Nutrition of Fats and Oils

Oils and fats, also called lipids, are one of the three basic types of calorie sources, the others being carbohydrates and proteins. With 9 calories per gram (38 kJ/g), lipids have the highest food energy content of the three. The other two have 4 calories per gram. In general, the difference between oils and fats is that, at normal room temperature, fats are solid while oils are liquid. Palm, palm kernel, and coconut oils are an exception to this rule.

Role in Human Health

Many lipids are absolutely essential for life. However, abnormally high levels of certain lipids, particularly cholesterol and trans fatty acids, are risk factors for heart disease amongst other diseases, and so should be limited in one's diet.

Humans have a dietary requirement for certain essential fatty acids, such as linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid) because these fats cannot be synthesized from simpler components in the diet. Most vegetable oils (including safflower, sunflower, and corn oils) are rich in linoleic acid. Alpha-linolenic acid is found in the green leaves of plants, and in selected seeds, nuts and legumes (such as flax, canola, walnuts and soy). Fish oils are particularly rich in the omega-6 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).

A minimum amount of dietary fat is necessary to facilitate absorption of fat-soluble vitamins (A, D, E and K) and carotenoids.

High fat intake contributes to increased risk of obesity, diabetes and atherosclerosis (the primary cause of coronary and cardiovascular diseases, and the leading cause of illness and death in North America). Saturated fats have a profound hypercholesterolemic effect, whereby blood cholesterol levels increase.

Intake of monounsaturated fats in oils is thought to be preferable to consumption of polyunsaturated fats in oils because the monounsaturated fats apparently do not lower levels of HDL cholesterol (the "good" cholestrol, versus its "bad" counterpart: LDL). Keeping cholesterol in the normal range not only helps prevent heart attacks and strokes but may also prevent the progression of atherosclerosis.

Food Sources for Different Types of Lipids

The foods listed next to each type of lipid contain high concentrations of that lipid.

• Saturated. Butter, ghee, suet, tallow, lard, coconut oil, cottonseed oil, and palm kernel oil, dairy products (especially cream and cheese), meat, chocolate, and some prepared foods.

• Monounsaturated (a type of unsaturated). Nuts, avocados, tea seed oil, olive oil. Canola oil is 57%–60% monounsaturated fat, olive oil is about 75% monounsaturated fat while tea seed oil is commonly over 80% monounsaturated fat. Other sources include grapeseed oil, ground nut oil, peanut oil, flaxseed oil, sesame oil, corn oil, popcorn, whole grain wheat, cereal, oatmeal, safflower oil, sunflower oil, tea-oil Camellia.

• Polyunsaturated (a type of unsaturated). Grain products, seafood (herring, salmon, mackerel, halibut, fish oil), soybeans, sunflower oil, safflower oil. Foods like mayonnaise and soft margarine may also be good sources, but nutritional facts vary by style and brand.

• Trans. The majority of trans fats consumed are created by the processed food industry. As such, these fats can be found in many fast foods, snack foods, fried foods and baked goods made in (generally larger) facilities. Naturally occurring: the fat in the milk and body fat of ruminants (such as cattle and sheep) is about 2–5% of the total fat.

Fats

• butter
• cocoa butter
• dripping (sometimes called tallow)
• lard
• margarine
• schmaltz (rendered chicken fat)
• shortening (including Crisco, Copha)
• spek
• strutto
• suet

Oils

• coconut oil
• corn oil
• cottonseed oil
• garlic oil
• ghee (India) = clarified butter (US)
• grape seed oil
• groundnut fruit oil (peanut oil)
• olive oil
• palm oil
• low erucic acid rapeseed oil (LEAR oil, marketed as Canola)
• safflower oil
• sesame oil
• soybean oil
• sunflower oil