By Christine Haran
People with elevated cholesterol have heard the mantra from their doctors: eat a healthy diet and exercise more, or you may up your risk of a heart attack. But as anyone who has struggled to lower their cholesterol through diet knows, it is no easy task. Cholesterol can be obtained when you eat foods high in cholesterol, but it is also made by the liver. Consequently, it has been thought that dietary changes could not lower cholesterol as effectively as the cholesterol-lowering medications known as statins. But a recent study that compares the two approaches shows that a diet that includes almonds and several other specific plant foods can lower cholesterol—specifically LDL, the "bad" cholesterol—as significantly as a leading cholesterol-lowering medication.
In the study, which was published in the July 23 issue of the Journal of the American Medical Association, researchers divided participants into three diet groups. One group ate a diet low in saturated fat, the second group received the same diet, along with a statin, and the third group ate a diet containing specific cholesterol-lowering foods. Below, lead researcher Cyril Kendall, PhD, a research associate in the department of nutritional science at the University of Toronto, discusses how diet can quickly and safely reduce cholesterol levels, and whether people can learn to stick with it.
Why did you and your colleagues decide to conduct this study?
There are a number of reasons. Obviously, heart disease is the number-one killer in North America. I think there's been a growing trend to treat the disease with drug therapy, and there is nothing wrong with this. The drugs are quite effective and work well, but if you look at the American Heart Association guidelines and the National Cholesterol Education Program (NCEP) guidelines, the first strategy for primary prevention of the disease is diet and other lifestyle modification.
We had some interest in looking at the evolution of the human diet. The thinking was that for much of our evolutionary development over the last 10 or 15 million years, we would have been predominantly vegetarian. And if you look at the great apes living presently, they are, for the most part, eating a vegetarian diet. So genetically we're designed for basically a fruit, nut and vegetable diet.
This led to a study that we conducted about three or four years ago looking at that sort of diet, a simian diet. We had about a 35 percent reduction in LDL cholesterol. So we knew the diet could achieve a much greater reduction than that which was generally recognized by health professionals.
The problem with a simian diet was that it's a full-time job. You were basically eating about 5.5 kilos of food a day, which took about eight hours a day, so for our modern-day lifestyle that's completely impractical. So what we wanted to do was take the four main components of that diet—vegetable proteins, plant sterols, almonds and soluble fibers—and put those into foods or into a diet that is better adapted to our modern lifestyle. So that's what we've done with the current portfolio diet, as we call it.
What did you study compare?
Our control diet was one that is low in saturated fat and dietary cholesterol. It has about seven servings of fruits and vegetables per day, which is what is recommended by American Heart Association and the NCEP for reducing the risk of heart disease.
We also fed that diet to our positive control, so that group had the very healthy diet, plus a statin. For our portfolio diet group, we took the NCEP diet as a template, but we increased the soluble fiber, soy and plant and vegetable proteins, almonds and plant sterols. Each of those four components has independently demonstrated 5 percent to 10 percent reductions in cholesterol in clinical studies. And the FDA now has health claims for each of those four components.
What did your study measure, and what kinds of reductions were seen?
Our primary outcome measure was LDL cholesterol, and that has been demonstrated quite consistently to be a risk factor for heart disease. We know that if you lower LDL cholesterol either through dietary means or through drug therapy, your risk of heart disease is greatly reduced.
In our statin group, which involved a low-dose, first-generation statin, we had a reduction in LDL of around 31 percent. The NCEP diet by itself had a reduction of around 10 percent, and then our portfolio diet had a reduction of 29 percent in LDL. So basically the portfolio diet and the statin achieved the same level of reduction.
We also looked at C-reactive protein (CRP), because it is an inflammatory biomarker. It has been demonstrated in some studies to increase risk for heart disease. We did see a nice reduction, and basically it was the same level of reduction achieved through statins.
Is there a certain group of those people who should still go on a statin?
What we were trying to demonstrate is the effectiveness of diet. I think that any dietary change that one does should be done in consultation with your physician. And if the physician thinks that medication is the best approach, then by all means discuss medication. Some people with very high cholesterol must be on a statin. I think that's very important. What we're trying to do is give people options.
Some of the super-statins are reporting reductions of around 50 percent in cholesterol. If an individual needs that level of reduction, then they should be on a statin. But it's also good to be on a healthy diet. That's not going to hurt people.
There are some potentially negative side effects with statins such as muscle aches and pains. Some people have liver trouble. So I think even if you can adapt some of these dietary factors into your daily eating pattern, maybe you can lower the dose of the statins somewhat and possibly reduce some of the potential negative side effects.
Do you think people can manage this diet on their own?
All of the three studies on this diet that we've conducted are tightly controlled studies, and that means that the subjects are basically eating the foods that we tell them to eat, and we are supplying most of those foods at this point. So under very controlled conditions, this diet is extremely effective.
A number of the subjects who have completed the study have continued purchasing the foods themselves and have apparently maintained that level of cholesterol reduction. This has not been closely monitored, however, and we are planning on running these kinds of studies very shortly.
Additionally, not everybody needs a 30 percent reduction in cholesterol. Others have mildly elevated cholesterol, and maybe they just need a 10 percent or 15 percent reduction. So maybe they can incorporate the almonds in their diet, or maybe they like the plant sterol margarine, or particular soluble fiber foods.
How quickly were the reductions seen?
The reduction in LDL was observed in two weeks. So you're seeing a very rapid reduction. You also see that type of reduction with a statin. The thing is, you have to maintain that diet. You don't stay on the diet for two weeks to get your cholesterol down and then go back to your old diet, because your LDL is going to shoot up just as rapidly.
Can you give examples of some of the cholesterol-lowering foods that were added to the diet?
The almonds were basically just raw almonds, and they were either eaten as a snack or put on salads or into different entrees. Some of the soluble fiber sources were oat bran. We also had different bean entrees, such as Mexican-style bean entrees or Indian curries with legumes, which are high in both vegetable protein and soluble fiber. Some vegetables that are high in soluble fiber are okra and eggplants.
In terms of the plant sterol, there is a plant sterol margarine known as ProActiv in the United States, and that was basically just used as the spread instead of butter or another type of margarine. And then the soy products were incorporated into some vegetable-based entrees. We also had soy burgers and hotdogs, cold cuts and soy milk.
What might be included in your follow-up studies?
The next stage in the testing for this research is to say, "Okay, can we give people dietary advice? Can we tell them to go out and can they purchase their own foods and survive on this diet happily for longer periods of time and still achieve the same level of reduction in cholesterol?" Those studies still have to be undertaken.
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