Fat gets a bad rap. It's an unfair one, too, because fats are one of 4 key nutrients that we need to survive. In order of volume they are water, carbohydrates, proteins and fats. When a healthy person eats a naturally-occurring fat, it gets broken down into small units used to build cell membranes and tissues, to cushion organs and keep us warm. Fat is also used by our cells to make important hormones. It's also a great source of energy with each gram of fat providing 9 calories, whereas carbohydrates and proteins only provide 4 calories per gram.
Fat can either be eaten in our diet or manufactured in the body from other materials but 2 fats in particular are essential. That is, we need to eat these fats because our body cannot make them. These fats are Omega 3 and Omega 6, also known as essential fatty acids (EFAs).
Dietary fat in our diet is classified in ways that may sound familiar. They are either saturated fat (animal fats and others such as avocado which are solid at room temperature), monounsaturated fats such as olive oil or polyunsaturates which are unstable fats sourced from plants and some cold-water fish. Omega 3s and 6s fall into the polyunsaturated category and this means that their molecular structure is ready to accept hydrogen atoms. Being exposed to, and accepting hydrogen would create a molecular change for these fats and so we call them unstable. They are best when kept protected from light, heat and air: kept in a dark, airtight container in the fridge.
What about transfats? Some transfats naturally occur in small amounts in animal foods, but most are made artificially when trying to make shelf-stable solidified fats out of liquid polyunsaturated oils, as is the case with margarine. These oils are forced to artificially accept hydrogen atoms by adding metal particles to the oil and spraying it with hydrogen at high temperatures. Transfats have been linked to ill health and specifically heart disease.
The instability of fats is something to be aware of when we buy, store and cook with oils. Most people know that butter can be left out on the counter for a little while and it does not go rancid. This is due to its being a mostly saturated fat. Similarly, olive oil and peanut oils do not need to be kept in the fridge and can last several months in a dark, glass bottle. But when we come to the polyunsaturated oils like flaxseed and walnut, these unstable oils must be refrigerated and kept in dark bottles to protect them from light, air and heat. Most oils, such as canola, are refined to make them shelf-stable and able to withstand heat and light. Those canola oils you see in clear plastic bottles at the grocery store have been boiled, filtered and bleached so they can last for years.
When you go to cook with oils, what's the type to choose? There are a number of saturated oils that can be used safely at higher temperatures such as avocado, almond, coconut, or butter mixed with olive oil. These can be used for frying without concern about them smoking. An oil's smoke point is when the oil starts to burn and smoke; carcinogens are released into the air and harmful free radicals are produced within the oil. Monounsaturated and some polyunsaturated oils such as canola, corn, soy have a higher smoke point and can be cooked at temps up to 350 – 400F. This means light sautéing will not ruin the oils or make them unhealthy. Grapeseed oil is an exception to the rule: it's a polyunsaturated fat and yet qualities in the oil protect it at higher temperatures, so it can be used for stir frying. Finally, keep your polyunsaturated oils like sesame and flax oils in the fridge and do not cook with them. When I want the taste of sesame oil on an Asian dish, I drizzle it over the food once it's on the plate. Flax oil is a great ingredient in salad dressing, and it is safe from heat on your salad. When you open a bottle of flax oil, be very careful to cap it again right away after you've poured, to protect it from the air.
Let's not shun fats in our diet but instead focus on consuming the healthy ones. Try not to consume more than 30 – 50 grams of fats in a day. Forty grams of fat is approximately what you'd find in 2 small avocados, 4 tablespoons of olive oil or 1/2 cup of almonds. Since animal-source saturated fats have been linked to heart disease in some studies, it's best to choose leaner cuts of meat, and to choose fish before other meats. Try to focus on monounsaturates or polyunsaturated oils such as grapeseed, safflower and olive oil for cooking. And don't forget to try and get 5 grams of Omega 3 oils each day. You can get this from 2 tsp of flax or hemp, or several fish oil capsules. The optimal ratio of required Essential Fatty Acids (EFAs) in the diet is 3:1 of Omega 6 to Omega 3. However, so many of the foods we eat are made with canola oil – a source of omega 6 – that we should concentrate on getting more omega 3s into our diet to balance this out. Your best bet is always to eat a variety of foods, and a varied source of fats in the diet will ensure you're getting all the nutrients your body requires.
Caroline Rechia is a Registered Holistic Nutritionist (RHN) and chocolate maker. Her blog, C is for Cookie can be found here: http://carolinescookies.blogspot.com
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