poultry

Why Are Dietary Studies So Confusing? 

Author: Dr. Stephen Chaney

You are concerned about your heart.

• Perhaps it is because of genetics. Everyone on one side of your family tree had their first heart attack in their mid-forties.

• Perhaps it is because your doctor has warned you that your heart is a ticking time bomb. Unless you make some drastic changes, you will die of a heart attack in the near future.

• Perhaps you already have some symptoms of heart disease, and you are scared.

You want to make some changes. You want to protect your heart. What should you do?

The short answer is that a holistic approach is best, and I will share the American Heart Association recommendations below. But let’s start by asking what you should eat. There are two important questions:

#1: Which diet is best for your heart?

• A whole food vegan diet, the Mediterranean diet, and the DASH diet are all strong contenders for the best heart healthy diet.

• But there are many other diets that claim to be heart healthy. Some enthusiasts even claim the Paleo and keto diets are heart healthy.

• The problem is that few studies have compared these diets against each other. That makes it difficult to settle the question of which diet is best for your heart.

#2: Which protein source is best for your heart – plant protein, fish, poultry, or red meat?

• Plant and fish protein are both strong contenders for the most heart healthy protein.

• Poultry has the reputation of being more heart healthy than red meat. But this has become controversial. Some recent studies suggest poultry is no better than red meat in terms of heart health.

Fortunately, a recent study (F Petermann-Rocha et al, European Heart Journal, 42: 1136-1143, 2021) has made this comparison. It compared vegetarians, fish eaters, poultry eaters, and red meat eaters for the risk of developing heart disease.

How Was This Study Done?

This study made use of data from the UK Biobank program. The UK Biobank program recruited over 500,000 participants (ages 37-73) from England, Wales, and Scotland between 2006 and 2010 and followed them for an average of 8.5 years.

At entry into the program, each participant filled out a touchscreen questionnaire, had physical measurements taken, and provided biological samples.

Dietary intake was assessed based on the touchscreen questionnaire and the average of 5 24-hour dietary recalls. The participants were divided into four groups based on this dietary analysis:

• Vegetarians (All participants in the study consumed cheese and eggs, so this group would more accurately be described as lacto-ovo-vegetarians).

• Fish eaters.

• Poultry eaters.

• Red meat eaters.

Over the next ~8.5 years, each group was compared with respect to the following heart health parameters:

• Risk of developing cardiovascular disease (all diseases of the circulatory system).

• Risk of developing ischemic heart disease (lack of sufficient blood flow to the heart. The most common symptom of ischemic heart disease is angina).

• Risk of having a myocardial infarction (commonly referred to as a heart attack).

• Risk of having a stroke.

• Risk of developing heart failure.

Which Diet Is Best For Your Heart?

The study compared vegetarians, fish eaters, and poultry eaters with red meat eaters with respect to each of the heart disease parameters listed above. The results were:

• When fish eaters were compared with meat eaters, they had:

• • 7% lower risk of cardiovascular diseases of all types.

• • 21% lower risk of ischemic heart disease (angina).

• • 30% lower risk of myocardial infarction (heart attack).

• • 21% lower risk of stroke.

• • 22% lower risk of heart failure.

• When vegetarians were compared with meat eaters, they had:

• • 9% lower risk of cardiovascular diseases of all types.

• • Lower, but statistically non-significant, risk of other heart disease parameters.

• When poultry eaters were compared with meat eaters there were no significant differences in heart disease outcomes.

The authors concluded, “Eating fish rather than meat or poultry was associated with a lower risk of adverse cardiovascular outcomes…supporting its role as a healthy diet that should be encouraged. Vegetarianism was only associated with a lower risk of cardiovascular disease incidence.”

Why Are Dietary Studies So Confusing?

So, you are probably thinking, “Are diets with fish protein really more heart healthy than diets with plant protein?”

Fish have a lot going for them. They are an excellent source of heart healthy omega-3 fats. And, when substituted for red meat protein, they decrease intake of saturated fats.”

But plant protein has a lot going for it as well. Numerous studies have shown that vegetarian diets are more heart healthy than the typical American diet. And only plant-based diets have been shown to reverse atherosclerosis.

So, why are dietary studies so confusing? The problem is that diets are complex. They have many moving parts. When we focus on one aspect of a diet, we are ignoring the rest of the diet. The food we have focused on may be healthy. But if it is paired with unhealthy foods, the overall diet can still be unhealthy.

