Do Low Fat Diets Reduce The Risk Of Diabetes?

Why Is Nutrition So Confusing?

Author: Dr. Stephen Chaney

EpigeneticsSometimes the professor likes to introduce you to the frontiers of nutrition. Epigenetics is such a frontier. In recent years, the hype has centered on DNA sequencing. It seems like everyone is offering to sequence your genome and tell you what kind of diet is best for you, what foods to eat, and what supplements to take. But can DNA sequencing fulfill those promises?

The problem is that DNA sequencing only tells you what genes you have. It doesn’t tell you whether those genes are active. Simply put, it doesn’t tell you whether those genes are turned on or turned off.

This is where epigenetics comes in. Epigenetics is the science of modifications that alter gene expression. In simple terms, both DNA and the proteins that bind to DNA can be modified. This does not change the DNA sequence. But these modifications can determine whether a gene is active (turned on) or inactive (turned off).

This sounds simple enough, but here is where it really gets interesting. These modifications are affected by our diet, our lifestyle (BMI and exercise), our microbiome (gut bacteria), and our environment.

In today’s “Health Tips From The Professor” I am going to share a study (CQ Lai et al, American Journal of Clinical Nutrition, 112: 1200-1211, 2020) that looks at the effect of diet (low-fat versus low-carb diets) on a particular kind of DNA modification (methylation) that affects a gene (CPT) which influences our risk for metabolic diseases (obesity, high triglycerides, low HDL, insulin resistance, pre-diabetes, and type 2 diabetes).

[Note: For simplicity I will just refer to type 2 diabetes in the rest of this article. Just be aware that whatever I say about type 2 diabetes applies to other metabolic diseases as well.]

Previous studies have shown that:

  • Methylation of the CPT gene is the only epigenetic change in the entire genome that is associated with decreased risk of type 2 diabetes.
  • CPT gene activity regulates multiple metabolic pathways that influence the risk of type 2 diabetes.
  • High fructose and sucrose consumption increases CPT gene methylation in rats, and high fat diets suppress that methylation.

Based on those data, the authors hypothesized that carbohydrate and fat intake affect the methylation of CPT gene, which:

  • Alters the activity of the CPT gene and…
  • Affects the risk of developing type 2 diabetes.

Since we are talking about our diet making alterations to our DNA, we could consider this as an example of, “We are what we eat”.

Biochemistry 101: Why Is Nutrition So Confusing?

ConfusionNow it is time for my favorite topic, Biochemistry 101. Along the way you will discover why nutrition is so complicated – and so confusing.

The CPT gene codes for a protein called carnitine palmitoyltransferase or CPT. CPT transports fats into the mitochondria where they can be oxidized to generate energy. Simply put, without CPT we would be unable to utilize most of the fats we eat. And, as you might expect, CPT is not required for carbohydrate metabolism.

  • In a simple world where our DNA sequence determines our destiny, we would either have an active CPT gene or an inactive mutant version of the gene. If we had the mutant version of the CPT gene, we would be unable to use fat as an energy source.

However, we don’t live in a simple world. Epigenetic modifications alter the activity of the CPT gene. When the CPT gene is unmethylated it is fully active. Methylation inactivates the gene.

  • In a simple world, a high fat diet would activate the CPT gene so our body would be able to utilize the fat in our diet. It would do that by decreasing methylation of the gene. Conversely, a high carbohydrate, low fat diet would decrease CPT gene activity by increasing methylation of the gene.

This is the one simple prediction that works exactly as expected. 

  • In a simple world, CPT would be involved in transport of fat into our mitochondria and nothing else. In that world, the activity of the CPT gene would only affect fat metabolism.

However, we don’t live in a simple world. By mechanisms that are not completely understood, carnitine palmitoyltransferase (CPT) also influences both insulin resistance and release of insulin by our pancreas. That means the activity of the CPT gene also affects our risk of developing type 2 diabetes. 

  • In the simplest terms, we can think of diabetes as an inability to properly regulate blood sugar levels. In a simple world, that would mean that carbohydrates are the problem, and we could reduce our risk of developing diabetes by restricting our intake of carbohydrates.

