How do my biomarkers affect my mental health?
We explore how nutrient deficiencies, inflammation, and hormones can influence your mental wellbeing.
Approximately 7.5 million people in the UK live with a diagnosed mental illness. And one in four of us will experience a mental health problem every year [1].
So if you’re not feeling yourself, you’re not alone.
Mental health is one of the more difficult conditions to diagnose, and getting to the root of the problem can feel overwhelming, especially if you’re experiencing a dip.
Our mental wellbeing is intrinsically linked to our physical wellbeing. So let’s take a look at some common biomarkers (signals in our blood) affected by nutrient deficiencies, inflammation, and metabolic health that can affect our mood.
We’ll look at:
- Why do my biomarkers affect my mood?
- Nutrient deficiencies
- Inflammation
- Hormones
- How could a blood test help me with low mood?
Why do my biomarkers affect my mood?
Everything in our bodies is connected.
Different processes use a variety of molecules and ions, and these molecules are made using other processes.
For example, low omega-3 levels have been linked to higher Alzheimer's disease risk [2] . Vitamin D is a precursor to serotonin, the feel-good neurotransmitter. Inflammation markers are consistently higher in patients with depression. And deficiencies or excesses of minerals such as iron or magnesium can affect our cognition.
This doesn’t automatically mean the answer to feeling better is to just take a long list of supplements. It’s important to identify the potential behaviour or lifestyle causes of abnormal biomarkers, rather than going straight to supplement bottles.
Looking at our biology can give us measurable signals as to how our bodies are functioning, and this includes our mental health.
Nutrient deficiencies
Vitamin D
How are your vitamin D levels?
If you live in the UK, it’s likely they’re low. And it could be giving you depression-like symptoms [3].
It’s thought vitamin D regulates synthesis of serotonin and dopamine (our feel-good chemicals), and also has a neuroprotective effect in our brains. It may also affect how much melatonin – a sleep-regulating hormone, is produced [4,5].
Again and again, studies have shown a link between vitamin D deficiency and mental health conditions including schizophrenia, autism, seasonal affective disorder (SAD), and depression [6].
Vitamin D deficiency can make you feel:
- Fatigue
- Hopeless
- Anti-social
- Anxious
- Low
What can you do?
Everyone in the UK is recommended to take vitamin D supplements from October to March, but some people may need to take them year round.
It’s a mixed consensus as to whether vitamin D supplementation can actually alleviate depression or anxiety. But if your symptoms are due to a vitamin D deficiency, a supplement might just help.
And of course, making sure you get outside every day is good for both your vitamin D and your mind. Studies have shown that just looking at pictures of nature can calm our nervous system and improve our mental wellbeing [7].
Iron
Low ferritin and iron deficiency anaemia are one of the most common deficiencies in the world.
In the brain, iron works in areas to do with glutamate and GABA homeostasis. The brain is quite sensitive to fluctuations. And it can affect memory, behaviour, learning, and emotion.
Additionally, neurodivergent adults, including people with ADHD or autism, are more likely to be iron deficient. One theory as to why, is that iron’s key role in brain energy means low levels can worsen symptoms like fatigue, poor focus, and mood swings. For autistic adults, selective eating or gut sensitivities can make it harder to get enough iron [8].
Both iron deficiency and depression have symptoms in common.
This includes:
- Low mood
- Fatigue
- Anxiety-driven behaviour
- Loss of concentration
Women are particularly susceptible to iron deficiency. And while ferritin levels over 30 μg/L are technical “normal”, you might find your focus and mood is better when you have optimal ferritin levels.
What can you do?
It’s really important that you don’t take iron supplements unless you need them – iron overload can cause serious health issues. If you think low ferritin or iron may be the cause of your low mood, ask your GP for a blood test, or take an Iron Blood Test at home.
Natural sources of iron include meat, leafy greens (like spinach and kale), pulses (like lentils, chickpeas, and beans), and nuts and seeds. Pairing your iron with vitamin C can also help with absorption.
