Saturday, 25 September 2010

MRCP revision battle 20.2: Folate

Have you ever been confused by the seemingly random use of either 'folate' or 'folic acid' and wondered what the difference is?  Well, just in case you have, here is the answer: folate is naturally occurring vitamin B9, while folic acid is the artificial form of vitamin B9.   With that cleared up, lets briefly look at folate.

Folate is important in DNA synthesis.  It is also vital in the remethylation of homocysteine, which is a current area of research I'll touch on at the end.

Low folate levels result in a macrocytic anaemia.  In pregnancy they also predispose to neural tube defects.

Good sources of folate include liver, green vegetables and nuts.

Drugs that decrease absorption of folate include phenytoin
Drugs that decrease its metabolism to its active form include trimethoprim, methotrexate and pyrimethamine

If a patient has low folate you should never give folic acid without B12 as doing so may precipitate, or worsen, subacute combined degeneration of the spinal cord (wait for the next battle...)

So just to round up by speaking about folate and homocysteine.  Raised homocysteine levels are associated with increased risk of cardiovascular events, cerebrovascular events and fractures.  Folate lowers homocysteine levels.  Unfortunately, despite this seemingly simple way to decrease risk trials so far have not shown lowering levels to decrease risk.

On that wet blanket of an observation lets progress to subacute combined degeneration of the spinal cord...