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  • Writer's pictureNancy Mullan, MD

Cutting to the Chase about MTHFR C677T

Updated: Jan 23, 2020

There is an enormous amount of focus lately on MTHFR gene mutations. MTHFR C677T is a common location for a mutation. And a mutation there can have a giant impact on your biochemistry. The MTHFR gene encodes for the MTHFR enzyme, and the MTHFR enzyme is the most important enzyme in the pathway that makes methyl groups. It is a very large enzyme with more than 500 bases in its sequence.

When you have a SNP, a single nucleotide polymorphism in the MTHFR gene, one of those bases is out of sequence. The wrong base is in an important position. Most of the time, a SNP doesn't matter. But a base out of order at the C677T position of the MTHFR gene does matter. It weakens the activity of the enzyme for which the gene encodes. And a homozygous mutation at C677T, a base out of order in both genes, profoundly weakens the enzyme it makes. A mutation in MTHFR 03 is an even more profound weakening of the enzyme than MTHFR C677T, but it is a more rare mutation.

MTHFR C677T and MTHFR 03 mutations reduce your ability to form methyl groups, the one carbon, three hydrogen molecule that moves biochemical pathways along. Methyl groups help to form some molecules and work to deactivate others. They are central to the smooth functioning of your biochemistry.

Even more critical is the function of the methyl group as a genetic regulator. At any given time, 80% of your genes should not be expressing. They should be silent. Methyl groups silence genes. If you can't make enough methyl groups, you can get aberrant gene expression and end up with a problem like an autoimmune disorder, delayed childhood development or autism, impaired heavy metal detox, or even certain forms of cancer. Too few methyl groups lead to big time health problems.

This is why Dr. Amy Yasko's protocol that I implement works on getting methyl group production in place first. The BHMT pathway is the quickest, easiest way to make methyl groups. It gets the least interference from other genetic mutations and is relatively easy to activate. Both DHA and Phosphatidyl serine complex get that pathway going. We call it 'the shortcut pathway' to methyl group formation.

The body's most robust producer of methyl groups, the pathway that we call 'the long route', uses the methionine and the folate cycles. In these two pathways there are a number of enzymes that are made by genes that can have SNPs that impair methyl group formation. The long route is the one that contains the MTHFR gene and enzyme. It needs a functioning folate cycle to be operational. It is more difficult to make these combined pathways work. It takes balanced biochemistry in your body overall to achieve this.

Your gastrointestinal tract can't be riddled with the wrong organisms sending the wrong metabolic byproducts to your liver. Your metal detox pathways need to be at least minimally functional. And there are SNPs that can send the substrates needed in this methyl group producing pathway off in other directions. All of these issues need to be recognized and supplementation put in place to bring them under control. Then the methyl group producing pathway can function to produce methyl groups.

Most doctors do not look at these pathways carefully. They give you 5 methyl folate and methyl B12 and hope. They may help,  or they may catapult you into symptoms. Or they might not have any impact at all because the other co-enzymes and substrates that this pathway needs to function are not present.

These clinicians may not concern themselves with diet or gastrointestinal function because they are just not aware of the inflammation that problem conditions in your GI tract can cause. You will not get past inflammation in any other part of your body when your GI tract is fueling it.

If you have an MTHFR mutation, it can have a massive impact on the ability of your body to function well. It impairs immunity so you get infections that weaken you further. It prevents genetic regulation and allows aberrant gene expression giving you symptoms that may confuse your doctor.

It's time for a doctor who makes sense and who knows the chemistry that needs to work well in your body for you to feel well.

I have a free, downloadable ebook at that gives you further detail about these issues. Click here to download.

If you have had it with half solutions, or no solutions, talk to me. Get an Exploratory Conversation with me. It does not involve becoming a patient and it is quick and easy to get. For a $129 fee, I will talk with you for 30 minutes, look at the test results you send and make recommendations that get you unstuck. It is so worth it to get help and get hope back again.

If you know that you have an MTHFR mutation and you are having problems with your health, contact me and ask for an Exploratory Conversation.

I look forward to being able to help,

Dr. Mullan

What people like you are saying about Dr. Mullan’s work:

I shudder at the thought of what my family would be like without Dr. Mullan. Thankfully, with her help, we have stopped my husband's chronic 30 year battle with kidney stones. He is no longer forming them and is stone free. My thyroid is now working normally, my body temperature is almost normal and my hair has grown back. My oldest daughter's Autism is in the process of being reversed and her hair pulling has stopped. The greatest blessing from our good health is the birth of my second daughter Ava, now one-year-old. At 50 years old I carried her to term. One of my doctors commented to me saying “ you are carrying this baby like a 22-year-old.” Yes, I am because of Dr. Mullan and working on my methylation pathway. One by one she is knocking off symptoms and bringing us back to health. The future is bright! Thank you, Dr. Mullan, for the work you do.


Wow. I feel great. Thank you for your help. It's amazing really. Like a light turned on. Curious to see what the next tests show. To ride this peak indefinitely is my goal. Ha. I have energy again. Yay!

Really grateful,


I am so relieved. My daughter is doing SO WELL since we started with you! We have been to so many doctors and tried so many things.Now I can start working on my own program with you....


So excellent! I literally learn something every single time and I get clarification on things that have been lingering in my mind… VB

You are giving people a huge gift by empowering them… It’s about helping the patient become their own healer by taking them to a higher level of consciousness… AL

Thank you so much, Dr. Mullan. Thank you so, so much for everything you do. MS

Wow! I have to tell you, this was such an uplifting session. It’s so nice to hear good news, especially about a child. Anxiety, OCD and a host of other mental/psychiatric symptoms have been a huge hurdle for me. So to hear this story of all those awful symptoms totally going away is such a bright light for me!!!! TR

Fantastic, caring, smart, savvy doc. I worked with Dr. Mullan for a couple of years to help MTHFR mutations and their associating expressions! To say the least! She's brilliant. At that time she had weekly calls for her patients - free - where we could ask questions and she would reply. What doctors do this? She does. She's also an animal lover and is right on about the way she practices medicine. I highly recommend her. In good health!


"Dr. Nancy Mullan is a beautiful person. She is an expert in her field and has helped our family so much. I am very grateful to her. She came highly recommended and I know why. I would recommend her and her website for information re: healing from a genetic point of view. Thank you, Dr. Mullan, for everything.”


"Dr.Mullan has helped me with issues that I have struggled with for years. She is knowledgable and practical. I would recommend her to others.”


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