Do Avocados Lower Cholesterol?

Written by Dr. Steve Chaney on . Posted in current health articles, Food and Health, Healthy Living

Should Avocados Be On The Super Fruits List?

Author: Dr. Stephen Chaney

 

super fruits listYou may have seen the recent headlines suggesting that avocados lower cholesterol, are a miracle fruit, and reduce your risk of heart disease. Some of those articles are suggesting that you try to eat an avocado every day. Are those headlines true? Should you be eating more avocados?

If you are like me that would be a bit of a stretch. I prefer my fruits tastier and a bit less greasy, but I won’t let my personal preferences color my analysis of the data. Let’s start by looking at the rationale for testing the effect of avocados on cholesterol levels.

The 2013 American Heart Association Guidelines on Lifestyle Management to Reduce Cardiovascular Risk recommends reducing saturated fats to no more than 5% to 6% of total calories (In the typical American diet about 13% of calories come from saturated fat). The AHA recommends replacing the saturated fat with either monounsaturated fat or polyunsaturated fat (vegetable oils and fish oil).

In addition, a major clinical study has recently shown that a Mediterranean diet supplemented with either olive oil or mixed nuts (walnuts, hazelnuts and almonds) lowers cholesterol and reduces the incidence of major cardiovascular events by ~30% over 5 years in men and women aged 50 to 80 who were at high risk for cardiovascular disease (Estruch et al, N Engl J Med, 368: 1279-1290, 2013).

One avocado has about the same amount of oleic acid (a monounsaturated fat) as 2 tablespoons of olive oil or 1.5 ounces of almonds, so it is logical to suspect that avocados might have a similar effect as olive oil or nuts.

How Was The Clinical Study Designed?

Because there is still a lot of controversy as to whether diets in which the saturated fat is replaced with healthier fat or no fat at all (low fat diets) are better, this study (Wang et al, J Am Heart Assoc, 2015;4: e001355 doi:10.1161/JAHA.114.001355) compared 3 diets:

  • A low fat diet in which most of the saturated fat was replaced with carbohydrate (24% total fat, 7% saturated fat, 11% monounsaturated fat, 6% polyunsaturated fat, 59% carbohydrate, 16-17% protein).
  • A moderate fat diet in which most of the saturated fat was replaced with pure oleic acid (34% total fat, 6% saturated fat, 17% monounsaturated fat from oleic acid, 9% polyunsaturated fat , 49% carbohydrate, 16-17% protein).
  • A moderate fat diet in which most of the saturated fat was replaced with avocado (34% total fat, 6% saturated fat, 17% monounsaturated fat from avocado, 9% polyunsaturated fat , 49% carbohydrate, 16-17% protein).

The study subjects were 45 healthy overweight or obese men and women (age 21 to 70, average = 45). Each subject was put on all 3 diets sequentially for 5 weeks each in a random order. That way each subject served as his or her own control.

The diets were carefully controlled to keep the calories the same so that none of the subjects lost weight during the study (weight loss would have confounded the results because weight loss lowers cholesterol in most individuals). The subjects were also told not to change their exercise habits. In short, it was a small study, but it was very well designed.

When the low fat diet was compared to the moderate (healthy) fat diets, the results were pretty similar to a number of other studies:

  • Total cholesterol and LDL cholesterol (the bad type) were lowered to about the same extent by both types of diets.
  • Triglycerides were higher and HDL cholesterol (the good type) was lower for the low fat diet compared to the moderate (healthy) fat diets.

Because this has been shown in previous studies, I won’t discuss it further here.

Do Avocados Lower Cholesterol?

lower cholesterolWhen the authors compared the diet in which saturated fat was replaced with avocados to the diet in which saturated fat was replaced with oleic acid there were a number of significant differences.

  • Both LDL-cholesterol and non-HDL cholesterol were significantly lower on the avocado diet than the oleic acid diet. The decrease was about 10%. Based on the metrics adopted by the American Heart Association this has the potential to translate into a 20% decrease in heart disease risk.
  • The avocado diet was the only one of the three diets that significantly decreased LDL particle number, small dense LDL cholesterol and LDL/HDL ratio, Many experts think that these parameters are better indicators of hearts disease risk than LDL cholesterol levels.

