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“Even one meal of a double cheeseburger with
fries and a Coke will mess up your system,
let alone a steady diet of it, which is a recipe for disaster."
~Cardiologist James O’Keefe, MD, Mid America Heart Institute, Kansas City (AP)
Every Meal Counts
(See below for follow-up on effect of exercise)
I may have to settle for one dessert at Christmas and Thanksgiving, instead of the 3 or 4 I usually enjoy. I always go back to healthy eating the next day and any weight gain goes away in a few days, so I didn’t see any harm in my holiday indulgence. A rather surprising new study at the Heart Research Institute in Sydney, Australia, has made me think anew; it shows precisely what saturated fat does to the arteries--and it ain't pretty. The study led by Dr. Stephen J. Nicholls, a cardiologist now at the famous Cleveland Clinic, is simple and straightforward in design and carries a powerful message. (The details are not so simple, as you’ll see.) The study is reported in the August 15, 2006, issue of the Journal of the American College of Cardiology.
Fourteen healthy normal-weight subjects, aged 18 to 40, 8 males and 6 females, were fed two meals separated by one month. Talk about real life: both meals consisted of a slice of carrot cake and a milkshake. The meals were equal in calories, with one gram of fat per kilo of body weight. The difference was in the nature of the fat. One meal was made with safflower oil, which is 75% polyunsaturated, 13.6% monounsaturated, and 8.8% saturated. The other contained coconut oil, which is 89.6% saturated, 5.8% monounsaturated, and 1.9% polyunsaturated. As you can see, one meal was high in unsaturated fat and the other meal high in saturated fat. Again, all subjects consumed both meals, a month apart. Neither the subjects nor the researchers knew which was saturated and which was unsaturated.
Saturated fat, of course, is generally thought to be unhealthy, and poly- and monounsaturated fat healthy. “Fatty acid composition has a profound impact on the influence that dietary fat exerts on cardiovascular risk,” the researchers wrote. “[Numerous] studies have reported that consumption of saturated fat promotes atherosclerosis [hardening and narrowing of the arteries], whereas polyunsaturated and monounsaturated fats are potentially protective.”
Now it gets a little more complicated. Stick with me. Dr. Nicholls and his colleagues investigated the effect of each meal “on the anti-inflammatory properties of high-density lipoproteins [HDL good cholesterol] and vascular function.” Specifically, they examined how the two types of fat affect the ability of HDL cholesterol “to inhibit the expression of proinflammatory adhesion molecules by endothelial cells on large and small vessel function.” In plain language, they undertook to find out how each meal influences the stickiness of molecules produced by the cells that line blood vessels, and how that influences the flow of blood in the arteries and veins. They wanted to know how the two types of fat help or hinder HDL cholesterol in protecting against clogged arteries.
They looked at artery function at three points in times: before and 3 and 6 hours after each of the meals. Bypassing much of the medical jargon, here’s what they found.
First, HDL cholesterol collected after the saturated fat meal was accompanied by a higher level of adhesion [sticky] molecules expressed [squeezed out] by artery wall cells. In contrast, HDL cholesterol collected after the unsaturated-fat meal was accompanied by a significantly lower level of sticky molecules. Importantly, the level of sticky molecules at both 3 and 6 hours after the unsaturated-fat meal were lower than before the meal.
My interpretation: After a meal high in saturated fat, the blood is more likely to clump and stick to the artery wall, impairing blood flow. On the other hand, a meal high in unsaturated fat may actually improve the ability of arteries to accommodate blood flow. That’s essentially what the researchers found.
Blood flow increased twice as much after the unsaturated-fat meal than after the saturated fat meal: 45% after the unsaturated fat meal and 21% after the meal with saturated fat. “Flow mediated dilation (FMD) decreased at 3 h following consumption of the saturated meal, but not 3 h after the polyunsaturated meal.” (Emphasis added) In other words, the artery was stiff and unable to expand to accommodate increased blood flow after the saturated fat meal.
Blood flow equalized after 6 hours, but the anti-inflammatory (good) action of the HDL cholesterol was reduced after the saturated fat meal. The poly- and monounsaturated meal, on the other hand, seemed to increase the anti-inflammatory qualities; fewer inflammatory agents were found than before the meal.
Dr. Nicholls and his colleagues concluded: “Consumption of a saturated fat reduces the anti-inflammatory activity of HDL, and impairs arterial endothelial [lining]function. In contrast, the anti-inflammatory activity of HDL improves after consumption of polyunsaturated fat.” (Emphasis mine.)
Dr Nicholls told the Associated Press: “It’s further evidence to support the need to aggressively reduce the amount of saturated fat consumed in the diet.”
Dr. Charles McCauley, a cardiologist who reviewed the study, added, “What we put into our mouth makes a big difference in terms of our health."
