Fats in Human Health

Introduction

There are numerous types of fat. Your body makes its own fat from taking in excess calories. Some fats are found in foods from plants and animals and are known as dietary fat. Dietary fat is one of the three macronutrients, along with protein and carbohydrates, that provide energy for your body. Fat is essential to your health because it supports a number of your body's functions. Some vitamins, for instance, must have fat to dissolve and nourish your body.

Role of Fats in Nutrition

Your body needs fat to function properly. Besides being an energy source, fat is a component used in the production of several hormone-like compounds called prostaglandins that help regulate blood pressure, heart rate, blood vessel constriction, blood clotting and the nervous system. In addition, dietary fat carries fat-soluble vitamins A, D, E and K from your food into your body. Fat also helps maintain healthy hair and skin, protects vital organs, keeps your body insulated, and provides a sense of fullness after meals (satiety).

But clearly, too much fat can have a negative impact on your health. A high-fat diet can increase your risk of heart disease, high blood cholesterol, diabetes and some kinds of cancer and is a major culprit in weight gain. It may also lead to obesity, a risk factor for several diseases, including cancer, gallstones, diabetes, liver disease and osteoarthritis.

The good fats compete with bad fats, so it's important to minimize the intake of trans fats and cholesterol (animal fat) while consuming enough good fats. Also, good fats raise your HDL or "good cholesterol". One of the jobs of this High Density Lipoprotein (HDL) or "good cholesterol" is to grab your bad cholesterol, LDL (Low Density Lipoprotein), and escort it to the liver where it is broken down and excreted. In other words, these good fats attack some of the damage already done by the bad fats. This is very important in an age when so many people are struggling to get their cholesterol down, and fight heart disease and obesity.

Nuts	Avocado	Butter
© Biovision	© Biovision	© Biovision

Know your Fats

Since fat plays a significant role in health, choose your foods and the types of fat you use wisely. When you have cholesterol (fat droplets that deposit along blood vessels) you need to be more careful about what type of fat you use. Here's a primer on the common types of fat found in food:

a) Trans Fat (the worst, dangerous if taken in plenty)

Along with saturated fat, trans fat will adversely raise your blood cholesterol levels and increase your risk of heart disease. It will raise both the bad cholesterol (LDL) and total cholesterol. Tran?s fat also referred to as trans-fatty acids comes from adding hydrogen to vegetable oil through a process called hydrogenation. This is the process where the vegetable oil is made into solid. This makes the fat more solid and less likely to turn rancid. This also makes the fat easily usable in things like bread. Hydrogenated fat is a common ingredient in commercial baked goods such as crackers, cookies and cakes and in fried foods such as doughnuts and Chips (French Fries). Shortenings and some margarine are high in trans fat. It can also be used to make things like peanut butter soft and so easily spread on the bread. Look for the words HYDROGENATED or PARTIALLY HYDROGENATED in the list of ingredients to see if Trans fat is included. Some margarine labels state if the product has no trans-fatty acids.

b) Saturated Fat (not as bad as was thought of long time ago)

When you think of "bad" fats, think saturated. Most saturated fats can increase your blood cholesterol levels and risk of coronary artery disease. Usually solid or waxy at room temperature, saturated fat is most often found in animal products - such as red meat, poultry, butter and whole milk. Other foods high in saturated fat include coconut, palm and other tropical oils.

c) Polyunsaturated Fat (good)

Usually liquid at room temperature and in the refrigerator, polyunsaturated fats when used instead of saturated fats help lower blood cholesterol levels. In addition, they may help reduce the amount of cholesterol deposits on your arteries. Foods high in polyunsaturated fats include vegetable oils such as safflower, corn, sunflower, soy and cottonseed oils. Sunflower and corn (maize) oil are commonly found in our market.

One type of polyunsaturated fat omega-3 fatty acids may be especially beneficial to your health. Omega-3 fat decrease your risk of heart attack, protect against irregular heartbeats and lower blood pressure levels. It may even protect against some cancers. You'll find omega-3s mainly in fish particularly in fatty, cold-water fish, such as salmon, mackerel and herring. Lesser amounts are in flaxseeds, soybeans and canola oil (mainly found in the European market).

You can get sufficient omega-3 fatty acids by consuming two to three servings of fish per week. Pregnant women and women who plan to become pregnant during the next few years should consume a lot of fish. After all it has also been found to improve the intellectual development of the children. 

d) Monounsaturated Fat (very good)

If used in place of other fats, monounsaturated fat can lower your risk of heart disease by reducing your blood cholesterol level. In addition, monounsaturated fat, unlike polyunsaturated fat, is more resistant to oxidation a process that leads to cell and tissue damage in your body. This type of fat is usually liquid at room temperature but may start to solidify in the refrigerator. Foods high in monounsaturated fat include olive, peanut and canola oils.

