Dietary Fats

Fats and oils may well be the most important part of your daily diet. Over the past 20 years, there has been an explosion of research on the significance of fats in health and disease. There is considerable evidence that links certain fats with many of the most common forms of degenerative diseases afflicting society today, including cancer and heart disease. But it is fundamental to realize that not all fats are created equal. Simply put, there are actually “good” fats and “bad” fats—fats that support beneficial body processes and fats that have detrimental effects. Becoming familiar with different types of fats and oils will help you make informed, health-enhancing decisions.

In order to understand the subject, we need to start with some basic definitions. All fats are known as lipids, and the two words are often used interchangeably. Lipids include fats and oils (the difference between them is that fats are solid at room temperature, whereas oils are liquid), as well as fat-like substances that are greasy and waxy such as cholesterol. All lipids are insoluble in water and contain one or more fatty acids in their structure. Fatty acids are the basic units of all fats. The physical characteristics and nutritional activity of a fat depends on the kind of fatty acids it contains. A fat is classified as saturated, monounsaturated, or polyunsaturated according to the type of fatty acids that occurs in the greatest quantity.

Dietary fats are available primarily from two basic sources: animal and vegetable. Animal fats (butter and lard) are saturated and tend to be solid. Vegetable fats like olive oil (monounsaturated) and sesame oil (polyunsaturated) tend to be liquid.

Dietary fats serve many functions in the body. Perhaps the most important is structural—they are the major constituent of every cell membrane in the body. The membrane, or outer lining, of a cell determines what goes into and out of that cell like a gatekeeper. Therefore, fats are critical in the proper functioning of the cell.

The polyunsaturated and monounsaturated oils are more fluid and generally allow easier and healthier function. There are also some natural, unprocessed saturated fats that participate in many functions such as repair of gut cells and formation of healthy brain and nerve cells. These saturated fats are short- and medium-chain saturated fats like butter, ghee, and coconut oil.

Bad monounsaturated and polyunsaturated fats include those that undergo high-temperature (trans fats) processing, which alters their shape and changes their function, causing irregularities in the cell structure and changing the permeability of the cell membrane. Recent research has linked trans fats to certain cancers. Hydrogenated and partially hydrogenated saturated fats are also bad fats because they are sticky and tend to clump together, causing problems for cell health (see below).

There are two families of fats that are termed essential, meaning that the body cannot make them and they must be obtained from the diet. They are the omega-3 and omega-6 essential fatty acids (EFAs). These fats perform a crucial function by producing messengers called prostaglandins.

Prostaglandins are hormone-like substances that can be thought of as “master switches” that regulate and control almost all cellular activity. Examples of their work include controlling inflammation, blood pressure, and immune system activity. Omega-3 fats, for example, affect the balance of certain prostaglandins. The regulation of this balance is crucial for proper function. Under ideal circumstances, the diet supplies the appropriate ratio and amount of EFAs, resulting in a balance of prostaglandins.

EFAs are very important, but are, unfortunately, fragile and easily “deactivated.” The main processes that alter EFAs are heat, oxygenation, and hydrogenation. Oils can be exposed to high heat during processing and cooking. Oxygenation, a more subtle process, occurs when oils are exposed to air and light, such as when oils sit on grocery shelves. Hydrogenation occurs when hydrogen is bubbled through oils, as is done in the making of margarine. The process that is labeled “hydrogenated” or “partially hydrogenated” extends the shelf life of the oil and, as in the case of margarine, turns a liquid vegetable oil into one that is solid at room temperature.

There are two key detrimental effects that occur when EFAs undergo the above processes:

  • First, they can release what are called free radicals. Think of free radicals as particles zipping around cells looking to attach or “link” with just about anything. In doing so, they damage the other molecules in the cell and set off chain reactions producing other free radicals. Premature aging, heart disease, cancer, and other degenerative processes are the result of unbridled free radical activity.
  • Second, the beneficial natural oils actually change their molecular configuration or shape when processed, forming what are termed trans fatty acids. These fatty acids are biochemically different and are not able to fulfill the same function as the original oil. Unfortunately, they can still take the place of the biochemically active EFAs in cell membranes, acting to slow production of the beneficial prostaglandins. There is also some evidence to suggest that they may act like free radicals and promote tissue destruction.

A variety of dietary and lifestyle factors are known to interfere with proper EFA function. These include:

  • Hydrogenated or partially hydrogenated saturated fats
  • Trans fatty acids (found in starchy foods such as crisps, chips, and bread, as well as microwaved foods)
  • Alcohol
  • Refined sugar and flour
  • Pesticides and environmental pollutants such as lead and cadmium
  • Aspirin, acetaminophen, and other anti-inflammatory drugs
  • Cortisone found in topical creams, nasal sprays, and inhalers
  • X-rays

The American diet, full of processed foods, supplies a substantial amount of bad (trans and hydrogenated saturated) fats. Consuming the wrong types of fats, consuming altered good fats, or just not enough of the good fats can result in a myriad of health problems, including vascular damage, eczema, immune dysfunction, and slow wound healing. The consumption of good-quality EFAs and natural fats is crucial for optimal cellular function and health. To rephrase an old adage, your cells are what you eat.


  • For most people, total fat consumption should be about 20–30% of total calories. A 1,500-calorie diet should include no more than 35–50 grams of fat; a 2,000-calorie diet should include no more than 45­66 grams of fat; and a 2,500-calorie diet should include 55–83 grams of fat.
  • Eat at least half of your fat intake as essential unprocessed fats.
  • Cook with olive oil or small amounts of medium-chain, natural saturated fats/oils, like coconut oil. It is best to keep high-heat or deep frying to a minimum since EFAs are destroyed with cooking. When you do cook with oils, however, olive oil, a monounsaturated oil, and the medium-chain saturated fats/oils are more stable and don’t have the health risks associated with hydrogenated, processed saturated fats.
  • Add healthy monounsaturated and polyunsaturated fats to your foods. The best to use is cold-pressed extra-virgin olive oil, along with sesame (tahini), flax, walnut, almond, macadamia, and avocado oils.
  • Keep processed fats to a minimum. This includes margarine, processed baked goods, and chips—anything labeled “hydrogenated” or “partially hydrogenated.” These are unnatural, damaged fats and there is absolutely nothing good about them. If you have to choose between butter and margarine, choose butter (and use it sparingly). Smart Balance and Earth Balance are two newer margarines that contain healthier oils with no trans fats.
  • Keep saturated fat consumption to a minimum. Avoid fatty cuts of meat and items cooked or prepared with high amounts of saturated fats. Small amounts of the short- or medium-chain saturated fats, such as coconut oil, are acceptable.
  • Purchase good-quality oils. It is important that they be labeled “cold-pressed” so they are not exposed to high heat and chemical alteration. These oils should be kept in tinted, glass bottles with a tight lid, refrigerated, and not used for high-heat frying. Additionally, olive oil should be labeled “extra virgin” or “first pressing.”