Finally, James O’Keefe, MD, a cardiologist at Mid America Heart Institute in Kansas City, got to the heart of the matter: “When you eat the wrong types of food, inflammation and damage to the vessels happens immediately afterwards.” (Emphasis mine)
As most readers know, saturated fat is found mostly in animal foods, such as beef, pork, lard, butter, cheese, whole milk, and ice cream. It’s also in some plant foods; coconut oil, palm oil and cocoa butter are examples. Poultry is generally low in fat, but only if the skin is removed. Fried chicken is probably not a good choice.
Polyunsaturated fat is found in oils from plants, including safflower, sesame, sunflower, corn, and soybean. Where possible, I prefer whole foods, such as corn-on-the-cob, seeds and nuts, which are more filling and satisfying than concentrated oil.
Fish, especially salmon and sardines, are generally low in saturated fat and high in good fat. Olive oil and canola oil are high in monounsaturated fat, which is also thought to be protective.
Fast foods, cakes, pies and pastries are almost always loaded with saturated fat.
Care for a mouth-watering slice of carrot cake and a nice thick milkshake? Believe I'll pass, most of the time anyway.
And if I indulge, I'll be sure to exercise later in the day. (See follow-up below)
* * *
Exercise Counters High-Fat Meal
I have often tried to walk off the bloated logy feeling after a high-fat meal. (Bet you have too.) It always makes me feel better, but does exercise actually have a measurable effect on artery function? Does it counter the negative effect of the high-fat meal shown in the study discussed above? Doctoral candidate Jaume Padilla and his colleagues at the Departments Kinesiology Nutrition and Medicine at Indiana University, Bloomington, decided to investigate and find out. The report of their study is in the September 2006 issue of the European Journal of Applied Physiology (online August 3, 2006).
Exercise not only works, it makes artery function better than before the high-fat meal! Here's how the researchers came to this surprising (to some) conclusion.
They subjected eight healthy individuals to three treatment conditions administered 2-7 days apart: 1) low-fat meal alone (LFM), 2) high-fat meal alone (HFM), and 3) one session of aerobic exercise two hours after eating a high-fat meal (HFM+EX). The subjects were 5 men and 3 women, average age 25.5.
For each of the three treatment conditions, they measured flow-mediated dilation [also measured in above study] in the main artery of the upper-arm before, and four hours after, the meal. What they looked at was the ability of the artery to expand in response to an increase in blood flow before and after the three conditions. Specifically, they used a blood pressure cuff to stop and start blood flow and ultrasound technology to record artery expansion (dilation). FMD was expressed as the percentage change in the diameter of the artery before the meal and 4 hours later.
Both meals contained about 940 calories. The high-fat meal included eggs, sausage and hash browns; it contained 48 grams of fat (16.5 saturated and 4.5 trans fat). The low-fat meal included cereal with skimmed milk and orange juice; it contained no fat (5 mg. cholesterol). The high-fat meal had 91 grams of carbohydrate and 33 gm of protein; the low-fat meal had 209 and 23, respectively.
The subjects walked on a treadmill for 45 minutes at 60% of their measured VO2peak. The subjects rated the intensity "fairly light" to "somewhat hard"--so we're talking about a relatively comfortable pace.
As you would expect, all three pre-meal dilation readings were similar. The readings 4 hours later were significantly different, however. Artery expansion after the low-fat meal (LFM) and the high-fat meal plus exercise (HFM+EX) was significantly higher (+ 7.18 and 8.72%, respectively) than following the high-fat meal (HFM) alone (+ 4.29%). Importantly--this is the bell ringer--the change in diameter (FMD) following exercise was significantly greater than before the high-fat meal. In short, the artery responded better (was more flexible) after exercise than before consumption of the high-fat meal (+5.61% pre-meal versus +8.72% 4 h later).
The researchers concluded: "These findings suggest that a single aerobic exercise session cannot only counteract the postprandial [after meal] endothelial dysfunction induced by ingestion of a high-fat meal, but also increase brachial artery FMD in apparently healthy adults." Again, artery function was better after exercise than before the meal. Almost sounds like you can have your cake and eat it too--if you exercise. (Not quite)
Words to the Wise
This study is part of a growing interest in the direct effect food has on the body. An online press release from Media Relations at Indiana University states: "After a fatty meal, arteries lose their ability to expand in response to an increase in blood flow, with the effect peaking four to six hours after eating--just in time for the next meal." It seems that many of us are eating in a manner that impairs artery function virtually around the clock. That can't be good, and it's not.
"What happens four hours after that high-fat meal is that your artery looks just like the arteries of a person who has heart disease," said co-author Janet P. Wallace, a professor in the IU Department of Kinesiology. "What our study shows is that when you exercise after that meal, it doesn't look like a sick artery anymore."
The problem, of course, is that no one wants to exercise after every meal.
While the Indiana University research again demonstrates the adverse effect of high-fat eating, the type of fat is also important (as shown in the first study we discussed). One can't help wonder what the result would've been had Padilla and his colleagues included a fourth treatment condition combining exercise and a meal high in good fat. Would artery function four hours later have been even better? Sounds like a pretty good bet, doesn't it?
Bottom line: Eat smart--and exercise.
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