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There are still folks out there who believe that the 'high fat' content of avocados make them a liability for heart health. But the research on avocados simply doesn't support this lipid-phobic view. Take for example a recent study that looked at what happened when avocado was added to a heart-stopping American favorite, the hamburger meal.[i]
Researchers at the UCLA Center for Human Nutrition took eleven healthy subjects, and on two different occasions, fed them either 250 gram hamburger patty alone (ca. 436 cal and 25 g fat) or together with 68 grams of avocado flesh (an additional 114 cal and 11 g of fat for a total of 550 cal and 36 g fat).
The researchers then measured the degree of vasoconstriction following hamburger ingestion 2 hours later in test subjects given a hamburger meal either with our without avocado. The hamburger meal resulted in significant vasoconstriction, whereas the avocado+hamburger meal saw no change at all.
Next, the researchers isolated peripheral blood mononuclear cells from the test subjects in order to measure a protein known as Ikappa-B alpha, which is an indicator of inflammation. At 3 hours, there was a significant preservation of IkBa when avocado was consumed with the meat compared to meat lone, "consistent with reduced activation of the NF-kappa B (NFκB) inflammatory pathway." Another blood marker, interleukin-6 (IL-6), increased significantly at 4 hours after the consumption of the hamburger, but no change was observed when avocado was added.
Finally, researchers found that post-meal triglycerides did not raise in the avocado group, despite the additional fat, whereas they did increase in the hamburger alone group. The researchers concluded: "These observations are suggestive of beneficial anti-inflammatory and vascular health effects of ingesting added Hass avocado with a hamburger patty."
There are two main reasons why fats are labeled "bad." First, fatty foods that are comprised of a disproportionate amount of omega-6 fats (relative to omega-3 fats) contribute to the formation of pro-inflammatory eicosanoids, e.g. prostaglandin E2, leukotriene, thromboxane, etc. Corn, soy, peanut, grape, canola, and many other grain, seed and bean oils, are all extraordinarily high in omega-6 relative to omega-3 content. Peanut oil, for instance, has several thousand times more omega-6 than omega-3.
This is profoundly out of balance when you consider our evolutionarily-determined ideal ratio is closer to a 1:1-4:1 ratio of omega-6 to omega-3. When you feed cattle on these omega-6 rich foods, the problem only becomes exaggerated. Grain-fed cattle not only concentrate omega-6 fats in their flesh but inflammatory metabolites of omega-6 fats such as arachadonic acid, which is the fuel the Cox-2 enzyme "burns" (technically oxidizes) during the inflammatory process. This explains why the ordinary grain-fed hamburger can be so inherently toxic. And yet, there are grass-fed and organic alternatives much higher in beneficial omega-3 fats, as well as beneficial fats such as conjugated linoleic acid (CLA).
But even in this latter case, when the ratio and types of fats are generally "good," they can still undergo a process known as lipid peroxidation. This is the second way that fats can "go bad." Lipid peroxidation can occur both outside of the stomach (when grilled/cooked), or within the stomach during the normal process of digestion. Otherwise known as rancidity, lipid peroxidation results in quite a few adverse health effects, including inflammation and even damage to the arteries in our bodies. This is why antioxidants, as evidenced by avocado's beneficial role in the study above, are powerful inhibitors of this deleterious process.