Anxiety is often treated as a mental health issue alone, but physiology plays an important role as well. The brain depends on a steady supply of nutrients to regulate neurotransmitters, energy metabolism, and the body’s stress response. When nutritional status is suboptimal, the nervous system may be more vulnerable to stress, fatigue, irritability, and mood changes.

This does not mean every case of anxiety is caused by a nutrient deficiency. However, when someone is dealing with persistent anxiety, poor stress tolerance, fatigue, irritability, or low mood, it can be helpful to consider whether nutritional status may be contributing.

Below are several nutrients commonly evaluated in functional medicine when anxiety is part of the clinical picture.

Magnesium

Magnesium is involved in more than 300 biochemical reactions in the body and plays an important role in nervous system regulation. It helps regulate neurotransmitter activity, supports sleep, and influences the body’s stress response.

Magnesium depletion has been associated with increased neural excitability, sleep disturbances, and neuroendocrine changes. In clinical research, magnesium supplementation has been shown to improve symptoms related to stress, anxiety, and depression in some populations.

One randomized clinical trial found that 248 mg of elemental magnesium daily for six weeks significantly improved depression and anxiety scores in adults experiencing mild-to-moderate symptoms. Another study in individuals with low magnesium and high stress found that 300 mg of magnesium daily, with or without 30 mg of vitamin B6, reduced perceived stress levels over eight weeks, with the greatest improvements seen in those with more severe stress.

Because magnesium intake is commonly below recommended levels in the United States, ensuring adequate intake through diet or supplementation may help support nervous system health.

B Vitamins

B vitamins play a central role in brain chemistry. Vitamins B6, B12, and folate are involved in methylation pathways that influence the production of neurotransmitters such as serotonin, dopamine, and norepinephrine.

When these nutrients are insufficient, homocysteine levels may rise and neurotransmitter production may be impaired, which can influence mood regulation and stress response.

Research suggests that vitamin and mineral supplementation with B vitamins may help reduce perceived stress and mild psychiatric symptoms in otherwise healthy individuals. A clinical trial also found that vitamin B6 daily for one month significantly reduced self-reported anxiety while increasing inhibitory neural signaling in the brain through enhanced GABA activity. However, high doses of vitamin B6 taken for prolonged periods can lead to peripheral neuropathy, making it important to use appropriate dosing and clinical monitoring when supplementing. When supplementation is indicated, practitioners may also consider using active forms of vitamin B6 such as pyridoxal-5-phosphate (P5P), which are already metabolically active and may be better utilized by some individuals.

Ensuring adequate intake of B vitamins through diet, or targeted supplementation when appropriate, may therefore support individuals experiencing stress-related symptoms.

Amino Acids

Amino acids are the building blocks of neurotransmitters. The brain relies on specific amino acids to produce serotonin, dopamine, norepinephrine, and other signaling molecules involved in mood and stress regulation.

For example, tryptophan is required for serotonin production, while tyrosine and phenylalanine are involved in dopamine and norepinephrine synthesis. Without adequate dietary protein and amino acid intake, these pathways may be affected.

Ensuring adequate protein intake is an important starting point for supporting amino acid availability. The current recommended dietary allowance (RDA) for protein is 0.8 g/kg/day, though many nutrition experts suggest that 1.0–1.2 g/kg/day may better support metabolic and neurological health for many adults. Adequate protein intake provides the amino acid precursors required for neurotransmitter synthesis, including serotonin, dopamine, and norepinephrine.

In some cases, practitioners may also consider targeted amino acid supplements or balanced essential amino acid formulas when dietary intake is insufficient or when additional support is needed.

Iron

Iron plays an essential role in brain function, including energy metabolism and neurotransmitter synthesis.

Iron deficiency is the most common nutrient deficiency worldwide and is particularly common in menstruating women. Importantly, symptoms may appear even before anemia develops.

A recent systematic review and meta-analysis found that iron supplementation improved symptoms of anxiety, fatigue, physical well-being, and cognitive performance in iron-deficient individuals, including menstruating women and adolescents. Genetic studies also suggest that higher iron status biomarkers are associated with a lower risk of anxiety disorders.

For this reason, iron status, often evaluated through ferritin levels, can be an important factor to consider when anxiety is accompanied by fatigue, cognitive symptoms, or reduced exercise tolerance.

Zinc and Copper Balance

Zinc is involved in hundreds of cellular processes, including immune function, antioxidant activity, and neurotransmitter regulation.

A meta-analysis of randomized clinical trials found that antioxidant supplementation, including zinc, was associated with improvements in both depression and anxiety symptoms. Another study examining individuals with anxiety found lower zinc levels and higher copper levels compared with controls. After zinc supplementation, zinc levels increased, the copper-to-zinc ratio decreased, and participants experienced improvements in symptoms.

In functional medicine, the relationship between copper and zinc is often evaluated together. Neurologist Dale Bredesen, MD has suggested that a copper-to-zinc ratio of approximately 0.7–1.0 may be optimal for neurological health. When copper levels are elevated relative to zinc, it may influence oxidative stress and neurotransmitter balance.

Assessing both zinc status and the copper-to-zinc ratio can therefore provide additional insight when evaluating patients with persistent anxiety symptoms.

Final Thoughts

Anxiety is rarely caused by a single factor. However, nutritional status is one piece of the puzzle that is often overlooked. Magnesium, B vitamins, amino acids, iron, and zinc all play important roles in brain chemistry and stress resilience.

For individuals struggling with persistent anxiety, evaluating and correcting nutrient imbalances may be a helpful step toward supporting overall nervous system health.

-Carey Kunz, ND, IFMCP

Director of Education at FMP Essentials

References

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