The digestion and absorption of fats differ from other micronutrients and vitamins because carbs and proteins are water-soluble while fats aren’t. Therefore, while the fats are in the digestive tract, they cluster together because it’s a watery environment making it harder for the body to absorb them into the bloodstream. Whereas carbohydrates directly enter the bloodstream.
Fats and fatty acids have to follow a different route to be absorbed by the body. They enter the lymphatic system, where they’re absorbed through the lacteals, and as the lymphatic fluid mixes with the fats, the resulting chyle can be transported in the body and be absorbed into the bloodstream.
Follow us into the discussion as we look at fat digestion and absorption steps, causes of poor fat absorption, how we can improve fat absorption, and whether blocking fat absorption affects weight.
Fat Digestion And Absorption Steps
Fats and fatty acids, scientifically known as lipids, may be in liquid or solid form. They refer to triglycerides, steroids, phospholipids, cholesterol and cholesterol esters, carotenoids, and fat-soluble vitamins such as vitamin A, D, E, and K.
Because they’re all fats and oils, they’ll follow these same digestion and absorption steps below.
Digestion begins in the mouth, then continues in the stomach, and finally in the small intestines, after which they’re absorbed into the body.
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Lipid Digestion In The Mouth
Digestion of lipids begins in the mouth right after you consume it. As you chew, there will be a mechanical breakdown of fats into smaller particles that mix with saliva. At the same time, your serous lingual glands, also known as Von Ebner’s glands, will produce lingual lipase, which is the first enzyme/protein that helps catalyze the hydrolysis of triglycerides.
Lingual lipase will break down the fats into a single fatty acid (either single or medium-chain fatty acid) and diacylglycerol, which will be digested in the duodenum.
Lipid Digestion In The Stomach
When the mixture arrives in the stomach, lingual lipase is still active because the pH levels in the gut keep it active. However, through the gastric mucosa, the stomach will also release an enzyme called gastric lipase to aid with the digestion of triglycerides. The two will act together to further break down the food particles through mixing and churning, which then creates a milky substance referred to as chyme.
Chyme is a lipid emulsion with droplets smaller than 0.5 mm. Because they’re much smaller now, they will enter the duodenum for further hydrolysis.
Lipid Digestion In The Small Intestines
In the duodenum, its mucosal cells will stimulate the hormone cholecystokinin to release bile produced in the liver but stored in the gallbladder. During its release, it will include three components: bile salts, cholesterol, and phospholipids. The bile salts will mix with the chyme from the stomach in continuation of the digestion of triglycerides.
Since both bile salts and bile acid are amphipathic molecules, they will have a hydrophobic and a hydrophilic side which helps with the emulsification of lipid droplets. After emulsification, these droplets will have an increased surface area for hydrolase activity, meaning they’ll be easily accessible to digestive enzymes.
From the duodenum, digestion proceeds the jejunum, where the chyme is further broken down by pancreatic lipase; this is another enzyme from the exocrine glands in the pancreas. The cholecystokinin hormone also stimulates its release. Pancreatic lipase has a pH of 7, so it is not acids like gastric and lingual lipase; however, it will still break down the remaining triglycerides into free fatty acids and 2-monoacylglycerols. The 2-monoacylglycerols are now easily absorbed from the small intestines.
Lipid Absorption From The Small Intestines
The monoglycerides will combine with bile salts to form micelles, which are smaller aggregates of mixed lipids and bile acids suspended in the ingesta. Since the micelles are tiny, about four to eight nm in diameter, they’ll be closer to the microvilli edge of the small intestinal enterocytes. The bumping of micelles in the small intestines enterocytes causes the micelles to be taken up to the epithelial cells using chylomicrons, then transported into the bloodstream.
These tiny fatty droplets will get into transport vehicles called chylomicrons in the Golgi of the epithelial cells. They will transport the monoglycerides into the endoplasmic reticulum. Still, instead of being absorbed directly into the capillary blood, these chylomicrons have to first get into the lymphatic vessel, which will then penetrate each villus called the central lacteal.
Large chylomicrons will pass through small patches of the lacteal, where the endothelial cells hold their cellular junctions less tightly to allow for permeability.
Finally, the chylomicrons lymph rich with fats will drain the monoglycerides into the lymphatic system, flowing into the bloodstream.
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Poor Fat Absorption
The gastrointestinal tract is responsible for the digestion and absorption of fats in the body. When the absorption of fats impairs at any point in the track, especially in the intestinal lumen or the brush border of the small intestine enterocytes, malabsorption occurs. Malabsorption is the impaired absorption of fats, among other micronutrients in the small intestines, caused by a dysfunction in the gallbladder, pancreas, or small intestines.
Fat malabsorption is one of the most common malabsorption syndromes and has multiple causes (6).
Poor Fat Absorption Causes
Below are the causes of poor fat absorption in the body.
