Interviewer: Dr. James Dowd with us today, author of The Vitamin D
Cure. When people think of Vitamin D, I think they automatically think of
the immune system. If you've got a cold, you've got to have vitamin D.
Doctor, can you talk about its relationship with our immune system, first
of all, and then we'll a couple of other certain issues.
Dr. Dowd: I recently wrote a white paper for a company that
measures vitamin D, and it was on this exact topic of what is the
importance of vitamin D in our immune system, and so it's a timely summary.
Early on, when our immune system is developing, during fetal development
and early childhood. The placenta is this organ... and, I really think of
the placenta as an endocrine gland, and its secreted product is a new human
being. Because the placenta makes so many different hormones.
One of them is Vitamin D. It has the ability to take the active substrate
and turn it in to active hormone. But, the placenta is this engineered,
immunosuppressed environment, so that the mother doesn't reject the fetus.
Because the fetus is made of her husband, and it is foreign protein, and so
theoretically her immune system should reject this foreign thing. But it
doesn't, and it doesn't because of the cortisol, and DHEA, and Vitamin D,
and all of these are immunosuppressive hormones, that protect the fetus
during its development in the womb.
Vitamin D is playing an additional role at suppressing the immune system to
prevent reject of the fetus. At the same time, the fetal immune system is
developing what we call "central tolerance". Which is, it's learning who it
is, what itself is. It's learning self.
It gets introduced to proteins in its muscle, in its liver, its kidney, its
brain, its heart, and it says, "This is me. I'm this new human being,"
let's call it Joe, "and I'm being introduced to every little part of Joe.
And, it's okay, so I'm not going to have an immune response to
Then, the hormones of pregnancy, and Vitamin D, and the hormones the fetus
makes all contribute to suppressing the immune system and allowing it a
chance to develop recognition of self.
Then, after birth, it has to develop recognition of some key things in its
environment. It has to develop recognition of food, it has to develop
recognition of the bacteria that is growing in its gut.
Because there's a difference between getting the flu, and the bugs that are
in your gut all the time. And you don't want your immune system to attack
the bugs in your gut all the time because there's a symbiotic relationship
Dr. Dowd: They're helping you grow and digest your nutrients for
you. By the same token, you want to be able to fight off a virus that you
might bet infected with.
So, the immune system has to learn the difference between bugs that are
friendly and bugs that are not so friendly. And Vitamin D plays a key role
in the immune system being able to make that distinction.
And so, Vitamin D, in general, helps with tolerance, adapting to these
things... self, and the environment. And then after the child is relieved
from the mother's protection, because after birth the child is protected by
the mother's breast milk. There's lots of antibodies there, and the
mother's immune system is still doing most of the work.
Once the breast feeding stops, then the immune system takes on a much more
defensive posture. Which is why newborn babies who are still breastfeeding
rarely get sick, and they don't get sick until they stop breastfeeding,
because now the immune system is in defense mode. Everything changes
And now Vitamin D is no longer suppressing the immune system
to develop tolerance as much as it's alerting the immune system to protect
it, in defense mode from microorganisms like viruses, bacteria and fungi
that come along later in childhood.
So, Vitamin D is important for central tolerance, learning who you are,
self tolerance. it's important for peripheral tolerance, learning what
foods are okay and what bugs are okay. And then after that stage of
developing tolerance, Vitamin D becomes critical in managing and preventing
There are studies looking at children and influenza. This study was done in
Japan. And they said, "Well, lets put one group of kids on Vitamin D and
the other group not on Vitamin D, and follow them through a flu season and
see what the rate of contraction of the flu is between these two groups.
And what they found is the Vitamin D group had 30% or 40% lower risk of
developing the flu that the kids who are not getting Vitamin D.
So, it works with viruses... we have lots of animal studies and lots of
human data, looking at its relationship with diseases like Tuberculosis,
and Vitamin D seems to be critical in helping your immune system attack,
isolate and kill Tuberculosis.
So, it seems to be very important, and there's lots of research going on
now with HIV, and we're wondering, "Why is Africa the country that's
plagued with it?" Well, there're clearly issues with poverty and
malnutrition, but when you think of the malnutrition you think, "What about
Vitamin D deficiency?
Actually, despite being a country bathed in sunlight, because of severe
malnutrition these people are also Vitamin D deficient. Because, you need
enough fat and cholesterol in your diet to make Vitamin D, and if you don't
have enough fat and cholesterol from malnutrition you can't even make
Vitamin D from sunlight.
And that's what we're seeing in a lot of areas of Africa and India, is that
the equatorial populations are suffering from Vitamin D deficiency because
of the malnutrition. The general malnutrition is not giving the fat they
need to make Vitamin D from.
And they have many more infectious diseases there. Yes, there are public
health issues there too, but Vitamin D may be playing another role in why
these infection rates are so much higher in these areas.