Repairing the digestive system and optimizing the flora should be one of the first steps in correcting methylation deficiency.

There are countless reasons for this; however, the focus here is the relation between methionine synthase and acetylaldehyde.

One must first understand what methionine synthase is and why it is important.

Methionine synthase: What is it?
The critical enzyme which utilizes the substrate produced by the MTHFR enzyme, 5-methyltetrahydrofolate, along with the cofactor, methylcobalamin.

Methionine synthase: Purpose?
The purpose of methionine synthase is two fold:

  1. converting homocyteine into methionine.
  2. converting 5-methyltetrahydrofolate to tetrahydrofolate which is then used to make other forms of folate which are needed to produce and repair DNA

Methionine synthase: How does it work?
By donating a methyl group to homocysteine from 5-methyltetrahydrofolate. Methylated homocysteine becomes methionine and since 5-methyltetrahydrofolate donated its methyl group, it now becomes tetradhydrofolate.

Tetrahydrofolate proceeds down the folate pathway to produce nucleotide bases which are used for DNA repair and production.

This process can be limited in those with MTHFR mutations because those with MTHFR mutations have a limited ability to produce 5-methyltetrahydrofolate.

As you can see from the image above, if methionine synthase does not have 5-methyltetrahydrofolate or methylcobalamin available, it cannot function.

If methionine synthase is limited in function, elevated homocysteine is a likely result along with reduced folate levels.

This limitation may be bypassed by supplementing with vitamin B6, methylfolate, methylcobalamin and betaine.

This works quite well typically but there may be other aspects which must be addressed in order to optimize the function of methionine synthase.

Enzymes do not work well if they:

  1. lack the active substrate such as methylfolate
  2. lack cofactors such as methylcobalamin
  3. are exposed to inhibiting compounds such as heavy metals, solvents, chemicals, toxins

Points one and two have been addressed.

Point three has not yet.

Methionine synthase has a few potent inhibiting compounds and one is produced from Candida

Candida albicans produces a toxic byproduct called acetylaldehyde.[1]

Research cites:
“Acetaldehyde-induced inhibition of liver methionine synthase activity is thus proposed as the most likely explanation of the reported in vivo effect of ethanol upon methionine synthase.” [2]

Acetylaldehyde is also a byproduct of ethanol.

Let’s make this very clear.

What are the major symptoms of a hangover?

  1. headache
  2. foggy thinking
  3. irritability and/or depression
  4. fatigue
  5. soreness
  6. sensitivity

What are the major symptoms of yeast overgrowth?

  1. headache
  2. foggy thinking
  3. irritability and/or depression
  4. fatigue
  5. soreness
  6. sensitivity

What are some major symptoms of reduced methylation?

  1. headache
  2. foggy thinking
  3. irritability and/or depression
  4. fatigue
  5. soreness
  6. sensitivity

When approaching anyone with a MTHFR or methylation defect, it is critical to take a thorough history and examine the digestive system first.

Commonly, when I work with individuals experiencing MTHFR or methylation defects, I ask:

  • History of antibiotic use in the last 5 yrs?
  • Steroid use?
  • Flagyl?
  • Take a potent multistrain probiotic?
  • Digestive symptoms? Constipation, diarrhea, IBS, etc?
  • Itchy anus?
  • Lichen planus? Leukoplakia?
  • White tongue coating?
  • Desire for sweets?
  • Recurrent vaginal infections?
  • Nail fungus?
  • Weak immunity?
  • Fatigue level?
  •  Cloudy thinking?

These are often present in those with yeast overgrowth.

You now know that acetylaldehyde inhibits methionine synthase and now you must do something about it.

