Not all fats are bad --  load up on the good fats that could prevent heart disease, cancer, and more.

Monounsaturated fats

     Are liquid at room temperature.
     May help lower your total blood cholesterol level.
     Are thought to raise HDL (good) cholesterol and lower LDL (bad) cholesterol levels.
     Are found in greatest abundance in canola, olive, and peanut oils.

Polyunsaturated fats

     Are liquid at room temperature.
     Are found mainly in vegetable oils, except tropical oils (coconut, palm, and palm kernel oils).
     Are thought to lower both HDL (good) and LDL (bad) cholesterol.
     Have been implicated in colon cancer.

Saturated fats

     Are usually solid at room temperature.
     Are found in many animal products and tropical oils.
     Cause the total blood cholesterol level to rise.

So what do you do with these facts?  First, keep your calories from fat to 30 percent or less of your total calories. Less than a third of the fats you do eat should come from polyunsaturated fats. And less than another third of the fats you do eat may be
saturated. The remaining calories should be from monounsaturated fat.  To accomplish this, just simply eat more chicken and fish and less pork and beef. And choose oils over solid fats.

A good oil can be turned saturated.  Have you ever wondered how corn oil can turn into corn oil margarine? Or other vegetable oils become shortening? The process is called hydrogenation.  Hydrogenation is a process of changing a liquid oil into a hard or solid fat. Partial hydrogenation only changes some of the individual fat molecules from polyunsaturated to monounsaturated. More hydrogenation will then turn more polyunsaturated fats to monounsaturated fat or change monounsaturated fats to saturated fats. When enough have been changed, the oil becomes "visible" as a hard fat.  Food companies hydrogenate oils either to improve their shelf life or to make an oil into margarine or shortening. When oils are fully hydrogenated, the process turns them into saturated fats...the fat to be avoided.

The oil that may have been heart-healthy in the beginning, may then be no better than lard--so watch out.

Here are brief definitions of the key terms important to an understanding of the role of fat in the diet.

Cholesterol is a chemical compound manufactured in the body. It is used to build cell membranes and brain and nerve tissues.  Cholesterol also helps the body make steroid hormones and bile acids.

Dietary cholesterol is cholesterol found in animal products that are part of the human diet.  Egg yolks, liver, meat, some shellfish, and whole-milk dairy products are all sources of dietary cholesterol.

Fatty acid is a molecule composed mostly of carbon and hydrogen atoms.  Fatty acids are the building blocks of fats.

Fat is a chemical compound containing one or more fatty acids. Fat is one of the three main constituents of food (the others are protein and carbohydrate). It is also the principal form in which energy is stored in the body.

Hydrogenated fat is a fat that has been chemically altered by the addition of hydrogen atoms (see trans fatty acid). Vegetable shortening and margarine are hydrogenated fats.

Lipid is a chemical compound characterized by the fact that it is insoluble in water.  Both fat and cholesterol are members of the lipid family.

Lipoprotein is a chemical compound made of fat and protein. Lipoproteins that have more fat than protein are called low-density lipoproteins (LDLs). Lipoproteins that have more protein than fat are called high-density lipoproteins (HDLs).  Lipoproteins are found in the blood, where their main function is to carry cholesterol.

Monounsaturated fatty acid is a fatty acid that is missing one pair of hydrogen atoms in the middle of the molecule. The gap is called an "unsaturation." Monounsaturated fatty acids are found mostly in plant and sea foods. Olive oil and canola oil are high in monounsaturated fatty acids.  Monounsaturated fatty acids tend to lower levels of LDL-cholesterol in the blood.

Polyunsaturated fatty acid is a fatty acid that is missing more than one pair of hydrogen atoms.  Polyunsaturated fatty acids are mostly found in plant and sea foods.  Safflower oil and corn oil are high in polyunsaturated fatty acids.  Polyunsaturated fatty acids tend to lower levels of both HDL-cholesterol and LDL-cholesterol in the blood.

Saturated fatty acid is a fatty acid that has the maximum possible number of hydrogen atoms attached to every carbon atom. It is said to be "saturated" with hydrogen atoms. Saturated fatty acids are mostly found in animal products such as meat and whole milk. Butter and lard are high in saturated fatty acids.  Saturated fatty acids tend to raise levels of LDL-cholesterol ("bad" cholesterol) in the blood. Elevated  levels of LDL-cholesterol are associated with heart disease.

Trans fatty acid is a polyunsaturated fatty acid in which some of the missing hydrogen atoms have been put back in a chemical process called hydrogenation, resulting in "straighter" fatty acids that solidify at higher temperatures. Trans fatty acids are under study to determine their effects on cholesterol.
 

Specifically, here are the good fats you need ...

