very low fat diet

Which Diets Are Heart Healthy?

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Which Diet Is Best For You?

Author: Dr. Stephen Chaney 

strong heartThe top 3 claims the advocates of every popular diet make are:

  • It will help you lose weight.
  • It reduces your risk of diabetes.
  • It reduces your risk of heart disease.

The truth is any restrictive diet helps you lose weight. And when you lose weight, you improve blood sugar control. Which, of course, reduces your risk of developing diabetes.

But what about heart disease? Which diets are heart healthy? When it comes to heart disease the claims of diet advocates are often misleading. That’s because the studies these advocates use to support their claims are often poor quality studies. Many of these studies:

  • Look at markers of heart disease risk rather than heart disease outcomes. Markers like LDL cholesterol, triglycerides, c-reactive protein, etc. are only able to predict possible heart disease outcomes. To really know which diets are heart healthy you have to measure actual heart disease outcomes such as heart attacks, stroke, and cardiovascular deaths.
  • Are too short to provide meaningful results. Many of these studies last only a few weeks. You need much longer to measure heart disease outcomes.
  • Are too small to provide statistically significant results. You need thousands of subjects to be sure the results you are seeing are statistically significant.
  • Have not been confirmed by other studies. The Dr. Strangeloves of the world like to “cherry pick” the studies that support the effectiveness of their favorite diet. Objective scientists know that any individual study can be wrong. So, they look for consensus conclusions from multiple studies.

A recent study (G Karam et al, British Medical Journal, 380: e072003, 2023) avoided all those pitfalls. The investigators conducted a meta-analysis of 40 high-quality clinical studies with 35,548 participants to answer the question, “Which diets are heart healthy?”

How Was The Study Done?

Clinical StudyThe authors started by searching all major databases of clinical studies for studies published on the effect of diets on heart disease outcomes through September 2021.

They then performed a meta-analysis of the data from all studies that:

  • Compared the effect of a particular diet to minimal dietary intervention (defined as not receiving any advice or receiving dietary information such as brochures or brief advice from their clinician with little or no follow-up).
  • Looked at heart disease outcomes such as all cause mortality, cardiovascular mortality, non-fatal heart attacks, stroke, and others.
  • Lasted for at least 9 months (average duration = 3 years).
  • Were high-quality studies.

Using these criteria:

  • They identified 40 studies with 35,548 participants for inclusion in their meta-analysis.
    • From those 40 studies, they identified 7 diet types that met their inclusion criteria (low fat (18 studies), Mediterranean (12 studies), very low fat (6 studies), modified fat (substituting healthy fats for unhealthy fats rather than decreasing fats, 4 studies), combined low fat and low sodium (3 studies), Ornish (3 studies), Pritikin (1 study).

One weakness of meta-analyses is that the design of the studies included in the meta-analysis is often different. Sometimes they don’t fit together well. So, while the individual studies are high-quality, a combination of all the studies can lead to a conclusion that is low quality or moderate quality.

Finally, the data were corrected for confounding factors such as obesity, exercise, smoking, and medication use.

Which Diets Are Heart Healthy?

Now that you understand the study design, we are ready to answer the question, “Which diets are heart healthy?” Here is what this study found:

Compared to minimal intervention,

  • The Mediterranean diet decreased all cause mortality by 28%, cardiovascular mortality by 45%, stroke by 35%, and non-fatal heart attacks by 52%.
  • Low fat diets decreased all cause mortality by 16% and non-fatal heart attacks by 23%. The effect of low fat diets on cardiovascular mortality and stroke was not statistically significant in this meta-analysis.
    • For both the Mediterranean and low fat diets, the heart health benefits were significantly better for patients who were at high risk of heart disease upon entry into the study.
    • The evidence supporting the heart health benefits for both diets was considered moderate quality evidence for this meta-analysis. [Remember that the quality of any conclusion in a meta-analysis is based on both the quality of evidence of the individual studies plus how well the studies fit together in the meta-analysis.]
  • While the percentage of risk reduction appears to be different for the Mediterranean and low fat diets, the effect of the two diets on heart health was not considered significantly different in this study.
  • The other 5 diets provided little, or no benefit, compared to the minimal intervention control based on low to moderate quality evidence.

The authors concluded, “This network meta-analysis found that Mediterranean and low fat dietary programs probably reduce the risk of mortality and non-fatal myocardial infarction [heart attacks] in people at increased cardiovascular risk. Mediterranean dietary programs are also likely to reduce the risk of stroke. Generally, other dietary programs were not superior to minimal intervention.”

