Tuesday, January 3, 2012

Understanding Fats - Saturated, Hydrogenated, Unsaturated

 A focus for me this coming year is to better understand the scientific nutritional "underpinnings" of Clean Eating. In the coming months, I'll be sharing my research with you.

A first focus for me is fats - specifically fats that are good, fats that are bad, fats that have a bad reputation, and more importantly, fats that are naturally occurring and fats that are additives.While I know trans fats are bad for me - why are they bad for me? How can I be more efficient at recognizing good ingredients from poor choices? What is an acceptable fat?

Although all fats have the same amount of calories, some are more harmful than others: saturated fats and trans fats in particular and should be eaten in moderation. I'm definitely NOT telling you to be a vegetarian. Animals were put on this Earth for our consumption, and "If it walked the Earth it is a Clean choice" remains a standard for me. I think the value in this education lies in eating fewer servings of heavily fatted beef per week, and increasing the more wholesome fats that occur in things like cold water fish ( salmon ). Also, I believe weighing days where you do consume beef with a Meatless Monday is a much healthier and well rounded way to go. Meat has a place in our diet.

Much of this post is information gleaned from reputable online resources - The Harvard School of Public Health  and  The Mayo Clinic. I specifically avoided biased sites and sites that had no scientific backing.
While a bit long, if you've ever wondered about the oils you see listed in some products, this is important information to understand.

In the late 19th century, chemists discovered that they could add hydrogen atoms to unsaturated fats by bubbling hydrogen gas through vegetable oil in the presence of a nickel catalyst. This was far more than a chemical curiosity. Partially hydrogenated oils don't spoil as easily as nonhydrogenated fats. They can withstand repeated heating without breaking down. And the process can turn a liquid oil into a solid, which allowed for easier transportation and wider uses; this solid fat was also much less expensive than solid animal fats.

These characteristics were attractive to food makers. Over the last several decades, partially hydrogenated oils became a mainstay in margarines, commercially baked goods, and snack foods. When saturated fat was fingered as a contributor to high cholesterol, companies such as McDonald's and Dunkin' Donuts switched from beef tallow to partially hydrogenated vegetable oil for frying French fries and donuts.

At the time, switching from butter or lard (both of which contain high amounts of saturated fat) to a product made from healthy vegetable oil seemed to make sense. Intake of trans fat increased dramatically. Before the advent of partial hydrogenation, the only trans fat that humans consumed came from eating cows (or dairy products), lamb, and deer; in ruminants like these, bacteria living in the stomach make small amounts of trans fat. But due to the growth of partial hydrogenation, by the early 1990s, trans fat intake in the United States averaged 4 to 7 percent of calories from fat.

Saturated fats

These fats are derived from animal products such as meat, dairy and eggs. But they are also found in some plant-based sources such as coconut, palm and palm kernel oils. These fats are solid at room temperature. Saturated fats directly raise total and LDL (bad) cholesterol levels. Conventional advice says to Avoid them as much as possible. More recently, some have questioned this, as there are different kinds of saturated fats, some of which have at least a neutral effect on cholesterol.

Trans Fats or Hydrogenated Fats

Trans fats are actually unsaturated fats, but they can raise total and LDL (bad) cholesterol levels while also lowering HDL (good) cholesterol levels. Trans fats are used to extend the shelf life of processed foods, typically cookies, cakes, fries and donuts. Any item that contains “hydrogenated oil” or “partially hydrogenated oil” likely contains trans fats. Hydrogenation is the chemical process that changes liquid oils into solid fats. The tide is turning against trans fats. Since January 2006, all food manufacturers are required to list trans fat content on food labels.

Do all Foods listing hydrogenated oils contain trans fats? Foods that contain trans fats have "partially hydrogenated oil" or "hydrogenated oil" listed in the ingredients. Before trans fats were required to be listed on nutrition labels, from January 2006, this was our only way of knowing whether these harmful fats were present. Yet a number of products state "0g Trans Fat" or declare themselves to be trans-fat free but still have these oils listed in their ingredients. How can this be?
There are two reasons why foods containing hydrogenated oils may be labeled trans-fat free, or list 0g trans fats on the label. First, items that list partially hydrogenated oils in the ingredients but contain less than 0.5g of trans fats per serving are considered by the government to be trans-fat free. A good example of this would be commercial peanut butter, which contains a tiny amount of partially hydrogenated oil to prevent separation. The problem with this definition, though, is that if you eat more than the stated serving size, those fractions of a gram add up, and you are most certainly consuming trans fats. Second, products that contain fully hydrogenated oils are trans-fat free.

Unsaturated fats

Monounsaturated fats and polyunsaturated fats are two types of unsaturated fatty acids. They are derived from vegetables and plants.
  • Monounsaturated fats are liquid at room temperature but begin to solidify at cold temperatures. This type of fat is preferable to other types of fat and can be found in olives, olive oil, nuts, peanut oil, canola oil and avocados. Some studies have shown that these kinds of fats can actually lower LDL (bad) cholesterol and maintain HDL (good) cholesterol. 
  • Polyunsaturated fats are also liquid at room temperature. These are found in safflower, sesame, corn, cottonseed and soybean oils. This type of fat has also been shown to reduce levels of LDL cholesterol, but too much can also lower your HDL cholesterol.

Omega-3 fatty acids

These include an “essential” fatty acid, which means it's critical for our health but cannot be manufactured by our bodies. Good sources of omega-3 fatty acids include cold-water fish, flax seed, soy, and walnuts. These fatty acids may reduce the risk of coronary heart disease and also boost our immune systems.