Fats and Cholesterol - The Good, The Bad, and The Healthy Diet levels and increased HDL levels.
"Eat a low-fat, low-cholesterol diet." Most of us have heard this simple recommendation so Dietary Fats and Heart Disease--Beyond the "30%" Recommendation
often over the past two decades that we can recite it in our sleep. Touted as a way to lose
weight and prevent cancer and heart disease, it's no wonder much of the nation - and food Many health agencies, including the American Dietetic Association, the American Diabetes
producers - hopped on board. Association, and the American Heart Association, once recommend limiting fat intake to 30% or
less of total daily calories as a means of preventing disease. Today, these recommendations
Unfortunately, this simple message is now largely out of date. Detailed research -much of it focus on limiting intake of saturated fat, and have relaxed a bit with regard to total fat
done at Harvard - shows that the total amount of fat in the diet, whether high or low, isn't intake. That's a move in the right direction, because there is no good evidence for any
really linked with disease. What really matters is the type of fat in the diet.(1) Bad fats particular "optimal" amount of total fat in a healthy diet.
increase the risk for certain diseases and good fats lower the risk. The key is to substitute
good fats for bad fats. The relation of fat intake to health is one of the areas that Harvard researchers have
examined in detail over the last 20 years in two large studies. The Nurses' Health Study and
And cholesterol in food? Although it is still important to limit the amount of cholesterol the Health Professionals Follow-up Study have found no link between the overall percentage of
your eat, especially if you have diabetes, dietary cholesterol isn't nearly the villain it's
calories from fat and any important health outcome, including cancer, heart disease, and weight
been portrayed to be. Cholesterol in the bloodstream is what's most important. High blood gain.
cholesterol levels greatly increase the risk for heart disease. But the average person makes
about 75% of blood cholesterol in his or her liver, while only about 25% is absorbed from food. What was important in these studies was the type of fat in the diet.(3) There are clear links
The biggest influence on blood cholesterol level is the mix of fats in the diet. between the different types of dietary fats and heart disease. Logically, most of the influence
that fat intake has on heart disease is due to its effect on blood cholesterol levels.
The Cholesterol--Heart Disease Connection
Ounce for ounce, trans fats are far worse than saturated fats when it comes to heart disease.
Cholesterol is a wax-like substance. The liver makes it and links it to carrier proteins The Nurses' Health Study found that replacing only 30 calories (7 grams) of carbohydrates every
called lipoproteins that let it dissolve in blood and be transported to all parts of the body. day with 30 calories (4 grams) of trans fats nearly doubled the risk for heart disease.(4)
Why? Cholesterol play essential roles in the formation of cell membranes, some hormones, and Saturated fats increased risk as well, but not nearly as much.
vitamin D.
For the good fats, there is consistent evidence that high intake of either monounsaturated or
Too much cholesterol in the blood, though, can lead to problems. In the 1960s and 70s, polyunsaturated fat lowers the risk for heart disease. In the Nurses' Health Study, replacing
scientists established a link between high blood cholesterol levels and heart disease. Deposits 80 calories of carbohydrates with 80 calories of either polyunsaturated or monounsaturated fats
of cholesterol can build up inside arteries. These deposits, called plaque, can narrow an lowered the risk for heart disease by about 30 to 40 percent.(3)
artery enough to slow or block blood flow. This narrowing process, called atherosclerosis,
commonly occurs in arteries that nourish the heart (the coronary arteries). When one or more Fish, an important source of the polyunsaturated fat known as omega-3 fatty acid, has received
sections of heart muscle fail to get enough blood, and thus the oxygen and nutrients they need, much attention in the past for its potential to lower heart disease risk. And there have been
the result may be the chest pain known as angina. In addition, plaque can rupture, causing some studies to back this up, although not all have shown consistent benefits. One large trial,
blood clots that may lead to heart attack, stroke, or sudden death. Fortunately, the buildup of however, found that by getting 1 gram per day of omega-3 fatty acids over a 3.5 year period,
cholesterol can be slowed, stopped, and even reversed. people who had survived a heart attack could lower their risk of dying from heart disease by 25
percent.(5) The study participants got their omega-3s from a capsule - getting a gram a day
Cholesterol-carrying lipoproteins play central roles in the development of atherosclerotic from fish would mean eating a serving a day of fatty fish, such as mackerel, salmon, sardines,
plaque and cardiovascular disease. The two main types of lipoproteins basically work in or swordfish.
opposite directions.
