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Ask Dr. Sue
SUN EXPOSURE AND VITAMIN D IN BABIES
Dear Dr. Sue,
I recently read an article on the importance of vitamin
D (via sunlight) especially for baby girl's calcium
stores. What do you know about this? How
much sunlight per day is necessary to have an effect
(without being too much sun for their tender skin?)
Dear Mom,
For those who aren't familiar with it, let me first
discuss what Vitamin D is, and why it is necessary for
growing infants. Vitamin D actually acts more like
a hormone than a vitamin. It is different
from other hormones, though, in that its production
requires an interaction between the skin and ultraviolet
light. The newly formed molecule is then further
altered in the liver, and then in the kidney, before it
becomes the finished product.
Vitamin D has effects on the kidneys (regulating calcium
loss), on the intestines (controlling how much calcium
is absorbed from the diet) and on the bones and teeth
(governing the way calcium
is deposited there). Too little Vitamin D prevents
adequate use of calcium, putting baby girls at risk for
brittle bone disease in later life. Even worse,
too little Vitamin D can lead acutely
to rickets. Symptoms of rickets can include bone
pain and deformity, inappropriately loose or weak teeth,
muscle weakness, and rarely, even seizures or severe
muscle contractions caused by decreased body calcium.
While rickets can be caused by certain chronic medical
conditions, we are concerned here with the type of
rickets that anyone can get; that caused by too little
vitamin D or too little calcium. In the early part
of this century, it was believed that as many as 90% of
children in some of the crowded cities of northern
Europe and the northern U.S. had rickets. Since
the addition of vitamin D to milk products, however,
this disease had virtually vanished.
Recently, though, the problem has begun to resurface,
with cases noted throughout the U.S., even in sunny
climates. This resurgence is due in part to
decreased sun exposure for children, and the very real
concern that babies be protected from ultraviolet light.
Babies do not often spend large amounts of time in the
sun, and when they do, they tend to be coated in
sunscreen. Even adults don't get the sunshine that
they need: one study found that the average
Vitamin D levels throughout the year for people living
in Palm Beach were twice those of people living in
Seattle or Boston. But, for both of the less sunny
cities, men who worked outdoors had higher levels of
Vitamin D in February than everyone else did in August.
In other words, people who don't work outdoors, and who
don't live in places like Palm Beach, probably spend
their entire lives with relative Vitamin D deficiency.
The increase in cases of rickets has also has been
impacted by the increasing numbers of breastfeeding
infants. Breastmilk contains significantly less
vitamin D than formula does. Does
this mean than breastmilk is an inferior product?
Absolutely not! Many studies have supported the
benefits of breastfeeding in regard to the immune
system, the intestinal tract, cancer risks, bonding and
even intelligence. What is does mean is that the
human species was designed to spend more time outside
than we do, and that we were meant to still have that
protective ozone layer so that we didn't need to fear
sun exposure!
Most exclusively breastfed babies do not develop
rickets, since most manage to get the minimum amount of
sun exposure needed. (Many are also protected by the
addition of vitamin D supplemented foods to their diets
by age 6 months.) How much sunlight is enough? One
source says that exposing the hands, arms and face to
the sun for 30 minutes per day is sufficient.
Another source states that in the summer, a baby wearing
only a diaper needs only 30 minutes of sun exposure per
week, and in the winter, a clothed but hatless baby can
get enough sun in 2 hours per week. Neither source
identifies where their data came from, and most experts
feel that it is difficult to impossible to determine
whether a child is getting enough sun exposure to make
adequate vitamin D. The other problem involves the
availability of sun...in the northwest, we sometimes
don't see the sun for weeks at a time! Cold
temperatures also preclude taking a baby
with exposed arms, hands and face outdoors for 30
minutes in many parts of the world.
Dark-skinned babies are even more at risk, since they
require about six times the amount of UV light than
lighter-skinned babies. It is definitely wise for
all dark-skinned infants who are being
exclusively breastfed to receive a supplement of vitamin
D daily (400 IU once a day). Many pediatricians
feel that all breastfed babies should once again be
supplemented, beginning at two months of age. Dr.
Thomas Welch, an associate editor of the Journal of
Pediatrics, puts it this way. "In an era of expensive,
high-tech medicine, a serious disease is reappearing
because of neglect of a decades-old intervention that
costs pennies a day, is completely safe, and is 100%
effective."
 
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