QualPharma December 2020

MEDICAL
Vitamin B12 crosses the placenta during
pregnancy and is present in breast milk.
Exclusively breastfed infants of women
who consume no animal products may
have very limited reserves of vitamin B12
and can develop vitamin B12 deficiency
within months of birth. Undetected and
untreated vitamin B12 deficiency in infants
can result in severe and permanent
neurological damage.
The Academy of Nutrition and Dietetics
recommends supplemental vitamin B12
for vegans and lacto-ovo vegetarians during
both pregnancy and lactation to ensure
that enough vitamin B12 is transferred
to the foetus and infant. Pregnant
and lactating women who follow strict
vegetarian or vegan diets should consult
paediatrician regarding vitamin B12 supplements
for their infants and children.
Transfer to the Foetus. The serum B12
concentration of the new-born is twice
that of the mother, decreasing to adult
concentrations at about 6 to 7 months
postpartum. The placenta concentrates
B12, which is then transferred to the foetus
down a concentration gradient. Foetal
and maternal B12 serum concentrations
are quite strongly correlated.
It appears that only newly absorbed
B12 is readily transported across
the placenta and that maternal liver
stores are a less important source of the
vitamin for the foetus. This implies that
current maternal intake and absorption
of the vitamin during pregnancy
have a more important influence
on the B12 status of the infant
than do maternal B12 stores.
Lactation: Current maternal intake
of the vitamin may have an important
influence on secretion of the
vitamin in milk. In several studies of
infants with clinical signs of vitamin B12
deficiency caused by low maternal intake
or absorption of the vitamin, maternal
plasma concentrations of the vitamin
were found to be normal or low normal,
suggesting that maternal B12 stores
are less important than current maternal
intake.
The RDA Enigma
The Recommended Dietary Allowance
(RDA), by definition, is designed to provide
dietary guidance for healthy individuals.
An important consideration is
whether the recommended intake is adequate
to prevent the biochemical disturbances
that were recently recognized to
be widespread and sometimes associated
with subtle but important clinical disorders,
rather than preventing overt disease
as used in the design for establishing
RDA.
The intake of micronutrients in daily diet
is far from satisfactory and largely less
than 50% RDA is consumed by over 70%
of Indian population. Moreover, the loss
due to micronutrient deficiency costs
India a huge loss in terms of productivity,
illness, increased health care costs and
death.
As per National Institute of
Health (NIH),
dietary supplements against
vitamin B12 deficiency can also
contain methylcobalamin and
other forms of vitamin B12.
Need to Revisit the RDA Values with
Changing Times
In Western countries: It is imperative
to take cognizance that the current RDA
value of vitamin B 12 intake in Western
countries is primarily based on a 1958
study in which approximately one-half of
the subjects with pernicious anaemia
achieved and maintained maximum
erythropoiesis on long-term follow-up
with intramuscular administration of
vitamin B-12 (median: 1.4 µg/d). A physiologic
average requirement of 1.0 µg vitamin
B-12/d was measured after adjustment
for the extra loss of vitamin B-12 by
subjects with pernicious anaemia. After
adjustment for incomplete absorption of
vitamin B-12 from food (50%), an Estimated
Average Requirement (EAR) of 2.0
µg vitamin B-12/d was established. The
current RDA of 2.4 µg vitamin B-12/d was
derived by multiplying the EAR by 1.2.
Although this approach may have merit,
QualPharma *Dec 2020* , Vol.3 ISSUE 12