Your Chances of Getting Pregnant Reduced by Iodine Deficiency?

Written by Dr. Steve Chaney on . Posted in Chances of Getting Pregnant, Iodine Deficiency During Pregnancy

Your Chances Of Getting Pregnant Could Be Cut In Half

Author: Dr. Stephen Chaney

 

Are your chances of getting pregnant reduced by iodine deficiency?

It shouldn’t be happening. The introduction of iodized salt in the 1920s virtually eliminated iodine deficiency in this country. However, in just the past twenty years the incidence of iodine deficiency has increased 3-8-fold in women of childbearing age. Recent studies have estimated that today 30-40% of women of childbearing age are iodine deficient.

How did that happen?

  • We have been told to cut back on sodium. Many Americans have responded by throwing away the (iodized) salt shaker. Unfortunately, we still get a lot of salt from processed foods, and that salt is usually non-iodized.
  • When we do add salt to our foods it is usually the “healthier” designer salts. First it was sea salt. Now it is trendy versions like Pink Himalayan Salt. While sea salt might have some iodine naturally, the trendier versions are non-iodized.
  • The New-Age Whole Food diets often ban salt from the diet. That increases the probability of becoming iodine deficient. For example, a recent study reported that women who followed the Paleo diet for two years became iodine deficient (S. Manousi et al, European Journal of Clinical Nutrition, 72: 124-129, 2018 ).

The consequences of iodine deficiency, especially among women of childbearing age, are alarming. In a previous issue of “Health Tips From the Professor,” The Dangers of Iodine Deficiency During Pregnancy, I reported that iodine is essential for bone and neural development during fetal development and infancy. I also reported that the American Academy of Pediatrics, The National Institutes Of Health, and the World Health Organization have all declared that mild iodine deficiency during pregnancy can prevent normal cognitive development and reduce IQ levels in children.

This study (JL Mills et al, Human Reproduction, doi: 10.1093/humrep/dex379, 2018 ) reports that iodine deficiency also reduces a woman’s chances of becoming pregnant. [I might add, this almost seems to be part of Nature’s plan. If the consequences of iodine deficiency during pregnancy are so detrimental, the fact that iodine deficiency also reduces the chances of a woman becoming pregnant could be considered a good thing.]

How Was The Study Done?

This study recruited 501 couples (ages 18-40) from 16 counties in Michigan and Texas. The women had all discontinued contraception within the previous two months with the intention of becoming pregnant and were followed for an additional 12 months. Women with known thyroid disease were excluded from the study.

Urine samples were collected from each woman at the beginning of the study to determine iodine and creatine levels. The women used fertility monitors to time intercourse relative to ovulation (Basically, that means they optimized their chances of becoming pregnant). They then used digital home pregnancy monitors on the day of expected menstruation to identify pregnancies.

Finally, 90% of the women took either a multivitamin or a pre-natal vitamin during the study (The significance of this will be discussed later).

 

Are Your Chances of Getting Pregnant Reduced by Iodine Deficiency?

chances of getting pregnant iodine deficiency pregnancyThe results of the study were:

  • 3% of the women in the study were iodine deficient (defined as iodine-creatine ratios of <100 mcg/g). This was further broken down to:
  • 8% were mildly iodine deficient (50-99 mcg/g).
  • 8% were moderately iodine deficient (20-49 mcg/g).
  • 7% were severely iodine deficient (<20 mcg/g).
  • That is a total of 22.5% who had moderate to severe iodine deficiency.
  • Women who had moderate to severe iodine deficiency had a 46% decrease in the chance of becoming pregnant over each menstrual cycle compared to the iodine sufficient group.

A simple way of reporting those data would be to say that their chances of becoming pregnant were reduced by 46%, but that would not convey the whole picture. Most of the women did become pregnant during the 12-month study. However, it took the women with moderate to severe iodine deficiency twice as long to become pregnant. Iodine deficiency did not prevent pregnancy from occurring, but it delayed it.

The authors concluded: “In summary, our data show that groups of women with iodine concentrations in the moderate to severe deficient range experience a significantly longer time to pregnancy…The US and European countries where iodine deficiency is common should evaluate the need for programs to increase iodine intake for women of childbearing age, particularly those trying to become pregnant”.

 

Where Can You Get The Iodine You Need?

 

chances of getting pregnant iodine deficiency seafood seaweedThe important question becomes: “Where can you get the iodine you need?”