Do avocados lower cholesterol?  The short answer is yes, eating an avocado a day can lower cholesterol levels and might possibly lower heart disease risk. But to understand the true implications of this study we need to dig a little deeper.

What Is the Significance of This Study?

This study has one important take home lesson and raises two important questions.

Take Home Lesson: Foods Are More Important Than Fats We often hear about the benefits of including more monounsaturated fats in our diet, but when you actually make a direct comparison, such as was done in this study, it turns out that it is the foods that contain monounsaturated fats that make the difference, not the monounsaturated fats themselves. The oleic acid diet was only marginally better than the low fat diet at lowering total and LDL cholesterol.

This was the major conclusion of the authors of the study. Everything else was made up by the non-experts who write the articles that you see in the papers and on the internet. It is yet one more example of the headlines getting ahead of the science.

The authors admitted that we have no idea why avocados are more effective at lowering cholesterol than an equivalent amount of oleic acid. They speculated that it could be due to the high content of phytosterols in avocados. However, while the 114 mg of plant sterols in an avocado makes it an excellent source of plant sterols, it is far below the 2,000 mg of plant sterols that the NIH considers optimal for lowering cholesterol levels.

The authors also mentioned soluble fiber and specialized sugars in an avocado, but none of those was present in sufficient quantities to explain the cholesterol-lowering effect of avocados by itself. It is likely that all of those constituents plus others that we have not yet identified are what make avocados more effective than oleic acid at lowering cholesterol.

Question 1: Do We Really Want To Eat An Avocado a Day?

We need to keep in mind that a single avocado weighs in at around 234 calories. That is:

  • 2.5 times the calories in an apple
  • 4.7 times the calories in a peach or a cup of strawberries
  • 5.7 times the calories in a half cup of blueberries
  • 7.3 times the calories in a half cup of raspberries or blackberries

You get the point. What made this study so effective is that all three diets were designed to provide exactly the same number of calories so that nobody gained or lost weight. If you are thinking of adding an avocado a day to your diet, you are going to need to significantly cut back on calories somewhere else, or your weight gain will drive your cholesterol levels in the wrong direction.

Question 2: What Are The Long Term Implications of This Study?

The bottom line is that this and previous studies suggest that avocados should rightfully be included along with olive oil and nuts as healthy sources of monounsaturated fats that can help you lower cholesterol levels and may reduce your risk of heart disease.

However, we need to keep in mind that while a major clinical study has shown that adding either olive oil or nuts to your diet can reduce heart disease risk, we don’t have a comparable study showing that adding avocados to your diet will have the same benefit. It is plausible, but has not yet been demonstrated.

 

The Bottom Line

  • A recent clinical study has shown that eating an avocado a day was more effective at lowering bad cholesterol than adding an equivalent amount of the monounsaturated fat oleic acid to the diet. This suggests that it is the foods that contain the monounsaturated fats that make the difference, not the monounsaturated fats themselves.
  • This and previous studies suggest that avocados should rightfully be included along with olive oil and nuts as healthy sources of monounsaturated fats that can help you lower cholesterol levels and may reduce your risk of heart disease.
  • However, we need to keep in mind that while a major clinical study has shown that adding either olive oil or nuts to your diet can reduce heart disease risk, we don’t have a comparable study showing that adding avocados to your diet will have the same benefit. It is plausible, but has not yet been demonstrated.
  • You also need to keep in mind that a single avocado contains 234 calories. What made this study work so well is that each diet was carefully designed to provide exactly the same number of calories. If you are thinking of adding an avocado a day to your diet, you are going to need to significantly cut back on calories somewhere else, or your weight gain will drive your cholesterol levels in the wrong direction.
  • Finally, the American Heart Association Guidelines are to reduce saturated fats to no more than 6-7% of total calories. So while the low-carbohydrate, butter, bacon, and steak diet may give you temporary weight loss, it is definitely NOT recommended if you want to reduce your risk of heart disease. For more on this important topic, see my previous health tip “Are Saturated Fats Good For You?