Which Diet Is Best For You?

confusionThe fact that this study found both the Mediterranean diet and low fat diets to be heart healthy is not surprising. Numerous individual studies have found these diets to be heart healthy. So, it is not surprising when the individual studies were combined in a meta-analysis, the meta-analysis also concluded they were heart healthy. However, there are two important points I would like to make.

  • The diets used in these studies were designed by trained dietitians. That means the low fat studies did not use Big Food, Inc’s version of the low fat diet in which fatty foods are replaced with highly processed foods. In these studies, fatty foods were most likely replaced with whole or minimally processed foods from all 5 food groups.
  • The Mediterranean diet is probably the most studied of current popular diets. From these studies we know the Mediterranean diet improves brain health, gut health, and reduces cancer risk.

As for the other 5 diets (very low fat, modified fat, low fat and low sodium, Ornish, and Pritikin), I would say the jury is out. There is some evidence that these diets may be heart healthy. But very few of these studies were good enough to be included in this meta-analysis. Clearly, more high-quality studies are needed.

Finally, you might be wondering why other popular diets such as paleo, low carb, and very low carb (Atkins, keto, and others) were left out of this analysis. All I can say is that it wasn’t by design.

The authors did not select the 7 diets described in this study and then search for studies testing their effectiveness. They searched for all studies describing the effect of diets on heart health. Once they identified 40 high-quality studies, they grouped the diets into 7 diet categories.

I can only conclude there were no high-quality studies of paleo, low carb, or very low carb diets that met the criteria for inclusion in this meta-analysis. The criteria were:

  • The effect of diet on heart health must be compared to a control group that received no or minimal dietary advice.
  • The study must measure heart disease outcomes such as all cause mortality, cardiovascular mortality, non-fatal heart attacks, and stroke.
  • The study must last at least 9 months.
  • The study must be high-quality.

Until these kinds of studies are done, we have no idea whether these diets are heart healthy or not.

So, what’s the takeaway for you? Which diet is best for you? Both low fat diets and the Mediterranean diet are heart healthy provided the low fat diet consists of primarily whole or minimally processed foods. Which of these two diets is best for you depends on your food preferences.

The Bottom Line 

Many of you may have been warned by your doctor that your heart health is not what it should be. Others may be concerned because you have a family history of heart disease. You want to know which diets are heart healthy.

Fortunately, a recent study answered that question. The authors performed a meta-analysis of 40 high-quality studies that compared the effect of various diets with the effect of minimal dietary intervention (doctors’ advice or diet brochure) on heart disease outcomes.

From this study they concluded that both low fat diets and the Mediterranean diet probably reduce mortality and the risk of non-fatal heart attacks, and that the Mediterranean diet likely reduces stroke risk.

Other diets studied had no significant effect on heart health in this study. That does not necessarily mean they are ineffective. But it does mean that more high-quality studies are needed before we can evaluate their effect on heart health.

So, what’s the bottom line for you? Both low fat diets and the Mediterranean diet are heart healthy provided the low fat diet consists of primarily whole or minimally processed foods Which of these two diets is best for you depends on your food preferences.

For more information on this 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.

___________________________________________________________________________

My posts and “Health Tips From the Professor” articles carefully avoid claims about any brand of supplement or manufacturer of supplements. However, I am often asked by representatives of supplement companies if they can share them with their customers.

My answer is, “Yes, as long as you share only the article without any additions or alterations. In particular, you should avoid adding any mention of your company or your company’s products. If you were to do that, you could be making what the FTC and FDA consider a “misleading health claim” that could result in legal action against you and the company you represent.

For more detail about FTC regulations for health claims, see this link.

https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance

Which Diets Are Heart Healthy?

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What Does A Heart Healthy Diet Look Like?

Author: Dr. Stephen Chaney 

heart attacksHeart disease is a big deal. According to the CDC, “Heart disease is the leading cause of death for men, women, and people of most racial and ethnic groups in the United States. One person dies every 33 seconds in the United States from cardiovascular disease. About 695,000 people in the United States died from heart disease in 2021 – that’s 1 in every 5 deaths”.

This doesn’t have to happen. According to the Cleveland Clinic, “90 percent of heart disease is preventable through healthier diet, regular exercise, and not smoking”. For this issue of “Health Tips From the Professor”, I will focus on the role of diet on heart health.