  • You could start by using old-fashioned iodized salt rather than designer salts in your salt shaker. However, I am reluctant to recommend anything that would increase sodium intake. We get far too much from processed foods already.
  • Seafood (or seaweed, if you are a vegetarian) are the best food sources of iodine. However, our oceans are so contaminated I would recommend consuming those foods only occasionally.
  • You will often see bread and dairy mentioned as good food sources because iodine was used in the preparation of those foods. However, iodine has largely been replaced by other agents, so those foods should no longer be considered good sources. For example:
  • Iodine in commercial breads has traditionally come from the use of iodate as a dough conditioner. Today iodate has largely been replaced with bromide in commercial bread making. Not only does this trend decrease the amount of iodine available in our diet, but bromide also interferes with iodine utilization in our bodies
  • Iodine in milk has traditionally come from the use of iodine-containing disinfectants to clean milk cans and teats. However, they have largely been replaced with other disinfectants
  • Fruits and vegetables are a variable source of iodine, depending on where they were grown. That is because iodine levels in the soils vary tremendously from region to region.
  • That leaves multivitamins and prenatal vitamins as your best source. However, you do need to read labels. You should look for supplements that provide 150 mcg of iodine. Unfortunately, only 50% of prenatal supplements in the United States even contain iodine. Remember, 90% of the women in this study took either a multivitamin or prenatal supplement and 44.3% of them were iodine deficient.

 

The Bottom Line

 

The introduction of iodized salt in the 1920s virtually eliminated iodine deficiency in this country. Now, almost 100 years later, iodine deficiency is back. Recent studies estimate that 30-40% of women of childbearing age are iodine deficient. This is concerning. Previous studies have shown iodine deficiency affects mental development during fetal development and infancy. A recent study suggests that iodine deficiency may also make it more difficult for women to become pregnant. Specifically, the study reported:

  • 3% of the women in the study were iodine deficient. This was further broken down to:
  • 8% were mildly iodine deficient.
  • 8% were moderately iodine deficient.
  • 7% were severely iodine deficient.
  • That is a total of 22.5% with moderate to severe iodine deficiency.
  • Women who had moderate to severe iodine deficiency had a 46% decrease in their chance of becoming pregnant over each menstrual cycle compared to the iodine sufficient group.

A simple way of reporting those data would be to say that their chances of becoming pregnant were reduced by 46%, but that would not convey the whole picture. Most of the women did become pregnant during the 12-month study. However, it took the women with moderate to severe iodine deficiency twice as long to become pregnant. Iodine deficiency did not prevent pregnancy from occurring, but it delayed it.

For more details about why iodine deficiency has reemerged in this country and where we can get the iodine we need, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Comments (2)

  • Kathy Brauer

    |

    Fascinating article. One fairly important error slipped past the proofreader. In the description of study participants is says that they had “discontinued conception” in order to get pregnant. While the accrual meaning is probably clear to most readers from the context, it’s just tidier you use “contraception” which is what I believed you meant.

    I also wonder how much this iodine deficiency affects the number of women, in particular, who need to use thyroid medications. I’m also curious about its overall effect in the “obesity epidemic” in the population at large.

    Reply

    • Dr. Steve Chaney

      |

      Dear Kathy,
      Thanks for pointing out the typo. It will be corrected in the archive. Iodine deficiency does increase the risk of hypothyroidism and, potentially, the number of people who need thyroid medication. I have not seen an estimate of how much iodine deficiency contributes to use of thyroid medication in this country. I would hope most doctors would screen for iodine deficiency before recommending medication. Hypothyroidism can also contribute to obesity. Again its contribution is difficult to estimate because there are so many other contributors to obesity in this country.
      Dr. Chaney

      Reply

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Latest Article

Is Our Microbiome Affected By Exercise?

Posted November 6, 2018 by Dr. Steve Chaney

Microbiome Mysteries

Author: Dr. Stephen Chaney

is our microbiome affected by exerciseIn a recent post,  What is Your Microbiome and Why is it Important,  of “Health Tips From The Professor” I outlined how our microbiome, especially the bacteria that reside in our intestine, influences our health. That influence can be either good or bad depending on which species of bacteria populate our gut. I also discussed how the species of bacteria that populate our gut are influenced by what we eat and, in turn, influence how the foods we eat are metabolized.

I shared that there is an association between obesity and the species of bacteria that inhabit our gut. At present, this is a “chicken and egg” conundrum. We don’t know whether obesity influences the species of bacteria that inhabit our gut, or whether certain species of gut bacteria cause us to become obese.