 

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 (4)

  • Merlena Cushing

    |

    Good article…helpful, as usual. Please tell me if I needed to sign up again for these weekly updates. Nothing came through today – even checked my SPAM filter – so I came to your site and VIOLA! Here is today’s article.

    Thanks for letting me know if I need to do sign up again.

    Reply

  • Sheri

    |

    Hi, thanks for that important info. 2 ?? I heard that beef from cows that are grass fed & not given growth hormones etc don’t have healthier saturated fat than those that are not. I take a flax seed supplement because I read that in addition to omega 3 fats it also has omega 6 & 9 both said to be beneficial. are there studies on that? Thanks Sheri

    Reply

    • Dr. Steve Chaney

      |

      Dear Sheri,

      Those are very interesting questions and illustrate the incorrect information that abounds on the internet. It may be true that the saturated fat in grass fed beef is no healthier than corn fed beef, but the levels of omega-3 fatty acids are significantly higher so grass fed beef is a bit better for you.

      As for flax seeds, they are a healthy food, but they are no miracle food. Let’s look at each of the fatty acids in flax seed supplements individually. The American diet is generally deficient in omega-3s so they are an important component of the supplement. Unfortunately, the omega-3s in flax seed are short chain, most of the health benefits are from the long chain omega-3s, and conversion of short chain omega-3s to long chain omega-3s in the body is only around 10%. Fish oil supplements are a much better source of omega-3s because they provide predominantly long chain. In contrast, Americans generally get plenty of omega-6 fatty acids. They are found in seeds and most vegetable oils. Omega-9s are the monounsaturated fatty acids. They are found in avocados, nuts, nut oils, nut butters and olive oil. Our bodies can also make them from saturated fats. We get lots of them from our diet. A little more wouldn’t hurt, but the amount we get from a flax seed supplement is fairly insignificant compared to what we already get from our diet.

      Dr. Chaney

      Reply

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Latest Article

What Is The Planetary Diet?

Posted May 21, 2019 by Dr. Steve Chaney

Is Your Diet Destroying The Planet?

Author: Dr. Stephen Chaney

 

Earth Day has come and gone, but you are still committed to saving the planet. You save energy. You recycle. You drive an electric car. But is your diet destroying the planet?

This is not a new question, but a recent commission of international scientists has conducted a comprehensive study into our diet and its effect on our health and our environment. Their report (W. Willet et al, The Lancet, 393, issue 10170, 447-492, 2019 ) serves as a dire warning of what will happen if we don’t change our ways. I touched on this report briefly in a previous issue of “Health Tips From The Professor,” What Is The Flexitarian Diet , but this topic is important enough that it deserves an issue all its own.

The commission carefully evaluated diet and food production methods and asked three questions:

  • Are they good for us?
  • Are they good for the planet?
  • Are they sustainable? Will they be able to meet the needs of the projected population of 10 billion people in 2050 without degrading our environment.

The commission described the typical American diet as a “lose-lose diet.” It is bad for our health. It is bad for the planet. And it is not sustainable.

In its place they carefully designed their version of a primarily plant-based diet they called a “win-win diet.”  It is good for our health. It is good for the planet. And, it is sustainable.

In their publication they refer to their diet as the “universal healthy reference diet” (What else would you expect from a committee?). However, it has become popularly known as the “Planetary Diet.”

I have spoken before about the importance of a primarily plant-based diet for our health. In that context it is a personal choice. It is optional.

However, this report is a wake-up call. It puts a primarily plant-based diet in an entirely different context. It is essential for the survival of our planet. It is no longer optional.

If you care about global warming…If you care about saving our planet, there is no other choice.

How Was The Study Done?

The study (W. Willet et al, The Lancet, 393, issue 10170, 447-492, 2019 ) was the report of the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems. This Commission convened 30 of the top experts from across the globe to prepare a science-based evaluation of the effect of diet on both health and sustainable food production through the year 2050. The Commission included world class experts on healthy diets, agricultural methods, climate change, and earth sciences. The Commission reviewed 356 published studies in preparing their report.