The problem is many Americans are confused. They don’t know what a heart-healthy diet is. There is so much conflicting information on the internet.

Fortunately, the American Heart Association has stepped in to clear up the confusion.

In 2021 they reviewed hundreds of clinical studies and published “Evidence-Based Dietary Guidance to Promote Cardiovascular Health”.

And recently they have published a comprehensive review (CD Gardner et al, Circulation, 147: 1715-1730, 2023) of how well popular diets align with their 2021 dietary guidelines.

I will cover both publications below. But first I want to address why Americans are so confused about which diets reduce heart disease risk.

Why Are Americans Confused About Diet And Heart Disease Risk?

I should start by addressing the “elephant in the room”.

  • As I discussed in last week’s “Health Tips From the Professor” article, Big Food Inc has seduced us. They have developed an unending supply of highly processed foods that are cheap, convenient, easy to prepare, and fulfill all our cravings. These foods are not heart-healthy, but they make up 73% of our food supply.

The Institute of Medicine, the scientific body that sets dietary standards, states that a wide range of macronutrient intakes are consistent with healthy diets. Specifically, they recommend carbohydrate intake at 45% to 65%, fat intake at 20% to 35%, and protein intake at 10% to 35% of total calories. (Of course, they are referring to healthy carbohydrates, fats, and proteins.)

The authors of this article pointed to several reasons why Americans have been misled about heart-healthy diets.

  • Many of the most popular diets fall outside of the “Acceptable Macronutrient Range”.
  • Many popular diets exclude heart-healthy food groups.

And, the words of the authors,

  • “Further contributing to consumer misunderstanding is the proliferation of diet books, [and] blogs [by] clinicians with limited understanding of what the dietary patterns entail and the evidence base for promoting cardiometabolic health.” I call these the Dr. Strangeloves of our world.

What Does A Heart Healthy Diet Look Like?

Let me start by sharing the American Heart Association’s 10 “Evidence-Based Dietary Guidelines to Promote Cardiovascular Health.

#1: Adjust energy intake and expenditure to achieve and maintain a healthy body weight
#2: Eat plenty of vegetables and fruits; choose a wide variety
#3: Choose foods made mostly with whole grains rather than refined grains
#4: Choose healthy sources of protein
Mostly from plants (beans, other legumes, and nuts)
Fish and seafood
Low-fat or fat-free dairy products instead of full-fat dairy products
If meat or poultry are desired, choose lean cuts and avoid processed forms
#5. Use liquid plant oils (olive, safflower, corn) rather than animal fats (butter and lard) and tropical oils (coconut and palm kernel)
#6. Use minimally processed foods instead of highly processed foods
#7: Minimize intake of beverages and foods with added sugars
#8: Choose and prepare foods with little or no salt
#9: If you do not drink alcohol, do not start; if you choose to drink alcohol, limit intake
#10: Adhere to this guidance regardless of where food is prepared or consumed

Here are my comments on these guidelines:

  • If you have been reading my “Health Tips From the Professor” blog for a while, you probably realize that these aren’t just guidelines to promote heart health. These guidelines also reduce the risk of diabetes, cancer, inflammatory diseases, and much more.
  • If you have read my post on coconut oil, you will know that I have a minor disagreement with the AHA recommendation to avoid it. There is no long-term evidence that coconut oil is bad for the heart. But there is also no long-term evidence that it is good for the heart. My recommendation is to use it sparingly.
  • And you probably know there has been considerable discussion recently about whether full fat dairy is actually bad for the heart. In my most recent review of the topic, I concluded that if full fat dairy is heart healthy, it is only in the context of a primarily plant-based diet and may only be true for fermented dairy foods like unpasteurized yogurt and kefir.
  • Finally, guideline 10 may need some translation. Basically, this guideline is just asking how easy it is to follow the diet when you are away from home.

Which Diets Are Heart Healthy?

confusionIn evaluating how well diets adhered to the American Heart Association guidelines the authors ignored item 1 (energy intake) because most of the diets they evaluated did not provide any guidelines on how many calories should be consumed.

Each diet was given a score between 0 (Fail) and 1 (A+) for each of the other 9 guidelines by a panel of experts. The points for all 9 guidelines were added up, giving each diet a rating of 0 (worst) to 9 (best). Finally, a score of 9 was assigned 100%, so each diet could be given a percentage score for adherence to heart-healthy guidelines.

