Although both animal and plant foods contain fats (or lipids), much of the fat consumed by North Americans comes from animal products in the form of meat, fatty fish, eggs, and dairy products such as butter, cream, cheese, and whole milk. Vegetable fats are found in vegetable oils and vegetable shortenings.
Fats are an essential nutrient and have many beneficial functions in the body. They supply a steady source of energy, regulate certain body functions, contribute to the feeling of “fullness” after eating, and absorb and transport fat-soluble vitamins. There are two main types of fat: saturated and unsaturated. Saturated fats come from animal and tropical plants sources while unsaturated fats come from plant sources and fish. Unsaturated fats are further divided into monounsaturated and polyunsaturated fats.
The classification of a fat depends on its atomic structure. Fat is composed of carbon and hydrogen atoms bound together in long chains. If the chain has as many hydrogen atoms as it can possibly have, the fat is said to be saturated. If there is room on the chain for more atoms of hydrogen, the fat is unsaturated. The difference in atomic structure means that at room temperature most saturated fats are solid and unsaturated fats are liquid. If there is one double space free of hydrogen atoms in the chain, the unsaturated fat is monounsaturated. If there are two or more double spaces free of hydrogen atoms in the chain, the fat is classified as polyunsaturated. The best sources of polyunsaturated fats are fish and most vegetable oils, including corn oil, safflower oil, and sunflower oil.
One way of viewing the difference between saturated and unsaturated fats is to consider the atomic structure of fat to be like a sponge. If the “sponge” is totally full of hydrogen atoms, the fat is saturated. If the “sponge” can still hold more hydrogen atoms, the fat is unsaturated. Knowing the molecular structure of fat is not as important as knowing that saturated fats tend to have negative health effects; polyunsaturated fats are better for us than saturated fats, and mono-unsaturated fats may even be more beneficial. Another point to remember about lipids is that, in general, animal fats are saturated while most plant fats are unsaturated. However, lipids in tropical oils tend to be saturated fats. This means that cocoa butter, coconut oil, palm kernel oil, and palm oil are saturated oils. The best sources of polyunsaturated fats are fish and most vegetable oils including corn oil, safflower oil, and sunflower oil.
Fatty fish such as mackerel, tuna, salmon, trout, and herring are rich in special fatty acids belonging to the omega-3 group. There is some evidence that one of the omega-3 chemicals, eicosapentaenoic acid (or EPA for short), helps to prevent coronary heart disease, provides relief for arthritis victims, and may reduce the frequency and intensity of migraine headaches (Harvard Medical School Patient Education Centre, 2015). Inconsistent findings in nutritional research suggest there is some controversy about the validity of medical claims for fish oils.
Significant amounts of monounsaturated fats are found in olive oil, almond oil, canola oil, and peanut oil. The types of fatty acids found in a variety of oils are shown in Table 5.
|Type of Lipid (15 mL)||Total Fat (g)||SFA (g)||MUFA (g)||PUFA (g)|
Saturated fat and trans fats have one combined % DV in the nutrition facts table. Both may have negative effects on blood cholesterol levels and health.
Below is an excerpt from Healthy Eating Canada that explains how the % DV for saturated and trans fat is calculated.
The combined Daily Value in nutrition labelling is based on 20 g of saturated and trans fats for a reference diet. For example, in the Nutrition Facts table below (Figure 1), the food product has 7 g of saturated and 0.5 g of trans fats for a total of 7.5 g. The product would therefore, have a % Daily Value for saturated and trans fats of 38%.
(7.5 g ÷ 20 g) × 100 = 38%
Nutrition Facts: Per burger (85 g)
|Amount||% Daily Value|
|Fat 18 g||28 %|
|Saturated 7 g
+ Trans 0.5 g
|Cholesterol 55 mg|
|Sodium 330 mg||14 %|
|Carbohydrate 1 g||1 %|
|Fibre 0 g||0 %|
|Sugars 12 g|
|Protein 12 g|
|Vitamin A||0 %|
|Vitamin C||0 %|
“Remember: 5% DV or less is a little and 15% DV or more is a lot for all nutrients” (Government of Canada, Healthy Eating, 2015, para 8).
Canada has implemented measures to control the amount of trans fat over the past several years. Although initiated in 2004 by Jack Layton of the New Democratic Party, it took several years to be mandated. In 2008, Calgary was the first city in Canada to ban trans fats, and British Columbia was the first province to mandate that that trans fat be limited, following a June 2006 recommendation by “a task force co-chaired by Health Canada and the Heart and Stroke Foundation of Canada [which] recommended a limit of 5% trans fat (of total fat) in all products sold to consumers in Canada (2% for tub margarines and spreads)” (Trans Fat Task Force, 2006).
Although measures to reduce the amount of trans fats are in effect, it is still not well understood by the general public which trans fats may be bad (i.e., contribute to high cholesterol and should be avoided), and which trans fats may have a positive health effect. It has, however, become more and more known that naturally occurring trans fats are not the culprit, negatively affecting cholesterol, but hydrogenated fats (man-made by changing an oil to a hard fat) are. You can find more information on hydrogenated fats in the Understanding Ingredients for the Canadian Baker open textbook.
- Note: SFA = Saturated fatty acid, MUFA = Monounsaturated fatty acid, PUFA = Polyunsaturated fatty acid ↵