Eating fish may help prevent heart disease or deaths from heart disease in several ways. it
Low-density lipoproteins (LDL) carry cholesterol from the liver to the rest of the body. When may replace red meat or other less-healthy sources of protein. And the omega-3 fats in fish
there is too much LDL cholesterol in the blood, it can be deposited on the walls of the appear to protect the heart against the development of erratic and potentially deadly rhythm
coronary arteries. Because of this, LDL cholesterol is often referred to as the "bad" disturbances. Although more research is needed, adding fish to the diet may help protect you
cholesterol. from heart disease, and it doesn't have any known risks. The American Heart Association
currently recommends that everyone eat at least two servings of fish a week.(6)
High-density lipoproteins (HDL) carry cholesterol from the blood back to the liver, which
processes the cholesterol for elimination from the body. HDL makes it less likely that excess Dietary Fats and Cancer
cholesterol in the blood will be deposited in the coronary arteries, which is why HDL
cholesterol is often referred to as the "good" cholesterol. Heart disease is not the only condition that has been linked with fat intake. Researchers once
suspected an association between dietary fat and certain cancers. Here again, the type of fat
In general, the higher your LDL and the lower your HDL, the greater your risk for - and not the total amount - seemed to be most important.
atherosclerosis and heart disease.
Breast Cancer
For adults age 20 years or over, the latest guidelines from the National Cholesterol Education
Program recommend the following optimal levels: By the early 1980s, most nutrition experts believed that dietary fat was a major cause of
breast cancer.(7, 8) This thinking was largely based on international comparisons showing
* Total cholesterol less than 200 milligrams per deciliter (mg/dl) higher breast cancer rates in countries with higher per capita fat intake. But such comparisons
* HDL cholesterol levels greater than 40 mg/dl are very broad in nature. As more detailed studies were performed over the next couple of
* LDL cholesterol levels less than 100 mg/dl decades, the apparent link between total fat intake and breast cancer has faded.(9)
Dietary Fat, Dietary Cholesterol, and Blood Cholesterol Levels Many newer studies - including those by Harvard researchers - of different types of fat have
failed to find a link with breast cancer. However, some European studies have reported
One of the most important determinants of blood cholesterol level is fat in the diet - not suggestive findings of lower breast cancer risk among women with a high intake of
total fat, as mentioned already, but specific types of fat. Some types of fat are clearly good monounsaturated fats (mainly in the form of olive oil).(10, 11)
for cholesterol levels and others are clearly bad for them.
Colon Cancer
Cholesterol in food
As with breast cancer, international comparisons initially suggested an association between
While it is well known that high blood cholesterol levels are associated with an increased total dietary fat intake and colon cancer risk. But later studies contradicted these earlier
risk for heart disease, scientific studies have shown that there is only a weak relationship findings and revealed instead an association that was weak at best. Although fat intake doesn't
between the amount of cholesterol a person consumes and their blood cholesterol levels or risk seem to increase colon cancer risk, high consumption of red meat still does appear to do
for heart disease. For some people with high cholesterol, reducing the amount of cholesterol in so.(12)
the diet has a small but helpful impact on blood cholesterol levels. For others, the amount of
cholesterol eaten has little impact on the amount of cholesterol circulating in the blood. Prostate Cancer
In a study of over 80,000 female nurses, Harvard researchers actually found that increasing Although the exact connection between dietary fat and prostate cancer is far from clear, there
cholesterol intake by 200 mg for every 1000 calories in the diet (about an egg a day) did not is some evidence that diets high in animal fat and saturated fat increase prostate cancer
appreciably increase the risk for heart disease.(2) risk. However, some studies have also shown no association, while others have implicated
unsaturated fats. Clearly much more research is needed to clear up the exact links between
Eggs dietary fat and prostate cancer.
Long vilified by well-meaning doctors and scientists for their high cholesterol content, eggs Other Cancers
are now making a bit of a comeback. Recent research by Harvard investigators has shown that
moderate egg consumption--up to one a day--does not increase heart disease risk in healthy Preliminary research has also linked the intake of certain kinds fat with other cancers,
individuals.(2) While it's true that egg yolks have a lot of cholesterol--and, therefore may though much more research is needed to confirm these results. In the Nurses' Health Study,
slightly affect blood cholesterol levels--eggs also contain nutrients that may help lower the Harvard researchers found that a high intake of trans fats increased the risk for non-Hodgkin's
risk for heart disease, including protein, vitamins B12 and D, riboflavin, and folate. lymphoma and that a high saturated fat intake increased the risk for endometrial cancer.
