Factors That Affect Vitamin Absorption

Erin Coleman, R.D., L.D.
leaf with supplements

Unfortunately, just because you're getting plenty of essential vitamins and minerals in your diet doesn't mean your body is properly absorbing these nutrients. How well your body absorbs vitamins from foods and supplements plays a key role in preventing nutrient deficiencies and the side effects associated with them. Numerous factors can affect proper nutrient absorption.

1. Intrinsic Factor Deficiency

A protein made by cells in your stomach lining called intrinsic factor is needed for proper vitamin B12 absorption. When your body is deficient in intrinsic factor, poor B12 absorption can lead to B12 deficiency and pernicious anemia. Your body might not make enough intrinsic factor if you've had part of your stomach removed or have an autoimmune disease. If this is the case, your doctor may prescribe high doses of vitamin B12 supplements or give you vitamin B12 injections to correct the problem.

2. Smoking and Alcohol

Steering clear of tobacco products and alcohol helps maximize vitamin absorption in your body. You probably already know smoking can cause numerous health problems, such as lung disease and cancer, but you might be surprised to learn smoking reduces vitamin absorption. According to Mayo Clinic, smoking lowers vitamin C absorption, and excessive alcohol consumption reduces your body's ability to absorb folate. One 2013 study found smoking reduces calcium absorption, which may be due to nicotine's interaction with calcium receptors. Avoid tobacco products and limit or avoid alcohol to maximize vitamin absorption. Harvard School of Public Health says if you do drink, limit it to two drinks daily for men and one drink per day for women.

3. Nutrients

Believe it or not, nutrients also affect vitamin and mineral absorption. For example, beta-carotene and vitamin C enhance iron absorption, while calcium and polyphenols appear to reduce the absorption of iron, according to the Iron Disorders Institute. Your body needs plenty of vitamin D to absorb calcium properly, so getting too little vitamin D leads to calcium deficiency and osteoporosis. To maximize vitamin absorption, it's important to get recommended amounts of essential vitamins and minerals daily, but not exceed tolerable upper intake levels. Don't worry about taking absorption-enhancing nutrients with or without other nutrients, just get a good balance of all essential nutrients over the course of the day or take multivitamin supplements as recommended by your doctor.

4. Foods

ceviche and citrus

The foods you eat also affect how you absorb vitamins and minerals. For example, the Office of Dietary Supplements notes meat and seafood enhance iron absorption. Because vitamin C also improves iron absorption, orange juice and citrus fruits are beneficial. The Iron Disorders Institute says coffee, tea, soy protein, calcium-rich foods, and fiber may inhibit iron absorption. To maximize all benefits, eat foods with absorption-enhancing qualities during the same meal. However, since so many foods either enhance or inhibit absorption of different nutrients, it's best to get a variety of healthy foods in each day and take a multivitamin supplement if your doctor recommends it.

5. Sunscreen

Many Americans aren't getting enough vitamin D according to one 2011 study. Sunlight exposure is one way to boost vitamin D in your body, but using sunscreen with a sun protection factor (SPF) of 8 or higher blocks the sun's rays and your body's ability to make vitamin D from it according to the Office of Dietary Supplements. However, because sunscreen protects against skin damage caused by ultraviolet (UV) rays, it's important to use it - especially when you're in hot summer temperatures for long time periods. Just be sure to eat plenty of vitamin D rich foods (like dairy foods and fish) or take a vitamin D supplement. MedlinePlus notes that getting 10 to 15 minutes of sunscreen-free sun exposure three times per week is enough to meet your vitamin D needs.

6. Medical Conditions

Certain medical conditions affect the way your body absorbs vitamins and can lead to nutrient deficiencies. Examples of these diseases include:

  • Pernicious anemia (lack of intrinsic factor)
  • Whipple's disease (a bacterial infection affecting the intestines)
  • Inflammatory bowel disease (IBD) (Crohn's disease and ulcerative colitis)
  • Human Immunodeficiency virus (HIV) (a viral infection)
  • Cystic fibrosis (a genetic disorder infecting the lungs and digestive system)
  • Celiac disease (gluten intolerance)
  • Pancreatic, liver, and gallbladder diseases - and gallbladder removal
  • Radiation treatment that causes intestinal inflammation

If you suffer from one of the above medical conditions that can reduce vitamin absorption, ask your doctor which vitamin supplements (or injections) you should take, and get checked for deficiencies regularly.

7. Intestine or Stomach Resection

If you've had part of your stomach or intestine removed, as in the case of bariatric weight loss surgery, your body likely won't absorb vitamins and minerals as efficiently as it did before surgery. This is because most nutrients are absorbed through these two organs. So, if you've had gastrointestinal surgery to remove parts of your digestive tract, have your doctor monitor your vitamin and mineral levels regularly, and ask which vitamin supplements you should take. If you're deficient in certain nutrients, your doctor may recommend multivitamin supplements, or vitamin injections depending on the severity of the malabsorption, and which nutrients you're deficient in.

8. Parasite Infections

Parasitic infections (such as tapeworm, hookworm, and giardia) can also cause nutrient malabsorption, according to a 2008 review published in Clinical Infectious Diseases. This is because parasites in the human gastrointestinal tract feed on nutrients, taking them away from their human hosts. Fortunately, most parasitic infections can be successfully treated, although some are easier to treat than others. The infection must be treated to improve absorption, but your doctor may recommend a vitamin supplement as well.

9. Some Medications

Taking certain medications can lower vitamin and mineral absorption by interfering with receptor sites or fat absorption (which affects fat soluble vitamins). Examples include proton-pump inhibitors, some antacids, weight loss medications, antibiotics, some anti-inflammatory medications, diabetes medications, and anti-seizure medications, according to MedlinePlus. If you're taking any of these medications for long periods, ask your doctor about taking vitamin or mineral supplements to offset malabsorption.

10. Intestinal Bacteria Imbalance

Sometimes the good and bad bacteria in your gut become unbalanced, which can alter vitamin absorption. According to a 2011 issue of Today's Dietitian, small intestinal bacterial overgrowth (SIBO) occurs when excessive bacteria builds up in the small intestine and utilizes nutrients there, which can lead to vitamin malabsorption -- especially vitamins B12, A, E, and D. Luckily, this condition can be treated with medication, which then improves vitamin absorption. Vitamin supplements help, as well.

Vitamin Deficiency Prevention

Because so many factors affect vitamin and mineral absorption in your body, the best ways to meet daily nutrient needs are to eat a well-balanced diet, treat medical conditions properly, take multivitamin supplements when your doctor recommends it, avoid smoking, and drink alcohol in moderation. Have your doctor monitor micronutrient blood levels regularly.

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Factors That Affect Vitamin Absorption