Essential Fatty Acids in Vegetarian Nutrition
Mahatma Ghandi once said, “Where ever flaxseeds become a regular food item among the people, there will be better health.” While this prediction was based on simple observation, scientific evidence would suggest there is more than a grain of truth to his words. Flaxseeds are an exceptional source of lignans, a potent anticarcinogen and the richest known source of the essential omega-3 fatty acid, alpha-linolenic acid.
It is generally assumed that North Americans need not worry about getting enough fat of any kind, but as research unfolds, a fatal flaw in this thinking is revealed. Not all fats are damaging to health. Some fats are protective, and two in particular are essential to life - they are the essential fatty acids (EFA), linoleic acid (omega-6) and alpha-linolenic acid (omega-3).
Changes in our food supply since the industrial revolution have jeopardized both the quantity and balance of these nutrients. Our current dietary pattern provides excessive amounts of omega-6 fatty acids in relation to omega-3 fatty acid content. This imbalance of essential fatty acids affects vegetarians at least as much as omnivores. In addition, the trend towards very low fat vegetarian diets (10% or less of calories from fat) may further compromise essential fatty acid intake.
How can vegetarians insure an adequate intake of omega-3?
The following four guidelines will help to insure an appropriate quantity and balance of essential fatty acids in vegetarian and vegan diets:
Limit intake of saturated fats and trans fatty acids. In vegetarian diets the primary sources of saturated fats are dairy products and eggs, while vegan diets are low in saturated fats, unless there is a heavy reliance on tropical oils. Trans fatty acids come primarily from hydrogenated vegetable oils. These fats have the potential to interfere with the conversion of alpha¬linolenic acid to DHA, in addition to increasing risk for degenerative diseases. Trans fatty acids are plentiful in shortening, hydrogenated margarines, processed foods containing hydrogenated and partially hydrogenated vegetable oils (crackers, cookies, cakes, pastries, frozen convenience foods, snack foods) and fast foods (hydrogenated oils are used for deep frying).
Make monounsaturated fats the principal fat in the diet. Monounsaturated fats should make up the largest portion of fat in the diet, as they have proven to have neutral or positive affects on health. In addition, emphasizing monounsaturated fats will help to keep saturated fats, trans fatty acids and omega-6 fatty acids to a modest level. Olive oil (77% mono-fat) and/or canola oil (58% mono-fat) would be the recommended oils to use. Avocados, olives, hazelnuts, pistachios, almonds, macadamia nuts, peanuts and pecans are also excellent sources of monounsaturated fats. These foods also provide valuable vitamins, minerals, phytochemicals and fiber, and when used moderately, make an excellent addition to the vegetarian diet.
Limit the intake of omega-6 rich vegetable oils. Minimizing the use of oils rich in omega-6 fatty acids is the easiest way to keep linoleic acid levels at a reasonable level. Oils that contain predominately omega-6 fatty acids include corn, sunflower, safflower, and cottonseed oils. Commercial products such as margarine, salad dressing and mayonnaise that are made with these oils should also be limited. Soybean oil and walnut oil are also rich sources of omega-6 fatty acids, but their omega-6 content is partially compensated for by an omega-3 content of 5 - 8%.
Include a source of omega-3 fatty acids in the daily diet. In order to obtain sufficient omega-3 fatty acids in the vegetarian diet, good plant sources of this nutrient must be incorporated into the daily diet. If we assume an energy intake of 2000 kcal/day, 5% of calories as polyunsaturated fats and an omega-6: omega-3 ratio of 4:1, one would require 8.9 g of omega-6 and 2.2 g of omega-3 fatty acids. It would not be a challenge to consume the 9 grams of omega-6 fatty acids, even on a very low-fat vegetarian diet. The Reversal Diet (the Dean Omish program that allows for no oils, nuts or seeds) provides an average 6 grams of linoleic acid primarily from whole grains and soy products. On the other hand, it would require considerable effort for vegetarians to get 2.2 grams of omega-3 fatty acids, by carefully selecting excellent plant sources of omega-3.
The best source of alpha-linolenic acid is flaxseed oil (57% omega-3 and 17% omega-6 fatty acids). Other omega-3-rich plant foods are much less concentrated sources of this nutrient, often coming packaged with much higher amounts of linoleic acid.
By Brenda Davis, RD (excerpted from www.andrews.edu)
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