Vitamins are carbon-containing substances that the body relies upon to perform essential functions.  With the exception of  vitamin D, vitamins cannot be synthesized by humans.  They, therefore, need to be ingested in the diet or through supplements to prevent severe disorders.

A multivitamin usually contains the recommended daily intake of all the vitamins.  They are recommended for people at risk for vitamin deficiencies, such as those with alcoholism, malabsorption, a vegan diet, a history of gastric bypass surgery, or some inborn errors of metabolism.  For the rest of the population, the available evidence suggests taking a multivitamin does not offer any significant health benefits.  This is because we are already receiving a sufficient amount of vitamins in our diets.

It would be a grand task to comment upon all of the vitamins, so I’ll briefly discuss a vitamin that commonly comes into play in my medical practice: Vitamin B12.  

Vitamin B12 deficiency is most commonly caused by poor absorption and inadequate intake of B12-containing food sources such as liver, milk, fish, and meat.  Why might somebody not absorb Vitamin B12?  In some people, the body forms an antibody against a protein called Intrinsic Factor, that is needed to absorb Vitamin B12 in our gut.  This is called Pernicious Anemia.  Malabsorption can also occur in people taking certain medications.  For instance, Metformin is a commonly used medication for diabetes that prevents the liberation of Vitamin B12 from foods. Strong antacids for acid reflux can also decrease the gut’s ability to absorb B12.  Finally, surgeries that remove part of the stomach, such as gastric bypass weight-loss surgery, can make it difficult for the gut to absorb adequate Vitamin B12. 

Vitamin B12 deficiency can damage the central and peripheral nervous system.   Low levels can cause cognitive impairment and even dementia, as well peripheral neuropathies and difficulty with balance.  It can also cause anemia, which is a low level of the red blood cells that carry oxygen to our body’s tissues.

Before Vitamin B12 was identified, people with B12 deficiency syndromes were treated by being fed a copious amount of liver.  Upon B12’s identification, Vitamin B12 injections became the standard means of replacement.  More recently, it has been found that most people with Vitamin B12 deficiency can attain an adequate level of B12 through high-dose oral supplementation.  When I detect low B12 levels, I offer people the oral or injection route of repletion, then later check a blood test to ensure they have achieved an adequate level.

In my next post, I’ll discuss Vitamin D.