How to Tell If Intestinal Woes Are Due to IBS or a Vitamin Deficiency

Work with a nutritionist to design a meal plan based on your diagnosis.
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Are your intestinal woes a symptom of irritable bowel syndrome (IBS) or a vitamin B12 deficiency? It can be hard to tell because some of the symptoms of these two conditions overlap, and one may affect the other. But if you're having stomach symptoms, you and your doctor should investigate.


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Symptoms: Separate and Overlapping

One of the most common symptoms of IBS is alternating between bouts of diarrhea and constipation, according to the Mayo Clinic. Other symptoms include cramping and bloating, difficulty swallowing and weight loss.


With a B12 deficiency, symptoms also include both diarrhea and constipation, as well as fatigue, muscle weakness and cognitive disturbances, says Marta Ferraz Valles, RDN, a dietitian at the Institute for Digestive Health and Liver Disease at Mercy Medical Center in Baltimore. Some people also may experience weight loss, a rapid heartbeat and numbness and tingling in their hands and feet, according to Cedars Sinai.


While some of the symptoms of the two conditions are the same, "there is no scientific evidence that IBS and vitamin B12 deficiency are connected in any way," Ferraz Valles says.

Still, Niket Sonpal, MD, a New York-based internist and gastroenterologist, says it's not uncommon for people with IBS to also have a vitamin B12 deficiency. "Due to their disrupted intestinal walls, it is difficult for the vitamin to be absorbed in the small intestine," he explains.


Understanding Irritable Bowel Syndrome

No one knows exactly what causes IBS, although the Mayo Clinic notes that these factors are believed to play a role:

  • Intestinal muscle contractions. Weak contractions slow food movement through the intestines and cause stools to become hard. Strong contractions can cause gas, bloating and diarrhea.
  • Nervous system signals. Nerves in your digestive system send signals between your brain and intestines, but the signals can go awry and cause your body to overreact. The overreaction can result in diarrhea or constipation.
  • Inflammation. Your body overproduces immune-system cells in your gut. They go into overdrive and can cause pain and diarrhea.
  • Bacterial overgrowth. Some people develop a surplus of bacteria in their gut after getting over a bout of gastroenteritis. The surplus bacteria cause diarrhea. People with IBS also may have an imbalance of "good" and "bad" bacteria in their gut.

Certain foods, such as beans, cabbage, carbonated drinks and dairy products, as well as stress and hormonal changes may make IBS symptoms worse, the Mayo Clinic notes.

Read more: How the Low-FODMAP Diet for IBS Works, and How to Get Started

Understanding B12 Deficiency

While most people consume enough vitamin B12 in their diet, some have difficulty absorbing it, including older adults and those with pernicious anemia (a blood disorder), states the National Institutes of Health's Office of Dietary Supplements. Overall, B12 deficiency affects between 1.5 and 5% of the population, it says.

As with IBS, the cause of B12 deficiency anemia is unknown. However, people most likely to suffer from B12 deficiency anemia lack a protein made in the stomach that is necessary to absorb the vitamin, according to Johns Hopkins Medicine.

Also, you're at greater risk if you've had surgery on the part of your small intestines where B12 is absorbed, says Johns Hopkins.

Diagnosis and Treatment

To determine whether you have either IBS or a B12 deficiency, your doctor will need to know your symptoms as well as your medical and family history and will also order blood tests. For IBS, your doctor may also order stool tests and consider a colonoscopy to look inside your lower colon and rectum, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

If a vitamin deficiency is found, your doctor may recommend B12 injections, depending on your age and health, according to Johns Hopkins Medicine. A diet that includes more foods rich in B12 — such as meat, poultry, shellfish, eggs and fortified cereals — may be recommended.

Treatment for IBS generally includes an IBS-friendly diet and possibly medications to control diarrhea and gastrointestinal pain, according to the Mayo Clinic.

Both conditions require that you avoid foods that can trigger your symptoms. Ferraz Valles suggests working with a nutritionist to devise a meal plan that's right for you and your health conditions. And she adds, "Anyone eating less animal-based foods or [who is] over 50 should supplement vitamin B12."

Read more: The Best Method to Increase Vitamin B12 Levels