Cholesterol-lowering landmark diet study: an interview with David Jenkins, M.D

David Jenkins

For people with high cholesterol levels, the idea of popping a pill and forgetting the problem may seem attractive, but the dangers of adverse effects and prohibitive costs often counteract any benefits.

A group of researchers, led by David Jenkins, M.D., set out to find an alternative way to lower cholesterol through the use of specific foods designed to lower serum cholesterol levels and reduce the risk of heart disease. Their findings--called the Portfolio study--are a landmark in cholesterol management.

Q. What is the Portfolio study?

A. The significance of the Portfolio study is that, for the first time, we have taken four groups of foods for which there is approval by the Food and Drug Administration (FDA) for a health claim for a reduced risk of heart disease because these foods lower serum cholesterol levels. The difference is that we've put them all together in one diet. You might ask, 'Do all of their effects just cancel out? Are you left with just the effect of the best of them, and do the rest of them become obscured?'

We also directly compared these foods with statin drugs. The four components that we used were (1) almonds, (2) soy foods (soy milk, soyburgers, and "hot dogs") (3) sticky (viscous) fiber (including oats, barley, psyllium, okra, and eggplant), and (4) a plant sterol-enriched margarine (the sterols tend to block cholesterol absorption in the gut).

The viscous fibers tend to wash out the products of cholesterol metabolism--the bile acid in the feces. The soy protein tends to reduce cholesterol synthesis when you compare it with animal proteins. Finally, the almond is a combination of all these things. It's a vegetable protein, the right sort of fat, some plant sterol, and tends to be a mini-Portfolio in itself.

We combined these foods in the same diet, along with other foods like fruits and vegetables, and then studied people after a month on one of these diets--either the Portfolio diet or a very good low-fat, low-cholesterol diet, or a low-fat, low-cholesterol diet with a statin drug.

Q. Was the Portfolio diet a vegan diet (no animal foods)?

A. Yes. The other was lacto-ovo vegetarian. It was very low in saturated fat because we used skim milk products and products like Egg Beaters[R] and that sort of thing.

Q. Have any of these foods that are said to lower the risk of heart disease ever been tested before?

A. They have been tested individually many times, and we were among those who tested them in the earlier days to establish their efficacy and effectiveness. The FDA has given them health claim status, so we do know what the amounts are that can give you a health claim on your package. In general, we used amounts that were either equal to, or just above, the amounts advocated by the FDA for a health claim.

Q. Were all of the people in the study meat eaters?

A. I think that for probably 90 percent of them, this was a new type of diet; some of them would have been on strict diets before but on not this particular diet.

Q. What is C-reactive protein?

A. C-reactive protein (CRP) is a marker of inflammation in the blood. If CRP levels are low, not much inflammation is going on. If they are high, there is some inflammation going on. The inflammation can be anywhere. People with high levels of this marker in their blood have an increased risk of heart disease. It is like cholesterol; you want to lower it.

Q. Did the diet affect the C-reactive protein?

A. It lowered CRP levels to the same extent that statin drugs are known to lower CRP levels.

Q. What are triglycerides?

A. Triglycerides are fats that are similar to cholesterol, and they are sometimes called "grease." They are the fat that is transported in the largest quantity in the blood and that is formed in your fat stores.

Q. Did the diet affect triglyceride levels?

A. The diet tended to reduce them, although the effects were not dramatic.

Q. What is cholesterol?

A. Cholesterol is a component of cell membranes. It is a fatty type of material. The importance of cholesterol is that it can build up in cells and it can certainly--if it is circulating in higher levels in the blood--wind up in the arterial lining. It is a bit like calcium in hard water. It can accumulate in certain places, especially the coronary arteries.

Cholesterol can form plaques. Sometimes these plaques rupture, and a clot forms on them. Such a clot is called a thrombosis. The thrombosis blocks the blood vessel, which is already narrowed by the cholesterol plaque. So one way or the other, cholesterol in the wrong place is not so good for you because you can get a heart attack, depending on how large the clot is.

Q. What are the positive aspects of cholesterol?

A. Cholesterol also "proofs" membranes; if you have a cell wall, it helps to make it "waterproof" and maintains its structure.

Q. Does the body produce its own cholesterol?

A. The body synthesizes most of the cholesterol. We can synthesize more cholesterol than most people eat, especially if we are genetically programmed to do so.

