What are Macronutrients?
Macronutrients are the nutrients we need in larger quantities that provide us with energy. They are nutrients that provide calories or energy and are required in large amounts to maintain body functions and carry out the activities of daily life. There are three broad classes of macronutrient namely, proteins, carbohydrates and fats.
Dietary Fats as Macronutrients
Dietary fats in food are a type of nutrient. In nutrition, “Fat” is used to be a negative term. Years ago, to prevent weight gain and health issues such as heart disease and diabetes, it was widely advised that individuals reduce or avoid fat in their diet. Now it is obvious, however, that all fats are not bad. Some fats lower the level of cholesterol and help keep a person safe. People need some dietary fat. For many bodily functions, fat is essential. It is a source of energy, and the skeleton and the nerves are protected.
Fat also helps other nutrients to do their work. Fats have several essential body functions, including, but not limited to, energy supply, keeping the body warm, building cells, protecting many organs, helping the body absorb vitamins from foods, and producing hormones that make the body work the way it should. The key is to have in our diet a healthy balance of fats and other nutrients. Eat the healthiest fat types, in the right quantities.
Classification of Dietary Fats
The foods we consume have four major dietary fats, namely:
- Saturated fats
- Transfats
- Monounsaturated fats
- Polyunsaturated fats
Saturated fat
Saturated fat is a type of fat from a diet. It is one of the fats that is harmful. At room temperature, these fats are most often solid. At room temperature, saturated fats are solid and are often called solid fats. With hydrogen atoms, the essential carbon structure of these fatty acids is “saturated.” When an individual consumes too much over a long period, saturated fat can increase health risks.
A saturated fat-rich diet will push your total cholesterol up and tip the balance towards more harmful LDL cholesterol, which can lead to blockages in your heart and other parts of your body’s arteries. This, in fact, raises the risk of stroke and cardiovascular disorder.
Some sources of saturated fat include:
- animal meats and meat products
- dairy products, except those that are fat-free
- processed foods, including baked goods, snack foods, and French fries
- some vegetable oils, including coconut oil, palm oil, and cocoa butter
Trans Fats
Trans fatty acids, more generally called trans fats, are produced in the presence of hydrogen gas and a catalyst, a process called hydrogenation, by heating liquid vegetable oils. It makes them more stable and less likely to become rancid by partially hydrogenating vegetable oils. This method often turns the oil into a solid, which makes it act like margarine or shortening.
Partially hydrogenated oils can withstand repeated heating without breaking down, making them ideal for frying fast foods. For these purposes, partially hydrogenated oils have been a mainstay for frying, baked goods, and packaged snack foods and margarine in restaurants and the food industry. In our diets, partially hydrogenated oil is not the sole source of trans fats. Naturally, trans fats are often present in small quantities in beef fat and dairy fat.
In animal-based foods like meat and milk, small quantities of trans fats occur naturally. But in an industrial phase, most trans fats are made. To make them stable at room temperature, companies add hydrogen to liquid vegetable oils, so foods last longer. It also gives them a taste and texture that is pleasing.
Trans fat may taste good, but it’s not good for the body. This unhealthy type of fat increases the amount of LDL cholesterol, making it more probable for a person to have heart disease, stroke, and type 2 diabetes. It lowers “good” HDL cholesterol as well.
Trans fats are the worst form of fat for the heart, blood vessels, and the rest of the body because they induce inflammation, increase bad LDL and decrease good HDL, lead to insulin resistance and can have adverse health effects even in small quantities.
Trans fats are found commonly in these foods:
- French fries and other fried foods
- Cakes, pies, biscuits, cookies, crackers, doughnuts, and other baked goods
- Stick or tub margarines
- Microwave popcorn
- Frozen pizza
Monounsaturated fats
This type of fat is present in a number of foods and oils. Monounsaturated fat molecules are not saturated with hydrogen atoms—each fat molecule is bound to a single hydrogen atom. Monounsaturated fats can lower LDL or “bad” cholesterol levels and maintain healthy levels of “good” high-density lipoprotein (HDL) cholesterol. However, simply adding monounsaturated fat to the diet will not have that effect unless a person also reduces their intake of saturated fat.
