data on health outcomes associated with calcium and vitamin D. The IOM tasked a committee of experts with reviewing the evidence, as well as updating the nutrient reference values, known as Dietary Reference Intakes (DRIs). These values are used widely by government agencies, for example, in setting standards for school meals or specifying the nutrition label on foods. Over time, they have come to be used by health professionals to counsel individuals about dietary intake.

(Continue . . . )

 

And finally, we’ve this handy chart summarizing the new DRI recommendations for both Vitamin D & Calcium.

 

 

 

While this report will undoubtedly upset a lot of people who have embraced high dose Vitamin D as beneficial, it is important to remember that this isn’t necessarily the final word on the subject.

 

This simply represents the IOM’s best judgment based on the evidence available to date.

 

There are studies underway that could conceivably alter these recommendations sometime in the future.

 

Good science takes time, and is constantly evolving.

 

Until then, however, the IOM finds that the existing evidence of health benefits from high daily doses of Vitamin D remains inconsistent and inconclusive.

 

 

 

Full Disclosure:  While I don’t promote Vitamin D in this column, I have blogged on several flu-related Vitamin D studies over the years, Including:

Study: Vitamin D And Flu-Like Illnesses

Scientists To Study Vitamin D And The Flu

Vitamin D To Ward Off Flu?

 

And . . .  on the advice of my doctor I’ve been taking 2000-3000 IU/Day of Vitamin D for a couple of years now.  I am pleased to find that this falls short of the IOM’s Maximum daily intake.

 

Admittedly, I have no direct evidence of benefit, but for the time being (and since I have at least a year’s supply in the cupboard) I have no plans of changing this regimen.

 

Not a recommendation or an endorsement.  Just what I plan to do.

Study: Vitamin D And Flu-Like Illnesses

 

 

# 4648

 

 

For years there has been speculation that the seasonality of influenza could be at least partially explained by lower levels of Vitamin D experienced by most people during the winter.

 

While cooler temperatures and lower humidity levels have been linked to flu transmission, along with increased indoor contacts during the winter, anecdotal evidence has often linked Vitamin D deficiency as well.

 

Last summer we learned that the Public Health Agency in Canada was looking at the protective qualities of Vitamin D in Scientists To Study Vitamin D And The Flu, and in February of 2009 we saw a study (see  Vitamin D To Ward Off Flu?) that found an inverse relationship between a person's  level of serum 25-hydroxyvitamin D and a recent bout with a cold or flu. 

 

Those who had recently experienced an ILI or other respiratory illness, were more likely to have lower than normal Vitamin D levels.

 

The median serum level of 25-hydroxyvitamin D, among more than 18,000 people tested, was 29 ng/ml.

 

Those with a serum level below 10 ng/ml (considered very low), were 40% more likely to have had a recent respiratory illness than those with a serum level above 30 ng/ml.

 

The link between Vitamin D levels and the risk for respiratory infections was stronger in those with asthma or COPD.

 

Today (well, yesterday actually . . . ) PLoS One  published a study that strongly suggests that raising the blood serum level of Vitamin D to over 38 ng/ml could result in a significant reduction in viral respiratory illnesses.

 

I’ve reproduced the abstract below, but follow the link to read the report in its entirety.  

 

 

 

Serum 25-Hydroxyvitamin D and the Incidence of Acute Viral Respiratory Tract Infections in Healthy Adults

James R. Sabetta, Paolo DePetrillo, Ralph J. Cipriani, Joanne Smardin, Lillian A. Burns, Marie L. Landry Research Article, published 14 Jun 2010 doi:10.1371/journal.pone.0011088

 

Background

Declining serum concentrations of 25-hydroxyvitamin D seen in the fall and winter as distance increases from the equator may be a factor in the seasonal increased prevalence of influenza and other viral infections. This study was done to determine if serum 25-hydroxyvitamin D concentrations correlated with the incidence of acute viral respiratory tract infections.

Methodology/Findings

In this prospective cohort study serial monthly concentrations of 25-hydroxyvitamin D were measured over the fall and winter 2009–2010 in 198 healthy adults, blinded to the nature of the substance being measured. The participants were evaluated for the development of any acute respiratory tract infections by investigators blinded to the 25-hydroxyvitamin D concentrations.

The incidence of infection in participants with different concentrations of vitamin D was determined. One hundred ninety-five (98.5%) of the enrolled participants completed the study. Light skin pigmentation, lean body mass, and supplementation with vitamin D were found to correlate with higher concentrations of 25-hydroxyvitamin D.

Concentrations of 38 ng/ml or more were associated with a significant (p<0.0001) two-fold reduction in the risk of developing acute respiratory tract infections and with a marked reduction in the percentages of days ill.

Conclusions/Significance

 

Maintenance of a 25-hydroxyvitamin D serum concentration of 38 ng/ml or higher should significantly reduce the incidence of acute viral respiratory tract infections and the burden of illness caused thereby, at least during the fall and winter in temperate zones.

The findings of the present study provide direction for and call for future interventional studies examining the efficacy of vitamin D supplementation in reducing the incidence and severity of specific viral infections, including influenza, in the general population and in subpopulations with lower 25-hydroxyvitamin D concentrations, such as pregnant women, dark skinned individuals, and the obese.