The MTHFR gene, or methylenetetrahydrofolate reductase, provides the body with instructions for making an enzyme of the same name. This enzyme participates in the chemical processing of folate, a B vitamin. Genetic variations in the MTHFR gene are common and have drawn interest for their influence on health, particularly concerning the body’s use of folic acid, the synthetic version of folate.
The MTHFR Gene and Folate Metabolism
The MTHFR gene is fundamental to a process called methylation, a biochemical process that helps regulate gene expression, detoxify compounds, and process hormones. The MTHFR enzyme has a specific role within the folate metabolism pathway, which is a key part of methylation. This pathway converts folate from food into a form the body can actively use.
The goal of this pathway is to produce L-methylfolate, also known as 5-methyltetrahydrofolate (5-MTHF). This is the “active” form of folate that can participate in various bodily functions, including the conversion of the amino acid homocysteine into methionine. The MTHFR enzyme is responsible for the final step in this conversion.
It takes an intermediate form of folate and converts it into active L-methylfolate. Without a properly functioning MTHFR enzyme, this conversion is disrupted. This hinders the body’s ability to generate the usable folate it needs for many cellular activities.
Distinguishing Folic Acid from Natural Folate
While often used interchangeably, folic acid and folate are distinct forms of vitamin B9, and the body processes them differently. Folate is the form of this vitamin that occurs naturally in foods. It is found in items such as leafy green vegetables like spinach, legumes, citrus fruits, and beans. This natural form is more readily available for the body’s metabolic processes.
Folic acid is a synthetic, oxidized version of the vitamin. It is widely used in dietary supplements and to fortify processed foods like flour, pasta, and breakfast cereals. Because it is a synthetic compound, the body must go through several additional enzymatic steps to convert folic acid into active L-methylfolate.
This conversion process for folic acid is more complex and places a higher demand on the body’s metabolic resources compared to the pathway for natural folate. The efficiency of this conversion can be influenced by a person’s genetic makeup, which is why the difference between these two forms is a topic of interest.
How MTHFR Variants Create a Problem with Folic Acid
Genetic variations, or polymorphisms, in the MTHFR gene can alter the function of the MTHFR enzyme. The two most studied variants are C677T and A1298C. Inheriting these variants can decrease the enzyme’s efficiency by 30% to 70%.
This reduced enzyme function impairs the ability to convert synthetic folic acid into active L-methylfolate, leading to two main problems. The first is a functional deficiency of active folate, where the body lacks enough L-methylfolate to perform its duties, even with high folic acid intake. This deficiency also hinders the conversion of homocysteine to methionine, which can lead to elevated homocysteine levels in the blood.
The second problem is the accumulation of unmetabolized folic acid (UMFA) in the bloodstream. Since the synthetic folic acid cannot be processed efficiently, it builds up in the body. This buildup may interfere with the function of the small amount of active folate that is produced.
Alternative Folate Supplementation and Dietary Choices
For individuals with MTHFR gene variants, a targeted approach to folate intake can bypass the metabolic issues. The most direct solution is to supplement with L-methylfolate (or 5-MTHF). This is the “body-ready” form of folate that is already active and does not require conversion by the MTHFR enzyme, circumventing the genetic bottleneck.
When choosing supplements, read labels carefully to ensure they contain L-methylfolate rather than folic acid. This is particularly relevant during pregnancy, when adequate folate is needed to prevent neural tube defects in the fetus. Using the active form ensures the body receives the necessary folate without relying on a compromised enzyme.
In addition to supplementation, a diet rich in natural folate sources is recommended. Foods such as lentils, asparagus, spinach, and avocados provide folate in a form that is more easily used by the body than synthetic folic acid. Prioritizing these whole foods helps support overall folate status and provides other beneficial nutrients that work in concert with B vitamins.
Identifying MTHFR Gene Variants
The only definitive way to determine if you have a variation in the MTHFR gene is through genetic testing. This is done with a simple blood or saliva test ordered by a healthcare provider, which analyzes your DNA for common polymorphisms like C677T and A1298C.
A physician might suggest testing for several reasons, including:
- A personal or family history of cardiovascular events at a young age
- Persistently elevated homocysteine levels found in blood work
- A history of recurrent pregnancy loss
- Other conditions associated with MTHFR issues
Test results can inform discussions with a healthcare provider about personalized nutritional strategies. A professional can interpret these results in the context of your overall health and guide any necessary dietary or lifestyle adjustments.