Avocados and most nuts also have high amounts of  monounsaturated fat.If used in place of other fats, monounsaturated fat can lower your risk of heart disease by reducing your blood cholesterol level. In addition, monounsaturated fat, unlike polyunsaturated fat, is more resistant to oxidation a process that leads to cell and tissue damage in your body.

This type of fat is usually liquid at room temperature but may start to solidify in the refrigerator. Foods high in monounsaturated fat include olive, peanut and  canola oils. Avocados and most nuts also have high amounts of  monounsaturated fat.

e) Cholesterol (important)

Your body manufactures all of the cholesterol it needs, but you also get cholesterol from eating foods derived from animal sources, such as meat and organ meats, poultry, seafood, eggs, dairy products, lard and butter and trans fatty acid (explained above). Cholesterol is vital to the structure and function of all cells in your body, but it's also the main substance in fatty deposits (plaques) that can develop in your arteries. Plaques that build up can reduce blood flow, increasing your risk of heart disease and stroke.

f) Essential Fatty Acids

Essential Fatty Acids (EFAs) are necessary fats that humans cannot synthesize, and must be obtained through diet. EFAs are long-chain polyunsaturated fatty acids derived from linolenic, linoleic, and oleic acids. There are two families of EFAs: Omega-3 and Omega-6. Omega-9 is necessary yet "non-essential" because the body can manufacture a modest amount on its own, provided essential EFAs are present.Omega-3 fatty acids are derived from Linolenic Acid, Omega-6 from Linoleic Acid, and Omega-9 from Oleic Acid.

Food rich in mega-3 fatty acids

© www.adam.com

EFAs support the cardiovascular, reproductive, immune, and nervous systems. The human body needs EFAs to manufacture and repair cell membranes, enabling the cells to obtain optimum nutrition and expel harmful waste products. A primary function of EFAs is the production of prostaglandins, which regulate body functions such as heart rate, blood pressure, blood clotting, fertility, conception, and play a role in immune function by regulating inflammation and encouraging the body to fight infection. Essential Fatty Acids are also needed for proper growth in children, particularly for neural development and maturationof sensory systems, with male children having higher needs than females. Fetuses and breast-fed infants also require an adequate supply of EFAs through the mother's dietary intake

EFA deficiency and Omega 6/3 imbalance is linked with serious health conditions, such as heart attacks, cancer, insulin resistance, asthma, lupus, schizophrenia, depression, postpartum depression, accelerated aging, stroke, obesity, diabetes, arthritis, ADHD, and Alzheimer's Disease, among others.

Table: Essential Fatty Acids, sources and uses

Adapted from (Holford 2007) 

Choose your dietary fats wisely 

Be aware that many foods contain different kinds of fat and varying levels of each type. The rest can be used in moderation. Limit fat in your diet, but don't cut it out completely. The worst kind of fat is the trans-fat. If you have been diagnosed with high cholesterol, you should eliminate from your diet. Focus on reducing foods high in saturated fat and select more foods made with unsaturated fats. Consider these tips when making your choices:

• Use olive oil instead of vegetable oil in salad dressings and marinades. 
• Sprinkle slivered nuts or sunflower seeds on salads instead of bacon bits. 
• Snack on a small handful of nuts mixed with seeds rather than potato chips or processed crackers. Or try peanut butter or other nut-butter spreads 
• Add slices of avocado, rather than cheese, to your sandwich. Try using avocado and peanut butter as spread rather than solid fats. 
• If you eat animal protein, eat rather fish than meat. Make sure you buy organic fish; purchase it at regular markets, rather than the butchers. If you eat eggs and meat, buy only local and organic free range eggs and meat.
• Most of your foods can be eaten without fat including your starches. Do not fry your foods. 

Unsaturated fats have few adverse effects on blood cholesterol levels, but you still need to consume all fats in moderation. Eating large amounts of any fat adds excess calories. Fat contains 9 calories per gram, compared with 4 calories per gram for protein and carbohydrates. In addition, make sure that fatty foods don't replace more nutritious options, such as fruits, vegetables or whole grains.

Types of fat
© www.Spreadfacts.com.au

Review Process

1. Draft by Infonet October 2011
2. Review by Dr Alice Ojwang-Ndong January 2012

Information Source Links

• Holford, Patrich (2007): New Optimum Nutrition Bible. Piatkus books www.piatkusbooks.net, An imprint of Little, Brown book group, 100 Victoria Embankment, London EC4Y ODY. ISBN No: 978-0-7499-2552-9. Available in Kenya through the Health Food shops
• www.livestrong.com
• www.mayoclinic.com
• http://en.wikipedia.org/wiki/Fat