However, we don’t live in a simple world. There are short-term studies supporting the effectiveness of both low carb and low fat diets at helping to control blood sugar levels. However, longer term studies generally show that only whole food, low fat diets are associated with reduced risk of developing type 2 diabetes.

In other words, healthy carbohydrates aren’t the problem. They are the solution for reducing your risk of type 2 diabetes. This isn’t intuitive. It isn’t simple. But the weight of evidence points in this direction.

[I should add the emphasis is on “healthy” carbohydrates. I am talking about diets that emphasize whole food sources of carbohydrates (fruits, vegetables, whole grains, and legumes), not diets loaded with sugar, refined carbohydrates, and highly processed foods.]

Confused yet? Don’t worry. The authors of this study combined all this information into a single, unifying hypothesis.

They proposed that the fat and carbohydrate content of the diet influence methylation of the CPT gene, which influences the activity of the CPT gene, which influences both fat metabolism and the risk of developing type 2 diabetes. Specifically, they proposed that:

  • High fat diets reduce methylation of the CPT gene. This activates the CPT gene which results in more carnitine palmitoyltransferase (CPT) being produced. This improves fat metabolism, but also increases the risk of developing type 2 diabetes.
  • High carbohydrate, low fat diets increase methylation of the CPT gene. This inactivates the CPT gene which results in less CPT being produced. This is OK because there is little fat to be metabolized. However, it also has the advantage of reducing the risk of developing type 2 diabetes.

This can be visually represented as:Diet And CPT

How Was This Study Done?

Clinical StudyThis study combined the results from 3,954 selected participants in three previous clinical trials:

  • The Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study.
  • The Framingham Heart Study.
  • The REGICORE study. This study is similar in design to the Framingham Heart Study except the participants were drawn from a region of Spain.

The participants were selected based on 4 criteria:

  • The study they were in measured metabolic disease outcome.
  • The study they were in included a detailed diet analysis.
  • A DNA methylation analysis was performed on blood taken from these participants so that the methylation status of the CPT gene could be determined.
  • mRNA levels were measured for the CPT gene (This is a measure of how active the gene is. Active genes will produce lots of mRNA. Inactive genes will produce very little mRNA).

The study then analyzed the data and looked at the associations between carbohydrate and fat intake with:

  • Methylation of the CPT gene.
  • Activity of the CPT gene (measured as the amount of CPT mRNA produced by the gene).
  • Type 2 diabetes and other metabolic diseases.

Do Low Fat Diets Reduce The Risk Of Diabetes?

The authors systematically tested the predictions of their unifying hypothesis (To help you understand the significance of their findings, I am repeating the visual representation of their unifying hypothesis below):

Diet And CPT

  1. Methylation of the CPT gene was negatively associated with type 2 diabetes. Simply put, when the methylation of the of the CPT gene was high, the risk of type 2 diabetes was low. This confirmed the results of previous studies.

2) Carbohydrate and fat intake influenced methylation of the CPT gene. Specifically:

    • Carbohydrate intake and the ratio of carbohydrate to fat intake were positively associated with CPT methylation. Simply put, a high carbohydrate, low fat diet resulted in increased methylation of the CPT gene.
    • Fat intake was negatively associated with CPT methylation. Simply put, a high fat, low carbohydrate diet resulted in decreased methylation of the CPT gene.

3) Carbohydrate and fat intake influenced the activity of the CPT gene. Specifically:Diabetes and healthy die

    • Carbohydrate intake and the ratio of carbohydrate to fat intake was negatively associated with CPT mRNA levels (a measure of CPT gene activity). Simply put, a high carbohydrate, low fat diet resulted in lower CPT gene activity. This means the CPT gene produced less CPT. And, combined with the previous data, it also means that methylation of the CPT gene decreases its activity.
    • Fat intake was positively associated with CPT mRNA levels. Simply put, a high fat, low carbohydrate diet resulted in greater CPT gene activity. This means the CPT gene produces more CPT. And, combined with the previous data, it also means that reducing methylation of the CPT gene increases its activity.

4) CPT gene activity influenced the prevalence of type 2 diabetes. Specifically:

    • High CPT gene activity was positively associated with the risk of type 2 diabetes.
    • Low CPT gene activity was negatively associated with the risk of type 2 diabetes.