If you need to supplement, we’ve written a guide with everything you need to know about iron supplements to help you. Don’t feel disheartened if your mood isn’t lifted immediately, it can take three weeks to four months to feel the full effects.
Folate (vitamin B9)
There seems to be a link between depression and folate levels. People with depression have often been found to have low folate, and people with low folate seem to be at a higher risk of developing depression [9].
You get folate from broccoli, asparagus, peas, chickpeas, and brown rice, so if you don’t eat these foods often, you may become deficient. Some anticonvulsant medications can affect your folate absorption.
Folate regulates our neurotransmitter production (serotonin, melatonin, dopamine, norepinephrine) and reduces inflammation levels [10,11]. It’s thought this is because folate is a precursor to many of the molecules involved in neurotransmitter production.
Vitamin B12
Vitamin B12 keeps your nervous system functioning normally. A deficiency is usually due an autoimmune condition called pernicious anaemia, but it can also be due to diet.
Deficiencies in these B vitamins can lead to:
- Low mood and low energy
- Memory and concentration problems
- Fatigue
- Feelings of guilt
- Psychosis (especially in elderly)
What can you do?
Consider supplementing vitamin B12, especially if you are vegan or vegetarian, as you can only get this from fortified foods or animal products. Try and up your intake of folate-rich foods.
Magnesium
Stress and trauma are thought to decrease magnesium levels in the brain. Having a deficiency of magnesium can lead to symptoms of low mood, and has been linked to an increased risk of depression.
Symptoms of magnesium deficiency that affect your mental health include:
- Fatigue
- Personality changes
- Loss of appetite
- Low mood
- Anxiety
Some evidence, at least in animal studies, points towards magnesium deficiency as something which can make people vulnerable to substance abuse or addiction even more vulnerable [12]. Since addiction is a dysregulation of the brain’s reward system, and magnesium may be involved in dopamine production.
What can you do?
Magnesium is one of the trendier minerals at the moment, so if you think your levels need a boost but you’re not into nuts or legumes, there’s all sorts of magnesium supplements and drinks you can buy.
Zinc
Zinc-containing neurons are found all over the brain, as well as in enzymes and proteins that help our bodies function normally.
In the brain, zinc affects neurotransmitters and antioxidant function, and may contribute to neurogenesis (cell growth).
Low zinc has been known to cause:
- Anxiety
- Depression
Zinc deficiencies can also exacerbate conditions such as:
- Parkinson’s
- Alzheimer’s disease
- Schizophrenia[13]
What can you do?
Some studies suggest zinc supplementation may improve symptoms of depression, but more work is needed on humans [14].
Oysters, chickpeas, and nuts are good sources of zinc.
Omega-3s
You can only get omega fatty acids from your diet. The second highest concentration of omega fatty acids in the human is in the central nervous system.
Omega-3 deficiency can affect your mental health, causing:
- Insomnia or poor sleep quality
- Fatigue
- Mood swings
- Anxiety
- Low concentration
Omega-3s have important anti-inflammatory effects, regulate neural pathways, and activate neurotransmitters which can prevent depression. It’s thought that omega-3 supplementation can reduce anxiety by altering inflammation, cortisol, and cardiovascular activity [15].
More studies are needed though, as some other trials showed no relation between omega-3 and anxiety, and the ideal dosage of omega-3 to reduce symptoms isn’t yet known.
What can you do?
If you want to try an omega-3 supplement, choose one that contains DHA and EPA omega-3s as these are two of the omegas with the most benefits. Try to limit your saturated fat intake.
Inflammation
C-reactive protein (CRP) is produced in the liver, and rises in response to inflammation.
Some inflammation, like a reaction to allergies, injuries, or infections, is normal and keeps us healthy. On the other hand, chronic inflammation can be the result of an unhealthy lifestyle or numerous inflammatory conditions.
