Fats: Functions, Sources, Recommended Intake

What Are Fats?

Fat is a macronutrient. It can either be solid at room temperature or liquid at room temperature. Liquid fat is called oil. When a fat is heated it melts and becomes oil. When oil is chilled it solidifies (hardens) and becomes a fat.

The chemical name for a fat molecule is triglyceride. Triglycerides are made of one part glycerol and three parts fatty acids. Fatty acids can be either saturated (full up) or unsaturated (not full up) with the element hydrogen. 

Saturated fatty acids are full up with hydrogen atoms and cannot take any more. Solid fats are mostly made of saturated fatty acids – butter, lard, suet, solid margarine, and the fat on meat.

On the other hand, unsaturated fatty acids are not full up with hydrogen atoms – they could take more by breaking the double bonds in the molecules and adding hydrogen. If there is one double bond it is called a monounsaturated fatty acid. If there are two or more double bonds it is called a polyunsaturated fatty acid. Liquid oils are mostly made of unsaturated fatty acids – sunflower oil, olive oil, rapeseed oil, corn oil, and nut oil.

It is possible to make a solid fat, like margarine, from liquid oil by adding hydrogen under special conditions in a factory. The process is called hydrogenation.

Functions of Fats in the Body

Fat is the main store of energy in the body. It is stored in special cells under the skin called adipose tissue. This tissue insulates the body to stop it from losing heat and protects the bones against physical damage by providing them with padding. Fat also gives us fat-soluble vitamins A, D, E, and K and it has a very important job in forming cell walls throughout the body.

Today, health experts have revised dietary recommendations to acknowledge that not all fats have damaging health consequences. In fact, higher intakes of some kinds of fats (for example, omega-3 fatty acids) support good health.

Instead of urging people to cut back on all fats, current recommendations suggest carefully replacing the “bad” saturated and trans fats with the “good” unsaturated fats and enjoying these fats within kcalorie limits. The goal is to create an overall eating pattern moderate in calories that provides enough of the fats that support good health, but not too much of those that harm health.

Learn more about the important functions of fat in the body.

Food Sources of Fats

Some fats and oils are visible (they are easy to see), such as the fat on cuts of meat, solid fats such as butter, lard and suet, margarine and low fat spreads, and liquid oils (like the ones described above). Vitamins A and D are also added by law to margarine to make it have a similar nutritional value to butter.

Some fats and oils are invisible (they form part of the food and cannot be seen on their own), such as the fats and oils in avocados, oily fish (tuna, sardines, mackerel), cakes, pastries, biscuits, burgers and other meat products, chips, potato crisps, sausages, cheese, egg yolk, cream, fried foods, some ready-made meals, nuts, chocolate and ice cream.

Some foods naturally contain little fat, such as fruits (except avocados), vegetables, cereals (rice, wheat) and white fish (cod, plaice, haddock).

If you are not sure about the amount of fat in a food, it is important to read the nutrition information on food labels. These show the amount of fat in 100g of the product.

Deficiency of Fats

Some fatty acids are essential for the correct growth and functioning of the body and must be obtained from food. If babies and young children do not have enough of these their normal growth will be affected. If we do not get enough energy from carbohydrates or fat in our food, we will use up our fat stores and become thinner. This will also mean that we may feel cold and will hurt our bones if we accidentally hit them.

Side Effects of Too Much Fat in Diet

Fat provides the body with a concentrated source of energy (over twice the amount that carbohydrate provides). If we eat too much fat and do not use up the energy will eaten, the body will store the excess energy in the adipose tissue, and we will gain weight. The extra fat may also build up in the liver and cause health problems.

Eating foods that are high in saturated fat can raise blood cholesterol levels, which increases the chances of developing heart disease. There is also concern about the amount of hydrogenated fats that people eat.

Hydrogenated fats and oils are used in many processed and ‘fast foods’. It has been discovered that the hydrogenation process can alter some of the fatty acids so that they turn into trans fats. The body is not able to use trans fats and health professionals think that they cause damage to some of the body’s cells, which may lead to a variety of health problems including heart disease, some forms of cancer, diabetes, obesity and problems with the bones. Like saturated fats, trans fats can raise blood cholesterol levels.

Recommended Intakes of Fats

Some fat in the diet is essential for good health. The Dietary Guidelines for Americans recommend that a portion of each day’s total fat come from raw oils. Oils are naturally present in foods such as nuts, avocados, and seafood. In addition, many commonly used oils such as olive, peanut, safflower, soybean, and sunflower oils are extracted from plants. When choosing oils, alternate among the various types to obtain the benefits different oils offer. Peanut and safflower oils are especially rich in vitamin E.

