Omega-3 and Heart Disease Risk

Written by Dr. Steve Chaney on . Posted in Omega-3s and Heart Disease

Why Is There So Much Confusion About Omega-3 and Heart Disease Risk?

Author: Dr. Stephen Chaney

 

omega-3 heart diseaseConcerning omega-3 and heart disease, the pendulum keeps swinging. In the 1990’s several strong clinical studies showed that omega-3s reduced heart disease risk. In fact, a major clinical study in Italy, (Lancet 354: 447 – 455, 1999 , Circulation 105 : 1897 – 1903, 2002 ), found omega-3s to be just as effective as statin drugs for preventing heart attacks, but without any of the side effects of statins.

At that time, everyone was talking about the benefits of omega-3s in reducing heart disease risk. The American Heart Association recommended an intake of 500-1,000 mg/day of omega-3s for heart health. Some experts were recommending even more if you were at high risk of heart disease.

In the 2000’s the pendulum swung in the other direction. Several clinical studies found no benefit of omega-3s in reducing heart disease risk. Suddenly, experts were telling us that omega-3s were overrated. They were a waste of money. The American Heart Association kept their omega-3 recommendations for heart health, but put more emphasis on omega-3s for people with elevated triglycerides (where the benefits of omega-3s are non-controversial).

Suddenly regarding omega-3 and heart disease, the pendulum is swinging back again. A recent meta-analysis (Alexander et al, Mayo Clinic Proceedings, 92: 15-29, 2017) reported that omega-3s do appear to be beneficial at reducing heart disease risk. An editorial accompanying that article (O’Keefe et al, Mayo Clinic Proceedings, 92: 1-3, 2017) called the meta-analysis “the most comprehensive of its kind to date…” Those experts went on to say “…omega-3-fatty acid intake of at least 1 gram of EPA + DHA per day, either from seafood or supplementation (as recommended by the American Heart Association) continues to be a reasonable strategy.”

This was followed by publication of three clinical studies that came to essentially the same conclusion (Kieber et al, Atherosclerosis, 252: 175-181, 2016 ; Sala-Vila et al, Journal of the American Heart Association, In Press ; and Greene et al, American Journal of Cardiology, 117: 340-346, 2016 ).

Why is there so much confusion about omega-3 and heart disease? Let’s start by reviewing the recently published meta-analysis.

 

Do Omega-3s Lower Heart Disease Risk?

omega-3 lowers heart disease riskThis study (Alexander et al, Mayo Clinic Proceedings, 92: 15-29, 2017) combined the data from 18 randomized controlled trials with 93,000 patients and 16 prospective cohort studies with 732,000 patients. This was the largest meta-analysis on omega-3s and heart health performed to date. The results were as follows:

  • The combined data from the randomized controlled studies showed that omega-3 supplementation resulted in a non-significant 6% reduction in heart disease risk. This is similar to other recently published studies (more about that later).
  • However, when the investigators looked at high risk populations within the randomized controlled studies, the results were strikingly different.
    • In patients with elevated triglycerides, omega-3 supplementation caused a significant 16% reduction in heart disease risk.
    • In patients with elevated LDL cholesterol, omega-3 supplementation caused a significant 18% reduction in heart disease risk.
  • In addition, the combined data from the prospective cohort studies showed that omega-3 supplementation resulted in a significant 18% decrease in heart disease risk.

The authors concluded “[Our] results indicate that EPA + DHA may be associated with reducing heart disease risk, with greater benefits observed among higher-risk populations…”

 

Why Is There So Much Confusion About Omega-3s and Heart Disease Risk?

confusionThere are several major clinical studies in progress looking at the effect of omega-3s on heart health. Some experts predict that the confusion will be cleared up once they are published. I predict they will only add to the confusion. Let me explain why.

You’ve heard the old saying “Garbage in – garbage out.”  Proper design of clinical studies is essential. If a study is poorly designed, it provides incorrect information. When you analyze the previous clinical studies carefully, you find that many of them are flawed. Their results are, therefore, incorrect. My fear is that many of the ongoing clinical studies will contain the same flaws and will provide the same incorrect information.

Let’s look at the flaws, and why they provide incorrect information.

Flaw #1: Omega-3 supplementation will only be beneficial for people who are omega-3 deficient. The authors of the Mayo Clinic Proceedings editorial provided a useful analogy. They said: “Vitamin C bestows dramatic and lifesaving benefits to persons with scurvy, but is no better than placebo for persons who are replete with vitamin C.”

That means a well-designed study should measure omega-3 levels in red blood cells both prior to and at the end of the clinical study. The data analysis should focus on those individuals who started the study with low omega-3 status and whose omega-3 status improved by the end of the study. Unfortunately, few of the previously published studies have done that, and I am not confident that the ongoing studies have incorporated that into their experimental design.

Flaw #2: Omega-3 supplementation will be of most benefit for those people who are at highest risk for heart disease. This has been a recurrent pattern in the literature. Many of the clinical studies focusing on high-risk individuals have shown a beneficial effect of omega-3 supplementation on heart disease risk. Most of the studies focusing on the general population (most of which are of low risk for heart disease) have failed to show a benefit of omega-3 supplementation. The current meta-analysis is no exception. When they looked at the general population, there was a non-significant reduction in heart disease risk. However, when they looked at high-risk populations the beneficial effect of omega-3s was highly significant.

I can’t predict how the ongoing studies will analyze their data. If they focus on high-risk groups they are more likely to report a beneficial effect of omega-3s on heart health. If they only report on the results with the general population, they are likely to conclude that omega-3s are ineffective.

