sun may prevent type 1 diabetes

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Sun May Prevent Type 1 Diabetes

Lack of exposure to the sun could play a role in development of type 1

diabetes and that vitamin D supplementation in early childhood may offer

protection

against the development of type 1 diabetes.

The rate of type 1 diabetes was higher in countries at higher latitudes

(r2=0.25, P0.001), where solar irradiation per square meter per day is

lower, reported

Cedric F. Garland, Dr.P.H., of the University of California San Diego,

and colleagues online in Diabetologia.

After adjusting for cloud cover and per capita healthcare expenditures,

the researchers also found that ultraviolet B irradiance was negatively

correlated

with rates of type 1 diabetes (r2=-0.42, P0.05). " This natural

experiment found that 25% of the variation in incidence rates [for type

1 diabetes] among

regions of the world can be accounted for on the basis of latitude, and

that 42% can be accounted for on the basis of solar UVB irradiance and

percentage

cloud cover, the main atmospheric determinants of vitamin D

biosynthesis, " the researchers wrote.

They recommended a combination of brief daily exposure to sunlight and

dietary vitamin D for all young children, particularly those living in

northerly

climes.

This study is the latest publication by Dr. Garland at the University of

California San Diego, to link sun exposure and vitamin D to a major

disease.

The new study is their first to connect sun exposure to a non-malignant

disease. Dr. Garland and colleagues said it was prompted by a series of

national

analyses indicating that, for example, rates of type 1 diabetes are 370

times higher in Finland than in China.

" The pattern follows a latitudinal gradient that is the inverse of the

global distribution of ultraviolet B irradiance, " they explained.

Additionally, several

earlier studies had found higher incidence of type 1 diabetes in

children with low dietary intake of vitamin D.

The Diabetologia report describes a systematic analysis of type 1

diabetes rates from 51 regions of the world from 1990 through 1994,

originally collected

by the Diabetes Mondial Project Group.

They confirmed that per capita health expenditures were positively

correlated with diabetes rates (P=0.004), but that local UVB irradiance

remained a significant

predictor of diabetes rates in multivariate analysis.

They cited limitations to their analysis including lack of data on

dietary vitamin D intake and on typical attire, which may affect actual

skin exposure

to sunlight.

It's also possible, they noted, that UVB exposure prevents type 1

diabetes by mechanisms unrelated to vitamin D. Some studies have

suggested that the disease

is caused by viral pathogens such as sackie virus, which can be

killed on surfaces by exposure to sunlight.

Nevertheless, Dr. Garland and colleagues suggested that children older

than one year who live in high latitudes should take 25 to 50 mcg of

dietary vitamin

D3 daily, especially in winter.

The researchers defined high latitudes as beyond the 30th parallels,

which covers the entire United States except for Hawaii, south Texas,

and the Florida

peninsula.

They added that being outdoors in sunlight for a few minutes a day can

substitute for some but not all the recommended dietary vitamin D

intake.

" Further epidemiological studies would be desirable on the effect of

serum 25(OH)D [vitamin D's active metabolite] levels and oral intake of

vitamin D on

incidence of type 1 diabetes, " the researchers said.

" In the meantime, public health action seems warranted based on evidence

gathered to date from many studies. "

A meta-analysis of earlier studies of vitamin D and type 1 diabetes,

published in the June issue of Archives of Disease in Childhood by

researchers in

England, led its authors to offer a similar recommendation.

" Vitamin D supplementation in early childhood may offer protection

against the development of type 1 diabetes, " wrote Christos Zipitis,

M.D., of the Stockport

NHS Trust, and colleagues after reviewing five observational studies of

vitamin D intake and rates of type 1 diabetes.

Practice Pearls:

list of 3 items

.. Explain to interested patients that the study found lack of exposure

to sunlight may be related to development of type 1 diabetes.

.. Note that the researchers recommended that young children receive

brief daily exposure to sunlight, as well as dietary vitamin D for those

living in high

latitudes, including most of the U.S.

.. Point out that the proposed preventive effect on type 1 diabetes has

not been confirmed in a prospective trial and these studies cannot prove

causality

of the association.

list end

Diabetologia:Mohr S, et al " The association between ultraviolet B

irradiance, vitamin D status and incidence rates of type 1 diabetes in

51 regions worldwide "

Diabetologia 2008; DOI: 10.1007/s00-5

Archives of Disease in Childhood: Zipitis C, et al " Vitamin D

supplementation in early childhood and risk of type 1 diabetes: a

systematic review and meta-analysis "

Archives of Disease in Childhood 2008; 93: 512-17.

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