Q. To what extent are genetic factors responsible for high cholesterol?

A. Genetic factors are probably--100 percent or 90 percent--responsible for high cholesterol levels, certainly when you are talking about high cholesterol, as opposed to marginally raised cholesterol. I think that lifestyle is still a key element, because we haven't changed our genes and yet people were not dying of heart disease in bygone eras. So, something has happened to our lifestyle, and I consider eating and exercise patterns as being responsible for a large percentage of heart attacks in those people who are genetically predisposed to a heart attack.

So, you have a predisposition, but you may be perfectly fine, provided that you do not have the wrong lifestyle.

Q. So your lifestyle could tip you over the edge?

A. Absolutely. It is not that it tips you over the edge; rather, it pushes you a long way toward the edge and then tips you. It is not as if you were on the brink; it has to push a long way.

I think today we have got this global epidemic of obesity, and I think that a lot of that is due to diet and lifestyle. I think that people have only got to look at their work program and the fact that they have little time to go out and exercise. They do not necessarily eat the best food, and they spend a lot of time in front of word processors. As e-mail and the electronic age become more of the norm, it may become more of a problem with children when they start using the Internet and doing a lot of homework at night instead of playing out in a field or in a park. I think that the chances of being abducted by evildoers or aliens is far less of a risk than of their dying prematurely as a result of not being able to go outside and being able to play.

Our Portfolio is a dietary one right now, but obviously it has to include other factors such as exercise and stress reduction--the sort of thing that Dean Omish has been so successful with.

Q. What is high-density lipoprotein (HDL) cholesterol?

A. HDL is called the healthy cholesterol carrier. The lipoproteins are like boats. The low-density lipoprotein-cholesterol (LDL or "bad" cholesterol) carries cholesterol to the arteries and the tissue from the liver. The "good" (HDL) cholesterol is carried back from the tissues, where it can be excreted in the bile and into the feces.

That is what makes HDL cholesterol healthy; the more boats you have coming back, the better you are. The more boats you have going away, the worse off you are.

Q. So the difference between HDL and LDL is direction?

A. Right. Well, they are chemically somewhat different, but from the layperson's point of view, they are carried in different directions.

Q. If a person has a cholesterol level of 250 mg./dl, with a high level of HDL, is that still considered unhealthy?

A. Well, this is probably not too bad. Especially if a person has an HDL level of 50 to 60.

Q. What if the person has a cholesterol level of 150 but with a high level of LDL?

A. If you have a total level of 150, then you do not have much room for anything else, so I would not worry. It would be difficult to get up to an LDL level of 160, which is where we are really concerned. If you have a very high LDL and a low total cholesterol level, you probably do not have much HDL cholesterol. You have to watch out if you start raising your total cholesterol with that low HDL cholesterol, then you are not going to be in very good shape. You are OK as long as your total cholesterol counts remains low.

Q. If a person is following a low-cholesterol diet, would the food help remove the cholesterol or would the body burn the excess off?

A. The body doesn't really burn cholesterol, unfortunately. You either tend not to synthesize it, or you lose it as cholesterol in the bile or as bile acids in the bile, which goes into the feces. If you have a lot of viscous fiber there and a lot of plant sterol, you can get rid of that cholesterol.

Q. Does a lower cholesterol level mean a lower risk of heart disease?

A. Yes.

Q. Automatically?

A. If it's a low LDL to HDL cholesterol ratio, then yes.

Q. Do you think that most people who have grown up with a meat-based diet would have trouble sticking to the low-cholesterol diet?

A. You can never tell. We have brought people in who have eaten mostly meat and potatoes and the occasional vegetable and then changed to the Portfolio diet and accepted it. We have taken people who we thought were eating fairly healthfully, and they found the diet difficult. It is difficult for us to tell. I can only say that when we have taken a group of 30 people who were initially enthusiastic, they stuck with us for these particular studies. Then we stopped giving the support of giving them food and told them to fend for themselves.

Probably about 30 percent have done extremely well. Another 30 percent do not do that well. As for the other 30 percent, you are not sure that you are making much of an impact at all. Compliance, I think, is sometimes quite low; thus, in an enthusiastic group, about a third will do extremely well.