Putting this all together, as the authors had predicted,

  1. High fat, low carbohydrate diets reduce methylation of the CPT gene. This activates the CPT gene which results in more CPT being produced. This improves fat metabolism, but also increases the risk of developing type 2 diabetes.

2) High carbohydrate, low fat diets increase methylation of the CPT gene. This results in less CPT being produced. This is OK because there is little fat to be metabolized. However, it also has the advantage of reducing the risk of developing type 2 diabetes.

In short, the results of the study confirmed all the predictions of the author’s unifying hypothesis.

Putting it all together, the authors concluded, “Our results suggest that the proportion of total energy supplied by carbohydrate and fat can have a causal effect on metabolic diseases [like type 2 diabetes] via the epigenetic status (DNA methylation) of the CPT gene.” Simply put, their data suggested that high carbohydrate, low fat diets reduced the risk developing type 2 diabetes.

What Does This Study Mean For You?

Peek Behind The CurtainLet me start by saying that occasionally I like to give you a peak behind the curtain and talk about emerging areas of research. We should think of this article as the beginning of an exciting new area of research rather than as a definitive study.

I should start with the disclaimer that this study looks at associations between diet, methylation of the CPT gene, and risk of developing type 2 diabetes.

Associations do not prove cause and effect. This study does not prove that epigenetic changes to the CPT gene caused the reduction in type 2 diabetes risk.

High carbohydrate and high fat diets likely influence the risk of developing type 2 diabetes in other ways as well. For example, the fiber in healthy high carbohydrate diets may support friendly gut bacteria that reduce the risk of developing type 2 diabetes.

I also don’t view this study as one that settles the debate as to whether low carb or low fat diets are better for reducing the risk of type 2 diabetes. It does not clinch the argument for low fat diets. Rather, this study suggests a mechanism by which low fat diets may reduce the risk of metabolic diseases.

In summary, this study does not end the debate as to whether low carb or low fat diets are best. However, it does remind us just how complex the human body is. It reminds us that simple assumptions about how foods affect our bodies may not be the correct assumptions. It also helps us understand why nutrition can be so confusing.

The Bottom Line 

In recent years, DNA sequencing has become all the rage. It seems like everyone is offering to sequence your genome and tell you what kind of diet is best for you.

The problem is that DNA sequencing only tells you what genes you have. It doesn’t tell you whether those genes are active. Simply put, it doesn’t tell you whether those genes are turned on or off.

That is where epigenetics comes in. Epigenetics is the science of modifications that alter gene expression. In simple terms, both DNA and the proteins that bind to DNA can be modified. This does not change the DNA sequence. But these modifications can determine whether a gene is active (turned on) or inactive (turned off).

Epigenetics makes nutrition more complicated, and more confusing. For example, diabetes is characterized an inability to control blood sugar levels properly. Accordingly, it seems only logical that carbohydrates, especially sugars and simple carbohydrates, are the problem.

This study showed that high carbohydrate, low fat diets cause epigenetic modifications to a gene that reduces the risk of developing type 2 diabetes and other metabolic diseases. Conversely, high fat, low carb diets have the opposite effect.

This mechanism is consistent with multiple long-term studies showing that whole food, low fat diets reduce the risk of developing type 2 diabetes.

This study does not end the debate as to whether low carb or low fat diets are best. However, it does remind us just how complex the human body is. It reminds us that simple assumptions about how foods affect our bodies may not be the correct assumptions. It also helps us understand why nutrition can be so confusing.

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.

 

Do Processed Foods Increase Your Risk Of Diabetes?

Why Do We Keep Eating Processed Foods?

Fast Food DangersUnless you are Rip Van Winkle and have been asleep for the past 20 years you probably know that the highly processed foods in the typical American diet are bad for your health. But perhaps you didn’t realize just how bad they were.

But first, let’s start with a bit of perspective. Scientists like to be precise. Even healthy foods go through some processing.

  • The oatmeal you ate this morning was either steel-cut or ground. That is processing.
  • The almond butter you put on your whole grain toast this morning was made by roasting and grinding. That is processing.

