Vitamin D in brain function--supplementation for high risk groups may be warranted

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Public release date: 21-Apr-2008

http://www.eurekalert.org/pub_releases/2008-04/chr-vdi041808.php

Contact: Venita

vrobinson@...

Children's Hospital & Research Center at Oakland

Vitamin D in brain function

Vitamin D supplementation for high risk groups may be warranted

In a definitive critical review, scientists at Children’s Hospital &

Research Center Oakland ask whether there is convincing biological or

behavioral evidence linking vitamin D deficiency to brain dysfunction.

Joyce C. McCann, Ph.D., assistant staff scientist and Bruce N. Ames,

Ph.D., senior scientist at Children’s Hospital Oakland Research

Institute (CHORI) conclude that there is ample biological evidence to

suggest an important role for vitamin D in brain development and

function, and that supplementation for groups chronically low in vitamin

D is warranted. Their conclusions will be published on April 22, 2008 in

the Federation of American Societies for Experimental Biology (FASEB)

Journal.

“This critical analysis of vitamin D function and the brain is a model

of careful thinking about nutrition and behavior”, says Gerald

Weissmann, MD, Editor-in-Chief of the FASEB Journal “One wishes that all

studies of nutritional supplements or requirements were this thoughtful.

Drs. McCann and Ames deftly show that while vitamin D has an important

role in the development and function of the brain, its exact effects on

behavior remain unclear. Pointing to the need for further study, the

authors argue for vitamin D supplementation in groups at risk.”

Vitamin D has long been known to promote healthy bones by regulating

calcium levels in the body. Lack of sufficient vitamin D in very young

children results in rickets, which can be easily prevented by vitamin D

supplements. Only recently the scientific community has become aware of

a much broader role for vitamin D. For example, we now know that, in

addition to its role in maintaining bone health, vitamin D is involved

in differentiation of tissues during development and in proper

functioning of the immune system. In fact, over 900 different genes are

now known to be able to bind the vitamin D receptor, through which

vitamin D mediates its effects. In addition to protecting against

rickets, evidence now strongly indicates that a plentiful supply of

vitamin D helps to protect against bone fractures in the elderly.

Evidence also continues to accumulate suggesting a beneficial role for

vitamin D in protecting against autoimmune diseases, including multiple

sclerosis and type I diabetes, as well as some forms of cancer,

particularly colorectal and breast.

Vitamin D is present in only a few foods (e.g., fatty fish), and is also

added to fortified milk, but our supply typically comes mostly from

exposure to ultraviolet rays (UV) in sunlight. UV from the sun converts

a biochemical in the skin to vitamin D, which is then metabolized to

calcitriol, its active form and an important hormone. Formation of

vitamin D by UV can be 6 times more efficient in light skin than dark

skin, which is an important cause of the known widespread vitamin D

deficiency among African Americans living in northern latitudes. Dark

skin has been selected during evolution because it protects against the

burning UV rays of the sun in the tropics. White skin has been selected

for allowing as much UV exposure to make sufficient vitamin D in

Northern (high) latitudes. Thus, fair-skinned northerners are at risk in

Australia or Arizona for sunburns and UV-induced cancer, while

dark-skinned people in the Northern U.S. or European latitudes with

little exposure to the sun are at risk for rickets, bone fractures and

possibly other diseases including several types of cancer due to a lack

of vitamin D. Fortunately sun-screens and vitamin D supplements are

inexpensive.

McCann & Ames point out that evidence for vitamin D’s involvement in

brain function includes the wide distribution of vitamin D receptors

throughout the brain. They also discuss vitamin D’s ability to affect

proteins in the brain known to be directly involved in learning and

memory, motor control, and possibly even maternal and social behavior.

The review also discusses studies in both humans and animals that

present suggestive though not definitive evidence of cognitive or

behavioral consequences of vitamin D inadequacy. The authors discuss

possible reasons for the apparent discrepancy between the biological and

behavioral evidence, and suggest new, possibly clarifying avenues of

research.

Many vitamin D experts advise that the currently recommended level of

vitamin D intake is much too low and should be raised to protect against

bone fractures and possibly cancer in addition to rickets (2). Indeed,

even using present guidelines, too many Americans have low vitamin D

blood levels. McCann & Ames propose that, despite uncertainty regarding

all of the deleterious effects of vitamin D inadequacy, the evidence

overall indicates that supplementation, which is both inexpensive and

prudent, is warranted for groups whose vitamin D status is exceptionally

low, particularly nursing infants, the elderly, and African Americans

(e.g., see (3)).

This review is the fourth in a series by McCann & Ames that critically

evaluate scientific evidence linking deficiencies in micronutrients (the

approximately 40 vitamins, minerals, amino acids, and fatty acids

required for the body to function) to brain function. Other reviews in

the series discuss the long-chain polyunsaturated fatty acid

docosahexaenoic acid (DHA) (4, 5), choline (6), and iron (7).

###

1. McCann, JC, Ames BN (2008) Review Article: Is there convincing

biological or behavioral evidence linking vitamin D deficiency to brain

dysfunction " FASEB J. 22: 982-1001.

2. Vieth R, Bischoff-Ferrari H, Boucher BJ, et al. The urgent need to

recommend an intake of vitamin D that is effective. Am J Clin Nutr

2007;85:649-50.

3. Bodnar LM, Simhan HN, Powers RW, MP, stein E, JM.

High prevalence of vitamin D insufficiency in black and white pregnant

women residing in the northern United States and their neonates. J Nutr

2007;137:447-52.

4. McCann JC, Ames BN. Is docosahexaenoic acid, an n-3 long chain

polyunsaturated fatty acid, required for the development of normal brain

function " An overview of evidence from cognitive and behavioral tests in

humans and animals. Am J Clin Nutr 2005;82:281-95.

5. McCann JC, Ames BN. DHA and cognitive development: an update on the

science. Pediatric Basics 2007;April.

6. McCann JC, Hudes M, Ames BN. An overview of evidence for a causal

relationship between dietary availability of choline during development

and cognitive function in offspring. Neurosci Biobehav Rev 2006;30:696-712.

7. McCann JC, Ames BN. An overview of evidence for a causal relationship

between iron deficiency during development and cognitive or behavioral

function in children. Am J Clin Nutr 2007;85:931-45.

Research at Children’s Hospital & Research Center Oakland, CA

--

ne Holden, MS, RD

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