I do need to make an important distinction here. The inability to demonstrate a beneficial effect of omega-3 supplementation in the general population does not mean that there is no effect. It turns out to be incredibly difficult to demonstrate a beneficial effect of any intervention, including statins , in a healthy, low-risk population. Because of that, we may never know for sure about the relationship between omega-3 and heart disease. Do omega-3s reduce heart disease risk for the young and healthy. At the end of the day, you will need to make your own decision about whether omega-3s make sense to you.

omega-3 supplementationFlaw #3: Heart medications mask the beneficial effects of omega-3 supplementation. When the public hears about the results of a randomized controlled study they assume that the placebo group received no treatment and the omega-3 group was only receiving omega-3s. That is not how it works.  Medical ethics guidelines require that the placebo group receive the standard of care treatment – namely whatever drugs are considered appropriate for that population group.

That means that it has become very difficult to demonstrate that high-risk populations benefit from omega-3 supplementation. Back in the 90s, the standard of care for high risk patients was only one or two drugs. In those days, many studies were reporting beneficial effects of omega-3 supplementation in high risk populations. However, for the past 5-10 years the standard of care for high risk patients is 4-5 medications.

These are medications that reduce cholesterol levels, lower triglyceride levels, lower blood pressure, reduce inflammation, and reduce clotting time. In other words, the drugs mimic all the beneficial effects of omega-3s. (The only difference is that the drugs come with side-effects. The omega-3s don’t.) It is no coincidence that many of the recent studies have come up empty-handed.

The current studies are asking a fundamentally different question. In the 90s, clinical studies asked whether omega-3s reduced heart disease risk in high-risk patients. Today’s clinical studies are asking whether omega-3s provide any additional benefits for patients who are already taking multiple drugs. Personally, I think my readers are more interested in the first question than the second.

Once again, the current meta-analysis is perfectly consistent with this interpretation. The high-risk groups who clearly benefited from omega-3 supplementation were not ones with pre-existing heart disease or who had previously had a heart attack. They were the ones with elevated LDL cholesterol or triglycerides. They were patients who were, either not taking drugs for those risk factors, or patients for whom the drugs were ineffective.

Because subjects in future studies will be taking multiple medications, I predict that even those ongoing studies focusing on high-risk populations will come up empty-handed.

Now you understand why I started this section by saying that I predict many of the ongoing studies will provide incorrect results. I predict that you will see more headlines proclaiming that omega-3s don’t work. However, you won’t be swayed by those headlines because you now know the truth about the flaws in the clinical studies behind the headlines!

What Does This Mean For You?

omega-3 fish oilThe most recent meta-analysis and a careful evaluation of previous studies make two things clear:

  • If you are at high risk of heart disease, omega-3 supplementation is likely to reduce your risk.

We can divide risk factors for heart disease into those we know about, and those we don’t.

  • Risk factors we know about include previously diagnosed heart disease or heart attack, genetic predisposition, age, elevated LDL cholesterol levels, high triglycerides, high blood pressure, inflammation, obesity, metabolic syndrome and diabetes.
  • Unfortunately, there are also risk factors we don’t know about. For too many Americans the first sign of heart disease is sudden death – sometimes just after receiving a clean bill of health from their doctor.
  • If you are not getting enough omega-3s in your diet, omega-3 supplementation is likely to reduce your heart disease risk.

If you are young and healthy, the unfortunate truth is that we may never completely understand the relationship between omega-3 and heart disease. We may not know whether omega-3 supplementation reduces your risk of heart disease. However, I think the overall evidence is strong enough that you should consider adding omega-3s to your diet.

In short, I agree with the authors of the Mayo Clinic Proceedings editorial and the American Heart Association that omega-3-fatty acid intake of at least 1 gram of EPA + DHA per day, either from seafood or supplementation, is a prudent strategy for reducing heart disease risk.

 

The Bottom Line

  • There has been a lot of confusion about the role of omega-3s in reducing heart disease risk.
  • In the 90s, several clinical studies reported that omega-3 supplementation reduced heart disease risk. Most experts, including the American Heart Association, were recommending that most Americans would benefit from adding 500-1,000 mg of omega-3s to their daily diet.
  • In recent years, several clinical studies have reported that omega-3 supplementation has no effect on heart disease risk. [There were some important flaws in those studies, which I discuss in the article above]. Experts started saying that omega-3s were overrated. They were a waste of money.
  • The largest meta-analysis ever undertaken in this area of research has recently reported that omega-3 supplementation decreases risk of heart disease in high-risk population groups. Three subsequent clinical studies have come to essentially the same conclusion.
  • Other studies suggest that omega-3 supplementation is also likely to reduce heart disease risk in individuals with poor omega-3 status, and most Americans have poor omega-3 status.
  • We may never know whether omega-3 supplementation reduces heart disease risk if you are young and healthy. Simply put, not enough young & healthy people develop heart disease within the time-frame of a clinical study for the results to be statistically significant. For this group, the old saying about “An ounce of prevention…” just makes sense.
  • I agree with those experts who recommend at least 1,000 mg/day of omega-3s as a prudent strategy for reducing heart disease risk.
  • There are several major clinical trials in progress studying the efficacy of omega-3s for reducing heart disease risk. Some experts predict that the confusion will be cleared up once they are published. I predict they will only add to the confusion. I predict that many of those studies will show no benefit of omega-3 supplementation, and you will see more headlines proclaiming that omega-3s play no role in heart health. If you have read the article above, you won’t be swayed by those headlines because you will know the truth about the flaws in the studies behind the headlines.

 

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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Comments (1)

  • Susan Bodlak

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    Excellent, clearly reported, and very helpful. Thank you.

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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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