The word “fat” has become such an awful thing that everybody wants to get rid of it! Believe it or not, we can’t live without it even though so many of us are walking around with so much of around our waistlines. That is why, when one of my readers asked me to consider writing a post on healthy fats for children, I was immediately hooked on the idea. Here is a summary of what I found in my research from various sources. Leave a comment if you would like to know more about anything specific or if you want to suggest a topic for me to research and write about.
Fats are a very important part of diet, especially for growing children, because they serve many functions -
- supply energy (2 times as many calories as carbohydrates and proteins for the same weight)
- build tissues, especially brain tissue which is 60% fat
- dissolve vitamins A, D, E and K for absorption in the body
- protect the body from shock, maintain temperature
- maintain healthy skin and hair
- all cells have a fatty outer layer which controls what goes in and what goes out
What are fats?
Chemically, fats are long, chain-like molecules containing a “backbone” of glycerol and “side-links” of fatty acids. They are also called triglycerides.
Glycerol, commonly known as glycerin, is a small molecule containing carbon, hydrogen and oxygen. It has three hydroxyl functional groups, which make it soluble in water. The fatty acids, on the other hand, are longer chains containing carbon and hydrogen with an acid functional group at the end. They are not soluble in water. When glycerol and fatty acids combine, the acid group from the long chain fatty acids attaches with the hydroxyl groups on the glycerol to make a strong chemical bond. Because glycerol has three hydroxyl functional groups, three chains of fatty acids can combine to form a triglyceride. You can imagine a triglyceride molecule in the shape of a capital letter E as shown in this molecular model. You may have heard your doctor talk about the amount of your triglycerides after doing a blood test.
The exact chemical nature of the long-chain fatty acids linked to the glycerol backbone determines the overall nature of the fat molecule. Fats can be solids or liquids, saturated or unsaturated, trans or cis depending on the size and structure of these chains. You may have heard these different types of fats:
- Unsaturated fat – the chemical bonds between the carbon atoms of the fatty acid chains in unsaturated fats are double bonds. Double bonds are less stable, which means that unsaturated fats can be “broken” more easily by oxygen. Since the fatty acid chains can have a lot of carbon atoms, there can be one or more double bonds in these chains. Generally, unsaturated fats are in a liquid form at room temperature, that is why they are also known as oils. Oils from plants and nuts contain mostly unsaturated fats.
- Monounsaturated fat – these fats have only one double bond.
- Polyunsaturated fat – these fats have more than one double bond.
- trans fat - when double bonds are present in a fat molecule, the structure of the fatty acid chains can be either straight or kinked because of the arrangement of carbon and hydrogen atoms around the double bonds. In trans-fat, the chain is more straight compared to the other type called the cis-fat. As a result, the trans fats have a higher melting point and are usually solids at room temperature or even body temperatures. Cathy from A Life Less Sweet has written an excellent post on trans fats if you would like to learn more.
- Saturated fat – when there are no double bonds in the fat molecule, it is called a saturated fat. Dairy and meat products contain some of the natural fats. Most of the saturated fat in food products comes from hydrogenation of unsaturated fats.
- Omega-3 and omega-6 fatty acids – these are called essential fatty acids because the human body cannot make them, therefore they need to come from the diet. Example of omega-3 fatty acids are: ALA (alpha-linolenic acid), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Linoleic acid is an example of omega-6 fatty acids.
How much fat?
Here are some guidelines from the American Heart Association and the USDA -
- Children under the age of 3 should get about 30 – 35% of daily calories from fats
- Children between 4 – 18 years old should get about 25 – 30% of daily calories from fats
- Adults should get about 20 – 35% (preferably closer to 20%) of daily calories from fats
Each gram of fat contains about 9 calories, so a 2000 calorie diet should not have more than 67 g of fat for the 30% requirement. Active kids between 2 – 5 years old, who need about 1600 daily calories, should get about 55 g of fat.
Even though both omega-3 and omega-6 fatty acids are essential, too much of omega-6 and too little of omega-3 is also not good. In the modern meat-rich diet, the ratio of the two is about 20 to 1, which is much higher than the 2:1 recommended ratio.
What types of fats are good?
Simply put, select foods with unsaturated fats and essential fatty acids and stay away from saturated fats and trans fats.
Here are a few sources of “good” fats -
Monounsaturated fats – nuts, olive oil, canola oil, avocado
Polyunsaturated fats and fatty acids – plant oils (watch out for partially hydrogenated oils, see below), nuts, fish, flax seeds or powder, sunflower seeds, grass-fed beef
What types of fats should I avoid?
Some saturated fat is ok (about 10% of daily calories), but trans fat is a big no-no. The best way to check if trans fat is present in the food is to look for “partially hydrogenated” oils in the list of ingredients. Don’t fall for the zero trans fat on the nutrition facts panel because FDA allows it if the level of trans fat is less than 0.5 g per serving.
Here are a few sources of saturated and trans-fats- Cheese, beef, whole milk, baked foods, margarine, chips, fried foods, eggs, poultry.
Here are a few good resoures for further reading if you are interested:
Fear not the healthy fats – Seattle’s Child Magazine
2005 dietary guidelines for Americans – USDA, Dept of Health & Human Services