Previous studies have shown that there is also an association between exercise and the species of bacteria that inhabit our gut. In particular, exercise is associated with an increase in bacteria that metabolize fiber in our diets to short chain fatty acids such as butyrate. That is potentially important because butyrate is a primary food source for intestinal mucosal cells (the cells that line the intestine). Butyrate helps those cells maintain the integrity of the gut barrier (which helps prevent things like leaky gut syndrome). It also has an anti-inflammatory effect on the immune cells that reside in the gut.

However, associations don’t prove cause and effect. We don’t know whether the differences in gut bacteria were caused by differences in diet or leanness in populations who exercised regularly and those who did not. This is what the present study (JM Allen et al, Medicine & Science In Sports & Exercise, 50: 747-757, 2018 ) was designed to clarify.  Is our microbiome affected by exercise?

 

How Was The Study Designed?

is our microbiome affected by exercise studyThis study was performed at the University of Illinois. Thirty-two previously sedentary subjects (average age = 28) were recruited for the study. Twenty of them were women and 12 were men. Prior to starting the study, the participants filled out a 7-day dietary record. They were asked to follow the same diet throughout the 12-week study. In addition, a dietitian designed a 3-day food menu based on their 7-day recall for the participants to follow prior to each fecal collection to determine species of gut bacteria.

The study included a two-week baseline when their baseline gut bacteria population was measured, and participants were tested for fitness. This was followed by a 6-week exercise intervention consisting of three supervised 30 to 60-minute moderate to vigorous exercise sessions per week. The exercise was adapted to the participant’s initial fitness level, and both the intensity and duration of exercise increased over the 6-week exercise intervention. Following the exercise intervention, all participants were instructed to maintain their diet and refrain from exercise for another 6 weeks. This was referred to as the “washout period.”

VO2max (a measure of fitness) was determined at baseline and at the end of the exercise intervention. Stool samples for determination of gut bacteria and concentrations of short-chain fatty acids were taken at baseline, at the end of the exercise intervention, and again after the washout period.

In short, this study divided participants into lean and obese categories and held diet constant. The only variable was the exercise component.

 

Is Our Microbiome Affected By Exercise?

is our microbiome affected by exercise fitnessThe results of the study were as follows:

  • Fitness, as assessed by VO2max, increased for all the participants, and the increase in fitness was comparable for both lean and obese subjects.
  • Exercise induced a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise increased fecal concentrations of butyrate and other short-chain fatty acids in the lean subjects, but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production were largely reversed once exercise training ceased.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent of diet, and contingent on the sustainment of exercise.” [Note: To be clear, the exercise-induced changes in both gut bacteria and short-chain fatty acid production were independent of diet and contingent on the sustainment of exercise. However, only the production of short-chain fatty acids was dependent on obesity status.]

 

What Does This Study Mean For You?

is our microbiome affected by exercise gut bacteriaThere are two important take home lessons from this study.

  • With respect to our gut bacteria, I have consistently told you that microbiome research is an emerging science. This is a small study, so you should regard it as the beginning of our understanding of the effect of exercise on our microbiome rather than conclusive by itself. It is consistent with previous studies showing an association between exercise and a potentially beneficial shift in the population of gut bacteria.

The strength of the study is that it shows that exercise-induced changes in beneficial gut bacteria are probably independent of diet. However, it is the first study to look at the interaction between obesity, exercise and gut bacteria, so I would interpret those results with caution until they have been replicated in subsequent studies.

  • With respect to exercise, this may be yet another reason to add regular physical activity to your healthy lifestyle program. We already know that exercise is important for cardiovascular health. We also know that exercise increases lean muscle mass which increases metabolic rate and helps prevent obesity. There is also excellent evidence that exercise improves mood and helps prevent cognitive decline as we age.

Exercise is also associated with decreased risk of colon cancer and irritable bowel disease. This effect of exercise has not received much attention because the mechanism of this effect is unclear. This study shows that exercise increases the fecal concentrations of butyrate and other short-chain fatty acids. Perhaps, this provides the mechanism for the interaction between exercise and intestinal health.

 

The Bottom Line

A recent study has reported that:

  • Exercise induces a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise causes an increase in the number of gut bacteria that produce butyrate and other short-chain fatty acids that are beneficial for gut health.
  • These effects are independent of diet, but do not appear to be independent of obesity because they were seen in lean subjects but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production are largely reversed once exercise training ceases.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent on diet, and contingent on the sustainment of exercise.”

For more details and my interpretation of the data, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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