| |

What are Lipids in Food? Types, Sources and Functions

The most important lipid component of the human diet is the triglyceride fraction, which may amount to 100g per day.

Additionally, the diet contains phospholipids, about 5g per day, and minor contents of cholesterol, cholesteryl esters, and fat-soluble vitamins.

However, the phospholipid and cholesterol present in the digestive tract are not only derived from the diet but also from the bile.

In this post, we are interested in knowing lipids in foods, types, sources and the functions.

What are lipids in food?

Lipids in food are naturally occurring derivatives of fatty acids. Fats and oils consist mostly of triglycerides. They are reserves of energy for plants or animals. Examples of lipids are: lard, poultry, fish, groundnut oil, butter, cheese, margarine etc. Polar lipids, such as phospholipids, glycolipids and lipoproteins have important biological functions.

Lipids being hydrophobic are accompanied in natural fats and oils by non-lipidic hydrophobic substances such as sterols, lipophilic vitamins, hydrocarbons, terpenes, liposoluble phenolic derivatives, chlorophyll and carotenoid pigments.

What percentage of lipids do we need in our diet?

According to clevelandclinic, the dietary reference intake (DRI) for fat in adults ranges between 20% to 35% of total calories from fat. That is about 44 grams to 77 grams of fat per day if you eat 2,000 calories a day. Though fats in our body has healthy benefits, consumption of fat diet should be in low quantities to avoid health risks such as stroke, heart attack and high blood pressure.

What are the types of lipids in food?

The three lipids that exists in food are:

  • Triglycerides – Constitutes more than 95% of lipids in a diet. Naturally occurring triglycerides are found in avocados, olives, corn, and nuts.
  • Phospholipids – Make up only about 2% and they are water-soluble.
  • Sterols – Less than 0.5% in a fat diet.

Triglycerides

Fatty acids combine with glycerol to form a glyceride. When one fatty acid combines with a glycerol it forms monoglyceride. Diglycerides have two fatty acids, and triglycerides has three fatty acids attached to glycerol.

Most of the fatty acids in the body and also in foods occur in a form of triglycerides.

Triglyceride contains glycerol, that is a three carbon alcohol as a backbone.

Three fatty acids are attached to the three hydroxyl groups (–OH) of glycerol and three molecules of water are released in this formation of a triglyceride.

The fatty acids which combine with glycerol may vary in the length of the chain (–R) and vary in degrees and type of saturation.

In digestion, most triglycerides are hydrolysed to form free fatty acids, monoglycerides and glycerol are absorbed into the intestinal cells and the majority of these are rebuilt into triglycerides.

While fat may seem bad, triglycerides play many important roles in the body. For example, triglycerides can be used for energy storage in animals.

This food reserve can be called upon during periods of starvation, with the high-calorie
content of the fatty acids adding to the value of storing fat and providing much
needed energy.

Animal fats contain a high amounts of saturated triglycerides while vegetable oils contain a high amount of unsaturated triglycerides. While neither is healthy when consumed in excess, vegetable oils are far healthier than lard.

Phospholipids

Phospholipids, which are present in every cell, are formed mainly in the liver from fatty acids, glycerol, phosphoric acid and a nitrogenous base. Phospholipids look like triglycerides, but it contains a phosphate attached to glycerol in place of one fatty acid. For example, lecithin, a phospholipid contains choline-phosphate attached to one hydroxyl of the glycerol molecule.

Lecithin takes part in fat digestion and it is also found in egg yolk. It is not necessary to provide phospholipids in the diet, as our body makes these when and where it needs. They are powerful emulsifying agents and are essential for the digestion and absorption of fats. Phospholipids help to carry lipid particles across the cell membrane in the blood stream.

Sterols

Sterols are lipids with a steroid structure. Phytosterols, a different form of sterol are found in all plant foods, but the highest concentrations are found in unrefined plant oils, including vegetable, nut, and olive oils . Nuts, seeds, whole grains, and legumesare also good dietary sources of phytosterols. Cholesterol a popular sterol is found in foods like poultry, egg yolk, fish, and dairy products.

Three sterols with functions associated
with nutrition are:

  • Ergosterol – a vegetable sterol
  • 7-dehydrocholesterol – an animal sterol
  • Cholesterol – an animal sterol

What are the sources of lipids?

Lipids are found in many foods, and they exist in different forms, lipid fats are solid fats, and lipid oils is known as liquid fats.

Sources of lipid fat: Beef fat, poultry skin, butter, and bacon.

Sources of lipid oils: Skimmed milk, olive oil, coconut oil, vegetable oil and palm oil.

Functions of lipids in the body

Lipids have many functions in the body:

1. Storing energy

The energy we get from foods is provided by carbohydrates and lipids. When carbohydrate food is digested, the excess energy is absorbed into the fatty tissue, glucose from carbohydrate is stored as glycogen in a form of energy, and lipids mainly function as an energy reserve.

2. Regulating and signaling

Triglycerides controls the body’s temperatures, and maintains constant temperature. When your body has less fat, you begin to feel cold sooner, fatigued, and have pressure sores on the skin, because your body lacks fatty acids.

3. Insulating and protecting

About 30% of body weight is comprised of fat tissue made up of visceral fat surrounding delicate organs. Vital organs such as the heart, kidneys, and liver are protected by visceral fat. The subcutaneous fat also known as fat underneath the skin is a blanket layer of tissue that insulates the body from extreme temperatures.

4. Helps Digestion and Improves Bioavailability

The dietary fats in the foods we eat break down in our digestive systems and begin the transport of precious micronutrients. By carrying fat-soluble nutrients through the digestive process, intestinal absorption is improved. This is known as increased bioavailability.

Summary

Lipids are compounds of fatty acids with glycerol, sometimes also with other substances. They are present in animals or plants, and is obtained by heating in case of animal fats, and solvent extraction in case of plant raw materials.

Natural lipids are solid fat or liquid fat, that consist of triglycerides, phospholioids, and sterols, and is accompanied by polar lipids and lipophilic minor substances.

Lipids belonging to main nutrients, are indispensable in the nutrition. They are the most important source of energy; they contain essential fatty acids, sterols, and lipophilic vitamins.

Lipids are raw materials for many edible lipid products, such as frying oils, margarine, mayonnaise, and shortenings. The intake of lipids and their fatty acid composition have great impact on human health.

Lipids have nutritional importance to the body, such as storing energy, regulating body temperatures, insulating, protection, helping digestion and bioavailability.

Similar Posts