So, scientists have developed the term “ultra-processed food” to describe the worst of the worse. In short, ultra-processed foods:

  • Usually go through several physical and chemical processes, such as extruding, molding, prefrying, and hydrogenation that can lead to the formation of toxic contaminants. One example you may have heard about recently would be acrylamide in French fries.
  • Typically contain ingredients of no or little nutritive value, such as refined sugar, hydrogenated oils, emulsifiers, artificial sweeteners, thickening agents, and artificial colors. Some of these ingredients have been linked to cancer, heart disease, and premature death.
  • Have long shelf-lives because of added preservatives. This allows migration of chemicals such as bisphenol A from the packaging materials into the food.

Examples of ultra-processed foods include:

  • Sodas
  • Chips
  • Candy and packages of cookies or crackers
  • Most breakfast cereals
  • Boxed cake, cookie, and pancake mix
  • Chicken nuggets and fish sticks
  • Fast food burgers
  • Hot dogs and other processed meats
  • Infant formula
  • Instant noodles
  • Most store-bought ice cream
  • Flavored yogurt

In short, ultra-processed foods include sodas and the junk and convenience foods Americans hold so dear. Even things like infant formula and flavored yogurt make the list.

Evidence of the ill effects of ultra-processed foods on our health is becoming overwhelming. In previous issues of “Health Tips From the Professor” I have shared recent studies that have shown that heavy consumption of ultra-processed foods is linked to increased risk of obesity and cancer. Other studies have linked ultra-processed food consumption with increased risk of depression, heart disease, and premature death.

In this issue of “Health Tips From the Professor” I:

  • Ask the important question, “If we know these foods are so bad for us, why do we still keep eating them?”

How Was The Study Done?

Clinical StudyThe data from this study were taken from an ongoing study in France (the NutriNet-Sante study) looking at associations between nutrition and health. This study began enrolling French adults 18 and older in 2009.

This is a web-based study. Participants are prompted to go to a dedicated website and fill out questionnaires related to things like sex, age, height, weight, smoking status, physical activity, health status, and diet.

With respect to diet, participants filled out a series of 3 nonconsecutive 24-hour dietary records at the time of enrollment and every 6 months. This is a particularly strong feature of this study. Many studies of this type only analyze participant’s diets at the beginning of the study. Those studies have no way of knowing how the participant’s diets may have changed during the study.

Diagnosis of type 2 diabetes for study participants was obtained from the French centralized health records.

The study enrolled 104,708 participants, 20% men and 80% women, and followed them for an average of 6 years. The average age of the participants was 43 years.

Do Processed Foods Increase Your Risk Of Diabetes?

High Blood SugarIn this study the range of ultra-processed foods in the French diet ranged from 7% to 27% (average = 17%). High intake of ultra-processed foods was associated with:

  • Younger participants. Simply put, young people were more likely to drink sodas and eat junk food than older adults.
  • Increased caloric intake. Ultra-processed foods have a higher caloric density than whole, unprocessed foods.
  • No surprise here. Previous studies have shown that ultra-processed food consumption increases the risk of obesity.
  • Poorer diet quality. Again, no surprise. Junk foods tend to crowd healthier foods out of the dirt. Specifically, ultra-processed food consumption was associated with:
    • Higher intake of sugar and salt.
    • Lower intake of fiber.
    • Higher intake of sugary drinks, red and processed meats.
    • Lower intake of whole grains, yogurt, nuts, fruits, and vegetables.

However, even after statistically correcting for all these factors, there was a significant association between ultra-processed food consumption and the onset of type 2 diabetes in the 6-year follow-up period.

  • There was a linear relation between ultra-processed food consumption and the development of type 2 diabetes. Simply put, the more ultra-processed food the participants consumed the more likely they were to be diagnosed with type 2 diabetes.
  • There was a 15% increased risk of developing type 2 diabetes for every 10% increase in ultra-processed food consumption.

The authors concluded:

“In this large observational prospective study, a higher proportion of ultra-processed food in the diet was associated with a higher risk of type 2 diabetes. Even though these results need to be confirmed in other populations and settings, they provide evidence to support efforts by public health authorities to recommend limiting ultra-processed food consumption.”

What Does This Study Mean For You?

Questioning WomanYou might be tempted to say that a 15% increase in the risk of developing diabetes is a small price to pay for continuing to eat the foods you enjoy. However, you should be alarmed by this study. Here is why.