Olive oil contributes naturally occurring antioxidant phytochemicals with potential heart benefits, and canola oil is rich in monounsaturated and essential fatty acids. An adequate intake of the needed fat-soluble nutrients can be ensured by a small daily intake of oil: 27 grams (6 tsp) for a 2,000-calorie diet, for example.

Defining the exact amount of fat, saturated fat, or cholesterol that benefits health or begins to harm health, however, is not possible. For this reason, no RDA or UL has been set. Instead, the DRI and Dietary Guidelines suggest a diet that is low in saturated fat, trans fat, and cholesterol and provides 20 to 35 percent of the daily energy intake from fat. These recommendations recognize that diets with up to 35 percent of calories from fat can be compatible with good health if energy intake is reasonable and saturated and trans fat intakes are low.

When total fat intake exceeds 35 percent of calories, saturated fat intakes increase to unhealthy levels. For a 2,000-calorie diet, 20 to 35 percent represents 400 to 700 calories from fat (roughly 45 to 75 grams). Fat and oil intakes below 20 percent of kcalories increase the risk of inadequate essential fatty acid intakes. The FDA established Daily Values for food labels using 30 percent of energy intake as the guideline for fat.

Part of the allowance for total fat provides for the essential fatty acids—linoleic acid and linolenic acid—and Adequate Intakes (AI) has been established for these two fatty acids (see the inside front cover). The DRI suggests that linoleic acid provides 5 to 10 percent of the daily energy intake, and linolenic acid 0.6 to 1.2 percent.

Recommendations urge people to eat diets that are low in saturated fat, trans fat, and cholesterol. Specifically, consume less than 10 percent of calories from saturated fat, keep trans fat intakes as low as possible, and consume less than 300 milligrams of cholesterol each day. To help consumers meet these goals, the FDA established Daily Values for food labels using 10 percent of energy intake for saturated fat; the Daily Value for cholesterol is 300 milligrams, regardless of energy intake. There is no Daily Value for trans fat.

How To Reduce Fat Intake?

Asking consumers to limit their total fat intake was less than perfect advice, but it was straightforward—find the fat and cut back. Asking consumers to keep their intakes of saturated fats, trans fats, and cholesterol low and to use monounsaturated and poly-unsaturated fats instead may be more on target with heart health, but it also makes diet planning more complicated.

To make appropriate selections, consumers must first learn which foods contain which fats. For example, avocados, bacon, walnuts, potato chips, and mackerel are all high-fat foods, yet some of these foods have detrimental effects on heart health when consumed in excess, and others seem neutral or even beneficial.

There are various ways in which we can reduce the amount of fat we eat:

  • Choose lean cuts of meat.
  • When buying minced meat, check on the label for the fat content and try to buy minced meat that has no more than 5 per cent fat.
  • Trim the fat from meat and poultry before cooking.
  • Grill or oven bake foods such as meat, sausages and fish rather than fry them in fat or oil (because the fat will melt and drain away from the food).
  • When shallow frying or stir frying food, if the food starts to become dry, add a little water rather than more oil to continue the cooking.
  • Choose low or reduced fat versions of foods such as yogurt, cheese, milk, biscuits, low fat spreads.
  • Reduce the amount of butter or margarine that you spread on bread.
  • Instead of using mayonnaise in sandwiches or to mix salad ingredients, try using low fat versions of crème fraiche, salad dressing or fromage frais instead.
  • Buy canned oily fish such as tuna and sardines in tomato sauce, water or brine instead of oil.
  • Instead of adding butter or margarine to mashed potato, add wholegrain mustard.
  • Instead of eating ice cream, try sorbet which has a low fat content.

FAQs About Fats

Why some high-fat foods are compatible with a heart-healthy diet?

The traditional diets of Greece and other countries in the Mediterranean region are exemplary in their use of “good” fats, especially olives and olive oil. A classic study of the world’s people, the Seven Countries Study, found that death rates from heart dis-ease were strongly associated with diets high in saturated fats, but only weakly linked with total fat. In fact, the two countries with the highest fat intakes, Finland and the Greek island of Crete, had the highest (Finland) and lowest (Crete) rates of heart disease deaths. In both countries, people consumed 40 percent or more of their calories from fat.

Clearly, a high-fat diet was not the primary problem. When researchers refocused their attention on the type of fat, they found that the Cretes ate diets high in olive oil but low in saturated fat (less than 10 percent of kcalories), a pattern they linked with relatively low disease risks. Many studies that followed yielded similar results—people who follow “Mediterranean-type” eating patterns have low rates of heart disease, some cancers, and other chronic diseases, and their life expectancy is high.

