Are Avocados Healthy?

Michael Greger M.D. FACLM · October 23, 2017 · Volume 38

4.7/5 - (196 votes)

Avocado consumption can improve artery function, but what effect might guacamole have on cancer risk?

Discuss

Transcript

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In my last video about avocados, I described the anti-inflammatory effects and cholesterol- and triglyceride-lowering effects. But what about that video I did years ago about the chromosome-damaging effects in a petri dish? That all goes back to 1975, when a pesticide naturally produced by the avocado tree was discovered—thought to explain why lactating livestock suffered mammary gland damage nibbling on the leaves. The toxin was named persin, also found to be damaging to the heart, which is why you should never feed avocado to your pet birds.

But hey, if it attacks mammary cells in animals, might it attack breast cancer cells in humans? It did seem to have the same kind of cell cytoskeleton-clumping effect in vitro that chemotherapy can have, demonstrating potent cell growth-stopping and -killing effects of the “novel plant toxin” among various lines of human breast cancer cells. So, they’re thinking about how it might one day be used as chemo itself. But, here I am thinking, “Holy guacamole, Batman; please tell me it doesn’t have toxic effects on normal cells, too.”

In 2010, we got an answer: an “Evaluation of [the] Genotoxicity,” the toxicity to our chromosomes, of avocado extracts on human white blood cells in a petri dish. Normally, less than 10% of our dividing cells have any chromosome abnormalities, but drip some avocado fruit extracts on them, and up to half come out defective in some way. They conclude that there’s something in avocado fruit that “can potentially induce significant genomic instability and some genetic damage” in human white blood cells in a petri dish. If the same effect occurs in actual people, it could, for example, result in transforming cells into cancer. That’s a big if, though.

These were blood cells. You don’t inject guac into the vein. For anything to get into our bloodstream, it first has to survive our stomach acid, get absorbed through our intestines, and sneak past our liver’s detoxification enzymes. And indeed, persin may be affected, changed, by acidic conditions. So, given all the differences between what happens in a petri dish and a person, “it is essential to carry out [further] studies…before making a final remark” about its toxicity. Okay, but what do you do before these studies come out? I was concerned enough that I provisionally moved it from a stuff-your-face green-light food, to a moderate-your-intake yellow-light food, until we knew more, to err on the side of caution.

Even if persin was utterly destroyed by stomach acid, what about oral cancer? At high-enough concentrations, avocado extracts can harm the growth of the kinds of cells that line our mouths. Yeah, but this is in a petri dish, where the avocado is coming in direct contact with the cells. But that’s kinda what happens in your mouth when you eat it. But, it harms oral cancer cells even more. Here’s a bunch of oral cancer cells. Those red dots are the mitochondria—the power plants of the cells fueling cancer growth, extinguished by the avocado extract. But, since it does this more to cancerous than normal cells, they end up concluding avocados may end up preventing cancer.

What about the esophagus, which lies between the mouth and the stomach? They similarly found that an “avocado fruit extract [appeared to inhibit] cancer cell growth” more than normal cell growth, when it came to colon cancer cells, or esophageal cancer cells. But, rather than comparing the effects to normal colon and esophagus cells, they compared to a type of blood cell, which again is of limited relevance in a petri dish study of something you eat.

This study was pretty exciting, though. It looked at p-cresol, which is a “uremic toxin,” may also be toxic to the liver, has been found associated with autism, and it comes from eating high-protein diets, whereas if you eat a more plant-based diet, the only source of prebiotics, like fiber and resistant starch, your levels go down.

See, “fermentation of carbohydrates [in the colon, like fiber] is considered beneficial, whereas fermentation of [protein] [which is called] (putrefaction) is considered…detrimental.” So, you switch people to a high-protein diet, and within days, the excess protein putrefying in their gut leads to an increase in ammonia, as well as p-cresol—in fact, a doubling of levels within a week. But, might phytonutrient-rich plant foods, like “apples, cranberries, grapes, [or] avocados,…protect [the cells lining our colon] from the deleterious effects of p-cresol…in terms of cell viability, mitochondrial function, and epithelial integrity,” meaning like protection against gut leakiness?

Here are those data on barrier function integrity, damaged by p-cresol, but rescued by all the cranberry, avocado, grape, and apple extracts, though mitochondrial function was only improved by the cranberries and avocados, and they were also the only ones that appeared to prevent the “deleterious effect of p-cresol” on colon cell viability. But, bottom line, avocados appear to have beneficial effects on colon-lining cells; so, that’s a good sign.

Okay, but enough of these in vitro studies, already. Yes, an avocado extract can inhibit cancer cell growth in a petri dish, but unless you’re doing some unspeakable things to that avocado—like guacamole with benefits, there’s no way that the avocado is going to come in direct contact with your prostate cells. So, what does this study mean?

That’s why I was so excited to see this study: “the first” to actually look for a link between “avocado consumption [actual human beings eating avocados] and prostate cancer.” So, do avocado eaters have more cancer risk, or less cancer risk? We’ll find out…right now!

Men who ate the most avocado, more than about a third of an avocado a day, “reduced [their] risk of prostate cancer.” In fact, less than half the odds. So, with the data on improved artery function, lower cholesterol, and, if anything, an association with decreased cancer risk, I’d suggest moving it back into the green zone.

Please consider volunteering to help out on the site.

Sources

Acknowledgements

Icons created by Royal Razka and Gay Khoon Lay from The Noun Project.

Image credit: Kristina DeMuth. Image has been modified.

Motion graphics by Avocado Video.

Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.