Studies show that consuming foods high in monounsaturated fatty acids instead of saturated fats that enhance blood cholesterol levels can reduce the risk of heart disease and may also help to reduce the risk of type 2 diabetes.
Sources of monounsaturated fat include:
- olives and olive oil
- nuts and nut butters
- avocados
Polyunsaturated fats
This type of fat is often present in plant-based foods and oils. Evidence suggests that consuming foods high in polyunsaturated fatty acids instead of saturated fats increases blood cholesterol levels, which can minimize the risk of heart disease and may also help to reduce the risk of type 2 diabetes. Several spaces around each polyunsaturated fat molecule are not saturated with hydrogen atoms. Polyunsaturated fats are good for health, particularly fish and algae fats known as omega-3 polyunsaturated fatty acids. Omega-3 acids can help keep the heart healthy, reduce blood triglycerides, and improve brain, joint, and eye health. It protects against heart disease by lowering blood cholesterol levels and, if necessary, inflammation.
Omega-6 fatty acids are the other type of polyunsaturated fat. Most of these occur in vegetable oils and refined foods. Excessive consumption of omega-6 can, however, contribute to increased inflammation.
Sources of polyunsaturated fat include:
- oily fish, such as sardines, mackerel, trout, salmon, and herring
- safflower, grapeseed, soybean, and sunflower oils
- nuts, seeds, and pastured eggs
Functions of Dietary Fats in the Body
Fats perform useful roles both in the body and in the diet. In the body, fat serves as an important reservoir for energy storage, provides insulation and protection, and plays an important role in regulation and signaling. Large amounts of dietary fat are not needed to perform these roles, since most fat molecules can be synthesized by the body from other organic molecules such as carbohydrate and protein (with the exception of two essential fatty acids). However, fat also plays a special role in the diet, including increasing the absorption of fat-soluble vitamins and contributing to the taste and enjoyment of food. Let’s take a closer look at each of these fat roles in the body and in the diet.
Energy Storage
The extra energy of the food we eat is absorbed into adipose tissue or fat tissue. We draw on energy stored in fat to help meet our basic energy needs while we’re at rest and fuel our muscles to travel around the day, from walking to class, playing with our kids, dancing through dinner prep, or powering through a change at work. Being able to store energy when times are good will allow them to survive a period of food insecurity. In other cases, the energy stored in adipose tissue might allow a person to weather a long illness. Unlike other body cells that can store fat in a limited supply, fat cells are specialized in fat storage and are capable of extending almost indefinitely.
Insulating and Protecting the Body
Normal body fat for a man is 18 to 24 per cent and for a woman is 25 to 31 per cent, but adipose tissue can be a much greater proportion of body weight depending on the individual’s degree of obesity. Some of this fat is stored in the abdominal cavity, called visceral fat, and some is stored just below the skin, called subcutaneous fat. Visceral fat protects vital organs, such as the heart, kidneys, and liver. The blanket layer of subcutaneous fat insulates the body from high temperatures and helps to keep the internal climate under balance. It pads our hands and buttocks and prevents friction, as these areas frequently come in contact with hard surfaces. It also gives the body the extra padding needed to participate in physically challenging activities.
Regulating and Signaling of Hormones
Fat helps the body to produce and regulate hormones. For example, adipose tissue secretes the hormone leptin, which signals the energy status of the body and helps to control the appetite. Fat is also needed for reproductive health; a woman who lacks sufficient amounts will stop menstruating and be unable to conceive before her body can store more energy as fat. Omega-3 and omega-6 essential fatty acids help to regulate cholesterol and blood clotting and control inflammation of the joints, tissues and bloodstream. Fats also perform important functional roles in the maintenance of nerve impulse transmission, memory storage, and tissue structure. Lipids are particularly focused on brain activity in structure and function, helping to form nerve cell membranes, isolating neurons, and enabling the signaling of electrical impulses in the brain.
