Vitamin B6 requirements oral contraceptive&’ J. E. Lekiem, Ph.D., and H. M Linkswiler,
R. R. Brown, Ph.D.
ABSTRACT
Ph.D.,
Fifteen
and nine control
of women
using
2 D. P. Rose,
women
who
M.D.,
used
Ph.D.,
combined
estrogen-progestogen
oral
contraceptives
women
were given a vitamin B6 -deficient diet for 4 weeks and the same diet supplemented with 0.8, 2.0, or 20.0 mg of pyridoxine hydrochloride for an additional 4 weeks. At weekly intervals a variety of indices of vitamin B6 nutrition were measured to determine rates of depletion and repletion. The tryptophan load test (2.0 g) was significantly different in the contraceptive users. However, other indices, including urinary cystathionine (3.0 g L-methionine load), urinary 4-pyridoxic acid, plasma phosphate, and erythrocyte alanine and aspartate aminotransferases, were not significantly different. Since altered tryptophan metabolism persisted in contraceptive users even when other indices of vitamin B6 nutrition were normal, we suggest that the use of oral contraceptives specifically affects tryptophan metabolism by some means other than through a vitamin B6 deficiency. Am. J. Clin. Nutr. 28: 535-541, 1975.
Women using estrogen-containing oral contraceptives excrete elevated amounts of tryptophan metabolites after a tryptophan load test compared with women not taking oral contraceptives (1-3). Elevated levels of 3-hydroxyanthranilic
acid
were
also
observed
in
basal
urines from such subjects (4). When pyridoxine was administered to such subjects the excretion of tryptophan metabolites was decreased toward normal levels, but in some subjects large amounts of the vitamin may be required (3). These data have been widely interpreted as indicating that the use of oral contraceptive drugs
causes
an
increased
requirement
for
vitamin B6, although other explanations for the altered tryptophan metabolism may be possible. To evaluate the effect of oral contraceptive usage on the requirement for vitamin B6, a variety of indices of vitamin B6 nutrition were measured
control became
to
determine
a diet used to measure became physiological
Methods The cerning
the
rate
at
which
and oral contraceptive using women depleted of this vitamin while ingesting low in vitamin B6. The same indices were the
repleted levels
and
at which
these
‘From the Division of Clinical Oncology, University of Wisconsin Medical School and Department of Nutritional Sciences, University of Wisconsin College of Agricultural and Life Sciences, Madison, Wisconsin 53706. Supported in part by Wisconsin College of Agricultural and Life Sciences, Contract NIH, HICHD 72-2782 with the National Institute of Child Health and Human Development, and Grant No. CA-13302 from the National Cancer Institute, Public Health Service, Bethesda, Maryland 20014.
subjects with
materials
experimental the selection
The American
rate
when supplemented of pyridoxine.
Journal
details of these studies of subjects, diets used, of Clinical
Nutrition
conand
28: MAY
indices of vitamin B6 nutrition measured were reported previously (5). In brief, 9 healthy control women (average age 22.3 ± 1.9 years), and 15 women (23.2 ± 3.1 years) who had used oral contraceptive agents for at least 6 months were given a diet that contained only 0.19 mg of pyridoxine equivalents per day (6). Oral contraceptive users started the diet on day 1 1 of a 21-day pill sequence. Control subjects started 14 days after onset of the previous menses. For the first 4 days, while baseline studies were made, the diet was supplemented daily with 0.8 mg of pyridoxine hydrochloride (PN-HC1). This supplement was then withdrawn and both groups of subjects consumed only the deficient diet for 28 days. After this depletion period, subjects were supplemented with either 0.8, 2.0, or 20 mg/day of PN-HCI for another 28 days. Before release from the study, subjects were supplemented for a final 4 days with 100 mg PN-HC1/day. During the baseline period, and at weekly intervals throughout the study, several indices of vitamin B6 nutrition were measured in each subject. The indices measured included urinary tryptophan metabolites before and after a 2.0 g oral load of L-tryptophan (7, 8), urinary cystathionine after a load
1975,
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
pp. 535-541.
Printed
in U.S.A.