So, when eaten in moderation, eggs can be part of a healthy diet. People with diabetes, Dietary Fat and Obesity
though, should probably limit themselves to no more than two or three eggs a week, as the
Nurses' Health Study found that for such individuals, an egg a day might increase the risk for It is a common belief that the more fat you eat, the more body fat you put on, and the more
heart disease. Similarly, people who have difficulty controlling their blood cholesterol may weight you gain. This belief has been bolstered by much of the nutrition advice given to people
also want to be cautious about eating egg yolks and choose foods made with egg whites instead. over the past decade, which has focused on lowering total fat intake while increasing
carbohydrate intake. But it isn't completely true, and the advice has been misguided. For
Dietary Fats example, while Americans have gradually decreased the proportion of calories they get from fat
over the last decade, rates of obesity have increased steeply.
The Bad Fats
Over the short term, following a low-fat diet does lead to weight loss. But so does following
Some fats are bad because they tend to worsen blood cholesterol levels. a high-fat, low-carbohydrate diet. Actually, almost any diet that helps you take in fewer
calories works over the short term. In other words, low-fat diets appear to offer no apparent
Saturated Fats advantages over diets with fat levels close to the national average.
Saturated fats are mainly animal fats. They are found in meat, seafood, whole-milk dairy Although more research is needed, a prudent recommendation for losing weight or maintain a
products (cheese, milk, and ice cream), poultry skin, and egg yolks. Some plant foods are also healthy weight is to be mindful of the amount of food you eat in relation to the amount of
high in saturated fats, including coconut and coconut oil, palm oil, and palm kernel oil. calories you burn in a day. Exercising regularly is especially beneficial.
Saturated fats raise total blood cholesterol levels more than dietary cholesterol because they
tend to boost both good HDL and bad LDL cholesterol. The net effect is negative, meaning it's The Bottom Line: Recommendations for Fat Intake
important to limit saturated fats.
Although the different types of fat have a varied - and admittedly confusing - effect on
Trans Fats health and disease, the basic message is simple: chuck out the bad fats and replace them with
good fats. Try to limit saturated fats in your diet and eliminate trans fats and replace them
Trans fatty acids are fats produced by heating liquid vegetable oils in the presence of with polyunsaturated and monounsaturated fats.
hydrogen. This process is known as hydrogenation. The more hydrogenated an oil is, the harder
it will be at room temperature. For example, a spreadable tub margarine is less hydrogenated The trickiest of these to attack are the trans fats. That's because they lurk in many
and so has fewer trans fats than a stick margarine. different types of foods and aren't always included on the food label. But as awareness about
trans fats increases, more "trans-fat" free products are becoming available. Now there's even a
Most of the trans fats in the American diet are found in commercially prepared baked goods, trans fat-free Crisco! Labeling of trans fat content has long been up to the food maker's
margarines, snack foods, and processed foods. Commercially prepared fried foods, like French discretion. However, a report on trans fats from the Institute of Medicine concluding that
fries and onion rings, also contain a good deal of trans fat. there is no safe level of trans fats in the diet (13) has finally prompted the Food and Drug
Administration to require that all Nutrition Facts food labels list trans fats by January 1,
Trans fats are even worse for cholesterol levels than saturated fats because they raise bad 2006. Some foods - mostly those that are trans-fat-free - already list trans fats. Until all
LDL and lower good HDL. While you should limit your intake of saturated fats, it is important foods do, it will take some detective work to determine if a food contains trans fats. Check
to eliminate trans fats from partially hydrogenated oils from your diet. the ingredient list for "hydrogenated oils." The higher up these are listed, the more trans
fats the food contains.
The Good Fats
Tips for lowering trans fat intake:
Some fats are good because they can improve blood cholesterol levels.
* Choose liquid vegetable oils or a soft tub margarine that is contains little or no trans
Unsaturated Fats--Polyunsaturated and Monounsaturated fats.
* Reduce intake of commercially prepared baked goods, snack foods, and processed foods,
Unsaturated fats are found in products derived from plant sources, such as vegetable oils, including fast foods. To be on the safe side, assume that all such produts contain trans fats
nuts, and seeds. There are two main categories: polyunsaturated fats (which are found in high unless they are labeled otherwise.
concentrations in sunflower, corn, and soybean oils) and monounsaturated fats (which are found * When foods containing hydrogenated or partially hydrogenated oils can't be avoided,
in high concentrations in canola, peanut, and olive oils). In studies in which polyunsaturated choose products that list the hydrogenated oils near the end of the ingredient list.
and monounsaturated fats were eaten in place of carbohydrates, these good fats decreased LDL