Lipids are vital elements that we must eat.

Lipids are vital elements that we must eat.

Lipids’ significance in a person’s diet

A wide variety of foods include lipids. Consider solid or liquid fats, as well as dairy products, nuts, seeds, and seafood that are high in fat. Though in comparatively small amounts, fruits, vegetables, and legumes also contain lipids.

Lipid consumption, or the consumption of foods high in fat, is often linked to adverse health effects, particularly when it comes to saturated and trans fats. This is because, in contrast to other nutrients like protein and carbs, they have a high calorie content. Therefore, excessive fat consumption is associated with elevated cholesterol and the emergence of obesity, which raises the chance of developing diabetes, cardiovascular disease, and other metabolic illnesses.

Lipids, however, are also associated with certain beneficial health impacts, therefore it is not a good idea to cut them out of our diet. Lipids are a significant source of energy in daily life in this way. They also supply our body with vital nutrients, including lipid-soluble vitamins A, D, E, and K and essential fatty acids, which are the building blocks of lipids.

Lipids have significant sensory impacts in food products in addition to their health-related benefits. Specifically, they provide goods like dairy a desired creamy texture. The way that chocolate’s fats melt adds to a significant and satisfying sensory experience for customers. Lipids give food goods flavour in addition to texture. Consider frying potatoes to make fries and chips; also, the lipid concentration of butter explains why it gets rancid.

Finally, lipids also have significant impacts on dietary structure. For instance, the lipid content of ice cream influences its creamy texture, among other factors.

What distinguishes the digestion of lipids from that of other nutrients?

Because the human digestive tract is a wet environment, the digestion of lipids is more complicated than the digestion of other macronutrients. Due to their water solubility, proteins and carbohydrates are generally easy to digest and transport their broken down components.

Conversely, because they are lipid-soluble, lipids are not as readily dispersed in water. Therefore, in order for lipids to flow easily in the watery digestive environment, they must first organise themselves into specialised structures, also known as colloidal structures, like emulsions.

Emulsions: what are they?

Emulsions are one type of colloidal structure. In addition to being used in dairy products, sauces, and vinaigrettes, emulsions are also widely used in cosmetic items like body cream.

Two immiscible liquids, oil and water, are the primary components of emulsions. An oil-in-water emulsion forms when the oil separates into many tiny droplets, each encircled by water. Just blending water and oil will cause the liquids to separate very quickly. Ingredients are therefore added to stop this separation. Emulsifiers are the term for these substances. Compounds with two distinct structural regions—one that associates with oil droplets and the other that favours a wet environment—are known as emulsifiers. Emulsifiers can therefore effortlessly combine water and oil. Mayonnaise is a popular example of an emulsion. It is mostly made of of of water, oil, and yolk

Because egg yolks are high in emulsifying agents, making homogeneous mayonnaise just requires whisking together water and oil. Another illustration is milk, where the proteins function as an emulsifier to combine water and oil droplets. In addition to these natural emulsifiers, food products often contain chemical emulsifiers to maximise their long-term stability.

digestion of lipids

It’s critical to clarify lipids’ chemical structure in order to comprehend how our bodies process and digest lipids. Several triacylglycerol molecules make up lipids. These molecules can be thought of as having three branches on a tree.

It is necessary to first cut this three-branched molecule because it cannot be absorbed by our body as is. The stomach and small intestine are where lipids are mostly broken down. There, lipases—enzymes with the ability to cleave lipid branches—are present.

When food gets in our mouths, we will swallow it after chewing it if needed. The food travels down the throat and into the stomach, where digestion begins. It is necessary for gastric lipase to initially go from the aqueous environment to the lipid droplet surface. Secondly, in order to get into contact with the lipids themselves, it must remove the emulsifiers from the lipid surface. In the event that this is successful, the lipid structures outside the lipid droplet will have one branch removed by gastric lipases. The enzyme will eventually stop functioning because it will be encircled by fatty acids, which are the cut branches, and diacylglycerols, which are lipid compounds with two branches.

Digestive enzymes, like gastric lipase, frequently operate on extremely particular molecular configurations. In the stomach, about 30% of the lipids will be broken down, primarily into fatty acids and diacylglycerols. These fatty acids can only be absorbed to a certain extent through the stomach. But most of the fats in the stomach, which are made up of non-cut triacylglycerols, cut diacylglycerols, and fatty acids, will travel down the digestive tract and into the small intestine. Another lipase is present in the small intestine to further break down the lipids. Additionally, the small intestine releases bile salts, which function as emulsifiers and facilitate the breakdown of fats.

Fatty acids and a combination of two- and three-branched lipids, or triacylglycerols and diacylglycerols, make up the lipid droplets that enter the small intestine. To make room for intestinal lipase, bile salts will first remove fatty acids from the lipid droplet. Micelles, a different kind of colloidal structure, are formed by bile salts. Micelles can move lipid digestion products towards the intestinal wall with ease because of their lipid-friendly core and water-friendly outer layer.

Intestinal lipase will begin to break down the remaining two- or three-branched lipids into monoacylglycerols, or one-branched lipids, and release one or two fatty acids as a result. The remaining 70% of lipids are broken down into lipid digestion products (monoacylglycerols and fatty acids) by the very effective intestinal lipase Micelles are used to carry the byproducts of fat digestion to the intestinal wall, where the body may absorb them.

