Article: Understanding Dietary FatsMarch 7th, 2011 | by Pam Stuppy
Published in: Articles
Guidelines for intake of fats and fatty acids are based on both general health goals and recommendations for prevention and treatment of chronic disease. Some fats that are important to the body can be made internally, while others are considered “essential,” meaning required in the diet. Suggested intake of total fats ranges from about 20 percent to 35 percent of calories consumed.
Terms you may hear with regard to fats are based on their chemical structure — saturated, trans, unsaturated (which includes polyunsaturated and monounsaturated). Within the unsaturated fat category, we also find the omega-6 and -3 fatty acids. These are considered “essential fatty acids.” Each of these subcategories of fat has a set of functions they perform in the body.
Most fats contain a mix of all of these categories, but tend to have predominately one type. Fats that are more saturated come from animal foods and tropical oils. Trans fats are naturally found in very small amounts in the food supply, but greater amounts are found in processed foods and partially hydrogenated fats.
These two types of fats are termed “solid fats” in the newest Dietary Guidelines for Americans. It suggests keeping trans fat intake as low as possible and saturated fat intake to less than 10% of calories (the American Heart Association recommends less than 7 percent). Poly- and monounsaturated fats should make up the balance of our fat needs.
Monounsaturated fats come mostly from plant sources — olive and canola oils, nuts, seeds, nut butters, and avocado. Other vegetable oils (corn, safflower, soy, etc.) are mainly polyunsaturated and contain omega-6 fatty acids. These are common in many processed snack foods and desserts.
Omega-3′s are usually abbreviated ALA, EPA, and DHA. ALA is found in flaxseed oil, canola oil, walnuts, and dark leafy greens. EPA and DHA are found in cold water fish and algae. ALA can be converted to EPA and DHA, but very inefficiently. It appears that EPA and DHA are more effective than ALA when it comes to heart health.
The American Dietetic Association encourages Americans to make mono- and polyunsaturated fat a high percentage of the fats they consume. In addition, they suggest including more sources of omega-3 fatty acids to improve the ratio between the omega-3′s and the omega-6′s.
Why do we hear so much about omega-3′s? Research has established a number of health benefits from intake of these fatty acids. One of their biggest claims to fame is their anti-inflammatory function. Many of our major diseases — diabetes, heart disease, stroke, arthritis, and others — are related to inflammation in the body. This inflammation is caused by factors such as obesity, stress, food sensitivities, dietary habits, etc.
Some researchers are concerned that the typical American diet is not only low in omega-3′s, but also high in omega-6′s due to the high intake of processed foods. It is believed that this imbalance between the omega-3′s and omega-6′s can reduce the effectiveness of the omega-3′s.
For heart health, the general goal is to consume 600-1000mg of EPA plus DHA through diet and/or supplements. Higher doses (2000-4000mg) have proven helpful in lowering triglycerides in persons with elevated blood levels.
Omega 3′s can help keep blood vessel walls more flexible (countering “hardening of the arteries”), thin the blood which can decrease clumping, reduce the likelihood of plaque build-up, increase “good” cholesterol, and improve heart function. They can also improve the effectiveness of statin drugs. The FDA permits supplements containing omega-3′s to state, “supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.”
Besides the benefit to the cardiovascular system, omega-3′s are helpful to the eyes and brain. They are an integral part of retinal health and some studies suggest higher intakes may reduce the risk of age-related macular degeneration. It is recommended that persons with “dry eye” add omega-3′s as well. Studies are underway to determine more specific eye benefits.
DHA is an essential structural part of the brain. Studies have shown that DHA intake by pregnant and breastfeeding women (about 300mg/day) can be of benefit to the fetus and infant with regard to brain and eye development. Adequate intake may also lower the risk of premature birth and low birth weight. Women who want to increase their intake of DHA should be cautious about fish sources due to concerns for toxins. They should limit intake to food or supplement sources less likely to contain mercury and other contaminants.
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Other studies suggest less brain function decline in adults who consume higher levels of DHA. DHA and EPA may also help with depression, bipolar disease, and schizophrenia. Again, studies are currently looking into these areas.
Because of their anti-inflammatory properties, omega-3′s can help reduce the symptoms (but not progression) of arthritis. Reducing the risk of certain cancers (breast, prostate, colon) are other areas being investigated that may benefit from omega-3′s.
To date, not enough studies have looked specifically at the doses recommended for the potential non-cardiovascular benefits. Until that information is available, it is recommended to follow the same guidelines as those for general heart health. Because of their blood-thinning effect, persons considering taking the higher dose supplements of omega-3′s who are taking medications, should first check with their health care provider. It is often recommended to stop taking them about a week before any surgeries.
Pam Stuppy, MS, RD, CSSD, LD, is a registered, licensed dietitian with nutrition counseling offices in York, Maine, and Portsmouth. She is also the nutritionist for Phillips Exeter Academy and is teaching healthy cooking classes at Stonewall Kitchen. See www.pamstuppynutrition.com for some healthy recipe ideas.