The Dangers of Iodine Deficiency During Pregnancy

Written by Dr. Steve Chaney on . Posted in Iodine Deficiency During Pregnancy

Does Your Prenatal Contain Enough Iodine?

Author: Dr. Stephen Chaney

 

iodine deficiency during pregnancyA recent study (S.M. O’Kane et al, British Journal of Nutrition, doi.org/10.1017/S0007114516003925)  concluded that 2/3 of Irish women had no idea that iodine was important during pregnancy. In fact, 57% of the women had no idea what iodine was, and 41% were unable to name any health problem related to iodine deficiency. The authors of the study considered this ignorance about iodine to be alarming. I’ll discuss why below.

First, let’s consider the situation in the United States. I suspect ignorance about the importance of iodine is just as widespread in the United States as it is in Ireland. Think about the nutrients we have been told are essential for healthy pregnancy outcomes.

  • We have heard about the importance of iron and calcium for decades.
  • The importance of folic acid and other B vitamins has been widely publicized over the last 20 years.
  • In recent years, we have learned about the importance of omega-3s, especially DHA.

But who has been telling us about the importance of iodine? Almost nobody.

What Are The Recommendations For Iodine Intake?

The RDAs for iodine are:

  • 150 ug/day for adults
  • 220 ug/day for pregnant women
  • 290 ug/day for breastfeeding women

How Common Is Iodine Deficiency During Pregnancy?

iodine deficiency pregnant womenHere are some quick facts about iodine deficiency in the US from a recent American Academy of Pediatrics position paper  and the National Institutes of Health Consumer information site:

  • Approximately 1/3 of pregnant and lactating women in the United States are at least marginally iodine deficient.
  • To meet their RDA requirements for iodine during pregnancy and lactation the American Thyroid Association, The National Academy of Sciences, and The American Academy of Pediatrics all recommend pregnant and lactating women take supplements containing 150 ug of iodine.
  • Although most pregnant and lactating women take supplements:
    • Only 50% of prenatal supplements in the United States contain iodine.
    • Even worse, only 15% of the supplements pregnant and lactating women take contain iodine (some pregnant and lactating women take multivitamins rather than prenatal supplements).
  • Labeling can be deceptive. Most multivitamins and prenatal supplements specify the amount of potassium iodide in the supplement, not iodine. It requires at least 197 ug of potassium iodide to provide 150 ug of iodine.

In short, many pregnant and lactating women in this country are not getting enough iodine from their diet and the supplements they are taking may not provide the iodine they need.

 

Why Are So Many Americans Deficient In Iodine?

iodine deficiencyThe best and most reliable natural sources of iodine are seaweeds and ocean fish. Meats, dairy, and grains can be moderate sources of iodine, but their iodine content is highly variable. It depends on the iodine content of the soil in which they were produced and how they were processed.

Because the soil in the interior of this country is very low in iodine, crops and animals raised in much of our country are also low in iodine. That lead to widespread iodine deficiency in this country prior to the introduction of iodized salt in the 1920s. Iodized salt largely eliminated iodine deficiency in the 1920s. However, since the 1970s, iodine deficiency has been gradually returning to this country for many reasons.

  • In the 1920s most of our food was prepared at home, so most of the salt in our diet was iodized. However, today:
  • Processed foods are replacing home-cooked meals, and the salt used in processed foods is not iodized.
  • Much of the salt we use today is “gourmet” salt that is not iodized. Even sea salt often contains far less iodine than iodized salt.
  • Seaweed has never been considered a delicacy in this country, and increasingly, Americans are avoiding ocean fish because of concerns about our polluted oceans.
  • 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.

Together these trends have combined to create the “perfect storm”. Iodine deficiency has, once again, become a major health concern in the US and other developed countries.

 

The Dangers Of Iodine Deficiency During Pregnancy

dangers of iodine deficiency during pregnancyIodine is an essential component of the thyroid hormone. Accordingly, inadequate iodine intake leads to hypothyroidism. Thus, you might expect iodine deficiency to be associated with symptoms like fatigue, sensitivity to cold, dry skin, and unexpected weight gain.

However, you may not have known that thyroid hormone is also essential for bone and neural development during fetal development and infancy. Because of that, thyroid hormone production increases dramatically during pregnancy and lactation (Hence, the increase in iodine requirement for pregnant and lactating women).

I can’t emphasize strongly enough the consequences of iodine deficiency during pregnancy and lactation. Here is what the experts say:

 

The Bottom Line

 

  • Iodine is important for bone and neural development during both fetal development and infancy. Because of this, iodine requirements are significantly higher during pregnancy and breastfeeding.
  • The iodine content of the American diet has decreased significantly since the 1970s. Today approximately 1/3 of pregnant and lactating women in the United States are at least marginally iodine deficient.
  • The National Institutes of Health, the American Academy of Pediatrics, and the World Health Organization all warn that even mild iodine deficiency during pregnancy and lactation can result in cognitive impairment in children.
  • Because of this, the American Thyroid Association and the American Academy of Pediatrics recommend that pregnant and lactating women take a supplement providing 150 ug of iodine. That corresponds to at least 197 ug of potassium iodide (the unit shown on most supplement labels).
  • Only 50% of prenatal supplements and 15% of multivitamin supplements contain iodine. Many that do contain iodine do not provide the recommended 197 ug of potassium iodide.

