Absorption of digested food is the process by which the nutrients from food, broken down during digestion, are taken up by the body and transported into the bloodstream or lymphatic system for distribution to cells. It primarily occurs in the small intestine, which is specially adapted for this function with millions of tiny finger-like projections called villi and microvilli. These structures increase the surface area, allowing for maximum nutrient absorption.
During this process:
Simple sugars (from carbohydrates) enter the bloodstream through the intestinal walls.
Amino acids (from proteins) are absorbed into the blood to help in growth and repair.
Fatty acids and glycerol (from fats) enter the lymphatic system before reaching the bloodstream.
Vitamins and minerals are absorbed directly and used for various bodily functions.
Water absorption occurs in both the small and large intestines to maintain hydration and bodily functions.
Without proper absorption, nutrients would pass through the body without providing energy or nourishment. This process is essential for overall health, ensuring that our body gets the necessary fuel to function efficiently.
Why is Absorption in the Digestive Process Important?
Absorption is a crucial step in the digestive process, ensuring that the nutrients from digested food are effectively utilized by the body. Without absorption, the entire process of digestion would be meaningless, as the body would be unable to benefit from the food consumed. Here’s why absorption is so important:
Provides Energy for the Body
The absorption of glucose and other simple sugars into the bloodstream supplies the body with the necessary energy to perform daily activities. This energy fuels everything from basic metabolic functions to physical movement.
Supports Growth and Repair
Amino acids, absorbed from protein digestion, are essential for the repair of tissues, muscle growth, and the production of enzymes and hormones. Without proper absorption, wound healing and cell regeneration would be compromised.
Maintains a Healthy Immune System
Many vitamins and minerals, such as Vitamin C, Vitamin D, iron, and zinc, are absorbed to strengthen the immune system, helping the body fight infections and diseases.
Regulates Body Functions
Absorbed nutrients like calcium and potassium help regulate muscle contractions, nerve signals, and fluid balance, ensuring the proper functioning of vital organs.
Prevents Nutritional Deficiencies
A well-functioning absorption process prevents deficiencies that can lead to health problems like anaemia (iron deficiency), osteoporosis (calcium deficiency), and weakened immunity (vitamin deficiency).
Supports Hydration and Waste Removal
The absorption of water in the small and large intestines helps maintain the body's fluid balance and prevents dehydration. It also aids in the smooth elimination of waste from the body.
Absorption is the bridge between digestion and the body’s ability to use nutrients. It ensures that the food we eat contributes to our overall health, energy, and well-being. Without efficient absorption, even a nutritious diet would fail to support bodily functions.
Organs Involved in Absorption
The process of absorption primarily takes place in the digestive system, involving several important organs that work together to ensure nutrients are efficiently absorbed and transported to different parts of the body. Here are the main organs involved:
1. Small Intestine – The Primary Site of Absorption
The small intestine is the most important organ for nutrient absorption in the digestive system. It is responsible for absorbing almost 90% of all nutrients from digested food and plays a crucial role in ensuring that the body receives the essential substances needed for energy, growth, and repair.
Structure of the Small Intestine
The small intestine is a long, coiled, and narrow tube that plays a crucial role in digestion and absorption. It is about 6–7 metres long and is specially adapted to maximise nutrient absorption. Its structure includes different regions, layers, and specialised features that enhance its function.
Duodenum → Absorbs minerals like iron, calcium, and magnesium. The shortest but most active part of the small intestine. Receives digestive juices from the pancreas (enzymes) and liver (bile) to break down food further.
Jejunum → Absorbs most carbohydrates, proteins, and water-soluble vitamins. Has numerous folds and villi for maximum nutrient absorption.
Ileum → Absorbs vitamin B12, bile salts, and any remaining nutrients. Transfers undigested food to the large intestine.
Layers of the Small Intestine
The walls of the small intestine have four main layers, each contributing to digestion and absorption:
Mucosa (Inner Layer)
Contains villi and microvilli, which increase surface area for nutrient absorption.
Secretes enzymes and mucus to aid digestion.
Submucosa
Contains blood vessels, nerves, and lymphatic vessels to transport absorbed nutrients.
Muscularis (Muscle Layer)
Made up of smooth muscles that contract rhythmically to mix food and push it forward (peristalsis)
Serosa (Outer Layer)
Protects the intestine and reduces friction with surrounding organs.
