Advanced Mediterranean Diet

The Institute of Medicine is widely expected to recommend higher intake levels of vitamin D in 2010.  I’m not waiting - I’m starting now. 

I have great respect for Monica Reinagel at NutritionData.com.  I decided to review the issue when I read that vitamin D is one of only three supplements she takes - the others are fish oil and calcium.  Like me, she relies on a variety of natural, whole foods for the myriad vitamins and other nutrients we need. 

It’s not easy to miss all the medical journal articles on the effects and benefits of vitamin D published over the last 10 years.  Many of you know the time-honored role of vitamin D: bone health, including prevention of osteoporosis.  The major new developments in the vitamin D story are its potential benefits in terms of lower risk of type 2 diabetes, cardiovascular disease, dementia, some cancers, autoimmune diseases, infections, deaths, and falls in the elderly.  [Diabetes prevention may also require calcium supplementation.]  And we need higher blood levels of vitamin D for those benefits. 

The Institute of Medicine currently recommends 200 IU (international units) per day for people under 50, 400 IU for people 50-70, with an upper intake level of 2,000 IU per day.  I assume those amounts refer to a combination of food (or supplements) and the vitamin D your skin makes (but how do we know that?). 

The new recommendation is expected to be around 1,000-2,000 IU per day.  It’s quite difficult to get close to that just with food.  With adequate sun exposure, we can make some vitamin D.  But the dermatologists have scared us out of the sun with horror stories of skin cancer.  I’ve seen some tragic cases in my own patients.  Skin covered with sunscreen doesn’t make vitamin D.  It can be difficult to get enough sun exposure, especially at higher latitudes in winter. 

I’ll even admit I’m a little concerned about sunlight accelerating the changes of aging on my face,neck, and hands.  I grew up in the South (U.S.) and saw plenty of sun-worshipping young women who at age 35 looked closer to 50. 

I’m picking up a vitamin D supplement next time I’m at the supermarket - 1000 IU/day.

Steve Parker, M.D.

References:

Monica Reinagel.  Vitamin D: Now I’m a Believer.  Nutrition Data Blog, May 1, 2008.

Internal Medicine News, vol. 42, No. 8, April 15, 2009, pages 1 and 7.

American Medical News, April 27, 2009, pages 21-22.

Vitamin D deficiency is common in older folks due to low dietary intake, reduced ability of skin to make vitamin D, and restricted sunlight exposure.

Low vitamin D levels are associated with

• increased risk of fractures
• higher death rates
• tendency to fall
• type 2 diabetes
• several cancers
• heart attacks
• depression
• fibromyalgia
• osteoporosis
• multiple sclerosis
• and, classically, rickets

A few small clinical studies have associated low vitamin D levels with cognitive impairment and dementia.  The longer you live, the greater your chance of developing cognitive impairment and dementia.

A study published in the  Journal of Geriatric Psychiatry and Neurology last month found low levels of vitamin D associated with increased odds of cognitive impairment, which is often a precursor to dementia.  Study participants were 1,766 adults aged 65 years and older form the Health Survey for England 2000, a nationally representative population-based study.

Blood levels of 25-hydroxyvitamin D were analyzed and compared to participants’ performance scores on the Abbreviated Mental Test.  The test has 10 items, primarily covering orientation in time and space, memory, and attention.  Overall, 212 participants (12%) were cognitively impaired.  The lower the vitamin D level, the greater the odds of impairment.  For example, people with the lowest quarter of vitamin levels were over twice as likely to have cognitive impairment compared to the highest quarter.

The study authors point out that a number of studies seem to contradict their results, and they explain the differences in the various studies and possible reasons for the discordant results.  Nevertheless, they think their results are more valid.

How could vitamin D, best known for healthy bone effects, help preserve cognitive function?  The authors write:

Vitamin D may also be of interest in the prevention of neurodegenerative diseases as ample evidence from in vitro and animal experiments suggests an important role in the expression of neurotrophic factors, the stimulation of adult neurogenesis, calcium homeostasis, and detoxification.

My Comments

Vitamin D is starting to sound like a miracle drug, if you’ve been paying attention to all the recent research.  But let’s not forget all the hope and hype regarding the benefits of various supplements over the last decade that ended up disappointing us: vitamin E, vitamin C, Foltx, vitamin A analogs, and others.

I’m wondering if a vitamin D level should be part of the dementia evaluation process.  It is not at this point.  How about offering the test to everybody starting at age 50?

Vitamin D supplements are cheap, well-tolerated, and effective in treating at least some deficiency sydromes, such as vitamin D-deficient osteoporosis.

I certainly agree with the researchers, who write:

Further research is warranted to investigate if vitamin D supplementation is a cost-effective and safe way of reducing the incidence of cognitive impairment [and dementia] in the growing elderly population around the world.”

Many people over 50 are already taking vitamin D for bone preservation.  This study provides another reason to continue it.

Steve Parker, M.D.

Llewellyn, David; Langa, Kenneth; and Lang, Iain.  Serum 25-Hydroxyvitamin D Concentration and Cognitive Impairment.  Journal of Geriatric Psychiatry and Neurology, Epub ahead of print on February 4, 2009, as doi: 10.1177/0891988708327888