What are the deficiencies of people with CF?

November 18, 2025 •

4 min read

An estimated 85% of people with cystic fibrosis (CF) experience pancreatic insufficiency, a primary driver of the significant nutritional deficiencies of people with CF, including malabsorption of vital fats and vitamins. This complex genetic disorder affects the body's ability to properly transport ions, leading to thick, sticky secretions that cause a cascade of systemic problems.

Quick Summary

The core deficiencies in cystic fibrosis patients stem from pancreatic insufficiency causing malabsorption of fat-soluble vitamins and essential fatty acids, alongside excessive salt loss in sweat due to a faulty CFTR gene. Secondary complications like bone disease and diabetes are common.

Key Points

Fat-Soluble Vitamins: Pancreatic insufficiency in CF leads to severe malabsorption of vitamins A, D, E, and K, requiring specific supplementation.
Essential Fatty Acids: Deficiencies in essential fatty acids and an imbalance in omega-6 to omega-3 ratios contribute to chronic inflammation in CF.
Sodium Imbalance: Faulty CFTR channels cause excessive salt loss in sweat, making individuals with CF prone to hyponatremia, especially during exertion or heat.
Bone Disease: CF-related bone disease (CFBD) is a common complication driven by deficiencies in vitamins D and K, malnutrition, and inflammation, leading to low bone mineral density.
High Energy Needs: Due to increased metabolic demands from chronic infection and malabsorption, people with CF require a significantly higher caloric intake to prevent malnutrition and weight loss.
Multifactorial Causes: The underlying issue is a defective CFTR protein that affects ion transport across cell membranes, causing thick secretions that block ducts and disrupt normal function throughout the body.

The Genetic Root of CF Deficiencies

Cystic fibrosis is caused by mutations in the CFTR (cystic fibrosis transmembrane conductance regulator) gene, which is responsible for producing a protein that regulates chloride and bicarbonate transport across epithelial membranes. When this protein is defective or absent, it leads to the production of abnormally thick and sticky secretions in various organs, including the lungs, pancreas, and sweat glands. This dysfunction sets the stage for a range of systemic deficiencies that affect a person's overall health and nutritional status.

Pancreatic Insufficiency and Nutritional Deficiencies

In the pancreas, thick mucus obstructs the ducts, preventing digestive enzymes from reaching the small intestine. This condition, known as pancreatic insufficiency (PI), affects the majority of individuals with CF and is the main cause of malabsorption. As a result, individuals with CF have trouble digesting fats, proteins, and carbohydrates, which leads to a variety of nutritional deficiencies.

Malabsorption of Fat-Soluble Vitamins

Since fat-soluble vitamins require dietary fat for absorption, pancreatic insufficiency puts people with CF at high risk for deficiencies in vitamins A, D, E, and K. Even with pancreatic enzyme replacement therapy (PERT), absorption can remain suboptimal.

Vitamin A: Crucial for vision, immune function, and the health of respiratory epithelial cells. Deficiency can lead to night blindness and an increased risk of infection.
Vitamin D: Essential for calcium and phosphorus regulation, which is vital for bone health. Deficiency is a major contributor to CF-related bone disease (CFBD).
Vitamin E: A primary antioxidant that protects cells from oxidative damage, an issue exacerbated by chronic inflammation in CF. Severe deficiency is rare with adequate supplementation but can cause neurological problems.
Vitamin K: Necessary for blood clotting and bone formation. Subclinical deficiency is common and can contribute to CFBD and, in rare cases, bleeding problems.

Essential Fatty Acid (EFA) Deficiencies

Pancreatic insufficiency also disrupts the absorption and metabolism of essential fatty acids (EFAs). People with CF often have low levels of linoleic acid (an omega-6 fatty acid) and imbalances in their omega-6 to omega-3 ratios. This imbalance can contribute to the chronic inflammation seen throughout the body, particularly in the lungs.

Minerals and Electrolytes

Beyond vitamins and fats, mineral and electrolyte imbalances are a significant concern in CF.

Sodium: A hallmark of CF is excessively salty sweat due to the malfunctioning CFTR protein in sweat glands, which prevents proper sodium reabsorption. This can lead to hyponatremia (low sodium) and dehydration, especially during exercise, hot weather, or illness.
Zinc: Involved in growth, immune function, and enzyme activity. Zinc deficiency can be common due to chronic diarrhea and malabsorption.
Calcium and Magnesium: Malabsorption of dietary fats can lead to poor absorption of calcium, contributing to CFBD. Magnesium is also frequently deficient.
Iron: While iron status is often difficult to assess due to chronic inflammation affecting lab results, iron deficiency anemia can occur, especially in individuals with advanced lung disease.