Here are the results:

Tier 1 diets (the most heart healthy diets) received scores of 86% to 100%. Going from highest (100%) to lowest (86%), these diets were:

  • DASH, Nordic, Mediterranean, Pescetarian (vegetarian diets that allow fish), and Ovo-Lacto Vegetarian (vegetarian diets that allow dairy, eggs, or both).
  • You will notice that these are all primarily plant-based diets.

Tier 2 diets were Vegan and other low-fat diets (TLC, Volumetrics). They both received scores of 78%.

  • The Vegan diet received 0 points for category 10 (ease of following the diet when eating out). It was also downgraded in category 7 for not having clear guidance for the use of salt when preparing foods.
  • The other low-fat diets were downgraded in categories 7, 10, and 5 (use of tropical oils).

Tier 3 diets received scores of 64% to 72%. They included very-low fat diets (<10% fat, very strict vegan diets) and low-carb diets (Zone, South Beach, Low-Glycemic Index).

  • They received 0 points for category 10 and were downgraded for eliminating heart-healthy food groups (liquid plant oils for the very low-fat diets, and fruits, vegetables, whole grains, and plant proteins for the low-carb diets).

Tier 4 diets (the least heart healthy diets) were the Paleo diet with a score of 53% and very low-carb diets (Atkins and Ketogenic) with a score of 31%.

  • The Paleo diet received 0 points for categories 10, 3 (choose whole grains), and 5 (using liquid plant oils rather than animal fats or tropical oils). It was also downgraded for lack of healthy plant-based protein sources.
  • The very low-carb diets were the least heart healthy. They received 0 points for categories 2 (eat plenty of fruits and vegetables), 3 (choose whole grains), 3 (healthy protein sources), 5 (use liquid plant oils instead of animal fats), 7 (minimize salt consumption), and 10 (ease of following the diet away from home).

The authors concluded, “Numerous [dietary] patterns [are] strongly aligned with 2021 American Heart Association Dietary Guidance (ie, Mediterranean, DASH, pescetarian, vegetarian) [and] can be adopted to reflect personal and cultural preferences and budgetary constraints.

Thus, optimal cardiovascular health would be best supported by developing a food environment that supports adherence to these patterns wherever food is prepared or consumed.”

Given our current food environment that last statement is wildly optimistic. But at least you have the information needed to make the best food choices for you and your family

The Bottom Line 

In 2021 the American Heart Association published 10 guidelines for evaluating heart-healthy diets. A recent study looked at how well popular diets adhered to those guidelines. The authors separated the diets into four categories (tiers) based on how heart-healthy they were. The results were not surprising:

  • Tier 1 diets (the most heart healthy diets) were DASH, Nordic, Mediterranean, Pescetarian (vegetarian diets that allow fish), and Ovo-Lacto Vegetarian (vegetarian diets that allow dairy, eggs, or both).
  • Tier 2 diets were Vegan and other low-fat diets (TLC, Volumetrics).
  • Tier 3 diets included very-low fat diets (<10% fat, very strict vegan diets) and low-carb diets (Zone, South Beach, Low-Glycemic Index).
  • Tier 4 diets (the least heart healthy diets) were the Paleo diet and very low-carb diets (Atkins and Ketogenic).

The authors concluded, “Numerous [dietary] patterns [are] strongly aligned with 2021 American Heart Association Dietary Guidance (ie, Mediterranean, DASH, pescetarian, vegetarian) [and] can be adopted to reflect personal and cultural preferences and budgetary constraints.

Thus, optimal cardiovascular health would be best supported by developing a food environment that supports adherence to these patterns wherever food is prepared or consumed.”

Given our current food environment that last statement is wildly optimistic. But at least you have the information needed to make the best food choices for you and your family.

For more information on this 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.

____________________________________________________________________________

My posts and “Health Tips From the Professor” articles carefully avoid claims about any brand of supplement or manufacturer of supplements. However, I am often asked by representatives of supplement companies if they can share them with their customers.

My answer is, “Yes, as long as you share only the article without any additions or alterations. In particular, you should avoid adding any mention of your company or your company’s products. If you were to do that, you could be making what the FTC and FDA consider a “misleading health claim” that could result in legal action against you and the company you represent.

For more detail about FTC regulations for health claims, see this link.

https://www.ftc.gov/business-guidance/resources/health-products-compliance-guidance

Health Tips From The Professor