535
LEKLEM
536
El
AL.
of 3.0 g of L-methionine (9, 10), urinary 4-pyridoxic acid (5), plasma pyridoxal phosphate (5), and erythrocyte activities of alanine arninotransferase and aspartate aminotransferase (5). In order to study metabolism along the kynurenine pathway and to circumvent any variations in activity of tryptophan oxygenase, loading doses of L-kynurenine sulfate (200 mg/dose) were given initially, at the time of maximum deficiency, and after repletion with pyridoxine for 4 weeks.
At comparable times of depletion and at equal levels of PN -HC1 supplementation, the mean excretion of tryptophan metabolites was consistently greater than that of controls, and suggests that the requirement for vitamin B6 may be slightly greater in oral contraceptive users than in controls. However, it should be pointed out that because of large individual variations and limited numbers of subjects,
Results
many statistical
Measurement lites
after
the
deficient
ceptive
of urinary
tryptophan
loading
diet
users
showed
excreted
nine
,
and
xanthurenic
trol
subjects
tryptophan prior
that
the
to
starting
oral
contra-
acid
These
differences
a 3.0
persisted
,
During
subjects
depletion,
excreted
metabolites,
increasingly
with
the
both
groups
large
amounts
oral
contraceptive
larger
amounts
these differences significance. Details
g oral
Fig. 2. The tryptophan
and increased during the period of vitamin B6 depletion. This is summarized in Fig. 1 which shows the yield of tryptophan metabolites excreted.
of
of individual tryptophan lished elsewhere (8). The urinary excretion
elevated levels of kynure, 3-hydroxykynurenine compared with the con-
acetylkynurenine (8).
metabo-
load
are
pub-
of cystathionine L-methionine
1 levels groups.
occurred
not achieve the excretion
metabolites
at
after
is shown
pattern is different metabolite yield
tion and week similar in both differences
of
do of
in
from that of the in that predeple-
of
cystathionine However,
later
times,
were apparent
and
during
of of
users I
excreting
consistently
controls.
Supplementation
0.8
of
control
the third week of repletion had stabilized at essentially values. The oral contraceptive
the excretion level the predepletion users supple-
the
excretion
with 0.8 a marked
mented exhibited
tryptophan of
tion)
higher
the
time.
same
contraceptive
than The
mg
of
control
subjects
value 47
observed and
use
was
the
to
normal
by
also
promptly
ments
of
2.0
values
considerably
values
for
these
which which with
within
1 to
contraceptive by
PN-HC1,
lower subjects,
Supplementation with 20 mg/day to control
of
in oral
tryptophan
ranges
oral
than
daily
with the
users suppleexcretion
predepletion
but
stifi
not
of
oral
contraceptive
promptly
restored
--8,
STUDY
-$4-------------+6,
-,
at
subjects
restored
decreased
mg
+8,4-
interrupted.
daily
0 -i Ui
DLI’ OF
was
inflection
fmding during
of the control
Excretion
4
U. 0
was
and
low
‘Ii
(predeple-
subjects
at day
PN-HC1
metabolism
weeks.
users tion
the
after
C U) I” I0
of
excretion
starting
19 were a consistent with the 7-day period
contraceptive
levels.
the
these
users
excretion
a0
-J
also
even
the
than
Supplementation
was
in
However,
for
markedly
at day coincided
PN-HC1/day
reduction
higher
values
2.0
of
supplementation,
slightly
oral
mg
metabolites.
weeks still
PN-HC1/day
subjects
within
reduced
of
the
dramatically 1 week, and by
with
mg
than
at control excre-
levels.
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
2
FIG. 1 . Yield of metabolites excreted after a 2.0 g tryptophan load by control subjects and oral contracaptive users (O.C.). During the first 4 days the deficient diet (-B6) was supplemented with 0.8 mg pyridoxine hydrochloride. During the second +B6 period the diets were supplemented with the number of milligrams of pyridoxine hydrochloride indicated in the figure. The shaded bars below the figure designate the 7-day period when oral contraceptive use was discontinued. There were 9 control subjects and 15 contraceptive users. During the repletion period 6 controls were supplemented with 0.8 mg and 3 were given 2.0 mg of pyridoxine hydrochloride. Of the oral contraceptive users, 5 were supplemented with 0.8 mg, 6 with 2.0 mg, and 4 with 20 mg. The metabolites included in the yield value were kynurenine, N’-acetyl kynurenine, 3-hydroxykynurenine, anthraniic acid glucuronide, o-aminohippuric acid, kynurenic acid, and xanthurenic acid.
