Just an avocado a day can significantly lower your cholesterol and reduce the risk of heart disease, a new study shows.
Avocados are rich in so-called healthy fats and other nutrients and the study, published in the Journal of the American Heart Association, shows the creamy fruit can work within weeks to lower cholesterol.
Just like olive oil and nuts, avocados have plaque-busting monounsaturated fatty acids, and the effects seem similar to all the benefits from a Mediterranean diet, the researchers said.
And it’s one more piece of evidence in favor of adding good fats to the diet.
“In the past, we used to substitute carbohydrate for saturated fat, and that would result in a low-fat diet,” said Penny Kris-Etherton, chair of the American Heart Association’s Nutrition Committee and distinguished professor of nutrition at Pennsylvania State University.
“Now we’re seeing that it’s better for people to have good fats in their diet at the expense of saturated fat. And so the current message is to replace saturated fat with unsaturated fat, and in so doing, consume a moderate-fat diet, not too much, and also not too little,” Kris-Etherton told NBC News.
Kris-Etherton and colleagues did an intensive study with 45 typical Americans – all overweight or obese, but with healthy cholesterol and blood pressure levels.
It’s tough to test diets in real life, because people eat so many different things, but the team controlled what everyone ate, feeding them carefully calibrated diets. One was a lower-fat diet without avocado, another was a moderate-fat diet without avocado, and the third added one avocado per day to the moderate-fat diet.
The two moderate-fat diets looked a lot like the average American diet, with about a third of calories coming from fat. The lower fat diet provided 24 percent of calories from fat.
Everyone spent five weeks on each diet. No one lost weight, but their low-density lipoprotein (LDL or “bad” cholesterol) levels changed.
“All diets decreased LDL cholesterol, the main lipid risk factor for cardiovascular disease. But the diet with the avocado decreased LDL cholesterol the most,” Kris-Etherton said.
Americans are advised to keep total cholesterol below 200 and preferably below 180. LDL should be below 100.
While they were eating the avocado-a-day diet, the volunteers saw their LDL go down by more than 13 points compared to their usual levels, Kris-Etherton’s team reported in the Journal of the American Heart Association.
LDL was 8.3 points lower on the moderate-fat diet without the avocado and 7.4 points less on the lower-fat diet.
The volunteers all ate Hass avocados, which have bumpy green skin. The Hass Avocado Board helped pay for the research, which was also funded by the U.S. government.
In addition to monounsaturated fats, the avocados contain fiber, phytosterols and polyphenols – all of which can help lower cholesterol. Avocados also contain natural sugars that may help regulate blood sugar.
“We need to focus on getting people to eat a heart-healthy diet that includes avocados and other nutrient-rich food sources of better fats,” Kris-Etherton said.
“All the foods were exactly the same, except the avocado versus oils that were high in monounsaturated fat on the moderate-fat diet. So that was the only difference between the two diets, which then tells us that it’s the avocado that has additional benefits which are beyond the unsaturated fat.”
The findings are similar to a batch of studies that showed people who were given olive oil and nuts and told to add them to their diets ended up healthier. They were less likely to have strokes or heart attacks, and they were less likely to die over a period of years than people who didn’t get the extra oils.
Saturated fat – the kind found in meat and butter – has a different chemical structure from the unsaturated fats found in plant products. Repeated studies have shown it raises the risk of heart disease.
“We studied avocados but maybe a lot of other fruits and vegetables have these bioactive components which have additional cholesterol-lowering effects,” Kris-Etherton said. “And certainly there’s an emerging research base showing that some of these bioactive components may affect another lipoprotein particle favorably, like high-density lipoprotein. I think we need to stay tuned for that. “
Americans may not be used to eating avocado but Kris-Etherton says it’s easy to add.
“Consumers can include avocados in their diet in salads. They can include avocados on top of a sandwich, or in a sandwich. They can make guacamole and use vegetables rather than chips as the dip,” she said.
“I love guacamole and with my recipe, I’ll use avocados, cilantro, lime juice and garlic… and then sometimes I’ll put salsa in, or red pepper flakes.”
But like anything, too much of a good thing can be harmful. Avocados are definitely not low-calorie food.
“One avocado has around 200 to 250 calories. So I would strongly urge people not to just add an avocado a day to their diet but they have to substitute nutrient-poor calories, which are so popular in the U.S. diet.,” Kris-Etherton said.
Erika Edwards contributed to this story
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The story reports that a small study of overweight adults found that avocado consumption can lead to a decrease in LDL cholesterol levels. Thanks in part to extensive comments gleaned from one of the researchers in an interview (something lacking from some competing coverage that was based on a press release), the story does a good job of placing the findings in context and showing how LDL cholesterol is tied to human health. Notably, it was the only story we reviewed that explained what’s considered a healthy level of LDL cholesterol.