Large Surface Area for Maximum Absorption
The small intestine is about 6–7 metres long, providing a large surface for absorption. It contains millions of tiny finger-like projections called villi and microvilli, which further increase the surface area, ensuring efficient absorption of nutrients.
Absorption of Different Nutrients
Carbohydrates → Broken down into glucose, absorbed into the bloodstream for energy.
Proteins → Broken down into amino acids, absorbed to help with tissue repair and muscle growth.
Fats → Broken down into fatty acids and glycerol, absorbed through the lymphatic system.
Vitamins and Minerals → Essential for various body functions, absorbed in different parts of the small intestine.
Water → Some water is absorbed in the small intestine to maintain body hydration.
Transport of Absorbed Nutrients
Absorbed nutrients enter the bloodstream and travel to the liver via the hepatic portal vein for processing and distribution.
Fats are transported through the lymphatic system before entering the bloodstream.
Specialised Features of the Small Intestine
Here's a breakdown of the specialized features:
Villi and Microvilli – Maximising Absorption
Villi are tiny, finger-like projections that increase the surface area for absorption.
Each villus is covered with microvilli, further increasing absorption efficiency.
Villi contain capillaries (to absorb sugars and amino acids) and lacteals (to absorb fats).
Goblet Cells – Mucus Secretion
Produce mucus, which protects the intestinal walls and helps food move smoothly.
Peyer’s Patches – Immune Protection
Located in the ileum, these lymphoid tissues help protect the intestine from harmful bacteria.
2. Large Intestine – Absorption of Water and Minerals
The large intestine, also known as the colon, plays a crucial role in the final stages of digestion. While it does not absorb nutrients like the small intestine, it is responsible for the absorption of water, electrolytes, and some vitamins, helping to maintain the body’s fluid balance and overall health.
Absorption of Water
The large intestine absorbs excess water from the undigested food material, converting liquid waste into solid faeces. This process prevents dehydration and helps maintain the body’s fluid balance.
Absorption of Electrolytes (Minerals)
Essential minerals (electrolytes) such as sodium (Na⁺), potassium (K⁺), and chloride (Cl⁻) are absorbed to regulate nerve function, muscle contractions, and hydration levels.
Absorption of Vitamins
The gut bacteria in the large intestine help produce vitamins, particularly:
Vitamin K – Essential for blood clotting.
B-complex vitamins (e.g., B7 or biotin) – Important for metabolism and energy production.
These vitamins are absorbed into the bloodstream for use by the body.
Formation and Elimination of Waste
After absorbing water and minerals, the remaining indigestible material forms faeces, which are stored in the rectum and eventually excreted. This process ensures the removal of toxins and waste products from the body.
3. Stomach – Limited Absorption
The stomach plays a vital role in digestion by breaking down food with digestive enzymes and acids, but its ability to absorb nutrients is limited compared to the small intestine. The thick mucus lining of the stomach and the rapid movement of food prevents significant absorption. However, certain substances can be absorbed directly into the bloodstream through the stomach lining.
A small amount of water is absorbed in the stomach, but most water absorption occurs in the small and large intestines.
Ethanol (alcohol) is absorbed quickly through the stomach walls, which is why alcoholic beverages can take effect rapidly.
The rate of alcohol absorption depends on factors like food intake, concentration of alcohol, and individual metabolism.
Some drugs like aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) can be absorbed in the stomach.
This is why these medications can sometimes cause stomach irritation or ulcers when taken on an empty stomach.
Some glucose and other simple sugars may be absorbed in small amounts, but the majority is absorbed in the small intestine.
Why is Stomach Absorption Limited?
The stomach primarily acts as a storage and digestion organ, not a major site for absorption.
The presence of gastric mucus and a low surface area limits the direct passage of nutrients into the bloodstream.
Most nutrients require further breakdown and specific transport mechanisms, which are provided by the small intestine.
4. Liver – Processing and Distribution of Nutrients
After absorption, nutrients travel to the liver via the hepatic portal vein, where they are processed, stored, or distributed to different parts of the body as needed. The liver plays an important role in regulating blood sugar levels and detoxifying harmful substances.