In short, many pregnant and lactating women in this country are not getting enough iodine from their diet; the consequences of even mild iodine deficiency are significant; and the supplements they are taking may not provide the iodine they need.

 

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 (1)

  • Richard O Brouse

    |

    Dr. Chaney,
    What an excellent article on iodine and the need in pregnancy.

    Reply

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Latest Article

A Low Carb Diet and Weight Loss

Posted January 15, 2019 by Dr. Steve Chaney

Do Low-Carb Diets Help Maintain Weight Loss?

Author: Dr. Stephen Chaney

 

low carb dietTraditional diets have been based on counting calories, but are all calories equal? Low-carb enthusiasts have long claimed that diets high in sugar and refined carbs cause obesity. Their hypothesis is based on the fact that high blood sugar levels cause a spike in insulin levels, and insulin promotes fat storage.

The problem is that there has been scant evidence to support that hypothesis. In fact, a recent meta-analysis of 32 published clinical studies (KD Hall and J Guo, Gastroenterology, 152: 1718-1727, 2017 ) concluded that low-fat diets resulted in a higher metabolic rate and greater fat loss than isocaloric low-carbohydrate diets.

However, low-carb enthusiasts persisted. They argued that the studies included in the meta-analysis were too short to adequately measure the metabolic effects of a low-carb diet. Recently, a study has been published in the British Medical Journal (CB Ebbeling et al, BMJ 2018, 363:k4583 ) that appears to vindicate their position.

Are low carb diets best for long term weight loss?

Low-carb enthusiasts claim the study conclusively shows that low-carb diets are best for losing weight and for keeping it off once you have lost it. They are saying that it is time to shift away from counting calories and from promoting low-fat diets and focus on low-carb diets instead if we wish to solve the obesity epidemic. In this article I will focus on three issues:

  • How good was the study?
  • What were its limitations?
  • Are the claims justified?

 

How Was The Study Designed?

low carb diet studyThe investigators started with 234 overweight adults (30% male, 78% white, average age 40, BMI 32) recruited from the campus of Framingham State University in Massachusetts. All participants were put on a diet that restricted calories to 60% of estimated needs for 10 weeks. The diet consisted of 45% of calories from carbohydrate, 30% from fat, and 25% from protein. [So much for the claim that the study showed low-carb diets were more effective for weight loss. The diet used for the weight loss portion of the diet was not low-carb.]

During the initial phase of the study 161 of the participants achieved 10% weight loss. These participants were randomly divided into 3 groups for the weight maintenance phase of the study.

  • The diet composition of the high-carb group was 60% carbohydrate, 20% fat, and 20% protein.
  • The diet composition of the moderate-carb group was 40% carbohydrate, 40% fat, and 20% protein.
  • The diet composition of the low-carb group was 20% carbohydrate, 60% fat, and 20% protein.

Other important characteristics of the study were:

  • The weight maintenance portion of the study lasted 5 months – much longer than any previous study.
  • All meals were designed by dietitians and prepared by a commercial food service. The meals were either served in a cafeteria or packaged to be taken home by the participants.
  • The caloric content of the meals was individually adjusted on a weekly basis so that weight was kept within a ± 4-pound range during the 5-month maintenance phase.
  • Sugar, saturated fat, and sodium were limited and kept relatively constant among the 3 diets.

120 participants made it through the 5-month maintenance phase.

 

Do Low-Carb Diets Help Maintain Weight Loss?

low carb diet maintain weight lossThe results were striking:

  • The low-carb group burned an additional 278 calories/day compared to the high-carb group and 131 calories/day more than the moderate-carbohydrate group.
  • These differences were even higher for those individuals with higher insulin secretion at the beginning of the maintenance phase of the study.
  • These differences lead the authors to hypothesize that low-carb diets might be more effective for weight maintenance than other diets.

 

What Are The Pros And Cons Of This Study?

low carb diet pros and consThis was a very well-done study. In fact, it is the most ambitious and well-controlled study of its kind. However, like any other clinical study, it has its limitations. It also needs to be repeated.

The pros of the study are obvious. It was a long study and the dietary intake of the participants was tightly controlled.

As for cons, here are the three limitations of the study listed by the authors:

#1: Potential Measurement Error: This section of the paper was a highly technical consideration of the method used to measure energy expenditure. Suffice it to say that the method they used to measure calories burned per day may overestimate calories burned in the low-carb group. That, of course, would invalidate the major findings of the study. It is unlikely, but it is why the study needs to be repeated using a different measure of energy expenditure.

#2: Compliance: Although the participants were provided with all their meals, there was no way of being sure they ate them. There was also no way of knowing whether they may have eaten other foods in addition to the food they were provided. Again, this is unlikely, but cannot be eliminated from consideration.

