- Those who have trouble absorbing
vitamin D are at risk for bone fractures, osteoporosis, and more. - Having Crohn's or kidney disease and taking certain medications may inhibit vitamin D absorption.
- If you have trouble absorbing vitamin D, try a supplement with fatty and/or magnesium-rich foods.
Proper absorption of vitamin D enables your body to in turn absorb calcium, fight infection, and keeps your nervous system and muscles working as they should.
The most natural, direct way to get vitamin D naturally is through sun exposure, but people tend not to get enough sun to produce adequate amounts. Most doctors recommend supplementing it with food.
However, some people have a more difficult time absorbing vitamin D than others, and some medical conditions can make it difficult to absorb Vitamin D from food.
That's a problem since "not getting enough vitamin D leaves you at risk for bone fractures, osteoporosis, and muscle weakness," says Melissa Prest, a registered dietitian in the Chicago area and spokesperson for the Academy of Nutrition and Dietetics.
Learn more about how your body absorbs vitamin D and why some people may have trouble getting enough.
How does your body absorb vitamin D?
The way you absorb vitamin D depends on whether you're getting it from food or sunlight:
- Food/supplements: After you eat food or take supplements with vitamin D, your body stores it in fat cells until it is needed. At that point, the liver and kidneys transform the stored vitamin D into the active form the body needs - known as calcitriol - via a process called hydroxylation.
- Sunlight: Your body's process for making vitamin D works similarly after sun exposure. The main difference is that the sun first triggers a type of cholesterol found in the body called 7-dehydrocholesterol. This starts the process of vitamin D production and transport where it moves to the liver and kidneys, much like after you eat foods with vitamin D.
However, not everyone can easily obtain or absorb vitamin D.
Why am I not absorbing enough vitamin D?
There are a few reasons why people can have trouble absorbing vitamin D. Some factors that may reduce or block its absorption include:
- Conditions such as celiac disease, chronic pancreatitis, Crohn's disease, and cystic fibrosis. These can all affect the intestines, preventing them from absorbing vitamin D found in food.
- BMI (body mass index) higher than 30. Subcutaneous body fat can sequester, or trap, vitamin D, which is why deficiency is a greater concern in those who are obese.
- Liver or kidney disease. Both diseases can negatively affect how your body processes vitamin D. Kidney disease may cause a person to have trouble processing vitamin D to its active form, calcitriol, which is used throughout the body. Some forms of liver disease cause problems with fat absorption, also making it harder to absorb vitamin D.
- Radiation treatment. This type of cancer treatment can make it harder for the intestines to absorb vitamin D.
- Weight loss surgery. These procedures reduce the size of the stomach or bypass part of the small intestine, thus making it harder for the body to consume adequate levels of many
vitamins and minerals including vitamin D.
Antonette Hardie, a registered dietitian at the Ohio State University Wexner Medical Center's Comprehensive Transplant Center, says some medications can also impact or inhibit vitamin D absorption, these include:
- Oral steroids
- Orlistat, a weight-loss drug
- Statins
- Diuretics
Symptoms of low vitamin D levels
Some symptoms of low vitamin D include:
- General fatigue
- Muscle aches
- Mood changes
- Pain in your bones
When using a blood test to measure vitamin D, a normal level is 12 ng/mL to 20 ng/mL for healthy adults. A level less than 12 ng/mL indicates vitamin D deficiency and could be a sign of absorption issues, according to the National Institutes of
If you are concerned about your vitamin D levels, request a blood test from your doctor. There are also at-home tests that require a finger prick for a very small blood sample.
How to absorb more vitamin D
If you have problems absorbing vitamin D, Prests says to try consuming it along with fatty and/or magnesium-rich foods. Because vitamin D is fat-soluble, eating it with fatty foods can help the body to absorb and store it for future use, Prest tells Insider.
Fatty foods that also contain high levels of vitamin D are ideal, she says. These include:
- Cold-water fish, such as salmon
- Egg yolks
- Milk fortified with vitamin D and higher fat dairy products
- Nuts
Combining vitamin D with magnesium may also help to increase absorption. Foods that are naturally high in magnesium include:
- Pumpkin seeds
- Almonds
- Avocado
Although it is best to try to get your vitamin D from whole foods, there may be times when a prescription supplement is advised.
Health providers typically prescribe a high dose of vitamin D supplement only for a short time to avoid the risk of vitamin D toxicity, Prest says. It is possible to get too much vitamin D, so talk to your doctor about the proper individual dosage of supplements.
Insider's takeaway
Some factors that may inhibit your vitamin D absorption include taking certain medications and conditions such as Crohn's or kidney disease.
If you have trouble absorbing vitamin D, make sure to eat vitamin D-rich foods alongside fatty or magnesium-rich foods. You may also take a vitamin D supplement if advised to do so by your doctor.
"Working with a registered dietitian nutritionist can help you to ensure that you are getting adequate amounts of vitamin D, especially if you are someone who may be at risk of a vitamin D deficiency," Prest says.