Can You Believe Clinical Studies

Written by Dr. Steve Chaney on . Posted in Believe Clinical Studies

The “Secret” About Clinical Studies Nobody Is Telling You

Author: Dr. Stephen Chaney

 

can you believe clinical studiesIt is so confusing. You get lots of advice in today’s world.

  • Your friend shares a new diet they read about and tells you how well it worked for her.
  • Your trainer puts you on a diet his sports guru recommended.
  • You read Dr. Strangelove’s health blog and decide you need to throw out all the foods in your refrigerator.
  • Your doctor tells you what you should eat and whether you should take supplements.
  • You decide to follow the recommendations of the American Heart Association or American Diabetes Association because they are the experts.

The problem is you are told all this advice is based on clinical studies – AND – most of the advice is conflicting. You don’t know who to believe, and, even worse, you are starting to wonder whether you can believe clinical studies.

I have covered the source of much of this confusion in my two books “Slaying The Food Myths”  and “Slaying The Supplement Myths.”  The Cliff Notes summary from these books is:

  • The placebo effect approaches 50% for things like feeling good, energy and mood.
  • Reputable scientists ignore testimonials and look for clinical proof.
  • What works for your friend or trainer may not work for you.
  • Any extreme diet that eliminates foods and food groups from your diet will cause short-term weight loss and improvements in health parameters like cholesterol, blood sugar, and blood pressure.
  • Reputable scientists look for studies documenting the long-term health outcomes of those diets. Some diets that look healthy short-term are unhealthy long-term.
  • Advocates of these fad diets emphasize short-term successes of their favorite diet and don’t even look for studies on long-term health outcomes.

Every clinical study has its flaws.

  • can you believe clinical studies doctorReputable scientists recognize this and don’t base their recommendations on individual studies. Instead, they base their recommendation on the preponderance of evidence from multiple studies.
  • Strangelove and other bloggers don’t understand that. They select studies that support their viewpoint and ignore the rest.
  • Some clinical studies are better than others. In fact, some really bad clinical studies get published.
  • Reputable scientists know how to distinguish between good studies and bad studies. They ignore bad studies and base their recommendations on good studies.
  • Strangelove, other bloggers, and the news media aren’t scientists. They don’t know how to distinguish between good and bad studies. They simply report the studies that support their viewpoint.
  • Strangelove, other bloggers, and the new media prefer audience over accuracy. They measure success by the number of readers rather than the accuracy of their articles.
  • “Man bites dog” stories gather the most readers. Dr. Strangelove and the media focus on studies that challenge the advice you have been getting from the health and nutrition establishment. The studies may not be accurate, but they attract a lot of readers.
  • Responsible scientists will give you the boring truth, even if it doesn’t attract many readers.

In my books I help you navigate through the world of conflicting clinical studies, so you can base your decisions on the very best clinical studies. However, there is one more “secret” you need to know. It is one that every scientist knows, but the public almost never hears about.

However, before I tell you the secret, let me set up this discussion by talking about glycemic index and use one food, the lowly banana, as an example.

 

Glycemic Index – How Sweet It Is

can you believe clinical studies glycemic indexIf you are a diabetic or are following one of the many low-carb diets, you probably know all about glycemic index. You probably have a glycemic index list in your kitchen or on your phone. You probably consult that list often to determine which foods you can eat and which you can’t. (If you aren’t familiar with the term, it is simply a measure of how big a blood sugar increase each food causes).

What if I were to tell you the glycemic index list you are relying on may not apply to you?

Then there is the lowly banana. You have probably heard from your trainer or favorite nutrition blog that you should avoid bananas because they are too high in sugar. However, if you were to consult a nutrition expert, they would tell you that bananas are a great choice. Bananas are nutrient powerhouses. In addition, a ripe banana has a glycemic index of 51 and anything under 55 is considered low-glycemic.

What if I were to tell you that the advice about bananas that both your trainer and nutrition experts give you is correct for some people? You just need to find out which advice applies to you.

 

The Secret About Clinical Studies Nobody Is Telling You

 

can you believe clinical studies secretNow, you are ready to learn the secret. It is this: Clinical studies are based on averages, and none of us are average. Because of that, even the very best clinical study results may not apply to you.

In a way, this reminds me of “The Wizard Of Oz.” You remember the story. If you were sitting in front of the curtain, the wizard was impressive. He was all powerful. He was making learned pronouncements about the way things should be. But, behind the curtain, the reality was quite different.

The authors of most clinical studies and most nutrition gurus make learned pronouncements about the life changes you should make based on the results of their study. They seldom let you peak behind the curtain to see how much the results vary from one individual to the next.

One exception is a recent study that reported individual variation in blood sugar responses to various foods. There are lots of examples from that study I could share with you, but I will use bananas versus sugar cookies as an example.

When they reported average values, bananas had a glycemic index of 51 and sugar cookies had a glycemic index of around 59. Both of those values are very close to what you find in most glycemic index lists.