If we had to pick one way we’d like to see this story improved, it would be to explain how the changes observed in the study translate to overall cardiovascular risk. In other words, what does a 13-point drop in LDL mean for someone’s risk of a heart attack or stroke?
According to a 2011 report from the CDC, 71 million people in the United States have high cholesterol, which increases risk for heart disease and stroke (the first and fourth leading causes of death, respectively, in the U.S. as of 2010). LDL is the form of cholesterol that can build up in arteries, which is what causes that increased risk. Managing cholesterol is both a public health issue and an economic issue, given the enormous amounts of money spent in the U.S. on cholesterol management drugs, diets and other management techniques.
The story does not address costs. An avocado a day might add up to $30 or more per month, so that’s not irrelevant. Competing stories gave pricing information or at least noted that avocados can be expensive.
The story accurately compares the reduction of LDL cholesterol in study participants who ate avocado to reductions in LDL among study participants who did not — the avocado group’s LDL levels dropped by just over 13 milligrams per deciliter of blood (13.5 according to the news release), compared to reductions of 8.3 and 7.4 for two other groups. The story also provides readers with a frame of reference for those numbers, noting that overall LDL levels should be below 100 (which makes a difference of 5 or 6 mg/dl fairly significant). The story also explicitly makes the connection between LDL cholesterol and human health, noting that it is a significant risk factor for heart disease.
We wish the story had explained how the changes observed in the study would affect someone’s risk of a heart attack or stroke. In addition, there’s a reference to the “plaque-busting” properties of monounsaturated fatty acids that is a bit of unnecessary hype. There is no medication or nutrient that “busts” plaque, but rather a healthy lifestyle, diet, and medications for some will help prevent its accumulation. Given the other strengths discussed above, we don’t think these problems are sufficient enough to warrant an unsatisfactory rating.
The story explicitly states that “too much of a good thing can be harmful,” explaining that avocados are high in calories. The story quotes a researcher associated with the study as saying that people should not simply add avocados to their current diets, but find a way to incorporate the avocado into their diets without increasing overall calorie consumption. That’s the best discussion of this issue that we’ve seen in any of the four stories we reviewed on this topic.
This was a tough call. The story does explain that the study included only 45 participants, all of whom were obese or overweight. And the story also frames the findings in context, calling it “one more piece of evidence in favor of adding good fats to the diet,” and discussing related studies (with links). In short, for the most part the story doesn’t oversell the findings. We also appreciated this story’s clear explanation of the study design, and how we can be sure that it’s the avocados that are responsible for the drop in LDL cholesterol.
However, as we’ve noted in our reviews of the competing stories that covered this study, one of the crucial issues missing in this discussion is the fact that the primary outcome — LDL cholesterol — is an intermediate marker of heart disease risk and only one of many different factors that affects risk. Thus, the findings are not as strong as those of some other studies that the story linked to, which assessed the number of heart attacks and strokes that occurred after dietary changes. Our standard is for stories to mention such important limitations. We offer a primer on this general topic.
One of the researchers pointed to another key limitation in the news release that accompanied the study: “This was a controlled feeding study, but that is not the real world — so it is more of a proof-of-concept investigation.” The story could have earned a satisfactory by including some of that context.
The story didn’t engage in disease mongering.
The story does not quote any independent sources. But it somewhat makes up for this omission through an extensive interview with one of the study researchers, who provides excellent context. The story also clearly states that the study received funding from an avocado industry organization.
The story makes it clear that there are multiple ways that people can change their diet to improve cardiovascular health — avocados are not the only way to go. For example, the story points to studies which found that consuming other foods high in monounsaturated fatty acids (such as olive oil) were linked to reduced risk of heart disease and stroke. The story also notes that saturated fats increase heart disease risk. Ergo, another way to reduce risk is to lower consumption of meat and butter, rather than eating avocados. The story does not mention additional ways to lower LDL cholesterol, such as taking statin drugs, increasing exercise, quitting smoking, or limiting alcohol intake.
The story gives the impression (largely correct) that avocados are widely available. As with the competing stories, we would have liked to have seen some acknowledgment that there are areas where avocados may be more difficult to find.
While the story does place the work in context with other diet studies linked to cardiovascular health risk (which is great), it does not mention the multitude of other studies that have been done on avocados and cholesterol (many of which are — worth noting — not human diet studies). We wish the article had explained how the study fit into that larger body of literature on this specific subject, or why it was sufficiently novel that it falls outside of the previous work.
The story clearly went beyond the news release. It included an interview with the researcher and brought in a significant amount of additional context from other diet studies.