VITAMIN
B6 REQUIREMENTS
IN
ORAL to
CONTRACEPTIVE
restore
either
PLP
values
group.
mg/day
to
2
and
appreciably
537
predepletion
levels
supplements
of
2.0
in
PLP
However,
for
levels
USERS
3 weeks
higher
resulted
than
starting
in
values
in
I
both
C.,J
(5).
groups
To evaluate Ui -J
metabolic
ceptive use on way independent
0
of
Ui
z z
the
tryptophan
oxygenase,
L-kynurenine
0
before
I
4I-
sulfate
deficiency,
pyridoxine urenine,
4
and
urenine
at 3
WEEK -B,
4-
4
5
6
7
+8,
FIG.
2. Urinary excretion of cystathionine after a load of L-methionine in oral contraceptive users (O.C.) and control women. During the -B6 period the diet contained the equivalent of 0.19 mg of pyridoxine. During the +B6 period the diet was supplemented daily with 0.8, 2.0, or 20 mg of pyridoxine hydrochloride. Cystathionine was measured by an amino acid analyzer (modified Beckman model 1 20) using a modified buffer gradient system (9).
3.0 g oral
the
peak
individuals
and
because
of the
subjects, these differences cance statistically. Excretion of urinary creased
at
similar
rates
small
were
not
of
significant contraceptives
but
metabolism
number
they has
at
kynurenine
of given
and
The
after
excretions of , acetylkyn-
are
shown
in Fig.
and 3-hydroxykynin the oral contra-
deficiency. and
times when
Excretions
xanthurenic
Because of these
of
acid
were
of sizable differences
indiwere
suggest that the use of oral an effect on tryptophan
one
or
in addition
more
steps
to any
effects
beyond they
may
have on tryptophan oxygenase activity. Activity of erythrocyte alanine aminotrans-
CONTROLS
the first 2 weeks of repletion with PN-HC1 the excretion by oral contraceptive users remained above that of controls at comparable times. Again, because of wide variations between
loads were
acid
essentially unchanged. vidual variations, none
OF STUDY .#
mg
group than in controls at all three and were highest in both groups
acetylkynurenine
8
pathactivity
deficiency,
of kynurenine slightly higher
were
ceptive studied
2
at peak
xanthurenic
5. Excretions
z
contra-
200
, 3-hydroxykynurenine
kynurenine
of oral metabolic on the
monohydrate
supplementation.
U)
C.,
effects
tryptophan of any effects
0.8 2.0
#{149}
O.C. 0.8
#{149}#{163}-
2.0
0--0---
‘.7
.5
of
of signifi-
0 0
.3
>-
4-pyridoxic in
both
acid
-----
de-
groups
of
subjects (Fig. 3) and repletion rates during supplementation with PNHCl were also quite similar. These data suggest that use of oral contraceptives has no measurable effect on absorption, utilization or conversion of pyridoxine to 4-pyridoxic acid (5). Plasma pyridoxal phosphate (PLP) levels of oral contraceptive users were slightly lower than control values initially and remained slightly lower throughout the depletion period (Fig. 4). During repletion with PN-HC1 no differences between groups were found. Supplements of 0.8 mg PN-HC1/day were not enough
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
-------
-
9
25
3
-
i
39
47
53
59
DAY OF STUDY +8,
-B6
+8
FIG. 3. Urinary excretion of 4-pyridoxic acid by control subjects and oral contraceptive users (O.C.). During the first 4 days, the deficient diet (-B6) was supplemented with 0.8 mg of PN#{149}HC1.During the -B6 period, the basal diet containing 0.19 mg equivalents of pyridoxine was not supplemented with B6. This diet was supplemented in the +B6 period with 0.8 or 2.0 mg PN.HC1/day. The shaded bars indicate the 7-day period each month when oral contraceptive use was interrupted. Pyridoxic acid was assayed as previously described (7).
