Feeling sluggish this winter? These nutrient gaps could be contributing
Winter fatigue and low mood are common and often biological. Experts recommend targeted testing, not guesswork, to find nutrient, hormone and blood-sugar issues.
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By Torontoer Staff
Many people feel lower energy and mood during winter, and those symptoms often have biological causes. Clinicians say nutrient shortfalls, hormone shifts and blood-sugar swings can all contribute to fatigue, brain fog and irritability.
Toronto-based NiaHealth is among the clinics pushing biomarker testing to identify specific physiological drivers rather than treating symptoms alone. The approach pairs lab data with clinically guided action plans.
How biology shapes winter mood and energy
Reduced sunlight affects circadian rhythms and vitamin D production, which can impact sleep, energy and mood. Beyond light, common physiological factors include diminished nutrient stores, changes in hormones such as testosterone, and blood-glucose irregularities that alter concentration and stamina.
Blue Monday isn’t a scientifically determined day, but it’s a good reminder that at this time of year, people do struggle with things like fatigue and lower energy for many different reasons.
Tanya ter Keurs, co-founder and clinical director, NiaHealth
Traditional treatments for seasonal affective disorder, like cognitive behavioural therapy and light therapy, still have a role. Clinicians at NiaHealth say those approaches work best when paired with attention to underlying biology.
What biomarker testing can reveal
Biomarker testing measures blood and metabolic indicators to show how the body is processing nutrients and regulating systems. NiaHealth provides a clinician-reviewed dashboard and follow-up with a nurse practitioner to turn results into a practical plan.
According to the clinic’s data, most clients present at least one abnormal marker linked to mood, energy or cognition. Identifying these early allows targeted dietary, supplement or lifestyle changes that may improve resilience and long-term health.
- High calcium: linked to anxiety, brain fog, low mood
- Low ferritin (iron stores): causes fatigue and reduced concentration
- Low vitamin D: associated with fatigue and mood changes, common at northern latitudes
- Low vitamin B12: can present as depression, irritability or cognitive slowing
- Low testosterone: may cause fatigue and depressed mood in men
- High fasting blood glucose: often associated with low energy
- Low blood glucose: can produce irritability and difficulty concentrating
Which supplements help, and when to test first
Vitamin D is the most frequently recommended supplement for Canadians in winter, because sunlight remains the primary natural source. For other nutrients, clinicians advise testing before starting supplements, since excess intake can be harmful.
With most supplements, if we take too much of them, it can be not good for us. We definitely don’t want to be taking supplements just for the sake of taking supplements.
Tanya ter Keurs, NiaHealth
Small personal examples reflect common practice. Nico, who recently moved to Toronto and is training for a race, takes vitamin C in winter on his doctor’s advice. Marion was told by her doctor to take vitamin D to substitute for reduced sun exposure.
Practical steps to assess and address symptoms
- Book basic blood work to check vitamin D, ferritin, B12, fasting glucose and, if relevant, testosterone.
- Track sleep, energy peaks and diet for two weeks to help clinicians interpret results.
- Use light therapy or timed light exposure to stabilise circadian rhythm when mornings are dim.
- Adjust diet toward iron- and B-vitamin-rich foods, including lean meats, legumes and fortified cereals as appropriate.
- Consult a clinician before starting supplements beyond vitamin D, to confirm dosage and need.
- Address blood-sugar variability with regular meals that include protein, fibre and healthy fats.
Testing can be done through primary care providers or services that offer clinician-reviewed reporting. A coordinated approach makes it possible to pair psychotherapy or light therapy with concrete biological interventions when needed.
When to seek further care
If low mood, fatigue or changes in sleep and appetite are persistent or worsen, contact a family doctor or mental-health professional. Seasonal affective disorder is more severe than temporary winter blues and responds best to early, combined interventions.
Biomarker testing can clarify whether there are correctable physiological contributors. Where tests show deficiencies or imbalances, clinicians can tailor supplements, diet and follow-up to reduce symptoms and lower future risk.
Addressing winter fatigue does not rely on a single fix. A combination of light management, targeted testing and informed lifestyle changes offers the clearest path to better energy and mood through the season.
wellnessmental-healthvitamin-dseasonal-affective-disordernutrition