Once in our bloodstream, the byproducts of lipid breakdown are rearranged into triacylglycerols. The body uses these rearranged triacylglycerols for a variety of functions, including hormone synthesis, energy storage and distribution, cell building, and brain function protection.

Digestion of lipids and some health consequences

The majority of people have highly effective lipid digestion. This indicates that very few lipids end up in the colon and that practically all lipids are processed in the small intestine. Certain individuals, such as those with pancreatitis, cystic fibrosis, or gall bladder illnesses, may have less efficient lipid digestion because they produce less lipases and/or bile salts.

As a result, undigested fats travel through the large intestine and produce steatorrhea, or fatty stools. Although the long-term effects are yet unknown, some research suggests that it may cause colon cancer or inflammatory bowel disease.

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Furthermore, inadequate lipid digestion and absorption frequently coexists with vitamin deficits and malabsorption of fat-soluble vitamins (A, D, E, and K).

The satiating impact of fats has other physiological effects, in addition to the quantity of fats that are broken down at the end of our small intestine. The sense of fullness experienced during a meal that prompts one to stop eating is known as satiation.

Conversely, satiety is associated with the feeling of fullness that you experience between meals, which influences your decision about when to eat again. Both will have an impact on how much food is eaten in a given day. The research’s most significant finding is that since the regulation of appetite hormones is impacted by lipid digestion, lipids have satiating effects. Furthermore, the presence of lipids in a meal or diet frequently causes intestinal transit to be hampered and the stomach to take longer to empty, which prolongs the feeling of fullness.

Food technologists attempt to create foods with particular digestive patterns based on this knowledge.

(various degrees and/or rates). When it comes to emulsions of oil in water, research has demonstrated that smaller

droplets cause a quicker breakdown of lipids.1, 2 This is because enzymes break down smaller droplets more quickly since many little droplets take up more surface area than a small number of bigger droplets. The effect of emulsifier type on the degree and rate of fat digestion is also a subject of much research.3–7

While some emulsifiers—like milk proteins—are also broken down by our digestive systems, others—like most synthetic emulsifiers—are not. Both kinds of emulsifiers have benefits and drawbacks, and the effect they have on fat digestion varies depending on the particular kind. Since the presence of indigestible synthetic emulsifiers in the colon has been related to adverse health effects, more study is being done these days about the substitution of these undigestible synthetic emulsifiers with natural ones that can be digested. Researchers also investigate the potential for directing fat digestion in a more focused way by employing combinations of emulsifiers.8,9

Citations

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Size of emulsion droplets affects carotenoid bioaccessibility kinetics, micelle formation, and digestion. Food Chem 2017, 229.

2. Infantes-Garcia MR; Hendrickx MEG; Verkempinck SHE; Guevara-Zambrano JM; Andreoletti C;

Grauwet T, Guevara Zambrano JM, Verkempinck SHE, Infantes Garcia MR, Andreoletti C, et al.:

Emulsion droplet size behavior and the enzymatic and chemical transformations occurring during in vitro stomach lipid digestion. 2020; Food Chem, 326.

Mun S, Decker EA, McClements DJ: emulsifier type influences lipid in vitro digestibility

pancreatic lipase droplets. International Food Research Journal, 2007, 40: 770–781.

Tan Y, Zhang Z, Mundo JM, McClements DJ: Elements influencing the metabolism of lipids and nutritional

Emulsifier type is used to measure bioaccessibility using the standardized gastrointestinal model (INFOGEST).

137:109739. Food Research International, 2020.

5. Hendrickx ME, Grauwet, Van Loey AM, Moens LG, Charleer L, Salvia-Trujillo L, Verkempinck SHE

T: Lipid digestion kinetics are impacted by emulsion stability under gastrointestinal circumstances. Food

Chem 2018, 246.

6. Infantes-Garcia MR, Hendrickx ME, Grauwet T, Verkempinck SHE, Gonzalez-Fuentes PG: Lipolysis

the emulsion interfacial during in vitro stomach digesting influences the products formation

Food Hydrocoll 2021, 110:106163. composition.

7. Infantes-Garcia MR, Hendrickx ME, Grauwet T, Verkempinck SHE: Kinetic Modeling of in Vitro

The Effect of Gastric and Emulsion Interfacial Composition on Small Intestinal Lipid Digestion

J Agric Food Chem 2021, 69:4708–4719. Prelipolysis.

8. Infantes-Garcia MR, Hendrickx ME, Grauwet T, Verkempinck SHE, Saadi MR: In the Orientation

knowing how emulsions can modify the kinetics of gastrointestinal lipolysis in vitro

utilizing a variety of interfaces. Food Hydrocoll 124:107240 (2022).

9. Yan J, Yang Z, Qiao X, Kong Z, Dai L, Wu J, Xu X, McClements DJ: Properties of interfacial layers and in

In vitro breakdown of a mixture containing one or more natural emulsifiers, such as rice or lecithin

glutamate hydrolyzes. 2022; J Sci Food Agric 102:2990–2999.