Flashback Friday: Are Avocados Good for You?

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.

Avocados have been described as “a major dietary source of antioxidants,” and this may be true compared to much of the stuff people eat. But, compared to other common fruits, avocados are not necessarily anything to write home about.

They do, however, contain those two carotenoid eye nutrients found in dark green leafy vegetables, lutein and zeaxanthin, which may explain why Mexican-Americans tend to beat out other ethnicities. The critical carotenoids are concentrated “in the dark[est] green flesh close to the peel.” And, because of this, consumers should be advised to use the “nick and peel” method to obtain the nutrient-rich outer section of the avocado. The Tufts University Nutrition & Health Letter detailed what that means:

“1. …[C]ut [the avocado] in half lengthwise around the seed.

2. Rotate a quarter-turn and cut lengthwise [again] to make quarter-avocado segments.

3. …[S]eparate the quarters and remove the seed.

4. …Starting from the tip, nick and carefully peel,” so as not to lose that nutrient-rich darkest green flesh immediately under the skin.

Avocados can also boost the absorption of the carotenoid phytonutrients in other vegetables, because carotenoids, like beta-carotene, are fat soluble. “However, many of our best foods for obtaining carotenoids—[like] sweet potatoes, carrots, and…greens, contain very little fat.” So, if you eat them straight, without any source of fat in your stomach, you may end up flushing a lot of that nutrition down the toilet.

Remember, it’s not what you eat; it’s what you absorb. Here’s the amount of beta-carotene that ends up in your bloodstream two, three, four, five, six hours after eating a little over a cup of salsa. There’s a little bump. And, the same thing with the red pigment lycopene. Okay, but now here’s that same amount of salsa with an avocado added—tripling the absorption. That means if you eat tomatoes without some source of fat at the same meal—avocados, or nuts and seeds—most of that bright red, beautiful lycopene will end up in the toilet bowl rather than your bloodstream.

Same thing eating a salad composed of lettuce, spinach, and carrots. With a fat-free dressing, hardly any beta-carotene makes it into your body. But, add an avocado and 15 times more beta-carotene ends up circulating throughout your body. Do you have to use a whole avocado, though? What about half an avocado? Pretty much same effect; works just as well. What about a quarter of an avocado? We don’t know “the [minimum] amount of dietary fat required for optimum carotenoid absorption.” It may just be a few grams per meal though, in which case an eighth of an avocado would fit the bill, or just one or two walnuts.        

Interestingly, avocado consumption may not just enhance absorption of carotenoids, but then also enhance their subsequent conversion inside the body into vitamin A. People were given baby carrots with and without guacamole, and the same thing we saw before: way more beta-carotene in the bloodstream in the hours following the meal with the guacamole added, compared to the same amount of carrots alone. In fact, over six times more. And, since beta-carotene is turned into vitamin A in the body, there should be six times more vitamin A too, right? No; they ended up with over 12 times more vitamin A.

There was also a big increase in vitamin K levels, another fat-soluble vitamin, though that’s partially because avocado contains vitamin K itself. Not too much, though, claims this avocado industry-sponsored review, that people on the anticoagulant medication Coumadin have to worry. But that’s not true. We’ve known for decades now that even though there’s not an inordinate amount of vitamin K in avocados, it still interferes with the drug Coumadin, also known as warfarin, though we’re not exactly sure why. It may boost your liver’s detoxifying enzymes or prevent absorption of the drug. But, either way, those on the blood thinner Coumadin may want to put walnuts on their salads instead.

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• Ameer K. Avocado as a major dietary source of antioxidants and its preventive role in neurodegenerative diseases. Adv Neurobiol. 2016;12:337-354.
• Kopec RE, Cooperstone JL, Schweiggert RM, et al. Avocado consumption enhances human postprandial provitamin A absorption and conversion from a novel high-β-carotene tomato sauce and from carrots. J Nutr. 2014;144(8):1158-1166.
• Unlu NZ, Bohn T, Clinton SK, Schwartz SJ. Carotenoid absorption from salad and salsa by humans is enhanced by the addition of avocado or avocado oil. J Nutr. 2005;135(3):431-436.
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• Lu QY, Zhang Y, Wang Y, et al. California Hass avocado: profiling of carotenoids, tocopherol, fatty acid, and fat content during maturation and from different growing areas. J Agric Food Chem. 2009;57(21):10408-10413.
• Blickstein D, Shaklai M, Inbal A. Warfarin antagonism by avocado. Lancet. 1991;337(8746):914-915.
• Tufts University. Avocados could improve your cholesterol and more. Tufts University Health & Nutrition Letter.
• Carlsen MH, Halvorsen BL, Holte K, et al. The total antioxidant content of more than 3100 foods, beverages, spices, herbs and supplements used worldwide. Nutr J. 2010;9:3.
• Essa MM, Akbar M, Guillemin GJ. The benefits of natural products for neurodegenerative diseases. Cham: Springer International Publishing; 2016.

Image credit: silviarita via Pixabay. Image has been modified.

Motion graphics by Avocado Video.