BodyTune Health
Unlocking Human Potential
Vitamin A: an antioxidant and general immune enhancer.
Elly Tulloch posted on February 04, 2010 14:20
This week I am going to discuss Vitamin A; an antioxidant and general immune enhancer
(specific against measles), which is commonly known as the “anti-infective vitamin.” Vitamin A is
a generic term for a large number of related compounds. Retinol (an alcohol) and retinal (an
aldehyde) are often referred to as preformed vitamin A. Retinal can be converted by the body to
retinoic acid (RA) → the form of vitamin A known to affect gene transcription. Retinol, retinal,
RA and related compounds are known as retinoids. Β-carotene and other carotenoids that can
be converted by the body into retinol are referred to as provitamin A carotenoids.
RA and its isomers act as hormones to affect gene expression and thereby influence numerous
physiological processes. All-trans RA and 9-cis RA are transported to the nucleus of the cell
bound to cytoplasmic retinoic acid-binding proteins. Within the nucleus, RA binds to retinoic acid
receptor proteins. This binding of all-trans RA and 9-cis RA regulates the rate of gene
transcription, thereby influencing the synthesis of certain proteins used throughout the body.
Through stimulation and inhibition of transcription of specific genes, RA plays a major in cellular
differentiation, the specialization of cells for highly specific physiological roles. Most of the
physiological effects attributed to vitamin A appear to result from its role in cellular
differentiation.
As stated above, Vitamin A is commonly known as the anti-infective vitamin this is because it is
required for normal functioning of the immune system (Semba, RD. 2001; Impact of vitamin A
on immunity and infection in developing countries). The skin and mucosal cells (cells that line
the airways, digestive tract, and urinary tract) function as a barrier and form the body’s first line
of defense against infection. Retinol and its metabolites are required to maintain the integrity
and function of these cells. Vitamin A and RA play a central role in the development and
differentiation of white blood cells, such as lymphocytes, which play critical roles in the immune
system response. Activation of T lymphocytes, the major regulatory cells of the immune system,
appears to require all-trans RA binding to its receptor protein.
Red blood cells, like all blood cells, are derived from precursor cells called stem cells. These
stem cells are dependent on retinoids for normal differentiation into red blood cells. Vitamin A
also appears to facilitate the mobilization of iron from storage sites to the developing red blood
cell for incorporation into hemoglobin, the oxygen carrier in red blood cells.
The retinoid receptor pathways are also critical for vision, sensory perception, language
processing and attentiveness. Sideways glancing may indicate poor rod (photoreceptor cells in
the retina of the eye) function and may be an indication of a G-alpha protein defect, especially if
family history shows others with night-blindness and hypothyroidism.
In 1999, Dr Mary Megson (a pediatrician in Richmond VA), showed that certain children
susceptible to autism are genetically at risk from a G-alpha protein defect and theorized that
vitamin A can help alleviate “defective G-alpha protein function in Autism.” The G-alpha protein
is part of a cell’s signal transmission system located in the outer (plasma) membrane. It gives
an energy push by dephosphorylating GTP (guanosine triphosphate) to form GDP (guanosine
diphosphate). This chemic change provides energy to support the movement of a message
from outside the cell into the cell’s inner workings – a necessary part of cellular perception. Dr
Megson also reports enhancement of beneficial effects when Bethanechol is used in
conjunction with vitamin A. Bethanechol is a prescription, choline-like substance that stimulates
the parasympathetic nervous system, which I will be discussing in more detail in a future
newsletter.
Both vitamin A excess and deficiency are known to cause birth defects. Retinol and RA are
essential for embryonic development. During fetal development, RA functions in limb
development and formation of the heart, eyes and ears (Olson, JA. 1996; Vitamin A).
Additionally, RA has been found to regulate expression of the gene for growth hormone (Aranda
A, Bedo G, Santisteban P. 1989; Retinoic acid regulates growth hormone gene expression).
There are only rare cases of vitamin A toxicity in our population, most of which are seen in longsustained high doses or mega doses in the millions.
Dosing Recommendations:
The principle forms of preformed vitamin A in supplements are retinyl palmitate and retinyl
acetate. Multivitamin preparations will generally provide a combination of vitamin A and βcarotene.
The tolerable upper level intake for preformed vitamin A (retinol) are:

Infants (0 – 12 months) → 600mcg/d (2000IU)

Children (1 – 3 years) → 600mcg/d (2000IU)

Children (4 – 8 years) → 900mcg/d (3000IU)

Children (9 – 13 years) → 1700mcg/d (5667IU)

Adolescents (14 – 18 years) → 2800mcg/d (9333IU)

Adults (19 years and older) → 3000mcg/d (10000IU)

Pregnancy → during pregnancy, excess preformed vitamin A is known to cause birth
defects, therefore pregnant women who are not at risk of vitamin A deficiency are
advised not to consume more than 800mcg/d (2600IU/d) of retinol supplement. (Please
Note – this level may be exceeded if necessary however the patient must be continually
monitored by their practitioner)
Dr. Jaquelyn McCandless (USA) is doing a lot of research into high-dose vitamin A for her ASD
patients. Her current protocol involves using a 2-day mega-dose (200,000IU to 400,000IU – in
the palmitate form) to combat gut measles in these children no more than every 6 months.