Does Vitamin D Help Prevent Asthma Attacks?

Written by Dr. Steve Chaney on . Posted in Prevent Asthma Attacks, Vitamin D, Vitamins and Health

Author: Dr. Stephen Chaney

breaking newsWhat do the experts say about vitamin D helping to prevent asthma attacks?  You’ve seen the headlines. Vitamin D is no longer just for healthy bones. It has become the latest “miracle” nutrient. If you believe everything you read, vitamin D can prevent or cure everything from multiple sclerosis to diabetes, heart disease, and cancer. Unfortunately, the evidence for many of those claims is weak.

However, the effect of vitamin D on the severity of asthma symptoms appears to be an exception. That relationship appears to be on much more solid ground.

A review published last year(S.K. Bantz et al, Annals of Pediatrics and Child Health, 3: pii: 1032, 2015) concluded “We emphasize that all children, especially those who are asthmatic, should be assessed to ensure adequate intake or supplementation with at least the minimum recommended doses of vitamin D. The simple intervention of vitamin D supplementation may provide significant clinical improvement in atopic disease, especially asthma.” [Note: Atopic disease refers to diseases characterized by a hyperallergenic response, such as eczema, hay fever, and asthma.]

That was followed by the recent publication of a Cochrane Review  that concluded “Vitamin D is likely to offer protection against severe asthma attacks”. To understand the significance of that statement you need to understand that this is not just another clinical study or another review. Cochrane Reviews are conducted by an international group of experts and are considered the “Gold Standard” for evidence-based medicine.

You may remember that famous commercial: “When E.F. Hutton speaks, people listen.”  In this case: “When Cochrane Reviews speak, doctors listen.”

Let’s look briefly at how the review was conducted, and then examine exactly what the review said, and what it didn’t say.

Does Vitamin D Help Prevent Asthma Attacks?

certifiedOne of the characteristics of Cochrane Reviews that set them apart from many of the other reviews that you find in the literature is that they include only the highest quality clinical studies in their analysis. This is one of the things that gives them such credibility.

This particular Cochrane Review included seven trials involving a total of 435 children and two trials involving a total of 658 adults. Most trial participants had mild to moderate asthma. The duration of the trials ranged from four to 12 months.  All studies were placebo controlled and used close to RDA recommended doses of vitamin D.

The results were pretty clear cut:

  • Vitamin D supplementation reduced the average number of severe asthma attacks requiring treatment with oral steroids by 36%.  This conclusion was based on 3 high-quality studies involving 680 participants.  Here, these studies clearly show vitamin D does  help prevent asthma attacks.
  • Vitamin D supplementation reduced the number of acute asthma attacks requiring emergency room visits and/or hospitalizations by 50%. This conclusion was based on 7 high-quality studies with 963 participants.  These studies also show vitamin D helps prevent asthma attacks.
  • None of the studies reported any severe adverse effects from vitamin D supplementation. (Compare that with all warnings associated with those ads for asthma medications you see on TV.)

However, they did not see any effect of vitamin D supplementation on day-to-day asthma symptoms.

What Does This Study Mean For You?

prevent asthmaThis study strongly suggests that vitamin D supplementation in the RDA range (600 IU for ages 1-70 and 800 IU for adults over 70) significantly reduces the risk of severe asthma attacks requiring steroids or hospitalization. Thus, if you or your child have asthma, vitamin D supplementation in the RDA range just makes sense.

However, this study also suggest that vitamin D is not a panacea that will make all asthma symptoms disappear.

Also, even Cochrane Reviews have limitations.

  • None of the studies included in this review looked at vitamin D status prior to the study. We simply don’t know whether vitamin D supplementation might be effective at reducing day-to-day asthma symptoms in individuals who were vitamin D deficient.
  • The studies included in this review did not include asthma sufferers with severe symptoms. Again, we don’t know whether vitamin D supplementation might make day-to-day symptoms more tolerable and easily controlled for people with severe asthma symptoms

One final thought: Blood levels of 25-hydroxy-vitamin D are the best indicators of vitamin D status. For reasons that we don’t understand, not everyone consuming RDA levels of vitamin D ends up with optimal levels (50-75 nmoles/L).  For that reason, it is a good idea to get your blood levels of 25-hydroxy-vitamin D tested as part of your annual physical exam.

If you are already getting RDA levels of vitamin D and your 25-hydroxy-vitamin D levels are not in the optimal range, you may want to supplement with extra vitamin D.  Just be sure to monitor your 25-hydroxy-vitamin D levels on a regular basis to make sure they don’t exceed the optimal range.

So, according to the Cochrane Review, vitamin D does help prevent asthma attacks.

 

The Bottom Line

 

  • A recent Cochrane Review concluded that vitamin D supplementation in the RDA range (600 IU for ages 1-70 and 800 IU for adults over 70) significantly reduces the risk of severe asthma attacks requiring steroids or hospitalization in both children and adults. This is significant because Cochrane Reviews are considered the Gold Standard for evidence-based medicine.
  • Thus, if you or your child have asthma, vitamin D supplementation in the RDA range just makes sense.
  • However, blood levels of 25-hydroxy-vitamin D are the best measure of vitamin status, and not everyone consuming RDA levels of vitamin D ends up with optimal levels (50-75 nmoles/L). If you are already getting RDA levels of vitamin D in your diet and your 25-hydroxy-vitamin D levels are not in the optimal range, you may want to supplement with extra vitamin D. Just be sure to monitor your 25-hydroxy-vitamin D levels on a regular basis to make sure they don’t exceed the optimal range.
  • This Cochrane Review did not find any effect of vitamin D supplementation on day-to-day asthma symptoms.
  • However, even Cochrane Reviews have limitations.
  • None of the studies included in this review looked at vitamin D status prior to the study. We simply don’t know whether vitamin D supplementation might be effective at reducing day-to-day asthma symptoms in individuals who were vitamin D deficient.
  • The studies included in this review did not include asthma sufferers with severe symptoms. Again, we don’t know whether vitamin D supplementation might make day-to-day symptoms more tolerable and easily controlled for people with severe asthma symptoms

 

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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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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