What is the MTHFR test?
The MTHFR test or methylenetetrahydrofolate reductase test has become extremely popular due to a number of alternative medicine practitioners promoting it as the source of many chronic illnesses.  But is it something you should worry about?

This test is basically looking for two types of genetic mutations known as C677T and A1298C that affect the MTHFR enzyme involved in folate metabolism in your body.

Proper MTHFR enzyme function ensures that homocysteine is properly metabolized to the amino acid methionine which then makes SAMe. SAMe is known as the “universal methyl donor” which is extremely important for serotonin, melatonin and your DNA.

Folate is a B-vitamin and is important because it is at the heart of metabolism and the production of all your cells. Without it, nothing really works well so our list of symptoms and health problems would be extensive.

The National Library of Medicine Genetics Reference states that MTHFR:

"The MTHFR gene provides instructions for making an enzyme called methylenetetrahydrofolate reductase. This enzyme plays a role in processing amino acids, the building blocks of proteins. Methylenetetrahydrofolate reductase is important for a chemical reaction involving forms of the vitamin folate (also called vitamin B9). Specifically, this enzyme converts a molecule called 5,10-methylenetetrahydrofolate to a molecule called 5-methyltetrahydrofolate. This reaction is required for the multistep process that converts the amino acid homocysteine to another amino acid, methionine. The body uses methionine to make proteins and other important compounds."
How common is it?
Approximately 5-14% of the US population has two copies of the MTHFR mutation.  It is the most common in those of Mediterranean descent and lowest in those of African ancestry.  In America, about 25% of people who are Hispanic, and 10-15% of people who are Caucasian have two copies of C677T.

Should you worry about Homocysteine and MTHFR?
Although controversial in its connection with cardiovascular disease, elevated homocysteine levels may damage blood vessel walls leading to plaque (atherosclerosis) development and thus the potential for a heart attack, stroke or blood clot.

Homocysteine requires healthy levels of folate, vitamin B12, and vitamin B6 to be metabolized properly.  Recent data, however, shows that supplementation with these vitamins to lower homocysteine levels does not produce any benefit regarding cardiovascular risk reduction.  This is most likely due to the complexity of cardiovascular disease which doesn't have a single cause such as elevated homocysteine.

Elevated homocysteine levels, however, are rarely connected to a single genetic variant.  Patients with elevated homocysteine should be thoroughly evaluated for the causes of elevated homocysteine such as:

Hypothyroidism
Obesity
Diabetes
Insulin resistance
Inflammation
High cholesterol
High blood pressure
Lack of physical activity
Aging
Smoking
Medications (atorvastatin, fenofibrate, methotrexate, and nicotinic acid)

Are there any disease connections to MTHFR?
The only conditions with significant scientific support connected to MTHFR are the following:

Spinda bifida
Homocystinuria
Age-related hearing loss
Anencephaly (neural tube defect)
Blood clots

There are many claims on the internet that MTHFR is linked to cardiovascular disease, high blood pressure, stroke, glaucoma, certain cancers, and some psychiatric disorders.  All of the studies related to these conditions with MTHFR have mixed results with some studies finding no association.  So at this point, there is no clear scientific evidence that MTHFR alone has any connection to these disorders.

This is a classic example of cherry picking by alternative practitioners extracting the information from the mixed studies that support their own agenda and ignoring the opposing evidence.