What Reduces Absorption of Vitamins and How to Boost Your Intake

December 15, 2025 •

3 min read

Approximately 1 in 10 adults over 65 may have atrophic gastritis, a condition that can significantly impair the absorption of key nutrients like vitamin B12. Beyond age-related issues, numerous dietary, medical, and lifestyle factors can hinder your body's ability to absorb essential vitamins from the foods you eat or supplements you take.

Quick Summary

Several factors can impede vitamin absorption, including antinutrients in certain foods, medication side effects, specific gastrointestinal disorders, and lifestyle choices like excessive alcohol or caffeine consumption. Understanding these inhibitors is crucial for optimizing nutritional health.

Key Points

Antinutrients: Compounds like phytates in grains and oxalates in spinach can bind with minerals, reducing their absorption.
Fat Intake: A low-fat diet hinders the absorption of crucial fat-soluble vitamins (A, D, E, K), as they require dietary fat to be assimilated.
Medications: Common drugs such as acid-reducing PPIs and diabetes medication Metformin can interfere with vitamin B12 absorption.
Health Conditions: Digestive disorders like Celiac and Crohn's disease, along with liver or pancreatic issues, can cause widespread malabsorption.
Lifestyle Factors: Excessive alcohol and caffeine intake, smoking, and high stress levels all negatively impact the body's ability to absorb or utilize vitamins effectively.
Nutrient Pairings: Avoid combining certain nutrients that compete for absorption, such as calcium and iron, or consuming tea and coffee near mealtimes.

Antinutrients in Your Diet

Antinutrients are compounds in foods that can interfere with the absorption of vitamins and minerals. While many foods containing antinutrients are healthy, awareness of their effects can be beneficial.

Phytates: Found in whole grains, legumes, nuts, and seeds, phytates can reduce the absorption of minerals like iron, zinc, and calcium. Preparation methods such as soaking or sprouting can lower phytate levels.
Oxalates: Present in vegetables like spinach and rhubarb, oxalates can bind to calcium, hindering its absorption. It is advisable to separate consumption of high-oxalate and high-calcium foods.
Tannins: These are found in tea, coffee, and certain wines and can inhibit non-heme iron absorption. Avoiding tea or coffee with iron-rich meals can help.
Avidin: In raw egg whites, avidin binds to biotin. Cooking eggs deactivates avidin.

Medical Conditions Affecting Absorption

Various health issues can impair the small intestine's ability to absorb vitamins, potentially leading to malabsorption syndrome.

Digestive and Intestinal Disorders

Conditions causing inflammation or damage to the small intestine's lining can severely affect nutrient absorption. These include Celiac disease, Inflammatory Bowel Diseases (like Crohn's), Cystic Fibrosis (affecting fat and fat-soluble vitamin absorption), and Small Intestinal Bacterial Overgrowth (SIBO), which can consume nutrients like B12.

Surgical and Organ-related Factors

Procedures like bariatric surgery can reduce nutrient absorption, requiring supplementation. Diseases affecting the liver, gallbladder, or pancreas can impair fat digestion and thus the absorption of fat-soluble vitamins.

Medications and Vitamin Absorption

Some medications can reduce or block the absorption of specific vitamins.

Common Medications and Their Effects

Acid-reducing drugs (PPIs and H2 blockers) can lower stomach acid, impacting B12 absorption. Metformin, for diabetes, also reduces B12 absorption. Antibiotics can disrupt gut bacteria involved in synthesizing vitamins like K. Corticosteroids affect calcium and vitamin D metabolism. The weight-loss drug Orlistat blocks fat absorption, reducing intake of fat-soluble vitamins (A, D, E, K).

Lifestyle Habits That Reduce Vitamin Absorption

Daily habits can influence nutrient uptake.

Excessive alcohol intake damages the digestive tract, reducing absorption of various nutrients, particularly B vitamins and folate. Smoking lowers vitamin C absorption. Chronic stress can negatively impact digestion. A diet too low in healthy fats can hinder absorption of fat-soluble vitamins (A, D, E, K).

A Comparison of Fat-Soluble vs. Water-Soluble Vitamin Absorption Factors


Factor	Fat-Soluble Vitamins (A, D, E, K)	Water-Soluble Vitamins (B-complex, C)
Fat Intake	Needs dietary fat for absorption.	Not dependent on fat for absorption.
Malabsorption	Particularly susceptible to fat malabsorption issues from liver, gallbladder, or pancreatic disease.	More affected by issues with stomach acid (e.g., PPIs for B12) or intestinal damage (e.g., IBD for Vitamin C).
Storage	Stored in the body's fatty tissues.	Not stored in the body and need to be replenished regularly.
Medication Effects	Orlistat and corticosteroids can significantly impact absorption.	PPIs, Metformin, and alcohol can hinder absorption of B12, folate, and others.
Lifestyle Habits	Affected by low-fat dieting and alcohol abuse.	Affected by alcohol, smoking (Vitamin C), and excessive caffeine (Vitamin C).

Conclusion

Identifying factors that reduce vitamin absorption is crucial for optimizing nutritional health. Antinutrients in food, long-term medication use, lifestyle habits, and various medical conditions can all impact how well your body absorbs vitamins. By being mindful of dietary choices, managing medication effects, addressing underlying health issues, and adopting healthier habits, you can improve vitamin absorption and support overall well-being.

For more information on dietary choices, refer to this comprehensive guide on antinutrients from The Nutrition Source at Harvard T.H. Chan School of Public Health: Are Anti-Nutrients Harmful?.

Frequently Asked Questions

Yes, excessive caffeine from coffee or tea can interfere with the absorption of several nutrients, including iron and vitamin C. It is best to wait at least an hour after a meal before consuming caffeinated beverages to minimize this effect.

Yes, many medications can reduce vitamin absorption. For example, proton pump inhibitors (PPIs) reduce stomach acid needed for vitamin B12 absorption, while corticosteroids can deplete vitamin D.

Antinutrients are compounds that interfere with nutrient absorption. Examples include phytates in grains and legumes, oxalates in spinach and beets, and tannins in tea and coffee. Preparation methods like soaking can reduce their effects.

Malabsorption disorders can be caused by conditions such as Celiac disease, Crohn's disease, cystic fibrosis, and certain liver or kidney diseases. These can damage the gut lining or disrupt digestive processes.

A very low-fat diet can hinder the absorption of fat-soluble vitamins—A, D, E, and K—because these vitamins require dietary fat to be effectively absorbed and utilized by the body. Inclusion of healthy fats is essential.

Yes, as people age, the body's ability to absorb certain nutrients, especially vitamin B12, can become less efficient due to factors like decreased stomach acid production.

To improve absorption, eat a balanced diet with healthy fats, pair complementary nutrients (like Vitamin C with iron), manage stress, and consider probiotics for gut health. Consult a doctor about potential medication interactions.