• omega-3 fats -- from foods such as salmon, flaxseed, and walnuts; and
• monounsaturated fats -- from olive oil, almonds, and avocados.

• help prevent HEART ATTACKS by helping the heart muscles to beat in a steady rhythm;
• help fight depression - nerve cell membranes in the brain are composed mainly of DHA at the point where one cell 'talks' to another;
• help tone down rheumatoid arthritis pain and severe menstrual cramps because they dampen out-of-control inflammatory processes.

EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the two principal fatty acids found in fish and are known as omega-3 fatty acids. DHA can also be obtained from other marine sources, such as algae (algal oil).  EPA and DHA are polyunsaturated fats ("good" fats, as opposed to saturated fats which increase the risk of heart disease.) The body has a limited ability to manufacture both EPA and DHA by converting the essential fatty acid, alpha-linolenic acid (ALA) — found in flaxseed oil, canola oil or walnuts.  But this ability is lessened if the diet is too high in omega-6 fatty acids from vegetable oils from corn, sunflower, soybean or safflower.

Omega-3 fatty acids have been most widely studied regarding their effects on cardiovascular health.  It's been discovered that EPA and DHA may help prevent heart disease and atherosclerosis by lowering triglyceride levels, raising HDL ("good") cholesterol and, possibly "thinning" the blood. They may also reduce the risk of one type of stroke and cardiac arrythmias. The U.S. Food and Drug Administration (FDA) now allows products containing omega-3 fatty acids to state: "The scientific evidence about whether omega-3 fatty acids may reduce the risk of coronary heart disease is suggestive, but not conclusive."

By decreasing inflammation, EPA and DHA can also reduce the pain of rheumatoid arthritis, although it appears to be most useful in the early stages of the disease and it is not clear if it affects the progression of the disease itself. Omega-3's may also reduce the pain associated with menstrual cramps.

Fish oils may also be useful in treating a host of conditions including bipolar (manic-depressive) disorder, Raynaud's phenomenon (abnormal sensitivity of hands and feet to cold), lupus, IgA nephropathy, kidney stones, chronic fatigue syndrome, Crohn's disease, cystic fibrosis, and ulcerative colitis. Omega-3's may also reduce the risk of premature delivery in pregnant women and prostate cancer in men. EPA specifically may be helpful for schizophrenia, while DHA may be more helpful in reducing high blood pressure. DHA is also important for normal development and functioning of the brain and retina in the fetus and in infants. This may explain the observation that the infants of women who consume fish during pregnancy and while nursing tend to have better vision. Consequently, DHA is often added to formula for premature infants and is also added to regular infant formulas in some other countries. DHA may be helpful in the treatment of disorders such as attention deficit disorders, dyslexia, and cognitive impairment and dementia.

Moreover, experts now believe that the American diet contains too little omega-3 fatty acids and too much omega-6 fatty acids, which interferes with the body's production of DHA and EPA and may contribute to an increased risk of heart disease and cancer. While the ratio of omega-6's to omega-3's in the American diet is believed to be as high as 14:1 (14 grams of omega 6's for every gram of omega-3's), a ratio of no more than 5:1 (5 grams of omega-6's for every 1 gram of omega-3) is recommended.

Because omega-3 fatty acids are obtained from natural sources, levels in supplements can vary, depending on the source and method of processing. Contamination has also been an issue, because fish can accumulate toxins such as mercury, dioxins, and PCBs. The freshness of the oil is also an important consideration because rancid fish oils have an extremely unpleasant odor and may not be as effective. Neither the FDA nor any other federal or state agency routinely tests fish or marine oil supplements for quality prior to sale.

ConsumerLabpurchased and tested a total of 20 supplements, 19 of which were EPA/DHA combination products made from fish oils and one of which was a DHA-only product made from algal oil.  Products were selected to represent the majority of those commonly sold and/or available nationally in the U.S. ConsumerLab.com purchased products on the open market through retail stores, on-line retailers, and direct sales or multi-level marketing companies. Products were not accepted directly from manufacturers.

Omega-3 marine oil products were tested for amounts of EPA and DHA, peroxide levels (which indicate spoilage) and potential contamination with  mercury. All products were analyzed for their EPA and DHA components by gas chromatography utilizing a modified AOAC (Association of Official Analytical Chemists, International) Official Method 991.39. Products not passing this initial assay for EPA and DHA were tested in a third independent laboratory utilizing modified AOCS methods for fatty acid determination. Peroxide values were analyzed using AOCS (American Oil Chemists Society) Methods CD 8-53 & 12-57. Products were tested for total mercury using a Cold Vapor Atomic Absorption method.

To achieve a "Pass" in the testing, a product had to:

    1) meet 100% of label claims for EPA and DHA — not to exceed 150% of claimed amount,
    2) have a peroxide value of no more than 10 meq/kg and 3) have a total mercury content of less than 100 parts per billion (ppb).