LEKLEM
538 -
1
PLP CONTROLS
6’.-
OC.
0.8.2.0’I
a.
El
0.8
0---
20
0---
and controls both groups
depletion ,
2
U)
0
a.
AL.
i0-
6-
0.
4-
the
Daily
of
4
In2
and
activity during
supplements
both
with
mg
mg
but not supple-
had
levels. 3 or
100
of supplement levels.
of the
of 0.8
activity 2.0-mg
groups
predepletion were after
supplementation
This level supernormal
initially similarly
increased the levels. With
activity
approximately points shown
x 0 0
period.
of PN-HC1 slowly to predepletion ments,
8
were found decreased
risen
to
The final 4 days of PNHC1/day.
resulted
in normal
or
4,
-J
a. 0
2
-
4---
3
WEEK
-
---Be
4
5
_L.-
L
7
8
OF STUDY
-
-
-64
i
6
erythrocyte preparations were after fortification in vitro with levels of PLP (Fig. 6). The percent
saturating stimulation
-,
FIG. 4. Concentration of plasma pyridoxal phosphate (PLP) in controls and oral contraceptive users. Footnotes are the same as in Fig. 3. PLP was assayed with tyrosine apodecarboxylase using L-tyrosine1-’ 4C as substrate.
HK--XR
YNB1
The above also assayed
CONTROL
by
PLP
increased
and
controls
says
did
as the
and
Similar were
oral
so to the
deficiency
extent in During deficiency, in vitro stimulation by PLP did not restore activity to predepletion levels, suggesting that the decreased activity was due, in part, to loss of apoenzyme. Dietary supplementation with PN- HC1 again decreased the percent stimulation with no consistent differences between comparable groups. progressed,
contraceptive
unstimulated done
for
same
users.
and PLP-stimulated aserythrocyte aspartate
a
q
‘23
I
‘23
23 Period
23
23
of Study
FIG. 5. Excretion of kynurenine (KYN), acetylkynurenine (AK), 3-hydroxykynurenine (HK), and xanthurenic acid (XA) by control subjects and oral contraceptive users (O.C.) (given an oral load of 200 mg of L-kynurenine sulfate) prior to vitamin B6 depletion (period 1), at the peak of deficiency (period 2) and after repletion with pyridoxine (period 3). The abbreviated metabolic pathway serves to identity the metabolites in each group of bars. Metabolites were measured as previously described (7). ferase
(not
weekly in Fig.
intervals 6. Details
No
differences
fortified
with
PLP
throughout the were reported between
oral
in
vitro)
at
study is shown elsewhere (5).
contraceptive
users
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
2
3
WEEK
FIG.
5
STUDY
6
7
8
The upper figure shows changes in alanine aminotransferase basal activity (without addition of PLP in vitro) in controls (CONT.) and oral contraceptive users (O.C.) during vitamin B6 depletion and repletion. The daily supplements of PN-HC1 (in mg) are shown on each curve. The lower figure shows the percent stimulation observed in the activity of this enzyme when saturated in vitro by added PLP. erytkrocyte
6.
4
OF
VITAMIN
, and
aminotransferase
those relative ficiency
B6 the
REQUIREMENTS findings
IN
paralleled
of
the alanine enzyme although the decreases induced by vitamin B6 dewere not as great. Details of these have been presented elsewhere (5).
studies
ORAL
CONTRACEPTIVE
which
time
control
The oral
load
may
excretion
of tryptophan
contraceptive
test,
users,
was loaded
after
significantly controls
metabolites the
by
different prior
to
from
induction
of
subjects bypass
slightly
that
B6
deficiency.
lower
in oral
contraceptive
users,
not statistically change of these
different. When the indices were compared dietary depletion of vitamin B6 in both the excretion of tryptophan metabolites cystathionine suggested that the oral ceptive group might be depleting at a rate
than
the
controls.
Other
were
rates of during groups, and contraslightly indices,
including 4-pyridoxic acid excretion, plasma Ply, and erythrocyte aminotransferases changed at virtually the same rate in both groups during depletion and reached the same nadir at the time of maximum deficiency. Supplementation with pyridoxine (0.8 mg/day) resulted in very similar restoration rates
of plasma
PLP,
erythrocyte
alanine
transferase and ever, correction
urinary 4-pyridoxic of urinary excretion
thionine slightly
tryptophan
and
users.