Increasingly, evidence points to a link between elevated levels of CRP and depression. That’s not to say that elevated CRP is a diagnosis of depression. But the two conditions do seem to be linked [16,17].
Similarly, there seems to be an association between general anxiety disorder (GAD), panic disorder, and other stress disorders and high CRP levels [18].
And the lifestyle causes of chronic inflammation, such as lack of exercise, a highly processed diet, and obesity, could also cause depression.
Some researchers believe CRP levels over 3 mg/L may cause inflammation in the brain. This results in decreased support for nerve cells and increased cell damage (due to oxidative stress). Additionally, transport of serotonin and dopamine might be affected. This results in reduced cognitive function, memory, motivation, focus.
Studies into the effectiveness of inflammation-reducing medications on depression is ongoing.
What can you do?
Lifestyle changes can lower your inflammation levels, and, in turn, may also lower your risk of depression.
Many people choose to follow an anti-inflammatory diet to decrease their flare-ups and pain.
Nourishing your body can go a long way to helping your mental health. Make sure you make small changes one by one, try incorporating one or two anti-inflammatory foods into your diet each week, and see you feel.
Hormones
Our hormones fluctuate for all kinds of reasons. Sometimes hormones can affect our mental health. We have a few blogs about how hormones such as Thyroid and Testosterone can affect our mental health.
Progesterone and cortisol
Progesterone is produced in testes and ovaries, and aids fertility.
But it’s also produced in the brain, where it has an important influence – emotion.
Some people are more sensitive to fluctuating progesterone than others.
In particular, the mood symptoms of premenstrual dysphoria disorder (PMDD) are thought to be down to progesterone and cortisol produced in the luteal phase [19,20].
PMDD is a severe form of premenstrual stress. For one or two weeks before your period you experience intense emotional and physical symptoms that have a serious impact on your life, relationships, and work.
The mental side of PMDD includes:
- Mood swings
- Anxiety
- Suicidal feelings
- Depression
- Feeling overwhelmed or out of control
What can you do?
PMDD treatments vary, from lifestyle changes to surgery. Before you make an appointment with your doctor, it’s best to track your cycle and symptoms for a few months, as this is information your doctor will likely you ask you for.
Mind has a lot of useful information about PMDD.
How could a blood test help me with low mood?
A blood test can't diagnose you with depression or other mental health conditions.
But we can help you look for an underlying physical cause for your low mood (as opposed to genetic or environmental).
If your results show abnormal levels of certain biomarkers, you can make informed lifestyle choices and even take your results to your GP and use it as evidence to help you in your diagnosis.
If you need support
Struggling with your mental health can feel lonely and debilitating, but reaching out to a doctor for help may be equally daunting. So, we’ve made a short checklist to help you in your first steps.
- Make your appointment. Ask for a double appointment if you feel you’ll need a bit longer to talk. It will give your doctor more time too.
If you have anxiety about phoning the doctors, try writing out what you need help with so you can just read it to the receptionist. - Write a list of everything you want to say at your appointment.
Include symptoms, how long you’ve felt like this, and how it affects your daily life. If you have them, you can also bring a print out of your blood test results.
Think about what you’re hoping to gain – perhaps medication, supplements or a therapy referral would be helpful. - Take notes if you think you might forget what the doctor has said – low mood can affect your memory.
- Make sure you book a follow-up appointment.
If you need urgent help, you can find your local 24/7 crisis line on the NHS website.
Samaritans offer 24-hour listening support on 116 123 or if a phone call is too overwhelming, you can text SHOUT to 85258. There will always be support for you.
References
- What we do. In: Mental Health UK [Internet]. [cited 16 Oct 2025].
- A startling omega-3 deficiency may explain women’s Alzheimer’s risk. In: ScienceDaily [Internet]. [cited 16 Oct 2025].
- Vitamin D. In: nhs.uk [Internet]. 23 Oct 2017 [cited 20 Oct 2025].