Low Ph Value In The Duodenum
The optimal ph value in the duodenum should be 6.5 to 7. Any pH values of less than 6.5 will affect the acidic reaction between chyme and bile acid, causing them to fail in fat digestion. The Zollinger-Ellison syndrome is known to lower pH by destroying pancreatic enzymes used for digestion using stomach acids with a pH of 4.
Lost Absorptive Intestinal Surface Area
Looking back to how the micelles are to get into the small intestines enterocytes, they ought to have enough functional surface area. If the small intestine mucosa loses its function, there will be decreased transit time for the fats and less time for digestion. Conditions such as celiac disease, enterocyte disease, Crohn’s disease, and small bowel resection can decrease the transit time of the fats.
Impaired Lipid Processing By Bile Acids
When lipid processing is incomplete, there’s not enough bile acid secretion to absorb fats and fatty acids fully. It means a failure in bile acid synthesis or transport, which can also result from bile acids remaining in the intestinal lumen instead of being absorbed and reused for fat digestion.
Conditions that cause impaired bile acid secretion include liver disease/ hepatic cirrhosis, cholestasis, or an inborn defect that decreases or obstructs bile acid secretion and flow.
Small Intestinal Bacterial Overgrowth (SIBO)
SIBO occurs when there’s a destruction of the small bowel leading to an overgrowth of bacteria. When there are too many bacteria in the intestinal lumen, they deconjugate bile acids rendering bile acids ineffective for fat absorption. SIBO can be present in conditions such as atrophic gastritis, use of proton pump inhibitors, IBD, gastric dumping of food, or prolonged lactose deficiency.
Pancreatic Exocrine Insufficiency
An exocrine insufficiency causes a defective production of pancreatic lipase, colipase, and bicarbonate which means impaired digestion of fats. Such an insufficiency is common in patients with pancreatic cancer, pancreatic resection, chronic pancreatitis, cystic fibrosis, gastric surgery, celiac disease, shwachman syndrome, and Zollinger-Ellison syndrome.
Defective Chylomicron/Lipoprotein Secretion
Impaired lipoprotein secretion affects how chylomicrons package and secrete lymphatics. Defective apoproteins can be from an MTP gene mutation or Abetalipoproteinemia.
Lymphatic System Disorders
Lastly, lymphatic disorders stem from either intestinal lymphangiectasia or Whipple disease. These conditions cause an impaired lymphatic flow that affects how fat and fatty acids are processed in the body. These conditions may present as diarrhea and weight loss, especially from cow’s milk allergy or cystic fibrosis.
Signs And Symptoms Of Fat Malabsorption
A disruption in the breakdown and absorption of fats in the body leads to oily stool, also known as steatorrhea; that’s the first sign of poor fat absorption. It tends to be foul-smelling, yellowish in color, and frothy or foamy. Other signs and symptoms include:
- Chronic diarrhea
- Abdominal bloating
- Significant weight loss
- A foul-smelling, pale, and bulky stool
- Severe mineral and vitamin deficiencies, especially iron deficiency
- Amenorrhea or mild abdominal pain
- Body discomfort
How To Improve Fat Absorption?
There are five ways to improve fat absorption in your body.
1. Increase Healthy Fats In Your Diet
Fats are essential in your body for multiple reasons, including providing a source of energy and allowing for the absorption of fat-soluble vitamins and minerals. The best way to ensure your body absorbs fats to avoid malabsorption is to consume healthy fats.
By healthy fats, we mean omega-three fatty acids, monounsaturated and polyunsaturated fats. Healthy fats include:
- Seafood is rich in omega-three fatty acids such as salmon, tuna, and sardines
- Coconut oil
- Peanut or sesame oil
- Cold-pressed olive oil
Avoid saturated and trans fats such as lard, fast food, and commercially baked pastries.
2. Increase Hydrochloric Acid In Your Diet
Hydrochloric acid is the acid in the stomach that helps boost acidity and digest foods. To increase hydrochloric acid, consume citric foods such as lemon, lime, or apple cider vinegar. You can take them alone or mixed with about half a cup of warm water, so it’s easily absorbed in the body.
You can also use hydrochloric acid supplements found in the chemist. They will rapidly increase your acid levels, so it’s best to speak to your health care provider first before adding supplements to your diet.
3. Improve Your Probiotic Diversity
You can also improve digestion in your intestines by increasing your probiotic cultures. These are bacteria found in the small intestines that will enhance the absorption and digestion of nutrients and fats. Some probiotic strains can also affect how bile is metabolized in the gut, affecting how fat will metabolize in the body.
Some studies have found that probiotic foods such as yogurt, kombucha, and sauerkraut kefir can change the biochemistry of gut microbes in the small intestines and improve digestion. A change in their biochemistry means a boost in their metabolic makeup (11).