However,
2.0
values
after
metabolites was stifi
supplementation
by elevated
the
was
oral above
with
2.0
4
contracontrol
mg,
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
have
(12,
13)
that
the
altered
in
or steroid
activity
of
the
tryptophan
of
the
kynurenine
and seems
it
the
Previous
steroids
the
kynureninase Thus,
contraceptive nal effects
sug-
hormones
elsewhere
enzymes
pathway, i.e., aminotransferase.
which
effects,
metabolism.
affect
PLP-dependent
loads,
effect
indicate
can
effects
of contraceptive an
of have
of this enzyme observations in
oxygenase
kynurenine
conjugates
activity in rats
kynurenine
usage
of
studies
kynurenine most likely
metabolism
of oral
users is the summation of hormoon tryptophan oxygenase and
kynureninase general vitamin
rather
than
the
production
B6 deficiency.
tion is in agreement with Lumeng et al. (14) in
This
the
acid
and
plasma
compared
in
oral
contraceptive
They
found
report
a by
urinary levels
PLP
that
of
interpreta-
recent
which
thurenic
cases,
the
weeks restored all indices in both groups to their respective predepletion levels and, in some cases, to ultranormal levels. The detailed data (8) show that the excretion of tryptophan ceptive group
may
pathway
activity present
small
the
the
studies
as adrenal-mediated
the the
tryptophan
not
in contrast that about
amino-
for
also
most
.
mg/day
that
spe-
of tryptophan B6 levels. This
on since
oral
xanwere
users
and
xanthurenic
acid
excretion was elevated in most contraceptive users even though plasma PlY levels were,
slower in the oral contraceptive group, although not significantly so. Similarly, repletion rates between groups supplemented with 2.0 mg of PNHCl were not significantly different. The data clearly indicate that a daily supplement of 0.8 mg of PN-HC1 for 28 days is not enough to replete either controls or oral contraceptive
gest
normal the
relatively
of vitamin
on
given
some
primarily
as well
any
controls.
acid Howof cysta-
metabolites
direct
within that
metabolism
oxygenase,
shown
This confirmed previous observations of altered tryptophan metabolism in oral contraceptive users (1-3). Other indices of vitamin B6 nutrition measured before vitamm B6 depletion were not clearly different in oral contraceptive users. Thus, urinary cystathionine and urinary 4-pyridoxic acid were not different from controls; and plasma PlY and the erythrocyte aminotransferases, while
vitamin
the
be
of estrogens ( 11). However,
tryptophan
were
have
is independent
tryptophan
similarly
faster
on
539
suggests
may
effect
which
indices
This
contraceptives
effect Discussion
all other
ranges.
cific
USERS
20-
to
plasma
levels
decreased
range
PLP. in
information of
was
reported users in subnormal
plasma
subjects
in
However,
had
Further, during
of oral contraceptive normal with continued
dietary biity
low.
study, they contraceptive
34-year-age
of
PLY
the
first
use but tended usage. Since no
presented,
the
contraceptive-induced
changes
possiin diet
must be considered. Salkeld et a!. (15) found the erythrocyte aspartate aminotransferase stimulation test to be abnormal in almost 50%
of
oral
effect
contraceptive of
duration
this index. 4-pyridoxic
Rose acid
users, of
but
observed
contraceptive
et al. (16) levels and
about the
19% mean
controls.
of oral 4-pyridoxic
was
not
no
usage
found increased
low
kynurenine-to-hydroxyanthranilate
group at
to the present 20% of oral
levels months toward
correspondingly
on
urinary hydroxyratios
contraceptive acid
significantly
users value
for
in
although the
different
whole
from
540
LEKLEM
The
activities
ferases, are
of
particularly
considered
of
(17).
the
or
vitamin
with
the
but there differences
and
contraceptive
oral
that
the
use
contraceptives
were no between
deficiency
in
study
in
vitamin
certain
subjects.