Consequences and Comorbidities

The ongoing nutritional deficiencies and systemic dysfunction lead to a number of other serious health issues, including:

Malnutrition and Growth Failure: The combination of poor absorption and high energy expenditure (from increased breathing effort and fighting infections) makes maintaining adequate weight a major challenge. Malnutrition is strongly linked to poorer lung function and overall worse outcomes.
Cystic Fibrosis-Related Bone Disease (CFBD): Multifactorial, including deficiencies of vitamins D and K, malnutrition, delayed puberty, and chronic inflammation. This results in low bone mineral density (osteopenia or osteoporosis) and increased fracture risk.
Cystic Fibrosis-Related Diabetes (CFRD): Damage to the pancreas can also affect the islet cells responsible for insulin production, leading to CFRD, a unique form of diabetes.

Management and Treatment

Effective management of CF deficiencies is multifaceted and involves a dedicated healthcare team. Key strategies include:

Pancreatic Enzyme Replacement Therapy (PERT): Prescribed for individuals with pancreatic insufficiency to help the body digest and absorb nutrients from food.
CF-Specific Vitamin Supplements: High-dose, water-miscible formulations of fat-soluble vitamins (A, D, E, K) are standard care to correct and maintain proper levels.
High-Calorie, High-Fat Diet: Patients are often encouraged to consume a diet with a higher caloric and fat content than is recommended for the general population to help counteract malabsorption and high energy expenditure.
Nutritional Supplements and Tube Feeding: For those unable to meet caloric needs through diet alone, nutritional supplement drinks or enteral feeding via a tube (often overnight) may be necessary.
Mineral and Electrolyte Management: Sodium supplementation is often required, especially for infants and those who exercise or are exposed to heat. Monitoring and treatment for zinc and calcium deficiencies are also important.

To learn more about the nutritional needs for people with CF, authoritative resources like the Cystic Fibrosis Foundation Nutrition Guidelines offer comprehensive information.

Comparison of Key CF Deficiencies


Deficiency	Primary Cause in CF	Potential Consequences	Standard Treatment
Fat-Soluble Vitamins (A, D, E, K)	Pancreatic insufficiency leading to fat malabsorption	Night blindness (A), bone disease (D, K), neurological issues (E), bleeding (K)	CF-specific vitamin supplements
Essential Fatty Acids (EFA)	Fat malabsorption and altered metabolism	Chronic inflammation, respiratory problems	High-fat diet, potential EFA supplementation
Sodium	Excessive loss through sweat glands due to faulty CFTR	Hyponatremia, dehydration, lethargy, cramps	Extra salt in food, salty snacks, sports drinks
Zinc	Malabsorption and chronic diarrhea	Growth failure, poor appetite, decreased immunity	Zinc supplements, addressing underlying issues
Calcium	Poor absorption (often linked to vitamin D deficiency)	Low bone mineral density, fractures	Calcium-rich foods, supplements
Energy	High metabolic rate plus malabsorption	Malnutrition, growth failure, low BMI	High-calorie, high-fat diet, nutritional supplements

Conclusion

The deficiencies of people with CF are a complex interplay of genetic dysfunction, malabsorption, and high metabolic demands. Pancreatic insufficiency severely impacts the absorption of fat-soluble vitamins (A, D, E, K), essential fatty acids, and key minerals like zinc, calcium, and magnesium. Furthermore, excessive salt loss in sweat can lead to dangerous electrolyte imbalances. These deficiencies contribute to serious comorbidities, such as CF-related bone disease and diabetes. Aggressive nutritional management, including PERT, CF-specific vitamins, and a high-calorie diet, is essential for improving overall health, maintaining optimal weight, and managing long-term complications in individuals with cystic fibrosis.

Frequently Asked Questions

The primary cause is pancreatic insufficiency, where thick mucus blocks the pancreatic ducts, preventing digestive enzymes from reaching the intestine. This leads to malabsorption of fats, proteins, and fat-soluble vitamins.

People with CF cannot absorb sufficient fat-soluble vitamins (A, D, E, and K) from their diet due to fat malabsorption. Supplements, often in water-miscible form, are required to prevent severe deficiencies that can affect vision, bone health, and immune function.

The excessive salt loss through sweat, a hallmark of CF, can lead to hyponatremia (low sodium levels), dehydration, and heat-related illness. Symptoms can include lethargy, muscle cramps, and confusion.

Cystic fibrosis can lead to bone disease (CFBD) through several factors, including deficiencies of vitamins D and K, poor nutrition, delayed puberty, and chronic inflammation. This can result in low bone mineral density, osteopenia, and osteoporosis.

Yes, people with CF often have low levels of essential fatty acids (EFAs), particularly linoleic acid, and an imbalance in omega-6 to omega-3 ratios. This contributes to chronic inflammation, a key feature of CF pathology.

Weight management is difficult due to the combined effects of poor nutrient absorption caused by pancreatic insufficiency and a higher metabolic rate from fighting chronic infections and increased breathing effort. This creates a high energy deficit.

CF-related diabetes (CFRD) is a unique form of diabetes common in people with CF. It results from pancreatic dysfunction, leading to insufficient insulin production and/or insulin resistance.