Staying Healthy Newsletter - <em>In the news:</em> Vitamin D and Brain Health: More Outdoor Time for Better Vision
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In the news: Vitamin D and Brain Health: More Outdoor Time for Better Vision

Low Vitamin D Linked to Faster Mental Decline

For older individuals, low levels of vitamin D might contribute to a more rapid decline in memory and thinking skills according to research published in the journal JAMA Neurology (1).

A team from Rutgers University and UC Davis analyzed information from a diverse group of older men and women who participated in Alzheimer’s research in Northern California.

The 382 participants in this analysis included people whose cognitive abilities were normal for their age, those with mild cognitive impairment (MCI), and those with dementia. MCI can involve problems with memory and thinking that are noticeably greater than the changes commonly seen with normal aging, but far less than the more serious decline of dementia

At the beginning of the study, more than a quarter of the participants were deficient in vitamin D, and 35% had inadequate blood levels (as measured by plasma 25-hydroxyvitamin D). Levels were lower in people of color (African-Americans and Hispanics) than in white participants.

After about 5 years of follow-up, the rate at which cognitive skills declined was found to be substantially faster – about 2-3 times faster – In those with deficient or low vitamin D levels compared to those whose blood levels were considered adequate.

The accelerated decline was seen in the cognitive processes called executive function and episodic memory, which is the ability to remember past experiences that happened at a particular time and place. Executive function refers to mental skills that help the brain organize and act on information – skills that allow us to organize, prioritize, pay attention, plan and get started on tasks.

This is not the first study to find that vitamin D insufficiency predicts cognitive decline, though whether vitamin D supplements can help slow down cognitive decline needs to be evaluated in future studies. In the meantime, we do know that nearly every tissue and cell type in the body has receptors for vitamin D, including the brain. So maintaining adequate levels of the vitamin makes good sense for overall health.

More Time Outside, Less Myopia: Follow-up

The May issue of Staying Healthy reviewed some of the theories for why the worldwide incidence of myopia, or near-sidedness, in children has increased
so dramatically. (For background, see May issue.

Here in the US, the commonness of myopia in those aged 12-54 grew from 25% in the early 1970’s to about 42% by 2004 according to National Eye Institute data. In some parts of China, 90% of high school graduates have near-sightedness, while myopia rates are lower but increasing in Europe and the Middle East, according to the authors of a new study from China (2).

The researchers assigned children in a dozen primary schools to an extra 40 minutes of outdoor activity or to continue their existing class schedule. Nearly 2,000 six year-old first-graders were included in the study.

After 3 years, about 30% of the outdoor activity group had developed myopia, versus almost 40% of children who continued their usual activity.

The study didn’t attempt to determine why more time outside – even a modest 40 minutes daily – was found to be protective, but the authors do note that bright light may help avert the development of myopia by affecting eye growth – one of the current leading theories for the increase in myopia. Some feel that the jump in myopia rates also may have something to do with too much time spent on near vision tasks like computer use, coupled with an inherited predisposition for the condition.

References

  1. Miller JW, et al. Vitamin D status and rates of cognitive decline in a multiethnic cohort of older adults. JAMA Neurol. Sept. 14, 2015. [Epub ahead of print].
  2. He M, et al. Effect of time spent outdoors at school on the development of myopia among children in China: A randomized clinical trial. JAMA. 314:1142-8, 2015.
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