Currently, I am researching thiamine status during pregnancy for a series of articles to be published by the newly formed Thiamine Advocacy Foundation. Over the next few months, I will be publishing snippets of that research, and of course, when the project is finished, I will let everyone know and provide links to the articles. Today, I want to discuss a study published in 1980 about thiamine deficiency in pregnant and non-pregnant women.
For this study, the thiamine status of 60, presumably healthy, pregnant women was assessed across multiple times points (second trimester, third trimester, and in the immediate postpartum. Not all women completed all assessments. Food diaries were collected for three days preceding each test time to identify thiamine intake and a lifestyle survey to assess contraceptive use, smoking and alcohol history was given. Samples and diaries from 20 non-pregnant women were collected as well.
To determine thiamine status the erythrocyte transketolase test with thiamine pyrophosphate activation was used. This is among the reasons I found this study useful. It is only one of only a few studies of this population using the transketolase test. Recall from Dr. Lonsdale’s discussion Understanding the Labs (and here), the transketolase test is arguably a more accurate measure of thiamine status than plasma, serum, and some measures using whole blood.
Using the transketolase test, researchers found that 30% of the non-pregnant women were deficient in thiamine as were 28-39% of the pregnant/postpartum women depending upon the phase of pregnancy. Importantly, not all women were deficient at all test times. This means that the deficiencies likely waxed and waned relative to other variables like intake and stressors. Intake was considered sufficient in all but 10 of the women and for those 10 women it was only minimally below the RDA. Additionally, the researchers reported that previous oral contraceptive use had no apparent effect on thiamine status during pregnancy but that there was a trend for an increased risk of deficiency with previous pregnancies.
While this was a small study, the percentage of women who are deficient in thiamine is striking, especially the non-pregnant controls. If thiamine is deficient before pregnancy, the risk of severe health issues across pregnancy increases. Here though, none of the women who were deficient in thiamine displayed the classical symptoms of thiamine deficiency, although details were lacking. Moreover, all of the women delivered presumably healthy children, or at least healthy weight children, as other parameters were not measured. Again, this finding is important because it suggests that either 1) what we expect to see with deficiency during pregnancy is not completely accurate, 2) that the persistence or chronicity of the deficiency matters, and/or 3) that it is not simply a deficiency in thiamine that causes some of the more severe complications of thiamine deficiency during pregnancy.
I have written previously about the mismatch between classically defined symptoms of thiamine deficiency and what we are more likely to see with modern diets and stressors. I suspect this applies to pregnancy as well. I have also written about how thiamine status is likely to change relative to intake and demand. Rodent studies have shown that the typical neurological symptoms of deficiency do not appear until there is 80% decline of thiamine stores. Since we store a little over two weeks of thiamine, one would have to completely eliminate intake for more than a week before those symptoms might emerge, and even then, it might be a while before they were recognized. This is certainly a factor with hyperemesis gravidarum, the severe vomiting that some women experience during pregnancy but perhaps not in non-HG related pregnancies.
It is important to note, however, HG and thiamine deficiency go hand in hand. Thiamine deficiency, along with other deficiencies, may trigger HG (think gastrointestinal beriberi) in the first place, and once the vomiting begins, will easily deplete thiamine stores. None of the women in the current study developed HG, however, or other complications, so that leads me to believe, that we need additional triggers and we need persistent or chronic thiamine deficiency before noticeable complications arise.
In this study, all we have are indications of deficiency at specific points in time. We have no evidence of how long those deficiencies were present or whether other variables were somehow buffering maternal and fetal health such that the typical complications associated with thiamine deficiency were not observed. Even so, a finding that upwards of 30% of a test population of women, both non-pregnant and pregnant thiamine deficient speaks to how common this deficiency may be and how close to the precipice of more severe health issues a percentage of the population resides. Although observable changes in health were not reported or perhaps even recognized in this report, knowing what we know about thiamine’s role in energy metabolism, it is not unlikely that there were many negative metabolic patterns brewing just below the surface.
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