Feeling Tired, Flat or Foggy? Ignoring This Can Affect Brain Health

At Health Dynamics, we educate our community on how to live a long, fulfilled and vibrant life, not simply a longer life marked by fatigue, decline and preventable disease.

One nutrient that repeatedly shows up as a silent limiter of energy, mood, brain health and heart health is vitamin B12.

This is not a “nice to have” vitamin.
It is foundational.

Much of the research below is inspired by the work of John Douillard, combined with what we observe every week in the clinic when reviewing pathology, medications, and long-term health patterns.

Why Vitamin B12 Matters More Than You Think

Vitamin B12 plays a critical role in:

• Brain and nervous system health

• Energy production and mitochondrial function

• Mood, motivation and mental clarity

• Red blood cell formation

• Cardiovascular health and inflammation control

B12 is required to synthesise neurotransmitters such as dopamine, serotonin and adrenaline, which regulate mood, sleep, appetite, drive and cognition.

When B12 is low, people often feel:

• Exhausted but wired

• Flat or low in mood

• Foggy or forgetful

• Unmotivated

• Short of breath

• Weak or unsteady

Importantly, these symptoms often appear years before a “clinical deficiency” is diagnosed.

Nearly 40% of People Have Low or Sub-Optimal B12

Large population studies suggest that around 40% of people have vitamin B12 levels that are low or borderline, even though they may still fall within the so-called “normal” laboratory range.

This is where prevention and longevity medicine differ from standard care.

In Australia, vitamin B12 is reported in pmol/L, and most pathology reports consider:

• Above ~150 pmol/L as “normal”

However, when we look at symptoms, brain health, cardiovascular risk and long-term outcomes, this threshold is far too low.

Research and clinical experience now suggest:

• Below 260 pmol/L is often considered low-normal and frequently symptomatic
  

• 260-350 pmol/L may already increase risk for fatigue, mood changes and cognitive decline
  

• 350-450 pmol/L is better, but often still sub-optimal for long-term brain protection
  

• 450-600+ pmol/L is where we commonly see stronger energy, clearer thinking and greater neurological and cardiovascular resilience, particularly as we age

This matters because you do not need to be clinically deficient for damage to occur.

By the time B12 falls below traditional deficiency cut-offs, changes to the nervous system, brain and heart may already be underway.

Can Low B12 Cause Brain Shrinkage?

Yes, and this is one of the most confronting findings.

Long-term studies using MRI brain imaging show that:

• People with higher B12 levels experience less brain shrinkage as they age

• Even individuals within the “normal” range, but on the lower end had greater brain volume loss

• Older adults with slightly low B12 and folate levels had double the risk of memory and cognitive concerns

This is why we do not wait for disease at Health Dynamics.
We look at trends, early warning signs and trajectory.

B12, Homocysteine and Heart Health

One of B12’s most important longevity roles is its ability to lower homocysteine, a key inflammatory marker linked to:

• Cardiovascular disease

• Stroke risk

• Cognitive decline

• Mood disorders

In Australia, homocysteine is often considered “normal” up to 15 µmol/L.
From a prevention and longevity perspective:

• Below 10 µmol/L is preferred

• 8-9 µmol/L is often considered optimal for heart and brain health

B12 (along with folate) is essential for converting homocysteine into methionine through a process called methylation.

When B12 is low:

• Homocysteine rises

• Inflammation increases

• Cardiovascular and neurological risk escalates

This raises an important question many of our clients ask:
Why are B12 and homocysteine not routinely screened when so much could be prevented early?

Why Are So Many People B12 Deficient?

From an Ayurvedic and functional perspective, the causes are clear.

1. Weak Digestion (Low Digestive Fire)

B12 is a large, complex molecule that requires:

• Adequate stomach acid

• Healthy enzyme production

• Intrinsic factor for absorption

Long-term use of antacids, reflux medication and PPIs significantly reduces B12 absorption by:

• Suppressing stomach acid

• Depleting intrinsic factor

This is something we see constantly in the clinic.
Medication may reduce symptoms, but the root cause is rarely addressed, leading to downstream deficiencies and long-term decline.

2. Ageing Without Digestive Support

As we age, digestive capacity naturally declines unless supported.
Enzyme production can drop by up to 40%, further reducing B12 absorption.

Ageing does not have to equal decline, but unsupported digestion accelerates it.

3. Dietary Patterns

• Vegetarians and vegans are at higher risk

• Reduced intake of animal foods

• Reliance on fortified foods rather than bioavailable sources

Both our doctors and I at Health Dynamics are vegetarians, which means we monitor B12 carefully and take this very seriously.

Longevity is about awareness, not ideology.

Best Food Sources of Vitamin B12

Top natural sources include:

• Fish (especially salmon and sardines)

• Eggs

• Dairy products

• Meat (for those who eat it)

• Fortified foods (less reliable)

• This is why vegans or vegetarians may need to have a supplement 

Food alone is often not enough, particularly with digestive weakness or medication use.

The Best Form of Vitamin B12

Not all B12 is created equal.

• Cyanocobalamin is cheap and inactive

• It must be converted in the body, which many people cannot do efficiently

The most active and effective form is:

• Methylcobalamin, ideally taken sublingually

Research now shows that sublingual methylcobalamin is:

• As effective as injections

• Easier to use

• More cost-effective

• Better tolerated long term

Folate Matters Too

(Especially If You Have MTHFR)

B12 works hand-in-hand with folate.

The best form of folate is:

• 5-MTHF (5-methyltetrahydrofolate)

This is particularly important if you have MTHFR methylation variations, which affect:

• Detoxification

• Neurotransmitter production

• Homocysteine metabolism

Folic acid (the synthetic form) is not ideal for everyone.

Practical Longevity Steps to Take Now

• Ask your GP to test:

  • Vitamin B12

  • Folate

  • Homocysteine

  • Consider MTHFR if indicated

• Review medications:

  • Especially long-term reflux or antacid use

  • Ask why you are on them and what the root cause is

• Support digestion:

  • Warm, cooked foods

  • Reduce ultra-processed foods

  • Strengthen digestive fire rather than suppressing it

• Supplement intelligently:

  • Methylcobalamin + 5-MTHF

  • Dose guided by your levels and genetics

• Think long-term:

  • Energy today

  • Brain health in 10 years

  • Independence and vitality later in life

Longevity Is Not Just About Living Longer

Longevity is about:

• Mental clarity

• Emotional resilience

• Physical vitality

• Purpose and fulfilment

It is about living well now, while protecting your future self from preventable decline.

This is the lens we use at Health Dynamics, and why nutrients like B12 are never treated as an afterthought.

If you would like support reviewing your levels, medications or digestive health, our team is here to guide you.

Warmly,
Jo Formosa
Clinical Director | Integrative Health & Longevity Strategist
Health Dynamics