The French diet is much healthier than the American. Remember that ultra-processed foods only comprised 17% of the French Diet. In contrast, a recent survey found that:

  • Ultra-processed foods make up 58% of the average American’s diet.
  • Ultra-processed foods account for 90% of the added sugar in our diet.

It is no wonder that obesity and diabetes are reaching epidemic proportions in our country.

You might also be tempted to think that you can just take some medications and live with type 2 diabetes. However, you should think of type 2 diabetes as a gateway disease. It increases your risk of heart disease, high blood pressure, Alzheimer’s disease, kidney damage, and neuropathy, just to name a few. These are diseases that make your life miserable and ultimately kill you.

More importantly, type 2 diabetes is completely reversible if you catch it early enough. Just lose some weight, exercise more, give up the ultra-processed foods, and eat a healthy diet. I recommend a whole food, primarily plant-based diet.

Why Do We Keep Eating Processed Foods?

Fast FoodsWe all know that ultra-processed foods are bad for us. Study after study show that they make us sick. They kill us prematurely. And, unlike most topics in the field of nutrition, this is not controversial.

For example, there have been lots of bizarre diets that have come and gone over the years. There have been books written on “The Steak Lover’s Diet” and “The Drinking Man’s Diet”. But nobody has written a book on “The Junk Food Lover’s Diet”. It simply would not be believable.

So why do we Americans keep eating such unhealthy foods. Part of the answer is physiological. A preference for sweet, salty, and fatty foods is hardwired into our brain. That’s because they had great survival value in prehistoric times.

If we think back to the time when we were hunters and gatherers:

  • Fruits are healthy foods. They are a great source of antioxidants, phytonutrients, and fiber, but there were no orchards or grocery stores back then. We had to search for fruits in the wild. Our desire for sweet tasting foods provided the motivation to seek them out.
  • Game was seasonal and sometimes scarce. We had to be prepared to go for days or weeks without eating except for the leaves and roots we could gather. Our bodies are designed to store fat as the primary energy source to get us through the lean times. Our preference for fatty foods encouraged us to store as much fat as possible in times of plenty so we would be prepared for times of scarcity.
  • If we fast forward to our early recorded history, salt was scarce. It was worth its weight in gold. Yet some salt is essential for life. Our preference for salty foods encouraged us to search out supplies of salt.

Unfortunately, the food industry has weaponized these food preferences to create the ultra-processed foods we know today. Their ads entice us by associating these foods with youth and good times. And ultra-processed foods have become ubiquitous. There are fast food restaurants on almost every street corner and shopping mall in the country.

Fortunately, we do not have to let the food industry destroy our health. We can retrain our taste buds to appreciate the sweetness of fresh fruits and vegetables. We can substitute healthy fats for the kinds of fat found in most ultra-processed foods. We can also retrain our taste buds to appreciate herbs and spices with just a pinch of salt.

The Bottom Line

Ultra-processed foods, such as sodas, junk foods, and convenience foods have become the biggest food group in the American diet. A recent study found:

  • Ultra-processed foods make up 58% of the average American’s diet.
  • Ultra-processed foods account for 90% of the added sugar in our diet.

That is scary because ultra-processed foods are deadly. Previous studies have shown that consumption of ultra-processed foods is linked to obesity, heart disease, cancer, and Alzheimer’s disease.

The study discussed this week looked at the association between ultra-processed food consumption and type 2 diabetes. It showed:

  • There was a linear relation between ultra-processed food consumption and the development of type 2 diabetes. Simply put, the more ultra-processed food the participants consumed the more likely they were to be diagnosed with type 2 diabetes.
  • There was a 15% increased risk of developing type 2 diabetes for every 10% increase in ultra-processed food consumption.

You might be tempted to think that you can just take some medications and live with type 2 diabetes. However, you should think of type 2 diabetes as a gateway disease. It increases your risk of heart disease, high blood pressure, Alzheimer’s disease, kidney damage, and neuropathy, just to name a few. This are diseases that make your life miserable and ultimately kill you.

More importantly, type 2 diabetes is completely reversible if you catch it early enough. Just lose some weight, exercise more, give up the ultra-processed foods, and eat a healthy diet. I recommend a whole food, primarily plant-based diet.

For more details and a discussion of why Americans continue to eat ultra-processed food even though we know it is bad for us, 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.

Health Tips From The Professor