The following is a list of the groups of good- and poor-quality fats and how they are identified:
Unsaturated fats are usually liquid at room temperature and are divided into two groups: polyunsaturated fats and monounsaturated fats. Polyunsaturated fats play a key role in brain development and growth, and they have a beneficial effect on health, when eaten in moderation. They include omega-3 and omega-6 fatty acids and can be found in a variety of vegetable oils, as well as fatty fish and some nuts. Monounsaturated fats, found in olive oil, avocados, and oily fish can lower bad cholesterol and support good cholesterol. They also support your baby’s immune system and the reduction of insulin resistance.
Saturated fats are found primarily in animal-based foods, including meat, eggs, butter, and other dairy products. These fats are typically solid at room temperature, hard to digest, and high in cholesterol. Examples of these saturated fats include butter (usually made from cows’ milk), lard (from pork), tallow (from beef), and schmaltz (from poultry). Some plant-based sources of saturated fats are palm oil and coconut oil, which are healthier and easier to digest than their animal-based counterparts.
Hydrogenated and partially hydrogenated oils (trans fats) are made by injecting hydrogen into liquid oil to make it stable and solid at room temperature. Hydrogenation prevents oil from becoming rancid and keeps it from separating into a solid and a liquid, the way that natural peanut butter separates. Many manufacturers started using hydrogenated vegetable oil, because it is cheaper, and it offers appealing characteristics to commercially baked and processed foods, such as structure, texture, and flavor to baked goods. Hydrogenated fats are often used for frying fast foods and in restaurants because they can withstand high heat and last longer. These fats raise levels of bad cholesterol and lower levels of good cholesterol.
Labeling laws regarding trans fats have become stricter and more transparent, but they allow companies to label their food as being trans fat-free if they contain less than 0.5 grams of trans fat per serving. As a result, many manufacturers switched to refined oils, such as cottonseed and soy oils, which are not much healthier. Most producers that sell to natural food stores have replaced partially hydrogenated oils with higher quality oils, but check the labels to be sure. If a label states that it contains fully hydrogenated oil, then it should be trans fat-free; if a food contains partially hydrogenated oils, then it contains trans fats.
The Top 10 Foods Most Like to have Trans Fats
- Margarine, processed peanut butter, and other non-butter spreads
- Packaged cakes, cookies, and baking mixes
- Instant ramen noddles and soups
- Fried fast food
- Frozen food
- Commercial baked goods
- Chips and crackers
- Breakfast cereal and energy bars
- Cookies and candy
- Toppings and drops
Tips for Monitoring Trans Fat Consumption
- Read labels, and choose foods made without hydrogenated oils.
- Cook your own meals.
- Avoid chain restaurants and fast food establishments.
- Shop at a local bakery.
- Buy nut butters that are freshly ground.
- Use natural oils, such as olive oil and sesame oil.
- Order fish and meat broiled or baked in a restaurant.
- Pop your own popcorn.
Oxidation of Oils
Oils oxidize and become rancid through a chemical reaction when they are exposed to air, light, and high heat. Consuming rancid oils can lead to digestive distress, the introduction of free radicals into the body, the depletion of vitamins B and E, and damage to DNA in cells. You know oil is becoming rancid by smelling or tasting it and looking at its color—if it is darker than normal, it may be turning rancid.
Each type of oil has a temperature at which it oxidizes and breaks down in both nutrition and flavor. This temperature is called its smoke point. At this point, a bluish smoke is produced that is irritating to the eyes and throat, and it can emit harmful fumes and free radicals. The smoke point of oils varies according to the type of oil and the degree to which it has been refined. Refining oil raises the smoke point, and lighter colored oils are usually more refined so they can be used for high-heat cooking like deep-frying.
The method of storing oils determines the speed at which it can go rancid. Store oils in an opaque container, because it deteriorates quicker when exposed to light. A glass, rather than plastic, container gives you the assurance that the plastic is not dissolving into the oil. Storing them near the stove for convenience shortens the life span of the oil due to exposure to the heat of the stove. High temperatures increase the speed of deterioration, so store oils in a cool, dark place.