When you think that raised cholesterol is so prevalent, that [some doctors are] advocating that possibly 50 percent of all middle-aged men and postmenopausal women might benefit from taking a drug to lower their cholesterol, obviously I think that there is a lot of room for diet.

Q. What are statin drugs?

A. Statin drugs inhibit the key enzyme in the liver in cholesterol synthesis. It is as simple as that--these drugs just cut cholesterol production off at the knees, as it were, and no cholesterol is produced.

Q. Are statin drugs dangerous?

A. Can you drive cholesterol levels down too low for bodily functions? That is a debatable point. Some people say that if you have very low cholesterol, you may have an increased risk of hemorrhagic stroke. That is one potential problem, but it has not been clearly shown--certainly not with the statin drugs.

Q. How do almonds affect cholesterol levels in the body?

A. As I said earlier, they seem to be a mini-Portfolio. They have vegetable proteins--almonds, of all the nuts, have [among] the highest protein content per calorie--that tend to lower cholesterol levels. They are also rich sources of monounsaturated fat, which is popular as olive oil in the Mediterranean diet. They contain the plant sterols in their oils, so that may give an additional cholesterol-lowering benefit. They also have other phytonutrients, which may be antioxidants, and they may have protective roles. Jeff Bloomberg at Tufts University has been looking at this sort of thing.

Q. Can any adverse effects come from eating too many almonds?

A. I cannot think of any. Some people are sensitive to various foods, and nuts are no exception. Even people who have mild allergies have had no sort of allergic response to almonds in the way one would, say, to peanuts. We have come across a few people over the years who have had so-called sensitivities to almonds, but nothing of any great extent, even though we have told them that--officially--they probably shouldn't eat northern tree nuts and they may have to stay away from things like Granny Smith apples, which often tend to go along with this. If they have these on occasion, it doesn't seem to hurt them. We have never come close to anything like the peanut's life-and-death effects.

Q. The Nutrition Facts for almonds list a high percentage of the Recommended Daily Allowance for fat. If you were to eat too many almonds, would that be bad for you?

A. It is good fat, that's the beauty of it. It is monounsaturated fat, and you are doing what people might do in the Mediterranean area with olives.

Dietary Patterns Affect Long-Term Weight Gain

Can single nutrients, such as fats, proteins, and carbohydrates, provide an answer to the weight gained over time by many adults? Not necessarily, according to researchers at the Jean Mayer U.S.D.A. Human Nutrition Research Center on Aging at Tufts University.

Lead author R K. Newby. Ph.D., recently examined how dietary patterns, in contrast to a single nutrient, contribute to weight gain. Because food is usually a combination of nutrients, the investigators suggest that studying people's natural eating behavior might be more helpful in understanding obesity and controlling weight gain.

The researchers evaluated the dietary patterns of almost 500 men and women over time to better understand the diet-obesity relationship. They used several technical measures to predict weight change, such as body mass index and waist circumference. Using the participants' diet records, the team derived five dietary patterns. Each participant was placed into one pattern type, according to the percentage of energy intake from selected food categories.

The researchers found differences in the amount of food people ate across all five dietary patterns, with the greatest contributors of calories being from foods such as white bread, alcohol, and sweets.

Not surprisingly, of the five patterns, the smallest changes were seen in participants consuming the "healthful" dietary pattern, which included more fruit, high-fiber cereal, and less fast food, non-diet soda, and salty snacks.

Q. What is the best form of almonds to eat: raw, dry-roasted, roasted in oil, or almond butter?

A. I would not roast them in oil because you do not need the extra oil, which may be hydrogenated. You have to be careful of that. We gave our people raw almonds. Gene Spiller in California has shown that there seems to be no difference between raw almonds and dry roasted almonds, so those seem to be good alternatives.

Although we have not used almond butter, Gene showed that it tends to be extremely good for raising HDL levels. It might not be as good as the whole almond, but it certainly raises the good cholesterol and tends to lower the bad. That sort of fat, the monounsaturated, gives a favorable profile.

Q. How does soy lower cholesterol?

A. Soy seems to inhibit cholesterol synthesis in the liver and regulates the receptor that takes up cholesterol level from the blood.