5. Lymphatic System – Absorption of Fats
Unlike other nutrients, fats (fatty acids and glycerol) are absorbed into the lymphatic system through structures called lacteals in the small intestine. Once nutrients are absorbed in the small intestine, they need to be transported to different parts of the body for energy, growth, and repair. The lymphatic system transports fats into the bloodstream, where they are used for energy or stored for later use. This is done by two major transport systems:
Role of the Bloodstream (Hepatic Portal System)
The bloodstream is responsible for transporting water-soluble nutrients from the small intestine to the liver and other tissues.
Nutrients Absorbed into the Bloodstream:
Glucose (from carbohydrates) – Used for energy.
Amino acids (from proteins) – Used for tissue repair and enzyme production.
Water-soluble vitamins (B-complex and vitamin C) – Essential for metabolism and immunity.
Minerals (like iron, calcium, and sodium) – Help in bone formation, nerve function, and muscle contraction.
Process:
These nutrients enter the capillaries present in the villi of the small intestine.
They travel through the hepatic portal vein to the liver for processing.
The liver regulates blood sugar levels, stores nutrients, and detoxifies harmful substances before releasing nutrients into general circulation.
Role of the Lymphatic System
The lymphatic system is responsible for transporting fat-soluble nutrients, which cannot dissolve in water-based blood plasma.
Nutrients Absorbed into the Lymphatic System:
Fatty acids and glycerol (from fats) – Used for energy and cell membrane formation.
Fat-soluble vitamins (A, D, E, and K) – Essential for vision, bone health, and immunity.
Process:
Fatty acids and glycerol combine to form tiny droplets called chylomicrons inside the intestinal cells.
These chylomicrons enter lacteals (small lymphatic vessels in villi).
They travel through the lymphatic system and eventually enter the bloodstream via the thoracic duct near the heart.
The absorption of digested food is a well-coordinated process involving multiple organs, each playing a vital role in ensuring that nutrients reach the body’s cells efficiently. Without proper absorption, the body would struggle to function properly, leading to malnutrition and other health issues.
Formation of Faeces from Unabsorbed Material
After digestion and absorption in the small intestine, the remaining unabsorbed material passes into the large intestine, where it undergoes further processing to form faeces. This process involves the absorption of water and electrolytes, bacterial fermentation, and waste consolidation before elimination from the body.
Movement of Unabsorbed Material into the Large Intestine
The small intestine absorbs most nutrients, leaving behind undigested food particles, fibre, water, and some electrolytes.
This unabsorbed material enters the caecum (the first part of the large intestine) through the ileocecal valve, which prevents backflow into the small intestine.
Absorption of Water and Electrolytes
The colon (part of the large intestine) absorbs most of the remaining water and electrolytes (sodium, potassium, and chloride).
This process solidifies the waste material, converting it from a liquid consistency to a semi-solid form.
If too much water is absorbed, faeces become hard and dry, leading to constipation.
If too little water is absorbed, faeces remain watery, causing diarrhoea.
Role of Gut Bacteria in Fermentation
Here's a detailed explanation:
Bacteria help break down undigested food
The large intestine contains trillions of beneficial bacteria, which play a role in the fermentation of undigested carbohydrates (fibre) and proteins.
Bacterial fermentation produces gases like methane, hydrogen, and carbon dioxide, which may cause bloating or flatulence.
Some bacteria produce vitamins (like Vitamin K and certain B vitamins), which are absorbed by the body.
Undigested substances fermented by bacteria:
Fibre (cellulose) – Found in plant-based foods, remains undigested but adds bulk to faeces.
Resistant starches – Found in unripe bananas and legumes.
Proteins – Broken down into ammonia and other nitrogenous compounds.
Formation of Faeces
All waste in our body, composed of undigested food, bacteria, and other substances, must be eliminated. This is how it happens.
Consolidation of waste into solid faeces
The unabsorbed material, combined with water, mucus, dead cells, bacteria, and waste products, gradually thickens and forms solid faeces.
The colour of faeces is due to bilirubin (a bile pigment) and bacterial activity.
Mucus secretion helps in binding and lubrication, making faeces easier to pass.
Composition of Faeces:
Water (about 75%)
Undigested food (fibre, cellulose, starch)
Bacteria and their metabolic products
Mucus and dead intestinal cells
Pigments from bile (e.g., stercobilin, which gives faeces a brown colour)
Storage and Elimination (Defecation Process)
Faeces are temporarily stored in the rectum before elimination
Faeces are stored in the rectum until the body signals the need for defecation.