Six of the 20 products failed to pass the review due to inadequate amounts of the DHA, which ranged from 50% to 83% of the amounts stated on the labels. Two of these six products were also found to contain only 33% and 82%, respectively, of their labeled amounts of EPA. Interestingly, two of the products that failed made claims on their labels that their "potency" had been "tested" or "verified." By providing less than claimed levels of EPA and DHA, products may have reduced potency. For example, research has suggested that doses of about five grams of omega-3's a day may help protect arteries from clogging for people at high risk. If your supplement is providing less than the dose you expect (say, if you're aiming for five grams and actually get only two and a half), you may not be getting the protection you are hoping for.

The human body can't make Omega-3 fats -- there are, however, two sources:

1.  fish, such as salmon, mackerel, sardines, herring, anchovies, rainbow trout, bluefish, caviar, and white albacore
     tuna, have high EPA and DHA (it is recommended that you get at least 0.5 g of EPA and DHA) per day;

eat fish at least twice a week; a serving of salmon (about 3 oz) gives almost 2 g of DHA and EPA;

make tuna salad sandwiches (white albacore tuna in water has more omega-3s than light tuna) a 3 0z serving will give about 1 g of DHA and EPA;

one tablespoon of caviar has 1 g of omega-3.

2.  plant products, such as canola oil, flaxseed, flaxseed oil, walnuts, walnut oil, and dark green, leafy vegetables,
     have alpha-linolenic acid (ALA), which are partially converted to the much more powerful EPA and DHA (it is
     recommended that you get at least 1.25 g per day).

• use canola oil for baking and cooking
• buy mayo, margarine, and salad dressing made with canola oil - one tbsp of canola oil has 1.3 g of ALA;
• make salad dressing from walnut oil and red wine vinegar - one tbsp of walnut oil has 1.4 g of ALA;
• sprinkle ground flaxseed (can be bought at health and natural food stores) on cereal or yogurt - flaxseed is the plant with the highest ALA levels by far and one tbsp of flaxseed has 2.2 g of ALA;

 

It will perhaps be surprising to many people that animal and human tissues are also rich in monounsaturated fatty acids, particularly oleic acid. For instance, butterfat, beef tallow, and lard may contain as much as 30% of their total fats as oleic acid. However, they are labeled as saturated fats because that's the fat that occurs in the greatest amount.  This contrasts with corn, safflower, sunflower, and soybean oil where oleic acid levels rarely exceed 25% (although the levels may be higher in genetically engineered varieties).

However, the more desirable monounsarated fats are those found in olive, hazelnut, and avocado oils, and canola, whose oleic acid levels can be as high as 70% or more, that's why they are labeled as monounsaturated fats, because that's the fat that occurs in the greatest amount.  In olive oil (and in other plant oils), the monounsaturated fatty acids are the fatty components of triglycerides which make up >98% of the oil. There are many different monounsaturated fatty acids in nature, but the major monounsaturated fatty acid in olive oil (and in most other animal or plants) is oleic acid. Oleic acid is made up of a chain of 18 carbon atoms, much like a chain of beads, with 34 hydrogen atoms and two oxygen atoms. It is termed a monounsaturated fatty acid because oleic acid has two less than the theoretical number of hydrogen atoms possible in a structure with 18 carbon atoms ie 34 not 36. If there were 36 hydrogen atoms associated with 18 carbon atoms then the substance would be termed a "saturated" fatty acid (the chemical name of this structure is stearic acid, one of the major saturated fats found in animals and plants).

If the two hydrogens were derived from adjoining carbon atoms then a "double bond" is formed. These adjoining carbon atoms which comprise the double bond are much more reactive, ie, they are much more likely to be able to interact with other substances. In addition, in the same way as a kink in a garden hose changes the shape of the hose, the loss of the two hydrogens changes the three dimensional shape of the fatty acid. With the loss of two hydrogens from adjoining carbon atoms, two quite different three dimensional structures are possible. These are termed "cis" or "trans". Oleic acid is a "cis" fatty acid and most naturally occurring monounsaturated fatty acids are cis fatty acids. If the other three dimensional shape were assumed the fatty acid would be termed a "trans" fatty acid, and the chemical term for this particular fatty acid is "elaidic acid". Elaidic acid occurs naturally in animals and plants but in much smaller amounts than oleic acid. However, under certain conditions, there may be a conversion of a cis fatty acid to its corresponding trans form. Remember, the only thing that has changed is the three dimensional shape. There are exactly the same number of carbon, hydrogen and oxygen atoms, but the differences in properties can be quite significant.