In
the
of
precise
clear-cut between
contraceptive vitamin B6
users nutrition
because
the limited might not
of
mental
subjects
induced
larger
was the to
differences in vitamin B6 control subjects and oral when a variety of indices of were measured. Perhaps
number of have obtained
susceptible
vitamin
much
control
was not possible (with the tryptophan load test)
requirements
, we
dietary
B6 present
to
contraceptive-
B6 deficiency.
number
of
subjects experi-
Perhaps
subjects
with
some
of
a the
minor differences would have reached significance. However, it is possible
statistical to say that
the
se does
use
of
oral
significantly
contraceptives or
quirement
for
women
using
subgroup
of
particularly min B6
per
consistently vitamin
these women
increase
B6 agents. may
abnormalities
re-
in the majority of However, a small well
exist
who
susceptible to steroid-induced deficiency, and in these women
metabolic
not
the
may
result
Fifteen
women
contraceptives
who
had
diet
deficient
equivalent
After with
never
who used in
of
used and
(19).
these
vitamin
0.19
estrogen-containing nine
mg
control
women
agents were given a B6 (containing the of
pyridoxine/day).
4 weeks, this diet was supplemented daily 0.8, 2.0 or 20.0 mg of pyridoxine
hydrochloride
for
an
additional
4
weeks.
Initially, and at weekly intervals, measurements were made of several indices of vitamin B6 nutrition, including urinary tryptophan metabolites (before L-tryptophan),
and urinary
after a 2.0 cystathionine
g
addition,
200 mg were given
sulfate
and
significant
urinary
4-pyri-
pyridoxal phosphate, and and aspartate aminotrans-
after
oral loads of initially, at the
pyridoxine
differences
were
repleobserved
between oral contraceptive users and controls in the above measured indices with the exception of the tryptophan load test, although very minor differences occurred in several of the indices. The data suggest that the use of oral contraceptives may specifically affect tryptophan metabolism by some means other than through a vitamin B6 deficiency, since altered tryptophan metabolism persisted even when other indices of vitamin B6 nutrition were normal. The amount of vitamin B6 (as pyridoxine) needed to maintain normal levels of these indices (except for tryptophan metabolism) was between 0.8 and 2.0 mg/day. The data suggest that if the use of oral contraceptives type
of does
the
effect
clinical
taking
the alter
combined estrogen-progestogen the requirement for vitamin
is a minor
significance
these
steroid
to
one the
and majority
preparations.
of
B6,
doubtful of women
LI
We gratefully acknowledge the competent and dedicated technical assistance of Joan Chesters, Jane Mueller, Rekha Anand, Pat Stauber, Heidi Kan, and Richard Arend throughout the conduct of this study and of Kay Deighton and Suzi Pertzborn for assistance in preparation of the manuscript.
are vitaother
Summary
oral
L-methionine),
plasma alanine
of deficiency,
No
oral
a
it
demonstrate
of estrogen-containing produce
which
maintained, exception
peak tion.
users.
may
In
of
L-kynurenine
Rose et al. (18) found an increased in vitro PLY stimulation of erythrocyte alanine aminotransferase in about 1 5% of contraceptive users. The brief review of the literature presented above indicates that ample evidence exists to suggest
erythrocyte
ferases.
these
induction
B6 deficiency, significant
subjects
B6
study
AL.
3.0 g load doxic acid,
thereof,
of
present
as expected
a vitamin
consistent
aminotrans-
activation
indices
In
changed
control
PLY
reliable
nutrition indices
erythrocyte the
El
load (after
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
of a
References 1. ROSE, D. P. The influence of oestrogens on tryptophan metabolism in man. Chin. Sci. 31: 265, 1966. 2. PRICE, J. M., M. J. THORNTON AND L. M. MUELLER. Tryptophan metabolism in women using steroid hormones for ovulation control. Am. J. Chin. Nutr. 20: 452, 1967. 3. LUHBY, A. L., M. BRIN, M. GORDON, P. DAVIS, M. MURPHY AND H. SPIEGEL. Vitamin B6 metabolism in users of oral contraceptive agents. I. Abnormal urinary xanthurenic acid excretion and its correction by pyridoxine. Am. J. Chin. Nutr. 24: 684, 1971. 4. PRICE, S. A., D. P. ROSE AND P. A. lOSELAND. Effects of dietary vitamin B, deficiency and oral contraceptives on the spontaneous urinary excretion of 3-hydroxyanthraniic acid. Am. J. Chin. Nutr. 25: 494, 1972. 5. BROWN, R. R., D. P. ROSE, J. E. LEKLEM, H. LINKSWILER AND R. ANAND. Urinary 4-pyridoxic acid, plasma pyridoxal phosphate, and
VITAMIN
6.