The rectal walls stretch, triggering the defecation reflex via the nervous system.
The anal sphincters (internal and external) control the passage of faeces.
When the external sphincter relaxes, faeces are expelled through the anus.
Factors affecting defecation:
Dietary fibre intake → Increases stool bulk and prevents constipation.
Hydration → Prevents hard stools and promotes smooth bowel movements.
Physical activity → Helps stimulate intestinal movement (peristalsis).
Neurological control → Conditions like spinal cord injuries can affect bowel movements.
Mechanism of Absorption
The mechanism of absorption refers to how digested nutrients pass from the small intestine into the bloodstream or lymphatic system for distribution throughout the body. This process occurs through different transport mechanisms, depending on the type of nutrient being absorbed.
Simple Diffusion (Passive Transport)
No energy required
Moves from high to low concentration
Process:
Nutrients pass directly through the cell membrane of the intestinal walls without assistance or energy use.
This occurs because of a concentration gradient, where molecules move from an area of higher concentration (inside the intestine) to an area of lower concentration (inside the blood or lymph).
Nutrients Absorbed by Simple Diffusion:
Small fat-soluble molecules (Vitamins A, D, E, and K)
Short-chain fatty acids
Gases like oxygen and carbon dioxide
Water (to some extent)
Facilitated Diffusion (Passive Transport)
No energy required
Requires carrier proteins
Moves from high to low concentration
Process:
Some larger or water-soluble molecules cannot pass through the intestinal cell membrane easily.
They require specific carrier proteins that help transport them across the membrane.
Even though a transport protein is involved, no energy (ATP) is needed as the movement still follows the concentration gradient.
Nutrients Absorbed by Facilitated Diffusion:
Fructose (a simple sugar found in fruits)
Some water-soluble vitamins (e.g., Vitamin C, Vitamin B group)
Active Transport (Energy-Dependent Transport)
Requires energy (ATP)
Moves from low to high concentration
Requires carrier proteins
Process:
Some nutrients need to be absorbed against their concentration gradient (from lower to higher concentration).
This requires energy (ATP) and specific carrier proteins that actively transport nutrients into the bloodstream.
Nutrients Absorbed by Active Transport:
Glucose and Galactose (from carbohydrates)
Amino acids (from proteins)
Minerals like sodium (Na⁺), calcium (Ca²⁺), and iron (Fe²⁺)
Endocytosis (Pinocytosis & Phagocytosis) – Cell Engulfing Process
Requires energy (ATP)
Used for large molecules
Process:
The cell membrane of the intestinal lining engulfs large nutrient molecules by surrounding them and forming a vesicle (small sac).
This vesicle then moves inside the cell for further processing.
This process is common in infants, who absorb certain large molecules like maternal antibodies from breast milk.
Types of Endocytosis:
Pinocytosis ("cell drinking") → The cell absorbs liquids and dissolved nutrients.
Phagocytosis ("cell eating") → The cell engulfs large solid particles.
Nutrients Absorbed by Endocytosis:
Large protein molecules (e.g., antibodies from breast milk in infants)
Some fat droplets
Factors Affecting Absorption
Nutrient absorption in the small intestine is a complex process influenced by various factors. Efficient absorption is essential for energy, growth, and overall health. The small intestine is the primary site for nutrient absorption, and its efficiency depends on the total surface area available.
Surface Area of the Small Intestine
More surface area = More absorption
The inner lining of the small intestine has folds, villi, and microvilli, which increase the surface area multiple times, allowing more nutrients to be absorbed.
Any damage or reduction in surface area leads to malabsorption.
Conditions that reduce surface area:
Surgical removal of part of the intestine (as in some weight loss surgeries).
Celiac disease – damages the villi, reducing absorption.
Crohn’s disease – causes inflammation, affecting the lining of the intestine.
Blood Supply to the Intestine
Good blood flow = Faster nutrient transport
Once nutrients are absorbed, they need to be transported quickly to the bloodstream or lymphatic system.
A strong and healthy blood supply ensures efficient absorption and distribution of nutrients.
Poor blood circulation slows down nutrient transport, leading to deficiencies and fatigue.
Factors that reduce blood supply:
Low blood pressure or shock – reduces blood flow to the digestive system.