4. Take Digestive Enzymes and Nutritional Supplements
Digestive enzymes are those secreted by the gallbladder and pancreas. They help with the breakdown of foods, including fats and fatty acids. Crucial digestive enzymes that will help with fat digestion and absorption include:
- Lipase. It helps with fat digestion.
- Amylase. It breaks down carbohydrates, papain, and bromelain, which further breaks down proteins.
- Ox bile. It also helps boost fat metabolism.
A study on digestive disorders revealed that papaya, which has a high concentration of papain, helped with digestion and relief of symptoms such as constipation, bloating, and irritable bowel syndrome (IBS) (8).
Lastly, you can get a prescription pancreatic enzyme that’ll help you digest food better, but its function is to control a side effect of a medical condition. For example, the pancreatic enzyme pancrelipase (Creon, Pancreaze, Zenpep) is given to patients with a medical disease such as pancreatic cysts, cancer, or cystic fibrosis, affecting how the pancreas produces pancreatic lipase for digestion. Despite that, the drugs are not available over the counter.
5. Use Spices
Lastly, a study on digestion and absorption of fats in rats revealed that some spices such as ginger curcumin, piperine, and capsaicin could stimulate bile secretion, which aids in boosting digestion and absorption of dietary fat (3). Note that this was a study on rats and will require additional research to confirm the results.
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Blocking Fat Absorption For Weight Management
There are rumors that blocking fat absorption can help with weight management, precisely, weight loss. While this may make sense, there are no real studies into it that may reveal side effects besides the negative impact of malabsorption.
First, when the body doesn’t absorb dietary fats, it causes symptoms such as diarrhea and general weight loss, which means you will lose weight, but that’s an unhealthy way to lose it and can cause severe health issues.
Another mechanism that aids weight loss through fat blocking is by use of drugs. The Food and Drug Administration approved a new class of anti-obesity drugs that work by blocking the body’s absorption of dietary fat, leading to weight loss.
An example of such a drug is Orlistat, medically sold as Xenical. The drug was to be a panacea for obesity where it works by inhibiting pancreatic lipase, thereby reducing the digestion and absorption of fat in the small intestine. By blocking fat absorption, there wouldn’t be an accumulation of dietary fats causing obesity.
While these supplements help block fat absorption and manage weight, it’s not the best way to lose weight because we still emphasize that dietary fats are essential in helping your body function effectively. That said, there are natural foods that block fat absorption as an alternative to the use of drugs.
Foods To Eat
There are healthier options, so you don’t have to worry about adverse side effects. Besides, they also provide the body with energy and fiber essential for proper absorption of other healthy fats. These foods include:
- Apples. They contain pectin, a complex fiber that may block fat absorption and can reduce low-density lipoprotein (9).
- Soy foods. Soybeans contain lecithin, which can break down fat and might prevent fat deposits in the body (2).
- Seaweed. It contains alginate, which is a water-soluble fiber that may prevent fat absorption (1).
- Whole grains. They contain plenty of soluble fiber that might curb the absorption of fat.
- Oolong tea. The tea has polyphenols that are said to block fat absorption and boost body metabolism.
- Apple cider vinegar. ACV contains pectin and acetic acid, believed to boost body metabolism and blocking excess fat absorption (15).
- Tomatoes. The fruit contains L-carnitine, an amino acid that helps to break down fat and convert fats into energy rather than deposits (5)
- Flax and almond seeds have omega-three fatty acids that slow down the digestion of fat in the body.
Fat absorption is a complex process, unlike absorption of carbs, proteins, vitamins, and minerals. However, this doesn’t mean our bodies don’t need to absorb fat and manage weight; you should stop the processes. Instead, discuss with your healthcare provider the four methods above that could improve your fat absorption so you can avoid fat malabsorption syndrome that can cause significant damage to your health.
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This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!
- Alginate (2012, ncbi.nlm.nih.gov)
- Everything you need to know about Lecithin (2017, medicalnewstoday.com)
- Fat absorption and digestion in spice-pretreated rats (2011, onlinelibrary.wiley.com)
- Intestinal lipid absorption (2009, ncbi.nlm.nih.gov)
- L Carnitine (2018, WebMD.com)
- Malabsorption Syndromes (2021, ncbi.nlm.nih.gov)
- Orlistat (2007, Sciencedirect.com)
- Papaya preparation (Caricol®) in digestive disorders (2013, pubmed.Nih.gov)
- Pectin (2019, WebMD.com)
- Prescription medication to treat overweight and obesity (2016, middle.nih.gov)
- Probiotics affect metabolism ( 2008, sciencedaily.com)
- Steatorrhea (2020, ncbi.nlm.nih.gov)
- Structured Lipids improve fat absorption (2000, academic.oup.com)
- The importance of fats (1998, Sciencedirect.com)
- Vinegar (2006, ncbi.nlm.nih.gov)