|Ask the RD: Brenda Davis|
|June 1, 2013|
Brenda Davis is a Registered Dietitian and nutritionist. She is the co-author of 8 books, including Becoming Vegan, Defeating Diabetes, Becoming Raw, and The Raw Food Revolution Diet. We are very excited to announce that Brenda will be presenting at both our Health Conference and Portland VegFest, September 20-22!
Q: What are the best fats and oils for vegetarians and vegans, and is it always better to follow a low fat diet?
A: Let's begin with the question of low fat diets always being better.
Very low fat diets have been popular among vegetarians because of their proven effectiveness in treating severe coronary artery disease. People often assume that such diets would therefore be the best choice for all vegetarians. But what’s best for healthy vegetarians, particularly growing vegetarian children, can be quite different from what’s best for people with serious chronic disease.
It’s important to realize that the adverse effects of excessive fat are consistently linked with animal fats and processed fats and oils containing trans fatty acids. The unprocessed fats and oils of whole plant foods have quite a different effect on health. Many studies have demonstrated that the fat in nuts, seeds, avocados, olives and other plant foods is actually protective. When people get most of their fat from these sources, they can consume relatively high amounts without adverse effects. In contrast, people who get most of their fat from animal foods and processed products tend to be at risk even at moderate fat intakes. They really do need to cut down on these potentially damaging fats and oils.
For healthy vegetarians, cutting down too much on wholesome, high-fat plant foods poses several problems:
- Very low-fat diets may provide excessive bulk and insufficient calories, particularly for infants, children, and people with very high energy requirements, like athletes or labourers.
- Very low fat diets often contain inadequate amounts of essential fatty acids, especially the omega-3 fatty acids (discussed below).
- Insufficient fat can compromise absorption of fat-soluble vitamins (A, D, E, and K), minerals (including iron, zinc, manganese, and calcium), and healthful phytochemicals (like the lycopene in tomato products).
- People on very low fat diets often become “fat phobic.” They assume all high fat foods are bad and that all low fat foods are good. This often leads them to choose foods that are actually “nutritional washouts” (packaged fat-free cookies, cakes, and chips, for example) while obsessively avoiding higher-fat plant foods that are very nutritious, like avocados, olives, nuts, seeds, and tofu.
- Very low fat diets can cause a drop in HDL-cholesterol (“good cholesterol”) and a rise in triglycerides (another potentially damaging blood fat, like LDL-cholesterol), actually increasing your risk for cardiovascular disease. However, this is not normally a problem unless you replace the fat with refined carbohydrates, like sugar and white flour products.
So, how much fat should you eat?
I’d suggest something in the range of 15 to 30 percent of calories. But remember, the quality of the fat is at least as important as the quantity.
Q: What are the best fats and oils for vegetarians?
A: Without a doubt the answer is whole plant foods, like nuts, seeds, avocados, olives, and soybeans. These foods are packaged by nature to protect their fats and oils from damaging light, heat, and oxygen. They also carry valuable vitamins, minerals, phytochemicals, plant sterols, essential fatty acids, and fiber.
As I’ve already suggested, the fats in these foods are actually good for us. That’s right: we need fat. It provides energy, insulation, and “padding,” not just for our posteriors but to protect internal organs. We need fat to absorb many vitamins, minerals and phytochemicals. Certain fats are required for healthy cell membranes and to maintain cell integrity, permeability, shape, and flexibility. These fats also are critical for the development and functioning of the brain and nervous system. Finally, they are the building blocks for hormone-like substances called eicosanoids that regulate many organ systems.
These special fats are known as essential fatty acids (EFA), because they are as essential for our survival as vitamins and oxygen.
Q: How do we ensure that we eat good fats?
A: Begin by reducing your intake of foods rich in saturated fats, cholesterol, and trans fatty acids. Unless you use large amounts of tropical plant oils (coconut, palm, and palm kernel oil), vegan diets are generally low in saturated fat. They’re always free of cholesterol.
On the other hand, lacto- and lacto-ovo vegetarian diets have the potential to be high in saturated fat and cholesterol if you eat a lot of eggs or full-fat dairy products.
There is considerable controversy about tropical oils. In less affluent parts of the world where the indigenous diet is plant-based and coconuts and other high saturated-fat plant foods are staples, the rates of chronic disease are relatively low. By contrast, tropical oils are scarce in most North American diets, yet chronic disease rates are high. Research suggests that – when consumed in moderation as part of a high fiber, cholesterol-free, plant-based diet – coconut and other saturated fat-rich plant foods do not increase cholesterol levels or heart attacks.
So it’s unnecessary for vegans or vegetarians to completely eliminate these foods from their diets. The small amount of saturated fat coming from whole plant foods may in fact be of benefit for vegans. These are very stable fats with a low risk of being damaged and made dangerous to your health by oxidation, in contrast to the unstable polyunsaturated fats that are generally very high in vegan diets.
What about cholesterol? Since it’s found only in animal foods, this potential artery clogger is rarely a problem in vegetarian diets, unless you eat a lot of eggs and high-fat dairy products.
