Friday, February 08, 2013

Link Between Low Vitamin D And Daytime Sleepiness  -- but not if you are black

Not a good start for suggesting cause/effect relationships

Individuals who find themselves getting sleepy during daytime hours may have vitamin D to blame, but the exact link between the two could depend upon their race, according to a new study.

Lead author David McCarty and colleagues discovered that in most patients, increasing levels of daytime sleepiness were inversely correlated with decreasing levels of vitamin D in their bodies.

However, the opposite was found to be true in African-American study participants, who felt higher levels of tiredness when their vitamin D levels were higher.

“While we found a significant correlation between vitamin D and sleepiness, the relationship appears to be more complex than we had originally thought,” McCarty said in a statement on Friday. “It’s important to now do a follow-up study and look deeper into this correlation.”

In a paper published online in Saturday’s edition of the Journal of Clinical Sleep Medicine, McCarty and colleagues Aronkumar Reddy, Paul Y. Kim, Andrew A. Marino, and Quinton Keigley, all from LSU, describe how they attempted to discover whether or not serum vitamin D levels were correlated with excessive daytime sleepiness, as well as to investigate whether or not a person’s racial background or innate vitamin D deficiency played a role in the relationship between the two.

“The study… involved a consecutive series of 81 sleep clinic patients who complained of sleep problems and nonspecific pain,” the American Academy of Sleep Medicine, which publishes the Journal of Clinical Sleep Medicine, explained.

“All patients eventually were diagnosed with a sleep disorder, which in the majority of cases was obstructive sleep apnea. Vitamin D level was measured by blood sampling, and sleepiness was determined using the Epworth Sleepiness Scale,” they added.

McCarty and his colleagues claim that this is the first study to demonstrate a “significant relationship” between sleepiness levels and vitamin D. They added that the racial factor makes sense because it has been established that higher levels of skin pigmentation is a risk factor for lower vitamin D levels.

While they did not intend for their work to establish a cause-and-effect relationship between the factors, they say that their research — when combined with previous studies — “suggests that suboptimal levels of vitamin D may cause or contribute to excessive daytime sleepiness, either directly or by means of chronic pain.”


High-dose vitamin C 'doubles kidney stone risk'

Maybe the C-fans were less healthy to start with

Regularly taking high-dose vitamin C pills can double the risk of kidney stones, say researchers.  They made their finding after looking at the incidence of kidney stones over 11 years in 23,355 men.

Those who took vitamin C supplements - which typically contain 1,000 milligrammes per tablet - were at twice the risk of developing the stones compared to men who took no vitamins.

Those who took the high-dose pills most regularly were at the highest risk.

But taking vitamin C as part of a multi-vitamin - which tend to contain much lower doses of the vitamin - did not raise the risk, found the researchers from the Karolinska Institute in Sweden.

Kidney stones are small crystals of waste matter that form and can block a part of the organ or the urinary tract, causing intense pain. They affect 10 to 20 per cent of men and three to five per cent of women.

According to the Department of Health, adults need just 40mg of vitamin C a day. Its advice notes that taking high doses can cause stomach pain, flatulence and diarrhoea, but it does not mention kidney stones.

While widely believed to fight off colds, recent trials have shown it has no discernable effect as a preventive agent. However, it does have a modest effect in shortening colds, if taken as a therapeutic medicine once the infection has begun.

Professor Agneta Akesson, who led the Karolinska’s study, published in the journal JAMA Internal Medicine, said: “Given that there are no well-documented benefits of taking high doses of vitamin C in the form of dietary supplements, the wisest thing might be not to take them at all, especially if you have suffered kidney stones previously.”

Dr Carrie Ruxton, from the Health Supplements Information Service, said as the study only looked at men results could not be assumed to be the same for women.

She added: "Since higher dose vitamin C - 500mg per day or more - is proven to reduce the duration of a cold or flu, it is worth taking these in the short-term when required.

"This study looked at people who were habitually taking around 1000mg several times a week.

"It is likely that short-term, sporadic use of higher dose vitamin C does not constitute a risk for kidney stones and can be helpful when people have a cold."


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