Unfortunately, many busy Mediterranean people today, especially the young, are trading labor-intensive traditional diets for convenient and fast Western-style foods. At the same time, their health advantages are rapidly disappearing.

When olive oil replaces saturated fats, such as those of butter, coconut oil or palm oil, hydrogenated stick margarine, lard, or shortening, it may offer numerous health benefits. Olive oil helps to protect against heart disease by:

  • Lowering total and LDL cholesterol and not lowering HDL cholesterol or raising triglycerides.
  • Reducing blood-clotting factors.
  • Providing antioxidant phytochemicals that may reduce LDL cholesterol’s vulnerability to oxidation.
  • Lowering blood pressure.
  • Interfering with the inflammatory process related to disease progression.

The phytochemicals of olives captured in extra virgin olive oil, and not its monounsaturated fatty acids, seem responsible for these potential effects. When processors lighten olive oils to make them more appealing to consumers, they strip away the in- tensely flavored phytochemicals of the olives, thus diminishing not only the bitter flavor of the oils, but also their potential for protecting the health of the heart.

It is important to recognize that olive oil is not a magic potion; drizzling it on foods does not make them healthier. Like other fats, olive oil delivers calories per gram, which can contribute to weight gain in people who fail to balance their energy intake with their energy output.

Its role in a healthy diet is to replace saturated fats. Other vegetable oils, such as canola oil or safflower oil, in their liquid unhydrogenated states, are also generally low in saturated fats and high in unsaturated fats. Such oils, when they replace solid, saturated fats in the diet, may help to preserve heart health.

Which foods are highest in saturated and trans fats?

The major sources of saturated fats in the U.S. diet are fatty meats, whole-milk products, tropical oils, and products made from any of these foods. To limit saturated fat intake, consumers must choose carefully among these high-fat foods. More than a third of the fat in most meats is saturated. Similarly, more than half of the fat is saturated in whole milk and other high-fat dairy products, such as cheese, butter, cream, half-and-half, cream cheese, sour cream, and ice cream.

Consumers rarely use the tropical oils of palm, palm kernel, and coconut in the kitchen, but these oils are used heavily by food manufacturers and are therefore commonly found in many commercially prepared foods.

When choosing meats, milk products, and commercially prepared foods, look for those lowest in saturated fat. Labels provide a useful guide for comparing products in this regard, and Appendix A lists the saturated fat in several thousand foods.

Even with careful selections, a nutritionally adequate diet will provide some saturated fat. Zero saturated fat is not possible even when experts design menus with the mission to minimize saturated fat. Eating patterns based on fruits, vegetables, legumes, nuts, soy products, and whole grains can, and often do, deliver less saturated fat than diets that depend heavily on animal-derived foods, however.

Are some fats “good” and others “bad” from the body’s point of view?

Saturated and trans fats do indeed seem mostly bad for the health of the heart. Aside from providing energy, which unsaturated fats can do equally well, saturated and trans fats bring no indispensable benefits to the body. Furthermore, no harm can come from consuming diets low in them. In contrast, unsaturated fats are mostly good for the health of the heart when consumed in moderation.

To date, their one proven fault seems to be that they, like all fats, provide abundant energy to the body and so may promote obesity if they drive calorie intakes higher than energy needs. Obesity, in turn, often begets many body ills.

When judging foods by their fatty acids, keep in mind that the fat in foods is a mixture of “good” and “bad,” providing both saturated and unsaturated fatty acids. Even predominantly monounsaturated olive oil delivers some saturated fat. Consequently, even when a person chooses foods with mostly unsaturated fats, saturated fat can still add up if the total fat is high.

For this reason, fat must be kept below 35 percent of total calories if the diet is to be moderate in saturated fat. Additionally, food manufacturers may come to the assistance of consumers wishing to avoid the health threats from saturated and trans fats. Some companies now make margarine without trans fats, and many snack manufacturers have reduced the saturated and trans fats in some products and offer snack foods in 100-kcalorie packages. Other companies are likely to follow if consumers respond favorably.

Eating a balanced diet based on vegetables, fruits, and legumes is a good idea, as is replacing saturated fats such as butter, shortening, and meat fat with unsaturated fats like olive oil and the oils from nuts and fish. These foods provide vitamins, minerals, and phytochemicals—all valuable in protecting the body’s health.

To further protect your health, you may want to reduce fats from convenience foods and fast foods; choose small portions of meats, fish, and poultry; and include fresh foods from all the groups each day. Take care to select portion sizes that will best meet your energy needs. Also, be physically active each day.

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