Alcohol & smoking → Damage the intestine and interfere with nutrient uptake.
8. Age & Metabolism
Absorption efficiency changes with age.
Infants & children have highly efficient nutrient absorption due to rapid growth.
Older adults often experience a decline in absorption of certain nutrients like vitamin B12, calcium, and iron, leading to deficiencies.
Age-related factors affecting absorption:
Reduced stomach acid in the elderly → Affects protein digestion and vitamin B12 absorption.
Slower metabolism → Reduces overall nutrient demand and processing.
Importance of a Healthy Diet for Efficient Absorption
A balanced diet is essential for effective nutrient absorption, supporting growth, energy, immunity, and overall well-being. Factors like nutrient composition, hydration, fibre, and probiotics influence how well the body absorbs vitamins, minerals, and macronutrients.
1. Provides Essential Nutrients for Absorption
A well-balanced diet aids digestion and ensures efficient absorption. The body needs proteins, carbohydrates, fats, vitamins, and minerals to function properly. Deficiencies can weaken digestion and reduce nutrient uptake.
Healthy fats (nuts, seeds, olive oil) aid in absorbing fat-soluble vitamins (A, D, E, K).
Protein-rich foods (meat, fish, dairy, legumes) help produce digestive enzymes.
Complex carbohydrates (whole grains, vegetables) provide fibre, promoting gut health.
2. Supports Gut Health and Microbiota Balance
A healthy gut microbiome improves digestion and absorption.
3. Maintains Optimal Stomach Acid and Enzyme Function
Proper stomach acid levels are crucial for digestion and nutrient breakdown.
Gastric acid (HCl) and digestive enzymes help absorb nutrients efficiently.
A diet rich in whole foods supports stomach acid balance.
4. Poor dietary habits that affect stomach acid:
Processed foods reduce enzyme efficiency.
Overuse of antacids & PPIs lowers stomach acid, affecting calcium, magnesium, and vitamin B12 absorption.
Low protein intake decreases enzyme production, impairing digestion.
Maintaining a nutrient-rich diet, supporting gut health, and balancing stomach acid can significantly improve nutrient absorption and overall health.
Disorders Related to Absorption
The process of nutrient absorption is essential for maintaining overall health as it ensures that the body receives the necessary vitamins, minerals, and macronutrients from food. However, certain medical conditions and digestive disorders can interfere with this process, leading to malabsorption syndromes, nutrient deficiencies, and various health complications. Below are some common disorders related to absorption:
1. Malabsorption Syndrome
A condition where the intestine fails to absorb nutrients properly
Intestinal damage due to infections, surgery, or inflammation
Structural abnormalities of the intestine
Symptoms:
Chronic diarrhoea
Weight loss despite normal food intake
Fatigue and weakness due to nutrient deficiencies
Bloating and gas
Common nutrient deficiencies:
Iron, calcium, and vitamin D → Leads to anaemia and weak bones
Vitamin B12 → Causes neurological issues and fatigue
Fats and fat-soluble vitamins (A, D, E, K) → Can lead to dry skin, poor vision, and weak immunity
2. Celiac Disease
An autoimmune disorder triggered by gluten consumption
Cause:
The immune system reacts to gluten (a protein in wheat, barley, and rye), damaging the small intestine’s villi (finger-like projections that aid absorption).
Symptoms:
Chronic diarrhoea or constipation
Abdominal pain and bloating
Weight loss and malnutrition
Fatigue and anaemia
Skin rashes and joint pain
Complications:
Osteoporosis (due to calcium and vitamin D malabsorption)
Neurological issues (due to vitamin B12 deficiency)
Delayed growth in children
Treatment:
Gluten-free diet → Complete avoidance of wheat, barley, and rye
Nutrient supplementation if deficiencies are present
3. Lactose Intolerance
Inability to digest lactose (milk sugar) due to lactase enzyme deficiency
Cause:
The small intestine does not produce enough lactase enzyme, which is needed to break down lactose.
Symptoms (after consuming dairy products):
Bloating and gas
Diarrhoea or stomach cramps
Nausea
Common in:
People of Asian, African, and Mediterranean descent
Those with intestinal infections or conditions like Crohn’s disease
Treatment:
Avoiding dairy or consuming lactose-free alternatives
Taking lactase enzyme supplements
4. Crohn’s Disease (A Type of Inflammatory Bowel Disease - IBD)
A chronic inflammatory disease affecting the digestive tract
Cause:
The autoimmune reaction leads to inflammation and ulceration in the intestines.