Recommendations for reducing yeast overgrowth (and eliminating an inhibitor of methionine synthase):

  1. Eliminate soda, sugars and simple carbohydrates
  2. Support the immune system with selenium, zinc, vitamin C, vitamin A, vitamin D, vitamin E
  3. Reduce the reproductive ability of candida albicans with biotin and saccharomyces boulardii
  4. Reduce the production of acetylaldehyde by using oral xylitol products
  5. Support beneficial bacteria growth by supplementing with a potent multistrain probiotic.
  6. Utilize antifungal herbs and nutrients to eliminate yeast.
  7. Support elimination of acetylaldehyde with molybdenum, vitamin C, NAC, glutathione
  8. Improve intestinal motility with chia seeds, hydration, magnesium and reducing intake of dehydrated foods
  9. Eat meals with quality protein and vegetables.
  10. Eliminate biofilm with specific enzymes to eliminate recurrent yeast overgrowth
  11. Support methylation with methylcobalamin and l-5-methylfolate

Find many of the above recommendations here – in the Yeast and Candida Overgrowth section.

Given the complexity of the topic of methylation, this is one consideration out of many. There are many variations on how one must approach elimination of candida overgrowth depending on their genetics, lifestyle, age and current symptomatic picture.

The point here is to educate you that methylation is more than just genetics and vitamins – it is also significantly affected by your internal environment.

UPDATE on Sept 19. 2013: The writer over at Magnesium Advocacy Group made an excellent point about the need to support acetylaldehyde. While I mentioned acetylaldehyde inhibited methionine synthase, in my haste, I did not tell you how to eliminate the acetylaldehyde – which – sadly – is a mistake. I was so excited about the connection between methylation and yeast that I forgot to tell you how to mend it. Stupid right?

Read this article on how magnesium is essential to elimination of acetylaldehyde – keep in mind that magnesium is not the only nutrient needed to support acetylaledyde elimination but it is a big player especially since many of us are deficient in it.




Further Reading:
Cobalamin-Dependent Methionine-Synthase










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Vince Sabio
10 years ago

Dr. Lynch,
What are your opinions on Food Grade Hydrogen Peroxide for getting rid of Candida overgrowth? Some studies suggest that it helps to get rid of Candida..
This is an amazing article. I wish more mainstream doctors are aware of this. My wife is suffering from this right now because of antibiotics and oral contraceptives. She suffered from Candida overgrowth and I think is still suffering from it systemically. I also think she is suffering from Adrenal Fatigue due to the infection, she is sensitive to indoor lights and some sounds. I did a pupil dilation test and found that her left pupil would pulsate while her right one would open up quickly, not dilate gradually under normal conditions. She recently had a MTHFR genotype test and she found out that she is A1298C Mutation Heterozygous.

Apart from the suggestions you’ve made in this article, is there anything else we can do to help in her recovery?

I look forward to your response. Thank you!

10 years ago

Hi Dr. Lynch,

My naturopath gave me my results for my MTHFR blood draw, and it states that I am Hetero for A1298C. I’ve been feeling REALLY unwell for the past 9 months and I’m pretty sure it stemmed from when I took anti-biotics and started BC (which I had not used either for years), last May. I am no longer on BC, I stopped after 2 month’s use. My life has literally been put on hold. I am not able to do the things I loved before, like jogging trails, having spontaneous beach trips, going on walks around the lake…

After I started getting unusual symptoms, I’ve seen 1 chiropractor, and 6 different doctors (PA or NP) at my local clinic (since I lost my job and did not have insurance)… I had to make do, and go to the nearest place that charged the least amount for not having insurance. This means sacrificing getting the best care. 🙁