 

Is Your Diet Destroying The Planet?

When they looked at the effect of food production on the environment, the Commission concluded:

  • “Strong evidence indicates that food production is among the largest drivers of global environmental change.” Specifically, the commission reported:
  • Agriculture occupies 40% of global land (58% of that is for pasture use).
  • Food production is responsible for 30% of global greenhouse gas emissions and 70% of freshwater use.
  • Conversion of natural ecosystems to croplands and pastures is the largest factor causing species to be threatened with extinction. Specifically, 80% of extinction threats to mammals and bird species are due to agricultural practices.
  • Overuse and misuse of nitrogen and phosphorous in fertilizers causes eutrophication. In case you are wondering, eutrophication is defined as the process by which a body of water becomes enriched in dissolved nutrients (such as phosphates from commercial fertilizer) that stimulate the growth of algae and other aquatic plant life, usually resulting in the depletion of dissolved oxygen. This creates dead zones in lakes and coastal regions where fish and other marine organisms cannot survive.
  • About 60% of world fish stocks are fully fished and more than 30% are overfished. Because of this, catch by global marine fisheries has been declining since 1996.
  • “Reaching the Paris Agreement of limiting global warming…is not possible by only decarbonizing the global energy systems. Transformation to healthy diets from sustainable food systems is essential to achieving the Paris Agreement.”
  • The world’s population is expected to increase to 10 billion by 2050. The current system of food production is unsustainable.

When they looked at the effect of the foods we eat on the environment, the Commission concluded:

  • Beef and lamb are the biggest contributors to greenhouse gas emissions and land use.
  • The concern about land use is obvious because of the large amount of pasture land required to raise cattle and sheep.
  • The concern about greenhouse gas emissions is because cattle and sheep are ruminants. They not only breathe out CO2, but they also release methane into the atmosphere from fermentation in their rumens of the food they eat. Methane is a potent greenhouse gas, and it persists in the atmosphere 25 times longer than CO2. The single most important thing we can do as individuals to reduce greenhouse gas emissions is to eat less beef and lamb. [Note: grass fed cattle produce more greenhouse gas emissions than cattle raised on corn because they require 3 years to bring to market rather than 2 years.]
  • In terms of energy use beef, lamb, pork, chicken, dairy and eggs all require much more energy to produce than any of the plant foods.
  • In terms of eutrophication, beef, lamb, and pork, all cause much more eutrophication than any plant food. Dairy and eggs cause more eutrophication than any plant food except fruits.
  • In contrast, plant crops reduce greenhouse gas emissions by removing CO2 from the atmosphere.

 

What Is The Planetary Diet?

In the words of the Commission: “[The Planetary Diet] largely consists of vegetables, fruits, whole grains, legumes, nuts, and unsaturated oils. It includes a low to moderate amount of seafood, poultry, and eggs. It includes no or a very low amount of red meat, processed meat, sugar, refined grains, and starchy vegetables.”

When described in that fashion it sounds very much like other healthy diets such as semi-vegetarian, Mediterranean, DASH, and Flexitarian. However, what truly distinguishes it from the other diets is the restrictions placed on the non-plant portion of the diet to make it both environmentally friendly and sustainable. Here is a more detailed description of the diet:

  • It starts with a vegetarian diet. Vegetables, fruits, beans, nuts, soy foods, and whole grains are the foundation of the diet.
  • It allows the option of adding one serving of dairy a day (It turns out that cows produce much less greenhouse emissions per serving of dairy than per serving of beef. That’s because cows take several years to mature before they can be converted to meat, and they are emitting greenhouse gases the entire time).
  • It allows the option of adding one 3 oz serving of fish or poultry or one egg per day.
  • It allows the option of swapping seafood, poultry, or egg for a 3 oz serving of red meat no more than once a week. If you want a 12 oz steak, that would be no more than once a month.

This is obviously very different from the way most Americans currently eat. According to the Commission:

  • “This would require greater than 50% reduction in consumption of unhealthy foods, such as red meat and sugar, and greater than 100% increase in the consumption of healthy foods, such as nuts, fruits, vegetables, and legumes.”
  • “In addition to the benefits for the environment, “dietary changes from current diets to healthy diets are likely to substantially benefit human health, averting about 10.8-11.6 million deaths per year globally.”