Facilitating Absorption and Increasing Bioavailability
Dietary fats in foods that we consume help transport fat-soluble vitamins, take them through the digestive process and increase their intestinal absorption. This increased absorption is regarded as an improvement in bioavailability. Dietary fats can also increase the bioavailability of compounds known as phytochemicals—non-essential plant compounds considered beneficial to human health. Many phytochemicals are fat-soluble, such as lycopene found in tomatoes and beta-carotene found in carrots, and dietary fat increases the absorption of these molecules in the digestive tract.
In addition to enhancing the bioavailability of fat-soluble vitamins, some of the best dietary sources of these vitamins are also high-fat foods. For example, nuts, seeds and vegetable oils are good sources of vitamin E. Vegetable oils also have some vitamin K, and fatty fish and eggs are good sources of vitamin A and vitamin D.
Enhances Smell, Taste, and Satiety of Foods
The fats satisfy the appetite because they add flavor to the food. Fat includes dissolved compounds that contribute to mouth-watering aromas and flavours. Fat also adds texture, makes cooked foods moist and flaky, fried foods crispy and adds creaminess to foods such as ice cream and cream cheese.
Fats satisfy appetite because they are slower to be digested and consumed than other macronutrients. Dietary fat, therefore, leads to satiety—the sensation of being fulfilled or complete. When fatty foods are ingested, the body responds by allowing digestion control mechanisms to slow down the flow of food along the digestive tract, giving fats more time to be digested and absorbed, and fostering an overall feeling of fullness.
Provision of Essential Fatty Acids
Many lipid molecules can be synthesized in the body from other organic molecules, so they don’t need to be directly fed into the diet. However, two are considered essential and must be included in the diet: linoleic acid and alpha-linolenic acid.
Digestion and Absorption (Metabolism) of Fats
Lipids are large molecules that are not water-soluble in general. Like protein and carbohydrates,
For absorption, lipids are broken into small components. When lipids encounter saliva, the first stage in the digestion of triacylglycerols and phospholipids starts in the mouth. Next, together with the action of emulsifiers, the physical action of chewing allows the digestive enzymes to
To do their assignments. The digestion process is triggered by the enzyme lingual lipase, along with a small amount of phospholipid as an emulsifier. These acts allow the digestive enzymes to become more available to the fats. The fats become tiny droplets and separate from the watery components as a consequence.
Gastric lipase begins to break down triacylglycerols into diglycerides and fatty acids within the stomach. Roughly 30 percent of triacylglycerols are converted to diglycerides and fatty acids within two to four hours of consuming a meal. The churning and contractions of the stomach allow the fat molecules to disperse, while the diglycerides derived in this process serve as additional emulsifiers. However, very little fat digestion occurs in the stomach, even in the midst of all this activity.
The digestive system sets out to manage a small challenge when stomach contents reach the small intestine, namely to mix the separated fats with its own watery fluids. Bile is the solution to this barrier. Bile contains bile salts, lecithin, and cholesterol-derived compounds, so it acts as an emulsifier. It draws and holds on to fat as it is drawn to and held on to by water at the same time. The surface area of lipids is increased by emulsification by more than a thousand times, rendering them more available to digestive enzymes.
Fat-breaking enzymes act on the triacylglycerols and diglycerides to sever fatty acids from their glycerol foundations after the stomach contents have been emulsified. This breaks down the fats into free fatty acids and monoglycerides as pancreatic lipase reaches the small intestine. And again, another challenge occurs. How is the fat going to pass through the mucous watery layer that covers the digestive tracts absorptive lining? The response, like before, is bile.
