It’s not as simple as saying all fats are bad, scientists say, because some of them are critically important. It’s certainly not an endorsement of stuffing yourself with ice cream and deep-fried chicken. And if you aren’t planning your diet fairly carefully, it could be that many people would benefit from supplements.

"We're learning more all the time about the effect of dietary fat on diabetes, heart disease, and even reproductive failure, learning disabilities and other health issues," said Donald Jump, a professor of nutrition with the Linus Pauling Institute at Oregon State University, and author of dozens of publications in this field.

"It's pretty clear that the average Western diet is too high in fat, but it’s not that simple," Jump said. "Dietary fat plays an essential role in our health, development and well being. The real issue is that people are eating too much of the wrong kinds of fat, and not enough of the right kinds. The type of fat you eat is very important."

The short version of a complex story, Jump said, is that most diets have too much saturated fat – like in meat and dairy products – and too much “trans” fats, most commonly found in processed foods like margarine or shortening. People also eat too much fat in general. And they often get too little of their fat in the form of unsaturated fatty acids, found to some degree in meats, and at higher levels in nuts or vegetable oils.

And the most scarce fat of all – but one very important for good health – is the omega 3 polyunsaturated fat found at some of the highest levels in fish.

The omega 3 fats have been the focus of extensive research in recent years for their value in preventing heart disease and acting as an anti-inflammatory agent.

"Omega 3 fatty acids will lower blood triglycerides and modulate inflammatory processes," Jump said. "Both of these effects are why physicians prescribe omega-3 supplements for patients with elevated blood lipids and who are at risk for atherosclerosis."

This can be necessary because a common Western diet too often emphasizes steak, pizza and ice cream instead of salmon, sardines and tuna. Too many cookies full of shortening, not enough vegetables sautéed in olive oil.

"The best approach, pretty much everyone agrees, is to develop a more sophisticated understanding of diet, including the right types and amounts of fat, and eat more healthy foods," Jump said.

"But if you are not going to do that," he said, "I would not hesitate to suggest people should consider fish oil supplements to help provide needed levels of omega 3 fat."

Some basic facts about fat:

Dietary fat provides flavor to food, is very important for the absorption of lipid-soluble vitamins like A, D, and E, and provides building blocks for all cells in the body.

Fat helps to maintain cellular structural integrity, regulates cell function and gene expression, and functions as signaling molecules.

The fat composition of foods is complex, and only a few foods such as vegetable oils, fish, and nuts contain higher levels of the unsaturated fatty acids that are comparatively healthy.

High fat diets and obesity can lead to heart disease, diabetes and other serious health problems. But deficiency of essential fatty acids can lead to reproductive failure, poor visual acuity, learning disabilities, skin lesions and other issues. The good fats tend to offset the negative effects of the bad fats.

Most Western diets contain too much saturated fat and too little omega 3 polyunsaturated fat. The latest studies suggest near elimination of dietary “trans fats.”

Humans do not efficiently convert omega 3 fatty acids from plants to the forms of omega 3 fatty acids found in our brain and eyes. The omega 3 fats in fish, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are essentially the same as those found in the brain and retina. These fats are available in fish, like salmon, and can also be obtained from fish oil supplements.

Proper diet and adequate levels of omega 3 fatty acids is especially important for pregnant and nursing women; brain tissue is very fatty, and proper neuronal development depends upon adequate nutrition. Some manufacturers of baby formula now supplement their products with DHA and another polyunsaturated fatty acid called arachidonic acid (ARA).

A website set up by the American Heart Association outlines the complexities of fat consumption, the foods to eat and avoid, and the overall role of fat in human health, Jump said. Additional information on dietary fat can also be found at the Linus Pauling Institute Micronutrient Information Center

About the Linus Pauling Institute: The Linus Pauling Institute at OSU is a world leader in the study of micronutrients and their role in promoting optimum health or preventing and treating disease. Major areas of research include heart disease, cancer, aging and neurodegenerative disease.