What Else Did The Commission Recommend?

In addition to changes in our diets, the Commission also recommended several changes in the way food is produced. Here are a few of them.

  • Reduce greenhouse gas emissions from the fuel used to transport food to market.
  • Reduce food losses and waste by at least 50%.
  • Make radical improvements in the efficiency of fertilizer and water use. In terms of fertilizer, the change would be two-fold:
    • In developed countries, reduce fertilizer use and put in place systems to capture runoff and recycle the phosphorous.
    • In third world countries, make fertilizer more available so that crop yields can be increased, something the Commission refer to as eliminating the “yield gap” between third world and developed countries.
  • Stop the expansion of new agricultural land use into natural ecosystems and put in place policies aimed at restoring and re-foresting degraded land.
  • Manage the world’s oceans effectively to ensure that fish stocks are used responsibly and global aquaculture (fish farm) production is expanded sustainability.

What we can do: While most of these are government level policies, we can contribute to the first three by reducing personal food waste and purchasing organic produce locally whenever possible.

What Does This Mean For You?

If you are a vegan, you are probably asking why the Commission did not recommend a completely plant-based diet. The answer is that a vegan diet is perfect for the health of our planet. However, the Commission wanted to make a diet that was as consumer-friendly as possible and still meet their goals of a healthy, environmentally friendly, and sustainable diet.

If you are eating a typical American diet or one of the fad diets that encourage meat consumption, you are probably wondering how you can ever make such drastic changes to your diet. The answer is “one step at a time.”  If you have read my books “Slaying The Food Myths” or “Slaying the Supplement Myths,”  you know that my wife and I did not change our diet overnight. Our diet evolved to something very close to the Planetary Diet over a period of years.

The Commission also purposely designed the Planetary Diet so that you “never have to say never” to your favorite foods. Three ounces of red meat a week does not sound like much, but it allows you a juicy steak once a month.

Sometimes you just need to develop a new mindset. As I shared in my books, my father prided himself on grilling the perfect steak. I love steaks, but I decided to set a few parameters. I don’t waste my red meat calories on anything besides filet mignon at a fine restaurant. It must be a special occasion, and someone else must be buying. That limits it to 2-3 times a year. I still get to enjoy good steak, and I stay well within the parameters of the Planetary diet.

Develop your strategy for enjoying some of your favorite foods within the parameters of the Planetary Diet and have fun with it.

The Bottom Line

 

Is your diet destroying the planet? This is not a new question, but a recent commission of international scientists has conducted a comprehensive study into our diet and its effect on our health and our environment. Their report serves as a dire warning of what will happen to us and our planet if we don’t change our ways.

The Commission carefully evaluated diet and food production methods and asked three questions:

  • Are they good for us?
  • Are they good for the planet?
  • Are they sustainable? Will they be able to meet the needs of the projected population of 10 billion people in 2050 without degrading our environment.

The Commission described the typical American diet as a “lose-lose diet.”  It is bad for our health. It is bad for the planet. And it is not sustainable.

In its place they carefully designed their version of a primarily plant-based diet they called a “win-win diet.”  It is good for our health. It is good for the planet. And, it is sustainable.

In their publication they refer to their diet as the “universal healthy reference diet” (What else would you expect from a committee?). However, it has become popularly known as the “Planetary Diet.”

The Planetary Diet is similar to other healthy diets such as semi-vegetarian, Mediterranean, DASH, and Flexitarian. However, what truly distinguishes it from the other diets is the restrictions placed on the non-plant portion of the diet to make it both environmentally friendly and sustainable (for details, read the article above).

I have spoken before about the importance of a primarily plant-based diet for our health. In that context it is a personal choice. It is optional.

However, this report is a wake-up call. It puts a primarily plant-based diet in an entirely different context. It is essential for the survival of our planet. It is no longer optional.

If you care about global warming…If you care about saving our planet, there is no other choice.

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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