Symptoms:
Severe abdominal pain and cramps
Chronic diarrhoea
Weight loss and nutrient deficiencies
Fatigue and fever
Complications:
Intestinal strictures (narrowing of the intestine) → Can cause blockages
Fistulas (abnormal connections between organs)
Severe malabsorption of vitamins and minerals
Treatment:
Anti-inflammatory medications and immune-suppressing drugs
Special diets (low-fibre, easily digestible foods)
Surgery in severe cases
5. Short Bowel Syndrome (SBS)
Occurs when a large portion of the small intestine is missing or damaged
Cause:
Surgical removal of parts of the intestine (due to Crohn’s disease, cancer, or trauma)
Congenital defects (born with a short intestine)
Symptoms:
Severe diarrhoea and dehydration
Malnutrition and weight loss
Electrolyte imbalances
Nutrient deficiencies:
Proteins and carbohydrates → Poor energy levels
Fats → Poor absorption of fat-soluble vitamins (A, D, E, K)
Electrolytes (sodium, potassium, magnesium) → Leads to weakness and muscle cramps
Treatment:
Nutritional support (IV fluids, supplements)
Special diets (high-calorie, easily digestible foods)
Medications to slow digestion and improve absorption
6. Bile Acid Malabsorption
Occurs when bile acids are not properly reabsorbed, leading to diarrhoea
Cause:
Gallbladder removal (cholecystectomy)
Intestinal disorders (Crohn’s disease, IBS-D)
Symptoms:
Chronic watery diarrhoea
Bloating and urgency to use the toilet
Treatment:
Bile acid sequestrants (medications that bind bile acids)
Low-fat diet
Diet and Nutrient Availability
A balanced diet is essential for providing the body with the nutrients needed for energy, growth, and overall health. Nutrient absorption depends on factors like food type, preparation, digestive health, and the presence of enhancers or inhibitors.
A nutrient-rich diet, including proteins, carbohydrates, fats, vitamins, minerals, and fibre, supports:
Energy production
Tissue repair and growth
Immune function
Brain health
Poor nutrition can lead to deficiencies (iron, calcium, vitamin D), weak immunity, fatigue, and slow healing.
To enhance nutrient absorption:
Eat a variety of whole foods (vegetables, grains, proteins, healthy fats)
Stay hydrated (water aids digestion and nutrient transport)
Limit processed foods, caffeine, and alcohol
The small intestine plays a key role in absorption, while the stomach and large intestine assist minimally. Poor absorption can cause deficiencies and health issues like malabsorption syndrome. A balanced diet, proper food combinations, and gut health improve nutrient uptake, preventing deficiencies and promoting well-being.
Frequently Asked Questions
1. What is absorption in digestion?
Absorption refers to the process where digested food molecules pass through the intestinal walls into the bloodstream or lymph.
2. Where does most absorption of digested food occur?
Most absorption occurs in the small intestine, specifically in the jejunum and ileum.
3. What structures help in food absorption in the small intestine?
The small intestine has villi and microvilli that increase surface area for efficient absorption.
4. What types of nutrients are absorbed in the small intestine?
Nutrients like glucose, amino acids, fatty acids, glycerol, vitamins, and minerals are absorbed in the small intestine.
5. How is glucose absorbed during digestion?
Glucose is absorbed into the bloodstream via active transport with the help of sodium-glucose transport proteins.
6. What happens to fats after absorption?
Fatty acids and glycerol are absorbed into the lymphatic system through lacteals and transported as chylomicrons.
7. What role does the large intestine play in absorption?
The large intestine absorbs water, electrolytes, and some vitamins like Vitamin K.
8. How does the liver contribute to nutrient absorption?
After absorption, nutrients are transported to the liver via the portal vein for metabolism and storage.
9. Why is absorption of nutrients important for the body?
Nutrient absorption provides the energy and building blocks needed for growth, repair, and overall function of the body.
10. What can affect the absorption of digested foods?
Factors like diseases (e.g., celiac, Crohn's), medications, poor diet, or damage to the intestinal lining can impair nutrient absorption.
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