Apples resist oxidation of LDL in humans
Scientists out of the University of California at Davis showed the apple's power over LDL cholesterol. They discovered that people eating two apples a day or drinking an equivalent amount of apple juice had a significant slowing of LDL oxidation, the process that results in plaque buildup. How do apples work to alter LDL metabolism?
Method of Attack #1. The scientists propose that the apple antioxidants are incorporated into the LDL molecule, so the antioxidant is oxidized in place of the LDL, preventing harm to the LDL molecule and thus helping to impede the progression of atherosclerosis.
Method of Attack #2. A doctoral student at Cornell University performed test-tube experiments showing that not only can an extract of Red Delicious apples prevent the oxidation of human LDL cholesterol, but the extract also prompts the liver to sprout more LDL receptors, thereby reducing LDL levels in the bloodstream. Furthermore, apple extract dampens the activity of a key protein in liver cells that functions to signal the start of the cholesterol production pathway (termed sterol regulatory element binding protein, or SREBP). Apples therefore work to squelch cholesterol production in a manner similar to statin drugs.
Apples cut LDL by 70 percent, at least in fat rats
It's a huge leap from rats to humans, but the results of one study are nonetheless eye-opening.6 French scientists gave obese rats with high cholesterol an "apple diet" of regular rat chow plus ground-up apples for three weeks. It turns out the apple diet cut LDL cholesterol by a whopping 70 percent. How did apples lower LDL to such a great extent?
Method of Attack #3. The scientists noted that there was a marked increase in the pool of bile acids in the intestines of the apple-fed rats compared to rats fed the control diet. Bile acids are formed in the liver from cholesterol. The increased amount of bile acids entering the intestine suggests the liver is working overtime to make new bile acids (requiring more cholesterol). This process results in less circulating LDL. Why would the liver increase its production of bile acids? The answer: less cholesterol is returning to the liver, as the recycling of bile acids is hindered by the apple diet.
The study authors suggested that the remarkable LDL-cutting ability of apples stemmed from the cholesterol-lowering effect of soluble fibers, primarily pectin, working together with the apple's polyphenol compounds to trap bile acids in the intestine. This is the same mechanism bile acid sequestrant drugs such as Questran use to lower LDL cholesterol.
Which of the compounds in apples is more effective at reducing LDL cholesterol, pectin or the polyphenols? Another group of French researchers fed rats with high cholesterol a typical rat chow with one of three different additives: isolated apple pectin, isolated apple polyphenols, or a more natural apple combination of both pectin and polyphenols. The natural combination additive of apple pectin and polyphenols was much more effective in lowering cholesterol than the isolated nutrients, suggesting that the interaction of the two components is best for maximum cholesterol reduction.
In addition, this same study noted that the antioxidant effects of the many polyphenols found in apples protect against heart disease by countering oxygen's damaging effects on cells and by preventing oxidation of LDL, an early step in cholesterol-filled plaque buildup. Thus, apple polyphenols reduce inflammation to decrease the risk of atherosclerosis in several ways.
Polyphenols cut LDL cholesterol
Method of Attack #4. Like many of the other foods in the Cholesterol Down Plan, the polyphenols in apples lower cholesterol absorption by interfering with cholesterol's ability to cross over from the small intestine into the intestinal cells. This disruption of cholesterol transport to the liver lowers the return rate of cholesterol. To compensate for this deficit, liver cells "turn on" more liver LDL receptors, resulting in a greater number of LDL particles being cleared from the bloodstream.
Method of Attack #5. Apple polyphenols affect the liver's construction of VLDL, the parent molecule of LDL, by modifying VLDL's packaging. Just like LDL, VLDL consists of an inner core of cholesterol and triglycerides, the entire particle encircled by a strand of protein called Apo B (VLDL has two additional proteins, Apo C and Apo E). Polyphenols interfere with the enzymes involved in production of both of these core components (cholesterol and triglyceride), leading to a decline in their availability. Without enough of these core components, degradation of the Apo B protein occurs. These changes lead to less secretion of VLDL from the liver. The end result is lower blood levels of LDL.
Method of Attack #6. Polyphenols found in apples have also been shown to positively affect blood vessel dynamics on several fronts. They reduce adhesion molecules, thus making the arterial wall less sticky and lowering the number of immune system blood cells that stick to the lining. This reduces inflammation and therefore helps protect against atherosclerosis. What's more, polyphenols reduce the ability of platelets to stick together, which lessens the ability of blood to clot, ultimately keeping a blood clot from choking off the blood supply to the heart muscle, and thereby lowering your risk of a heart attack. Finally, polyphenols alter blood vessel mechanics by increasing the vessels' ability to relax and dilate. This also helps blood to flow more easily, reducing inflammation and risk of atherosclerosis.
Apples top the produce list when it comes to the highest level of pesticide residues, according to the Environmental Working Group, a not-for-profit environmental research organization. Two previous investigations list apples among the four most contaminated fruits, along with peaches, strawberries, and nectarines. In order to remove as much of the chemicals from the outer skin as possible, thoroughly rinse apples before eating them. Don't let the ads for spray products claiming to remove harmful pesticides fool you. While they may help to remove some of the surface pesticide residue, they do not eliminate them. In fact, a scientific study found that spray washes or detergents were no more effective in removing pesticide residues than rinsing thoroughly with tap water alone.
The best way to avoid ingesting unacceptably high amounts of pesticides on a daily basis is to choose organically grown produce. Earthbound Farm sells packages of organic and presliced Gala apples (that don't turn brown!) in prewashed ready-to-ear snack bags, available at your local supermarket (a 12-ounce bag retails for about $2.99).