Lipids

Lipids (or fats) are also relatively maligned. Over thirty years ago, research into heart disease uncovered significant relationships between lipids and heart disease risk. Unfortunately, the end result was a rush by food manufacturers to re-configure higher fat foods into low- or no-fat foods. And many times, more simple carbohydrates were added to these foods to improve the flavor, leading to excess consumption of simple carbohydrates. While we are still learning about the importance of fats in the diet, the 'whole food rule' still reigns over many low- and no-fat options. In other words, when in doubt, choose a whole food rather than one that has been manipulated to remove some or all of its fat. And keep in mind moderation.

In nutrition, lipids are divided into three main groups: triglycerides, sterols and phospholipids. For this overview, we are going to examine triglycerides and sterols. Phospholipids are important in many ways (especially in cell membranes) but not a significant focus for our purposes.

Triglycerides

The most abundant form of fats in our diets are triglycerides- molecules that consist of a three-carbon backbone with different fatty acids attached to each of the three carbons.

Fatty acids are chains of carbons that are classified as short (<10 carbons), medium (10 to 16 carbons) or long-chain (more than 16). Fats are also classified as saturated, unsaturated or partially-unsaturated.

Practically speaking, saturated fats are the most stable lipid molecules and tend to be solid at room temperature- think fats like sticks of butter or tubs of coconut butter. Oils are lipids that are not solid at room temperature and are more likely to be poly-unsaturated or mono-unsaturated- such as olive oil and canola oil. The amount of saturation is a chemical term that classifies fats by the types of bonds in those chains of carbons. A mono-unsaturated fat has one double bond in the chain and poly-unsaturated fats have two or more double bonds in their chains. This is significant because these differences in chemistry translate to difference ways of functioning in our metabolism. Remember, all fats contain 9 calories per gram, but from a heart perspective, the best evidence for healthier fats points to more mono- and poly-unsaturated fats and less saturated fats.

There are two types of fats that are most implicated in increasing risk for heart disease: saturated fats and trans fats. (Trans fats are not fully saturated but they behave as if they are saturated in terms of increasing heart disease risk.) The trans fats we are most worried about are perhaps better known to you as hydrogenated or partially-hydrogenated fats. The easiest way to limit trans fats is to avoid highly processed foods like candy, baked goods, etc.

(If you'd like to learn a bit more, here's a link to a module on lipids from the Khan Academy: Khan Lipid module)

Sterols

As you might guess, cholesterol is a 'sterol'. Sterols are fats that serve important roles in cell membranes as well as being pre-cursors to hormones and certain vitamins. Cholesterol is a form of sterol that is only found in vertebrates; you will never consume any cholesterol by eating plant foods. In humans, we can make all the cholesterol we need, so we don't need to consume any, ever. The cholesterol contained in animal foods we consume will either be absorbed or excreted by the digestive tract. For most people, consuming high amounts of cholesterol does not mean your blood cholesterol levels will be high. Things like saturated and trans fat consumption and lack of fiber and limited physical activity are more likely to lead to high blood cholesterol levels.

Factors to consider when choosing fats

Emphasize fats that are found in plants, especially those that are polyunsaturated and mono-unsaturated, and the inflammation-reducing omega-3 polyunsaturated fats in cold water fish such as salmon. Fats make food tasty, they keep us feeling full longer and they carry important fat-soluble vitamins. Research is very clear around trans-fats- avoid them- by avoiding processed and ultra-processed foods. Cured meats such as salami, luncheon meats and red meats in general are best in limited amounts. The science is still in debate about grass fed red meat/dairy products and the relationship with increased risk for heart disease. And what about coconut oil? The exception to the rule about plant-based fats, coconuts are higher in saturated fat than butter. While the carbon chains are of the shorter variety, there are still concerns that coconut fat may contribute to heart disease risk. And for folks concerned about where food comes from...current growing climate doesn't especially support coconut palm cultivation in the Pacific Northwest!