- Alimohammadi‐Kamalabadi M, Ziaei S, Hasani M, Mohammadi S, Mehrbod M, Morvaridi M, et al. Does vitamin D supplementation impact serotonin levels? A systematic review and meta‐analysis. Health Sci Rep. 2024;7: e2276. doi:10.1002/hsr2.2276
- Kaviani M, Nikooyeh B, Zand H, Yaghmaei P, Neyestani TR. Effects of vitamin D supplementation on depression and some involved neurotransmitters. Journal of Affective Disorders. 2020;269: 28–35. doi:10.1016/j.jad.2020.03.029
- Huiberts LM, Smolders KCHJ. Effects of vitamin D on mood and sleep in the healthy population: Interpretations from the serotonergic pathway. Sleep Medicine Reviews. 2021;55: 101379. doi:10.1016/j.smrv.2020.101379
- Nature: How connecting with nature benefits our mental health. [cited 17 Oct 2025].
- Iron deficiency and common neurodevelopmental disorders—A scoping review | PLOS One. [cited 16 Oct 2025].
- Liwinski T, Lang UE. Folate and Its Significance in Depressive Disorders and Suicidality: A Comprehensive Narrative Review. Nutrients. 2023;15: 3859. doi:10.3390/nu15173859
- Vitamin B12 or folate deficiency anaemia - Symptoms. In: nhs.uk [Internet]. 20 Oct 2017 [cited 7 Oct 2025].
- Muscaritoli M. The Impact of Nutrients on Mental Health and Well-Being: Insights From the Literature. Front Nutr. 2021;8. doi:10.3389/fnut.2021.656290
- Nechifor M. Magnesium in addiction – a general view. Magnesium Research. 2018;31: 90–98. doi:10.1684/mrh.2018.0443
- Choi S, Hong DK, Choi BY, Suh SW. Zinc in the Brain: Friend or Foe? Int J Mol Sci. 2020;21: 8941. doi:10.3390/ijms21238941
- Yosaee S, Clark CCT, Keshtkaran Z, Ashourpour M, Keshani P, Soltani S. Zinc in depression: From development to treatment: A comparative/ dose response meta-analysis of observational studies and randomized controlled trials. General Hospital Psychiatry. 2022;74: 110–117. doi:10.1016/j.genhosppsych.2020.08.001
- Vitamin D and the omega‐3 fatty acids control serotonin synthesis and action, part 2: relevance for ADHD, bipolar disorder, schizophrenia, and impulsive behavior - Patrick - 2015 - The FASEB Journal - Wiley Online Library. [cited 9 Oct 2025].
- Orsolini L, Pompili S, Tempia Valenta S, Salvi V, Volpe U. C-Reactive Protein as a Biomarker for Major Depressive Disorder? Int J Mol Sci. 2022;23: 1616. doi:10.3390/ijms23031616
- Ji Y, Wang J, Chen H, Li J, Chen M. Association between hs-CRP and depressive symptoms: a cross-sectional study. Front Psychiatry. 2024;15: 1339208. doi:10.3389/fpsyt.2024.1339208
- Copeland WE, Shanahan L, Worthman C, Angold A, Costello EJ. Generalized Anxiety and C-Reactive Protein Levels: A Prospective, Longitudinal Analysis. Psychol Med. 2012;42: 2641–2650. doi:10.1017/S0033291712000554
- Bencker C, Gschwandtner L, Nayman S, Grikšienė R, Nguyen B, Nater UM, et al. Progestagens and progesterone receptor modulation: Effects on the brain, mood, stress, and cognition in females. Frontiers in Neuroendocrinology. 2025;76: 101160. doi:10.1016/j.yfrne.2024.101160
- Sundström-Poromaa I, Comasco E, Sumner R, Luders E. Progesterone – Friend or foe? Frontiers in Neuroendocrinology. 2020;59: 100856. doi:10.1016/j.yfrne.2020.100856