7.
8.
9.
10.
11.
12.
B6
REQUIREMENTS
IN
erythrocyte aminotransferase levels in oral contraceptive users receiving controlled intakes of vitamin B6 . Am. J. Chin. Nutr. 28: 10, 1975. SWAN, P., J. WENTWORTH AND H. LINKSWILER. Vitamin B6 depletion in man: Urinary taurine and sulfate excretion and nitrogen balance. J. Nutr. 84: 220, 1964. PRICE, J. M., R. R. BROWN AND N. YESS. Testing the functional capacity of the tryptophanniacin pathway in man by analysis of urinary metabohites. In: Advances in Metabolic Disorders, edited by R. Levine and R. Luft. New York: Academic, 1965, vol. 2, p. 159. LEKLEM, J. E., R. R. BROWN, D. P. ROSE, H. LINKSWILER AND R. A. AREND. Metabolism of tryptophan and niacin in oral contraceptive users receiving controlled intakes of vitamin B6. Am. J. Chin. Nutr. 28: 146, 1975. THOMSON, A. R., AND B. J. MILES. Ion-exchange chromatography of amino acids: Improvements in the single column system. Nature 203: 483, 1964. PARK, Y. K., AND H. LINKSWILER. Effect of vitamin B6 depletion in adult man on the excretion of cystathionine and other methionine metabolites. J. Nutr. 100: 110, 1970. BRAIDMAN, I. P., AND D. P. ROSE. Effects of sex hormones on three glucocorticoid-inducible enzymes concerned with amino acid metabolism in rat liver. Endocrinology 89: 1250, 1971. MASON, M., AND B. MANNING. Effects of steroid conjugates on availability of pyridoxal phosphate for kynureninase and kynurenine aminotransferase activity. Am. J. Chin. Nutr. 24:
Downloaded from https://academic.oup.com/ajcn/article-abstract/28/5/535/4732916 by Washington University in St. Louis user on 09 April 2018
ORAL
13.
14.
15.
16.
17.
18.
19.
CONTRACEPTIVE
USERS
541
786, 1971. ROSE, D. P., AND R. R. BROWN. The influence of sex and estrogens on liver kynureninase and kynurenine aminotransferase in the rat. Biochim. Biophys. Acta 184: 412, 1969. LUMENG, L., R. E. CLEARY AND 1.-K. LI. Effect of oral contraceptives on the plasma concentration of pyridoxal phosphate. Am. J. Cliri. Nutr. 27: 326, 1974. SALKELD, R. M., K. KNORR AND W. F. KORNER. Ihe effect of oral contraceptives on vitamin B6 status. Chin. Chim. Acta 49: 195, 1973. ROSE, D. P., R. STRONG, P. W. ADAMS AND P. E. HARDING. Experimental vitamin B6 deficiency and the effect of oestrogen-containing oral contraceptives on tryptophan metabolism and vitamin B6 requirements. Chin. Sci. 42: 465, 1972. SAUBERLICH, H. E., J. E. CANHAM, E. M. BAKER, N. RAICA, JR. AND Y. F. HERMAN. Biochemical assessment of the nutritional status of vitamin B6 in the human. Am. J. Chin. Nutr. 25: 629, 1972. ROSE, D. P., R. STRONG, J. FOLKARD AND P. W. ADAMS. Erythrocyte aminotransferase activities in women using oral contraceptives and the effect of vitamin B6 supplementation. Am. J. Chin. Nutr. 26: 48, 1973. ROSE, D. P., AND P. W. ADAMS. Oral contraceptives and tryptophan metabolism: Effects of oestrogen in low dose combined with a progestagen (megestrol acetate) given alone. J. Chin. Pathol. 25: 252, 1972.