Trans fatty acids are another story. The product primarily of hydrogenation (the food technology process of changing liquid oils into solid fats), the main sources of these harmful fats are: shortening, hydrogenated commercially prepared foods, like crackers, cookies, cakes, pastries, potato chips, frozen convenience foods (just about any commercial snack food) and, of course, any food that lists “hydrogenated” or “partially-hydrogenated” vegetable oil on the label. Also, beware of fast food establishments: they generally use hydrogenated oils for deep-frying. Because trans fatty acids increase the risk of degenerative diseases, they should be avoided.
Now for the healthy fats. One of the biggest problems with fat in the vegetarian diet (and many non-vegetarian diets, too) is that we get a poor balance of essential fatty acids.
There are two essential fatty acids:
Linoleic acid, from the omega-6 family, which can be converted and elongated in our bodies to two very important long-chain fatty acids named GLA (gamma-linolenic acid) and AA (arachidonic acid). Similarly, alpha-linolenic acid, from the omega-3 family, which can be converted and elongated to two other very important long-chain fatty acids: DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid).
Most people get too much of the omega-6 fatty acids in their diet and not enough of the omega-3s. This imbalance may result in poor brain development and reduced visual acuity in infants. In people of any age, it may also contribute to chronic diseases, immune/inflammatory disorders, and psychological disorders, too.
Linoleic acid is found mainly in seed oils (like sunflower, safflower, sesame, and grape), corn oil, soy, and grains. Alpha-linolenic acid is found mainly in flax seeds, hemp seeds, greens, canola oil, walnuts, and soy. Few plant foods contain the long-chain fatty acids, which are most commonly found in fish (omega-3s – namely EPA and DHA) and meat (omega-6s – namely AA). Algae and seaweed are the only exception. They contain long-chain omega-3s, but generally in very small amounts.
Thus, vegans (but not necessarily vegetarians, see below) get almost all their long-chain fatty acids from internal conversion of the short-chain EFA. Unfortunately, this conversion is very limited for omega-3 fatty acids: only about 4-10% of alpha-linolenic acid is converted into EPA, and just 2-5% becomes DHA. Worse, high intakes of omega-6 fatty acids can competitively block this conversion by up to 50%.
Fortunately, to optimize your essential fatty acid balance there are several things you can do:
- Limit your use of linoleic-acid-rich oils (see above).
- Select foods rich in monounsaturated fat as your primary fat source: nuts and nut oils, olives and olive oil (extra virgin is best), canola oil (preferably organic), and avocados.
- Include a good source of alpha-linolenic acid in your diet every day. We need about 2 to 3 grams. You can get this much from:
1 tsp. flax oil
1/4 cup walnuts
2 Tbsp. soy oil
1 Tbsp. hemp oil
20 cups dark greens
1 cup soybeans
1 Tbsp. ground flaxseeds
4 tsp. canola oil
12 ounces firm tofu
- Consider getting a direct source of EPA and DHA, especially if you’re pregnant or lactating.
For lacto-ovo vegetarians, omega-3 rich eggs are a reasonable source of DHA.
For vegans, microalgae-based supplements are the best option. While seaweeds themselves contain some EPA, they are so low in fat you’d have to eat enormous (and potentially unhealthful) amounts to make any significant contribution to omega-3 intake.
There are two companies that market vegetarian DHA. NuTru sells “O-Mega-Zen3” with 300 mg of DHA per capsule, and Seroyal of Toronto sells a 100 mg capsule, but only through licensed health practitioners. Martek and OmegaTech also sell microalgae-based DHA, but their capsules are made of nonvegetarian gelatin. A reasonable daily intake of DHA would be 100-300 mg. Use 200-300 mg during pregnancy and lactation.
To ensure the highest quality of fat in your diet, remember to use fresh, whole plant foods. Whenever possible, choose mechanically-pressed, unrefined oils.
Store nuts, seeds and oils in a cool, dry place in airtight containers away from direct sunlight. When properly stored, unshelled nuts and whole seeds last up to a year. Shelled nuts and ground seeds can be stored in the refrigerator for up to four months or in an airtight container in the freezer for up to one year. Ground flaxseeds are more unstable due to their high omega-3 content. They are best stored in the freezer after grinding. Nut halves keep better than pieces as they are less exposed to light and oxygen.
While refined oils last many months in the pantry, fresh-pressed oils (other than olive oil) go rancid much more quickly and need to be refrigerated and used within two months (flax oil is best used up within six weeks). Olive oil lasts longer than other fresh-pressed oils and can be stored in the pantry for up to three to four months.
Finally, oils are easily damaged by heat, especially those containing omega-3 fatty acids. But those like olive oil, organic canola oil, and high oleic sunflower or safflower oil that contain mostly monounsaturated fats are more stable when heated and are your best choice for cooking and baking. So is nonhydrogenated margarine (casein-free, if you’re vegan).
With just a little bit of care, a vegetarian diet can be a source of fats and oils that add savour to your meals and health to your years.
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