The fatty acids and monoglycerides are enveloped by bile salts to form micelles. Micelles have a center of fatty acid with an exterior which is water-soluble. This helps the intestinal microvillus to be transported efficiently. The fat components are released and diffused into the cells of the lining of the digestive tract here.
Much as lipids need special handling to pass through a water-based environment in the digestive tract, they need similar handling in the bloodstream to travel. The monoglycerides and fatty acids reassemble themselves into triacylglycerols within the intestinal cells.
When joined with a protein carrier, triacylglycerols, cholesterol, and phospholipids form lipoproteins. Lipoproteins have an inner center consisting mainly of triacylglycerols and esters of cholesterol (a cholesterol ester is a cholesterol linked to a fatty acid). The outer envelope is composed of proteins and cholesterol-interspersed phospholipids. Together, they build a Chylomicron, a large lipoprotein that is now entering the lymphatic system and will soon be released through the jugular vein in the neck into the bloodstream. Chylomicrons move food fats perfectly to particular destinations, such as the liver and other body tissues, via the water-based environment of the body.
As compared to phospholipids and triacylglycerols, cholesterol is poorly absorbed. The absorption of cholesterol is supported by an increase in components of dietary fat and is impaired by elevated fiber content. This is the reason why it is advised to provide a high fiber intake to minimize blood cholesterol. Bile salts and cholesterol can be bound by foods rich in fiber such as fresh fruits, vegetables, and oats, preventing their absorption and carrying them out of the colon.
Recommended Dietary Allowance (RDA) for Fats
In adults, the recommended Daily Allowance (RDA) or Dietary Reference Intake (DRI) for fat is 20% to 35% of total fat calories. If a person consumes 2,000 calories a day, that is around 44 grams to 77 grams of fat per day. Eating more of certain kinds of fats is advised because they have health benefits. Due to the detrimental effect on wellbeing, it is advised to consume less other forms of fat.
- Monounsaturated fat: 15% to 20%
- Polyunsaturated fat: 5% to 10%
- Saturated fat: less than 10%
- Trans fat: 0%
- Cholesterol: less than 300 mg per day
Effects of Fats Deficiencies on Health
An individual who suffers from dietary fats deficiency stand a risk of some health challenges which include:
- Depression
- Possible vitamin deficiency
- Cardiovascular diseases
- Cancers
- Increased Blood Pressure during Pregnancy and Lactation
Depression
As a consequence of inadequate fat intake, psychological and neurological disorders such as depression, behavioral changes such as anxiety, low moods, and irritability may be observed and may be due to serotonin dysfunction. A low fat diet reduces the brain’s productivity.
Possible vitamin deficiency
For the absorption of important vitamins, fats are necessary in the body. The body does not quickly extract fat-soluble vitamins A, D, E and K and they are retained in adipose tissue. Diseases induced by insufficient vitamins soluble in fat are rare. Due to poorly balanced diets, deficiencies may impact from the digestive system to bone and skin disorders.
Cardiovascular diseases
Decreased levels of blood omega-3 fatty acid can lead to coronary heart disease, hypertension, stroke, cardiac arrest, atherosclerosis, and cardiovascular diseases.
Auto-immunity and chronic inflammation
Depleted omega-3 fatty acid levels are associated with chronic inflammation, such as chronic obstructive pulmonary disease (COPD), Crohn’s disease, arthritis, rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, ulcerative colitis, and immunoglobulin A nephropathy.
Cancers
Studies have shown that the risk of prostate and colon cancer rises with reduced levels of omega-3 fatty acids.
Increased Blood Pressure during Pregnancy and Lactation
During pregnancy, low blood levels of essential omega-3 fatty acids raise the risk of hypertension, pre-eclampsia and eventual premature delivery. For the development of fetuses and infants, DHA is very important. During pregnancy, postpartum depression, ADHD and poor IQs are all the product of low DHA intake.