They all would tell me the same thing… Anxiety (You need anti-depressants). Which of course, I would decline. During the times I had been between doctors, I realized these symptoms could be due to yeast (I noticed some white on my tongue). One PA told me it was not thrush (he said “thrush was a band”), and I had no idea what I was talking about-the white coating was due to my intake of Vitamin C supplements and told me to get off the supplements for 1 month-which I did, and I think it made my symptoms worse!!! I did not go back to him. So when symptoms persisted, I visited another Doctor, I told him to run blood tests and that I noticed that I also had thrush on my tongue. He was pretty much the only one who acknowledged the white on my tongue, and prescribed me Nystatin mouth wash. To my regret, I did not take this due to not having funds, and I also read reviews online that it didn’t work for some (I probably just should’ve tried it anyway). So, I researched like a mad woman- started on the anti candida diet, and started taking anti-fungals, probiotics, milk thistle, you name it. But, I started to feel terrible. Probably due to die off. It was so bad, that I could not focus, or even walk at work and was fired in October. At that time, I had gone to a Naturopath and I told her my symptoms and showed her my tongue. She also said I most likely had yeast overgrowth. And that I had digestion issues- also have a large crack down the middle of my tongue. However, all she did was had me take blood tests for my thyroid and MTHFR. She did not run stool samples, because I had already done the blood tests for the others, and could not afford it the stool sample which was $340. I felt like she should’ve ran the stool sample FIRST before the thyroid and MTHFR tests. That way I could’ve known for sure what was going on with my digestion and start from there. Knowing that I had a yeast overgrowth, she should’ve given me a protocol that helped with my digestion. Not a treatment plan that recommended d-mannose, UNDA 243, or castor oil packs…. She honestly was of no help either. So, I just followed her protocol until I ran out of the supplements she recommended. I just don’t trust her judgement.

Then about six months after trying all these different things to get rid of the thrush & candida (I know it was most likely candida because I had white long string rhizomes in my stool in October), I started to realize that I started having food sensitivities. I’m thinking the rhizomes caused me to have leaky gut. Unfortunately, I am still dealing with all these symptoms and white tongue, and it is 9 months later… with no relief or help from Doctors (conventional or alternative)!

I wanted to know, is it safe to take H2o2 (food grade Hydrogen peroxide) to rid of the yeast? Also, I started taking l-glutamate to aide in healing my gut… is this going to make my methylation process worse because of amino acids?

One more thing, I really do not feel that my Naturopath is knowledgeable enough in MTHFR diagnosis. The only advice she gave was to stay away from folate foods, no juicing, and to take methylcobalamin and activated charcoal. Is this the correct protocol for my defect? Or, should I just stick to healing my gut FIRST with the plan you have above in helping heal candida? I’m in desperate need to feel well again!! I need to be able to work again, without terrible symptoms. I need to pay bills and get more assistance/supplements.

Any help, or response would be GREATLY appreciated!!!!! I’m serious, I have to get well soon, my health is at risk! Thank you!

8 years ago
Reply to  Robin

We all have to get well soon Robin, but I don’t think it’s reasonable to expect Dr. Lynch to answer all your questions for free, do you?

But if you haven’t done so already, I’d get rid of that doctor you were seeing. Avoiding folate foods is ridiculous advice for someone with MTHFR polymorphisms. Folic acid containing foods yes, but not foods with natural folate.

9 years ago

Hi Dr. Lynch,

IF Candida albicans produces acetylaldehyde AND IF acetaldehyde inhibits liver methionine synthase activity THEN…

IF my Homocysteine level is low, THEN that should mean I have no Candida overgrowth.


[…] of the first steps in correcting methylation deficiency”, and that especially includes treating candida because of the toxins it releases, inhibiting proper […]

9 years ago

Are yeast and heavy metals connected at all? I know they both inhibit methylation, but do heavy metals cause yeast overgrowth?

9 years ago

Dear Dr. Lynch,
Thank you so much for this website and the excellent articles on it . I have a comment on your recommendation of taking NAC in this article. I have reservations about using NAC because I have experienced increase fungal symptoms when I do. I attribute this to the cysteine in the NAC. I understand that fungus can be grown in the lab using sulfur so I am very careful with high sulfur foods and test them out first. My understanding is that the fungus can readily use certain sulfur compounds but not others. Do you have any information on this? Also I bought a zinc supplement to take but realize now that the zinc is complexed with methionine. Could this be a problem?(I do follow already most of the other recommendations you made.)