Q. What is the best way to eat soy?

A. I think that tofu (bean curd) is an excellent way to go, or soy protein isolate in simulated meat products, especially for people who eat meat. We fed our patients soy protein isolate in hot dogs, hamburgers, "sausage" links, and cold cuts. There are many ways to wean meat eaters from meat, such as using soy products in the same sort of meal setting, with similar tastes.

Q. Even if a soy product is in the frozen food section of the supermarket, is it still good for you?

A. Absolutely.

Q. The FDA recommends 25 grams of soy protein a day. Is this an appropriate amount?

A. I think that it is a modest amount. Our people found that if the participants were really interested in doing this, it was easier to have soy milk, soyburgers, and soy hot dogs and to get well above that into a range where people can be even more assured of seeing a cholesterol reduction.

Q. How do oats lower cholesterol?

A. Oats have the sticky (beta glucan) fibers, and they, along with the other viscous fibers, tend to thicken the inside of the intestine and stop us from taking up bile acids. Those bile acids are made from cholesterol. If you deprive the body of bile acids, it automatically has to grab some of the cholesterol in the blood and use it to replenish the bile acid pool. Obviously, with the increased uptake of cholesterol from the blood, the serum cholesterol levels fall.

Q. What is the best way to eat oats?

A. Well, we like oats. Oat bran is actually the concentrated form that we like to see people eat. Oats can be eaten hot as an oatmeal porridge, or they can be cold, as in a sort of mueslix form. If the oats are eaten cold, we suggest that you put soy milk on them, perhaps some chopped fruit, and have some cracked or crushed almonds with them. If you mix that up, it makes a very pleasant cold breakfast cereal or dessert. During cold weather, you would probably welcome having a lot of oatmeal and a little brown sugar. Again, you can have some cracked almonds and a banana or something on top of that.

Q. Is instant oatmeal on the same level?

A. Instant oatmeal is good, but it does not have quite as much fiber as we would advocate.

Q. A study in the British Medical Journal seems to indicate that dietary cholesterol has no real impact on health. What is your opinion?

A. Dietary cholesterol does influence serum cholesterol. If serum cholesterol is a risk factor for heart disease, what you eat deserves attention.

Q. Is the methodology in that study flawed, or have we just been misled about cholesterol?

A. I think that some studies, from time to time, have not been as bullish in terms of the effects of total cholesterol on heart disease risk. That is why we are now talking about LDL cholesterol and HDL cholesterol; we are trying to refine our tools for detecting risk.

I think that most people would still say that LDL cholesterol was a risk factor and that probably a better indicator is the ratio of LDL to total cholesterol. However, we do not want to get fixated on cholesterol alone, and that is why we have C-reactive protein and a number of other things that are worth focusing on.

Q. So is the British Medical Journal study just a different way of looking at the big picture?

A. I think so. That depends on which way you look at the cholesterols in the blood. People tend to want one test, and that is all they want.

Q. How much iron is in the Portfolio diet?

A. A fair amount of green vegetables have iron, so do beans. I think that we had our dietitians look over it, and it seemed to be satisfactory.

Q. Is there too much iron in a typical American diet?

A. There is some evidence that people who have lower iron stores live longer. It is a case of keeping it in its place and having the right balance. I think that you have enough iron in the body as long as your hemoglobin and red blood cells are OK.

Q. Is there any way to follow up on the people in the Portfolio study in future years to see whether they have stuck with the diet?

A. You've hit the nail on the head, that's exactly what we are doing right now. We have taken them off the diet, told them to have a sort of holiday, and now we have restarted them under their own steam. We are not providing any food or anything. We are watching them and giving them advice.

Q. Is this for the Portfolio IV study?

A. That's right. The Portfolio IV is a longer-term study.

Q. Can the diet be used to treat other health problems?

A. We think that one or two participants showed a tendency toward diabetes impaired fasting blood glucose levels. Their glucose levels have come down quite nicely on the diet, The foods in the diet are also low glycemic index.

Q. Was the vegan diet the one with the best results in the study?

A. It was. yes. The other good one was the lacto-ovo-vegetarian. David Jenkins. M.D. is currently a professor in both the Departments of Medicine and Nutritional Sciences. Faculty of Medicine. University of Toronto. a staff physician in the Division of Endocrinology and Metabolism and the Director of the Clinical Nutrition and Risk Factor Modification Center. St. Michael's Hospital. He has received National and International awards in recognition of his contribution to nutrition research.

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