In my last video about avocados, I described the anti-inflammatory effects and cholesterol- and triglyceride-lowering effects. But what about that video I did years ago about the chromosome-damaging effects in a petri dish? That all goes back to 1975, when a pesticide naturally produced by the avocado tree was discovered—thought to explain why lactating livestock suffered mammary gland damage nibbling on the leaves. The toxin was named persin, also found to be damaging to the heart, which is why you should never feed avocado to your pet birds.

But hey, if it attacks mammary cells in animals, might it attack breast cancer cells in humans? It did seem to have the same kind of cell cytoskeleton-clumping effect in vitro that chemotherapy can have, demonstrating potent cell growth-stopping and -killing effects of the “novel plant toxin” among various lines of human breast cancer cells. So, they’re thinking about how it might one day be used as chemo itself. But, here I am thinking, “Holy guacamole, Batman; please tell me it doesn’t have toxic effects on normal cells, too.”

In 2010, we got an answer: an “Evaluation of [the] Genotoxicity,” the toxicity to our chromosomes, of avocado extracts on human white blood cells in a petri dish. Normally, less than 10% of our dividing cells have any chromosome abnormalities, but drip some avocado fruit extracts on them, and up to half come out defective in some way. They conclude that there’s something in avocado fruit that “can potentially induce significant genomic instability and some genetic damage” in human white blood cells in a petri dish. If the same effect occurs in actual people, it could, for example, result in transforming cells into cancer. That’s a big if, though.

These were blood cells. You don’t inject guac into the vein. For anything to get into our bloodstream, it first has to survive our stomach acid, get absorbed through our intestines, and sneak past our liver’s detoxification enzymes. And indeed, persin may be affected, changed, by acidic conditions. So, given all the differences between what happens in a petri dish and a person, “it is essential to carry out [further] studies…before making a final remark” about its toxicity. Okay, but what do you do before these studies come out? I was concerned enough that I provisionally moved it from a stuff-your-face green-light food, to a moderate-your-intake yellow-light food, until we knew more, to err on the side of caution.

Even if persin was utterly destroyed by stomach acid, what about oral cancer? At high-enough concentrations, avocado extracts can harm the growth of the kinds of cells that line our mouths. Yeah, but this is in a petri dish, where the avocado is coming in direct contact with the cells. But that’s kinda what happens in your mouth when you eat it. But, it harms oral cancer cells even more. Here’s a bunch of oral cancer cells. Those red dots are the mitochondria—the power plants of the cells fueling cancer growth, extinguished by the avocado extract. But, since it does this more to cancerous than normal cells, they end up concluding avocados may end up preventing cancer.

What about the esophagus, which lies between the mouth and the stomach? They similarly found that an “avocado fruit extract [appeared to inhibit] cancer cell growth” more than normal cell growth, when it came to colon cancer cells, or esophageal cancer cells. But, rather than comparing the effects to normal colon and esophagus cells, they compared to a type of blood cell, which again is of limited relevance in a petri dish study of something you eat.

This study was pretty exciting, though. It looked at p-cresol, which is a “uremic toxin,” may also be toxic to the liver, has been found associated with autism, and it comes from eating high-protein diets, whereas if you eat a more plant-based diet, the only source of prebiotics, like fiber and resistant starch, your levels go down.

See, “fermentation of carbohydrates [in the colon, like fiber] is considered beneficial, whereas fermentation of [protein] [which is called] (putrefaction) is considered…detrimental.” So, you switch people to a high-protein diet, and within days, the excess protein putrefying in their gut leads to an increase in ammonia, as well as p-cresol—in fact, a doubling of levels within a week. But, might phytonutrient-rich plant foods, like “apples, cranberries, grapes, [or] avocados,…protect [the cells lining our colon] from the deleterious effects of p-cresol…in terms of cell viability, mitochondrial function, and epithelial integrity,” meaning like protection against gut leakiness?

Here are those data on barrier function integrity, damaged by p-cresol, but rescued by all the cranberry, avocado, grape, and apple extracts, though mitochondrial function was only improved by the cranberries and avocados, and they were also the only ones that appeared to prevent the “deleterious effect of p-cresol” on colon cell viability. But, bottom line, avocados appear to have beneficial effects on colon-lining cells; so, that’s a good sign.

Okay, but enough of these in vitro studies, already. Yes, an avocado extract can inhibit cancer cell growth in a petri dish, but unless you’re doing some unspeakable things to that avocado—like guacamole with benefits, there’s no way that the avocado is going to come in direct contact with your prostate cells. So, what does this study mean?

That’s why I was so excited to see this study: “the first” to actually look for a link between “avocado consumption [actual human beings eating avocados] and prostate cancer.” So, do avocado eaters have more cancer risk, or less cancer risk? We’ll find out…right now!

Men who ate the most avocado, more than about a third of an avocado a day, “reduced [their] risk of prostate cancer.” In fact, less than half the odds. So, with the data on improved artery function, lower cholesterol, and, if anything, an association with decreased cancer risk, I’d suggest moving it back into the green zone.

Please consider volunteering to help out on the site.

Icons created by Royal Razka and Gay Khoon Lay from The Noun Project.

Image credit: Kristina DeMuth. Image has been modified.

Motion graphics by Avocado Video.

Doctor's Note

The Effects of Avocados and Red Wine on Meal-Induced Inflammation and Are Avocados Good for You? were the first updated videos I’ve produced on avocado consumption, and there are more to come.

2022 Update: I now have more videos on avocados. See:

How Not to Die from Cancer is an overview on dietary approaches to cancer prevention and treatment, and I also have hundreds of videos on all of the common cancers.

What if you’ve already been diagnosed? Even if you already have prostate cancer, for example, it’s not too late to improve your diet. See:

If you haven't yet, you can subscribe to our free newsletter. With your subscription, you'll also get notifications for just-released blogs and videos. Check out our information page about our translated resources.

Pin It on Pinterest

Share This