9 years ago

My question is : I’m taking 15mg Deplin and 100mg Kuvan 2x a day together.

Kuvan says to: Monitor Patients when Co-administering Kuvan and Medications Known to Inhibit Folate Metabolism Co-administering Kuvan with drugs known to affect folate metabolism (e.g., methotrexate) and their derivatives may require more frequent monitoring of blood Phe levels because these drugs can decrease endogenous BH4 levels by inhibiting the enzyme dihydropteridine reductase (DHPR).

[…] Focusing on gut health: Especially when the body has impaired ability to use certain nutrients, it is important to focus on gut health so that the body can absorb the nutrients from food as effectively as possible. I personally avoid antibacterial soaps, vegetable oils, processed grains and refined sugars and support my gut with fermented foods and homemade broth. This also helps avoid candida, which can make MTHFR related problems worse. […]

8 years ago

Dr. Lynch,

I’m curious about the recommendation to use magnesium to lower aldehydes, as it has been shown in a couple of studies to promote candida growth:

I’d be curious about your take on this…

8 years ago

Very informative article, Dr. Lynch! I do have a question, if a person has the MTHFR polimorphisim & they decide to get pregnant, they go to their mainstream doctor & the doctor puts them on folic acid because they have not been educate. Doesn’t that mother have a much greater chance of having a baby born with Down’s syndrome? This is exactly what happened to my daughter-in-law. I tried with all of my being to get her to see a doctor who has been educated about the MTHFR gene marker before she got pregnant but she & my son wouldn’t listen to me. I believe she had & still has a candida issue. Now they are planning on having this baby vaccinated & I believe she will be terribly harmed if they vaccinate her. I am absolutely distraught. I need a miracle. Can you please give me some of your wisdom so I can enlighten them about the MTHFR issues?

Shelley Goforth
7 years ago

Here is something you may not have considered… What about toxic levels of formaldehyde and acetaldehyde from homes – could that also have the same effect in this model? We moved into a brand new house with all new furniture and all new bedding 2 years ago after getting out of a moldy house and purging everything. Every since, all four of my family have struggled with what I have narrowed down to methylation issues (what you stated below as well as very high histamine intolerance). House still has that “new house” smell.

[…] of the first steps in correcting methylation deficiency”2, and that especially includes treating candida because of the toxins it releases, inhibiting proper […]

[…] Methylation Inhibited by Candida’s Toxin […]

6 years ago

Hi there – after having two miscarriages, I did genetic testing and found out I have a single MTHFR mutation. I also did nutrition testing a few weeks ago and just got the results back that show I’m deficient in B9. I found out I was 4 weeks pregnant on the same day I discovered the B9 deficiency. I was already taking Seeking Health Optimal Prenatal for the past few months, but was still deficient in B9 and now I’m worried my baby may have a neural tube defect. My question is do you think the baby will be ok since I was taking the prenatal with 800 mg L-MTHF, or do you think I should be concerned as I was still deficient? I started taking an extra 1,000 mg of methyfolate on the day I found out about the pregnancy, but I read that’s probably too late. Thanks for an advice!

Rob de Heer
5 years ago

Candida is interesting because MTHFR in combination with vaccines, for example, can cause someone to become immune compromised. This can allow all sorts of infections such as Lyme, Epstein Barr, parasites, thrush, to flourish. Treating the infections with rife frequencies helped tremendously. Some infections have been given different forms/mutated and may not show up on tests. The spooky2 rife machine can test and treat all kinds of infections. I have no affiliation with spooky2.


3 years ago
Reply to  Rob de Heer

SPOOKY2? Really?


4 years ago

Dear Dr. Lynch,

If one has tested positive for both candida and undermythelation, do you treat them both at the same time or one first?

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