The current study is a perfect example of that principle:

• The participants represented a cross section of the British population. All the “diets” were high in sugar, sugary drinks, saturated fat, and processed meals bought from the supermarket. None of them were optimal.

• In addition to consuming cheese and eggs, “vegetarians” consumed more crisps, slices of pizza, and smoothie drinks than meat-eaters. [In case you were wondering, the English refer to small thin salty snacks like potato chips as crisps. They reserve the term chips for what we call French Fries.]

• “Vegetarians” also consumed a lot of highly processed vegetarian alternatives designed to taste like other meat products.

• On the other hand, fish eaters consumed more fruits and vegetables than meat-eaters. It wasn’t just the fish that made this diet more heart healthy.

In other words, the “vegetarian diet” in this study was not nearly as healthy as the whole food vegetarian diets that have previously been shown to be heart healthy. And the “fish-eaters diet” was healthier than the “meat-eaters diet” because of both the fish and the extra fruits and vegetables these people were consuming.

In the words of the authors, “…As a group, vegetarians consumed more unhealthy foods, such as crisps, than meat eaters. Therefore, vegetarians should not be considered a homogeneous group, and avoidance of meat will not be sufficient to reduce health risk if the overall diet is not healthy.”

My summary:

• Whole food plant-based diets (the true definition of vegetarianism) are very heart healthy. [Note: The diet in this study was lacto-ovo-vegetarian rather than a true vegetarian diet. However, recent studies have suggested that addition of small amounts of dairy and eggs to a vegetarian diet may make them more heart healthy rather than less heart healthy.]

• Primarily plant-based diets with fish as the main protein source (otherwise known as pescatarian diets) are also very heart healthy.

• If you want a healthy heart, choose the one that best fits your preferences and your lifestyle.

A Holistic Approach: The American Heart Association Recommendations

• If you smoke, stop.

• Choose good nutrition.

• • Choose a diet that emphasizes vegetables, fruits, whole grains, low-fat dairy products, poultry, fish, legumes, non-tropical vegetable oils, and nuts.

• • Choose a diet that limits sweets, sugar-sweetened beverages, and red meats.

• • Reduce high blood cholesterol and triglycerides.

• • Reduce your intake of saturated fat, trans fat and cholesterol.

• Lower High Blood Pressure.

• Be physically active every day.

• • Aim for at least 150 minutes per week of moderate-intensity physical activity per week.

• Aim for a healthy weight.

• Manage diabetes.

• Reduce stress.

• Limit alcohol.

• Have a regular physical checkup.

The Bottom Line

A recent study in the United Kingdom compared vegetarians, fish eaters, poultry eaters, and red meat eaters for the risk of developing heart disease and the risk of dying from heart disease. The results were:

• When fish eaters were compared with meat eaters, they had:

• • 7% lower risk of cardiovascular diseases of all types.

• • 21% lower risk of ischemic heart disease (angina).

• • 30% lower risk of myocardial infarction (heart attack).

• • 21% lower risk of stroke.

• • 22% lower risk of heart failure.

• When vegetarians were compared with meat eaters, they had:

• • 9% lower risk of cardiovascular diseases of all types.

• • Lower, but statistically non-significant, risk of other heart disease parameters.

• When poultry eaters were compared with meat eaters there were no significant differences in heart disease outcomes.

The authors concluded, “Eating fish rather than meat or poultry was associated with a lower risk of adverse cardiovascular outcomes…supporting its role as a healthy diet that should be encouraged. Vegetarianism was only associated with a lower risk of cardiovascular disease incidence.”

However, the “vegetarian diet” in this study was not nearly as healthy as the whole food vegetarian diets that have previously been shown to be heart healthy. And the “fish-eaters diet” was healthier than the “meat-eaters diet” because of both the fish and the extra fruits and vegetables this group of people were consuming.

In the words of the authors, “…As a group, vegetarians consumed more unhealthy foods, such as crisps [potato chips], than meat eaters. Therefore, vegetarians should not be considered a homogeneous group, and avoidance of meat will not be sufficient to reduce health risk if the overall diet is not healthy.”

My summary:

• Whole food plant-based diets (the true definition of vegetarianism) are very heart healthy.

• Primarily plant-based diets with fish as the main protein source (otherwise known as pescatarian diets) are also very heart healthy.

• If you want a healthy heart, choose the one that best fits your preferences and your lifestyle.

For more details about 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.