Most women I work with have never heard of homocysteine and women’s health, yet this small overlooked marker can influence mood, memory, hormones and long term brain health. It is also one of the easiest things to improve once you know what it is.

The surprising part is that your GP probably will not test it, even if you ask. But if you are dealing with brain fog, anxiety, low energy, perimenopause symptoms, heavy periods, poor stress tolerance or that nagging sense that your brain does not feel like your own, understanding your homocysteine levels can be genuinely life changing.

In this article I am breaking down the science in a simple way and showing how it applies to real women’s bodies in everyday life.

 

What is homocysteine?

Homocysteine is a natural by-product your body makes when it breaks down protein (specifically, the amino acid methionine).

It isn’t “bad” in itself – your body is designed to recycle and clear it using nutrients like:

• Vitamin B6
• Vitamin B12
• Folate
• Choline
• Betaine

But when your body doesn’t have enough of those nutrients, or your digestion isn’t working well, or your hormones shift (hello perimenopause), homocysteine can start to build up.

This is when problems begin.

High homocysteine has been linked to over 100 different health issues, including mood changes, cognitive decline, cardiovascular risk, PMS and hormonal imbalance.

I like to think of it as a check-engine light on the dashboard of your body – it tells you something needs attention and gives a bit of an overview of methylation.

 

Why homocysteine matters so much for women

Women’s bodies rely heavily on the methylation cycle (where homocysteine sits) to:

• make and metabolise hormones
• detoxify used oestrogen
• create neurotransmitters (like serotonin & dopamine)
• support healthy pregnancy and fertility
• regulate inflammation
• build brain chemicals
• protect DNA and cellular health

Oestrogen normally supports methylation – but as we go through our lives and enter perimenopause, oestrogen naturally fluctuates and decreases.

This can cause homocysteine to rise, leading to:

• anxiety or low mood
• irritability or “short fuse”
• PMS and heavy periods
• brain fog or slower thinking
• poor memory recall
• lower resilience to stress
• wired-but-tired feelings
• sleep issues
• fatigue

If you’ve been feeling “not quite yourself” mentally or hormonally, especially in midlife, homocysteine may be part of the puzzle.

But note it is not a diagnostic marker – it’s simply showing you how well your body is functioning – especially in this methylation pathway.

The research: B vitamins, brain shrinkage & cognitive health

One of the most important studies on homocysteine is from Oxford University, led by Professor David Smith.

The VITACOG trial (2010)

Older adults with mild cognitive impairment were given:

• B6
• B12
• Folate

for 2 years.

What happened? They experienced 30–50% slower brain shrinkage compared to the placebo group.

Let me repeat that:  Nutrients – simple, safe B vitamins – slowed down the physical shrinking of the brain.

And here’s the key part:  Those with the highest homocysteine saw the biggest improvements.

📄 Study link: https://pubmed.ncbi.nlm.nih.gov/20838622/

 

The “B vitamins + Omega-3” synergy women need to know

A later 2016 study (Oulhaj et al.) looked at the same people and found something even more interesting:

B vitamins only worked optimally when omega-3 levels were adequate.

If omega-3 levels were low, the B vitamins didn’t have nearly the same effect.

This makes sense because DHA (one of the omega-3 fats in fish oil) is a major structural fat in your brain. It literally helps build healthy neurons and cell membranes.

B vitamins lower homocysteine.
Omega-3 helps your brain use those nutrients.

Together, they’re a powerful combination for cognitive and hormonal health.

📄 Study link: https://pubmed.ncbi.nlm.nih.gov/26757190/

 

Symptoms of high homocysteine in women

You can’t feel homocysteine rising, but you may notice signs of poor methylation, such as:

• Brain fog, poor memory
• Anxiety, irritability or low mood
• Poor sleep or waking wired
• Heavy periods, PMS or tender breasts
• Perimenopause symptoms that feel “too intense”
• Fatigue or low resilience to stress
• Headaches
• Tingling or nerve-related symptoms
• Cardiovascular risk factors

Many women who come to me with these symptoms have homocysteine levels above 10–12 µmol/L.
Optimal functional range? Under 8.

 

How to test your homocysteine levels 

You can order a simple finger-prick home test here:

👉 Homocysteine Test (Food for the Brain):
https://foodforthebrain.org/product/homocysteine-hcy/ – available globally

It’s an easy way to check your risk and see whether your B vitamins and omega-3 are where they need to be.

(And no, I don’t make commission, but it is the research charity I work for a few days a month.)

 

How to naturally lower homocysteine

These steps are simple, powerful and very achievable:

1. Eat enough protein …and digest it!

You need amino acids to fuel the methylation cycle – but you need to be able to digest them too. This is where gut health and chemical digestion are important and where I work with my clients to sort out gut issues.

2. Make sure you’re getting B6, B12 & folate

Through foods like:

• Eggs
• leafy greens
• beef, lamb, chicken
• Fish
• chickpeas
• lentils
• beetroot

3. Increase omega-3 intake

Eat oily fish 3x week. And/or take a high-quality fish oil if you don’t eat fish (i eat fish a few times a week and take fish oil – FYI)

4. Reduce alcohol

As it depletes folate and raises homocysteine.

5. Manage stress

Chronic stress uses up a LOT of B vitamins.

6. Consider targeted supplementation

Especially if your levels are high – I personalise this for clients but often looks like getting more choline and a range of B vitamins.

 

Final Thoughts: Real science for real women

Homocysteine is one of the simplest, clearest markers that shows how well your brain, hormones, mood and metabolism are functioning.

It’s not diagnostic, but it is deeply informative.

And the best part? It’s highly modifiable.

When you give your body the right nutrients – B vitamins, omega-3, good protein, balanced meals –  your homocysteine can drop quickly.

If you’re in your late 30s, 40s, 50s or beyond, checking this one marker can help you understand your body in a whole new way.

Want personalised help?

If you want to understand your unique biochemistry, symptoms and root causes, you can book a deep-dive session with me:

👉 ROOT 1:1 Deep-Dive Session:
https://keziahall.com/root/

Together we can figure out what your body needs, so you can feel clear, energised and more like yourself again.

 

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