& Joannie Dobbs Wednesday,
Fat is essential for health, in right types and
NOW that you have "Fats 101" under your belt from last week's Health Options column, this week we move into "Fats 102."
Question: Do humans require dietary fat?
Answer: YES. Although the body can synthesize most fatty acids from protein, carbohydrates or even alcohol, there are a few beneficial fatty acids that the body cannot make or may not make in adequate amounts. These are called essential fatty acids. Without them, a number of physiological functions may become impaired, including normal blood-pressure regulation and blood clotting. Vitamins A, D, E and K also require dietary fat for proper absorption.
Q: Which fatty acids are essential?
A: Two are clearly essential in the diet: Alpha-linolenic acid and linoleic acid. Alpha-linolenic acid is an omega-3 fatty acid. The richest sources are flax, walnut, canola, and soy oils. Linoleic acid is considered an omega-6 fatty acid and is plentiful in most vegetable oils.
Two additional omega-3 fatty acids may also be beneficial in the diet. These are typically found in fish oil: eicosapentaenoic acid, which reduces inflammation, and docosahexaenoic acid, a major fatty acid in the brain that helps maintain healthy blood vessels in the retina.
Q: What is the minimum amount of dietary fat required?
A: People need to consume enough total fat to meet their essential fatty-acid requirement. Therefore the total amount of dietary fat required depends on the fatty-acid composition of the fat consumed.
Generally, 30 grams of fat from a variety of dietary sources is considered adequate to meet essential needs. It is also important to maintain a balanced ratio between omega-3 and omega-6 fatty acids. This ratio is about 1 to 6.
Q: How much olive oil is necessary to supply the essential fatty acids for a day?
A: If olive oil was the only source of essential fatty acids, an adult would need more than 1,500 calories worth of olive oil to meet the recommendation for omega-3 fatty acids. In contrast, less than a tablespoon of Canola oil (about 100 calories worth) would meet omega-3 recommendations. However, neither oil has the desired 1-to-6 ratio.
Q: Can a person get essential fatty acids in the correct amounts from flax or hemp seed oils?
A: NO. Although both flax and hemp are great sources of the omega-3 alpha-linolenic acid, neither oil contains adequate omega-6 fatty acids. Some studies have associated diets high in alpha-linolenic acid with an increased occurrence of prostate cancer as well as increased risk of age-related macular degeneration.
Q: Are fish oils important?
A: Based on current research, fish oils offer a number of protective functions. For example, adding fish oils to the diet reduces the risk of sudden heart attacks and strokes in women. These oils also reduce the risk of prostate cancer and macular degeneration.
Those who don't want to eat fish can get these longer-chain omega-3 fatty acids from another source. Most fish get their omega-3 fatty acids by eating certain types of algae. Supplements containing high docosahexaenoic acid algae oils now are available.
The bottom line is that fat is required in the diet, but too much or too little of any one type of fatty acid can cause significant health problems. Again, variety is the spice of life.
Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service
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