The glycemic index of a banana is only 13% less than the glycemic index of sugar cookies. However, since the cut-off between high and low glycemic indices is 55, bananas are classified as low-glycemic and sugar cookies are classified as high-glycemic. According to conventional wisdom, bananas are good for you and sugar cookies are bad for you. But, what about individual variation? Does that wisdom really apply to you?

can you believe clinical studies blood sugarBased on the range of blood-sugar responses reported in the paper, I have created the scatter plot on the left to help you visualize the range of individual responses. The horizontal line represents the average glycemic index for sugar cookies and bananas. The dots represent the glycemic response of individuals in the study. For some people in the study the glycemic response to bananas was greater than the average glycemic response to sugar cookies. For other individuals the glycemic response to sugar cookies was less than the average glycemic response to bananas.

You can see the extent of individual variability even more clearly in the figure on the right, which was reproduced from one of the figures in the paper. The authors reported that for some individuals, bananas caused no increase in blood sugar while sugar cookies caused a big spike in blood sugar (the response most people would expect). However, for other individuals, sugar cookies caused no increase in blood sugar while bananas caused a big spike in blood sugar.

can you believe clinical studies glycemic loadNow you understand why I told you the glycemic list you are relying on may not apply to you. You also understand why I said the advice you have been given about bananas might not apply to you.

Lest you think this just applies to bananas, the same study reported that individual blood sugar responses varied by:

  • 4-fold for sugar-sweetened soft drinks, grapes, and apples.
  • 5-fold for rice.
  • 6-fold for bread and potatoes.
  • 7-fold for ice cream and dates.

 

Can You Believe Clinical Studies?

 

can you believe clinical studies provenI used glycemic index as an example. The same principle is true for almost any clinical study.

Let’s consider clinical studies looking at the effect of diet on health outcomes such as heart disease.

  • The headlines may say that a particular diet significantly decreases your risk of heart disease.
  • When you read the paper behind the headlines, you discover that the diet decreases heart disease by 15%. That result may be statistically significant, but it is hardly life changing.
  • If you could peak behind the curtain you might discover that the diet cut heart disease risk in half for some individuals and had no effect on heart disease risk for others.

Clinical studies looking at weight loss are another example.

  • You might be told “Clinical studies show people who follow diet X lose 12 pounds in 6 weeks”.
  • That’s an average value. If you could peak behind the curtain, you would discover that nobody lost exactly 12 pounds. Some lost more. Some lost less. Some may have actually gained weight.

I am not saying that well-designed clinical studies are useless. They are a good foundation for general nutrition guidelines. What I am saying is that not every nutritional guideline applies to you.

What Does This Study Mean For You?

Some of you may be saying: “What does this mean for me?” When you carry the concept of individual variability through to its ultimate conclusion, the bottom line message is:

  • Conclusions from clinical trial results are based on averages – none of us are average.
  • Daily Values (DV) are based on averages – none of us are average.
  • Nutritional recommendations for optimal health are based on averages – none of us are average.
  • The identified risk factors for developing diseases are based on averages – none of us are average.
  • Glycemic index lists are based on averages. None of us are average.

That means lots of the advice you may be getting about your risk of developing disease X, the best diet to prevent disease X, the best foods to keep your blood sugar under control, or the role of supplementation in preventing disease X may be generally true – but it might not be true for you.

So, my advice is not to blindly accept the advice of others about what is right for your body. Just because some health guru recommends it, doesn’t mean it is right for you. Just because it worked for your buddy, doesn’t mean it will work for you. Learn to listen to your body. Learn what foods work best for you. Learn what exercises just feel right for you. Learn what supplementation does for you.

Don’t ignore your doctor’s recommendations, but don’t be afraid to take on some of the responsibility for your own health. You are a unique individual, and nobody else knows what it is like to be you.

 

Final Thought: Glycemic Index Versus Glycemic Load

Since I used glycemic index as an example in this discussion, I feel obligated to discuss the difference between glycemic index and glycemic load. Glycemic index is based on the blood sugar response to 50 gm of carbohydrate in various foods. Glycemic load is based on the blood sugar response to a serving of that food. In some cases, that’s a big difference.

Glycemic index can sometimes be deceiving. Let me give you two examples. Carrots and watermelon are often found on lists of high glycemic foods. If that sounds a bit weird to you, it is.

One serving (one medium carrot) of carrots has 6 grams of carbohydrate (of which, only 2.9 grams is sugar). To get 50 grams of carbohydrate, you would need to eat 8 carrots. Watermelon is, not surprisingly, mostly water. One serving (a 1-inch thick sliced wedge or one cup) of watermelon contains 11 grams of carbohydrate (of which, 9 grams of sugar). To get 50 grams of sugar, you would need to eat 4.5 cups of watermelon. For both carrots and watermelon, their glycemic load is a more accurate measure of their effect on your blood sugar than is their glycemic index.

Leaving individual variation out of consideration, here is a simple guide for choosing low-glycemic foods if you are trying to control your blood sugar levels.

  • Foods with a low glycemic index are generally a good choice.
  • Many foods with a high glycemic index also have a high glycemic load.
  • If you are uncertain about some foods on the high glycemic index list, also check their glycemic load.

 

The Bottom Line

Clinical studies are the bedrock on which we build recommendations for diet, exercise, and supplementation. In the article above I discuss how to distinguish between good and bad clinical studies. I also discuss how individual variability influences the interpretation of clinical studies.

 

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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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, 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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