While low-fat diets may undesirably reduce HDL levels, incorporating olive and avocado oils into the diet significantly counteracts the HDL-lowering effect.  This confirms the Mediterranean diet's benefits.

The Mediterranean diet refers to the typical diet of Mediterranean people such as those living in the southern European countries.
This diet was studied in heart attack survivors. Compared to a typical diet, the Mediterranean diet led to a 50% to 70% lower risk of
recurrent heart disease. This diet is consistent with the American Heart Association recommendations above as well as the specific
dietary tips in the next section of this page.

The Mediterranean diet emphasizes fruits, vegetables, grains such as bread and cereal, potatoes, beans, nuts, seeds and fish. Eggs
and red meat are avoided. Poultry is consumed in low to moderate amounts. Olive oil and canola oil are the preferentially used oils.
Instead of butter, margarine with low saturated fat but containing extra fats known as linoleic and alpha-linolenic acids is used. Wine
is allowed with meals in moderation.

However, too much total fat -- more than about 25% calories -- is still a bad idea.  You want to limit saturated fats and trans fats, and curb omega-6 fats, such as corn oil.

A Consumer's Guide to Fats, by Eleanor Mayfield.  This article originally appeared in the May 1994 FDA Consumer. The version below is from a reprint of the original article and contains revisions made in November 1994, January 1996, and January 1999.
 

Once upon a time, we didn't know anything about fat except that it made foods tastier. We cooked our food in lard or shortening. We spread butter on our breakfast toast and plopped sour cream on our baked potatoes.   Farmers bred their animals to produce milk with high butterfat content and meat "marbled" with fat because that was what most people wanted to eat. But ever since word got out that diets high in fat are related to heart disease, things have become more complicated. Experts tell us there are several different kinds of fat, some of them worse for us than others. In addition to saturated, monounsaturated and polyunsaturated fats, there are triglycerides, trans fatty acids, and omega-3 and omega 6 fatty acids.  Most people have learned something about cholesterol, and many of us have been to the doctor for a blood test to learn our cholesterol "number." Now, however, it turns out that there's more than one kind of cholesterol, too. Almost every day there are newspaper reports of new studies or recommendations about what to eat or what not to eat: Lard is bad, olive oil is  good, margarine is better for you than butter--then again, maybe it's not. Amid the welter of confusing terms and conflicting details, consumers are often baffled about how to improve their diets. Clearly though consumers are interested in obtaining this information. In a poll conducted by Nielsen marketing Research, people were asked to select the

food qualities that were "very important" to them, and knowing which foods were low in fat and cholesterol ranked highest: FDA regulations enable consumers to see clearly on a food product's label how  much and what kind of fat the product contains. (See "A Little 'Lite' Reading" in  the June 1993 FDA Consumer.) Understanding the terms used to discuss fat is crucial if you want to make sure your diet is within recommended guidelines. (See "Fat Words.") Fats and Fatty Acids Fats are a group of chemical compounds that contain fatty acids.  Energy is stored in the body mostly in the form of fat. Fat is needed in the diet to supply essential fatty acids, substances essential for growth but not produced by the body itself. There are three main types of fatty acids: saturated, monounsaturated and polyunsaturated. All fatty acids are molecules composed mostly of carbonand hydrogen atoms. A saturated fatty acid has the maximum possible number of hydrogen atoms attached to every carbon atom. It is therefore said to be "saturated" with hydrogen atoms. Some fatty acids are missing one pair of hydrogen atoms in the middle of the molecule. This gap is called an "unsaturation" and the fatty acid is said to be mono- unsaturated" because it has one gap.  Fatty acids that are missing more than one pair of atoms are called

polyunsaturated."  Saturated fatty acids are mostly found in foods of animal origin.Monounsaturated and polyunsaturated fatty acids are mostly found in foods of plant origin and some seafoods.                                                                       Polyunsaturated fatty acids are of two kinds, omega-3 or omega-6. Scientists tell them apart by where in the molecule the "unsaturations," or missing hydrogen atoms, occur. Recently a new term has been added to the fat lexicon: trans fatty acids. These are byproducts of partial hydrogenation, a process in which some of the missinghydrogen atoms are put back into polyunsaturated fats.                                                                       Some of the hydrogenated fatty acids take on a "straighter" structure: these are the trans fatty acids.                                                                       "Hydrogenated vegetable oils,"such as vegetable shortening and margarine, are solid at room temperature because straightening fatty acids allow them to pack more tightly.                                                                       Cholesterol Cholesterol is sort of a "cousin" of fat. Both fat and cholesterol belong to a larger family of chemical compounds called lipids. All the cholesterol the body needs is made by the liver. It is used to build cell membranes and brain and nerve tissues. Cholesterol also helps the body produce steroid hormones needed for body regulation, including processing food, and bile acids needed for digestion.