#3: Generalizability: This is simply an acknowledgement that the greatest strength of this study is also its greatest weakness. The authors acknowledged that their study was conducted in such a tightly controlled manner it is difficult to translate their findings to the real world. For example:

  • Sugar and saturated fat were restricted and were at very similar levels in all 3 diets. In the real world, people consuming a high-carb diet are likely to consume more sugar than people in the other diet groups. Similarly, people consuming the low-carb diet are likely to consume more saturated fat than people in the other diet groups.
  • Weight was kept constant in the weight maintenance phase by constantly adjusting caloric intake. Unfortunately, this seldom happens in the real world. Most people gain weight once they go off their diet – and this is just as true with low-carb diets as with other diets.
  • The participants had access to dietitian-designed prepared meals 3 times a day for 5 months. This almost never happens in the real world. The authors said “…these results [their data] must be reconciled with the long-term weight loss trials relying on nutrition education and behavioral counseling that find only a small advantage for low carbohydrate compared with low fat diets according to several recent meta-analyses.” [I would add that in the real world, people do not even have access to nutritional education and behavioral modification.]

 

low carb diet and youWhat Does This Study Mean For You?

  • This study shows that under very tightly controlled conditions (dietitian-prepared meals, sugar and saturated fat limited to healthy levels, calories continually adjusted so that weight remains constant) a low-carb diet burns more calories per day than a moderate-carb or high-carb diet. These findings show that it is theoretically possible to increase your metabolic weight and successfully maintain a healthy weight on a low-carb diet. These are the headlines you probably saw. However, a careful reading of the study provides a much more nuanced viewpoint. For example, the fact that the study conditions were so tightly controlled makes it difficult to translate these findings to the real world.
  • In fact, the authors of the study acknowledged that multiple clinical studies show this almost never happens in the real world. These studies show that most people regain the weight they have lost on low-carb diets. More importantly, the rate of weight regain is virtually identical on low-carb and low-fat diets. Consequently, the authors of the current study concluded “…translation [of their results to the real world] requires exploration in future mechanistic oriented research.” Simply put, the authors are saying that more research is needed to provide a mechanistic explanation for this discrepancy before one can make recommendations that are relevant to weight loss and weight maintenance in the real world.
  • The authors also discussed the results of their study in light of a recent, well-designed 12-month study (CD Gardener et al, JAMA, 319: 667-669, 2018 ) that showed no difference in weight change between a healthy low-fat versus a healthy low-carbohydrate diet. That study also reported that the results were unaffected by insulin secretion at baseline. The authors of the current study noted that “…[in the previous study] participants were instructed to minimize or eliminate refined grains and added sugars and maximize intake of vegetables. Probably for this reason, the reported glycemic load [effect of the diet on blood sugar levels] of the low-fat diet was very low…and similar to [the low-carb diet].” In short, the authors of the current study were acknowledging that diets which focus on healthy, plant-based carbohydrates and eliminate sugar, refined grains, and processed foods may be as effective as low-carb diets for helping maintain a healthy weight.
  • This would also be consistent with previous studies showing that primarily plant-based, low-carb diets are more effective at maintaining a healthy weight and better health outcomes long-term than the typical American version of the low-fat diet, which is high in sugar and refined grains. In contrast, meat-based, low-carb diets are no more effective than the American version of the low-fat diet at preventing weight gain and poor health outcomes. I have covered these studies in detail in my book “Slaying The Food Myths.”

Consequently, the lead author of the most recent study has said: “The findings [of this study] do not impugn whole fruits, beans and other unprocessed carbohydrates. Rather, the study suggests that reducing foods with added sugar, flour, and other refined carbohydrates could help people maintain weight loss….” This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.

The Bottom Line

 

  • A recent study compared the calories burned per day on a low-carb, moderate-carb, and high-carb diet. The study concluded that the low-carb diet burned significantly more calories per day than the other two diets and might be suitable for long-term weight control. If confirmed by subsequent studies, this would be the first real evidence that low-carb diets are superior for maintaining a healthy weight.
  • However, the study has some major limitations. For example, it used a methodology that may overestimate the benefits of a low-carb diet, and it was performed under tightly controlled conditions that can never be duplicated in the real world. As acknowledged by the authors, this study is also contradicted by multiple previous studies. Further studies will be required to confirm the results of this study and show how it can be applied in the real world.
  • In addition, the kind of carbohydrate in the diet is every bit as important as the amount of carbohydrate. The authors acknowledge that the differences seen in their study apply mainly to carbohydrates from sugar, refined grains, and processed foods. They advocate diets with low glycemic load (small effects on blood sugar and insulin levels) and acknowledge this can also be achieved by incorporating low-glycemic load, plant-based carbohydrates into your diet. This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.
  • Finally, clinical studies report averages, but none of us are average. When you examine the data from the current study, it is evident that some participants burned more calories per hour on the high-carb diet than other participants did on the low carb diet. That reinforces the observation that some people lose weight more effectively on low-carb diets while others lose weight more effectively on low-fat diets. If you are someone who does better on a low-carb diet, the best available evidence suggests you will have better long-term health outcomes on a primarily plant-based, low-carb diet such as the low-carb version of the Mediterranean diet.

For more details 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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