Wednesday, June 17, 2015

This High-Fat Food Can Lower Your Cholesterol

This High-Fat Food Can Lower Your Cholesterol

A number of years ago during my first year of residency training, I was talking with a group of residents around 2 a.m., when the hospital employee cafeteria opened for about an hour to feed the night shift. We often worked 80 to 100 hours a week, and even at 1 a.m., food was a welcome gift for the weary. Conversations during these meals often revolved around the events of the day and what we may have planned for our one day off each week.
On this particular night, we talked about what we would have as our last meal. Choices ranged from the gourmet to what we loved as a child. I quickly realized I had not put a lot of sophisticated thought into the topic: I was trying to decide between Mexican and Chinese food that you could get in almost any town in America.
Ultimately, I decided I would go out with a good plate of Mexican food, and for this reason you’ll understand my enthusiasm for this topic.

Avocados Are Nutrient Powerhouses

Avocados are on many short lists of superfoods because they are packed with vitamins and nutrients. Here is a list of some of what they contain, according to the U.S. Department of Agriculture’s National Nutrient Database for Standard Reference.
  1. Lutein. This powerful antioxidant tends to occur in high concentrations in our eyes. Lutein has a protective effect on ultraviolet light from the sun. It also improves vision in dim light.
  2. Vitamins. The numerous vitamins in avocados include vitamin B complex (B5, B6, B9) and folate, as well as vitamins C, D, E, and K.
  3. Potassium. Avocados are one of the richest sources of potassium. When I ask patients which foods contain potassium, almost all tell me bananas. Avocados contain more potassium per weight than bananas. Potassium is a necessary electrolyte in our body, and can lower blood pressure when consumed in healthy food sources.
  4. Fiber. An avocado contains about 11 grams of fiber, on average. This is about half of the recommended minimum daily fiber intake.
One of the problems with avocados is that they are high in fat. However, the fat source is healthy, as it is mainly comprised of monounsaturated fats. Fat consumption is essential to any conversation about heart health. Some fats are quite good for us and improve our heart health. Other fats can cause cholesterol levels to rise, increase body inflammatory markers, and raise risks of coronary atherosclerosis and heart attack.
Unfortunately, the high-fat content of avocados also makes them calorie-dense. An average avocado contains about 250 calories. As such, when you research recommended serving sizes for avocados you may not be surprised to find that they are small.

Bad Fats and High Cholesterol

People who have high cholesterol levels tend to rely on a few simple options. First, weight loss and changing to a healthier, fiber-rich diet. I dedicated a prior column to the past 50 years of heart-healthy diets.
The next step typically is adding a medication called a statin (HMG-CoA reductase inhibitor). These drugs have been shown to lower cholesterol, heart attack risk, stroke risk, and in people with high cholesterol or body inflammation improve mortality. They are a go-to drug in the tool chest of all cardiologists. Unfortunately, statins do have side effects. The most common is generalized muscle and joint pain. This can be disabling to some people, including some in my family. Rarely, this pain is from a severe inflammatory muscle injury called myositis. Fortunately, for most people the symptoms are not a reflection of actual muscle and joint injury.
For people with high cholesterol who cannot take a statin, there are a few other drug options, such as Zetia (ezetimibe). However, these medications are not equivalent to statins in regard to their ability to reduce cholesterol and lower heart disease risk.

The Avocado Effect on High Cholesterol

Where do avocados come in? A small study in the  Journal of the American Heart Association provides evidence of potent cholesterol-lowering benefits from avocados. Avocados are rich in monounsaturated fats, healthy fats that have been shown to lower LDL cholesterol, which is the bad cholesterol associated with coronary atherosclerosis and heart attacks. Could eating avocados be part of a cholesterol-lowering strategy in people with high cholesterol and at risk for heart disease?
Researchers studied 45 people who were considered overweight to obese and had high cholesterol. The participants were treated with three diets thought to be helpful in reducing cholesterol:
  • A general low-fat diet containing 24 percent of calories from fat.
  • A moderate-fat diet of 34 percent fat that included one fresh avocado per day (134 grams).
  • A moderate-fat diet with 34 percent fat, but that used high-oleic acid oils to match that fatty acids provided by the avocado – like olives, for example.
The researchers used the second moderate-fat diet to determine whether a supplement that contains an extract of what we believe makes avocado heart-healthy would be as effective as avocado itself. Participants were on each diet for five weeks. They would then go back to their usual routine for two weeks before starting the next diet. The order in which they tried each diet was randomized.
The effect of the diets on different types of cholesterol were quite interesting and encouraging:
  • The moderate-fat daily avocado diet resulted in a significant reduction in LDL cholesterol (a.k.a., bad cholesterol) after five weeks by 13.5 milligrams per deciliter (mg/dL) on average.
  • The moderate-fat diet without avocado also reduced LDL cholesterol at five weeks but not by as much –  on average 8.3 mg/dL.
  • The moderate-fat daily avocado diet lowered total cholesterol, too – an average of 18 mg/dL.
  • The moderate-fat diet lacking avocado lowered total cholesterol by less – an average of 11 mg/dL.
  • The low-fat diet had the least benefit on both LDL and total cholesterol, although both were lower after five weeks.
  • Unfortunately, none of the diets raised good cholesterol (HDL). However, the low-fat diet alone actually significantly lowered good cholesterol, by an average of 4 mg/dL.
  • One of the important aspects of understanding bad cholesterol is that size matters. The smaller and more dense the LDL cholesterol particle, the more likely it is to injure a heart artery wall. Because of this, researchers also looked at very small, dense LDL particles. Among all the diets, only the moderate-fat daily avocado diet lowered the very small, dense LDL particles. To me, this is an extraordinary finding, as these particles are very difficult to reduce in number and highly inflammatory to our blood vessels.
This study adds to the existing evidence of the heart benefits of monounsaturated fats from healthy food sources. It also demonstrates in a well-performed study design that the food source matters, and cannot always be replicated in a supplement or an extract. Finally, it provides a great option for people with high cholesterol who cannot tolerate a statin drug or are in an early stage of disease management in which their doctor is working with them to adopt lifestyle changes.
Clearly, there are a few additional things to consider. First, because avocados are calorie dense, you should eat them in moderation to avoid weight gain. Next, people with latex allergies may develop similar allergy symptoms when eating avocados. Finally, if you are allergic to avocados, there are other foods rich in monounsaturated fats, nuts for example.

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