Bipolar disorder (BD, formerly known as manic-depressive psychosis) is a chronic condition characterized by alternating episodes of mania (or hypomania) and depression, with periods of remission lasting variable lengths. It affects approximately 2% of the global population in combined types 1 and 2. Pharmacological therapy (lithium, valproate, lamotrigine, quetiapine, and others) is the cornerstone of treatment and must be maintained long-term. Diet does not replace pharmacological therapy in bipolar disorder; however, emerging research suggests that certain dietary choices can support mood stability through biological mechanisms that are now better understood.

The relationship between inflammation, the microbiome, and bipolar disorder

Bipolar disorder has a significant inflammatory component. During manic and depressive episodes, markers of systemic inflammation (IL-6, TNF-alpha, CRP) are elevated compared to remission phases. Chronic low-grade inflammation is associated with more frequent episodes and a more severe course. Diet can modulate inflammation directly: the Mediterranean diet reduces inflammation markers (Giugliano et al., 2006, American Journal of Clinical Nutrition) through its fatty acid profile (more omega-3, less omega-6, fewer trans fats), its richness in antioxidant polyphenols (fruits, vegetables, extra virgin olive oil, moderate red wine), dietary fiber, and its prebiotic effect on the microbiome. The microbiome in bipolar disorder: a 2019 study (Evans et al., Bipolar Disorders) found significant differences in the microbiome of people with BD compared to healthy controls, with reduced bacterial diversity and altered proportions of specific taxa. Diet is the primary modulator of the microbiome: a diet rich in fermented foods and prebiotic fibers can improve microbiome composition and, through the gut-brain axis, contribute to mood stability.

The most relevant nutrients in bipolar disorder

Omega-3: this is the most studied nutrient in bipolar disorder. A meta-analysis by Sarris et al. (2012, Journal of Affective Disorders) of 5 randomized trials found that omega-3s (especially EPA) improve the depressive component of bipolar disorder as augmentation (addition) to pharmacological therapy. The effect on the manic phase is less documented. Studied dosage: 1–3 g/day of EPA+DHA. Vitamin D: vitamin D deficiency is more common in people with bipolar disorder than in the general population. Some observational studies show a correlation between low vitamin D levels and more frequent episodes. Supplementation in deficient individuals is recommended even for its general health implications. N-acetylcysteine (NAC): not a food but a precursor to glutathione. Several randomized trials (Berk et al., 2008, 2012, Biological Psychiatry) show that NAC as an add-on to therapy reduces depressive symptoms in BD. The proposed mechanism is the reduction of oxidative stress. NAC is also found in foods rich in cysteine (eggs, chicken, legumes) and as a supplement. Folate and vitamin B12: deficiencies in these nutrients are associated with worsening of the depressive component in many psychiatric conditions, including BD. Polymorphisms of the MTHFR gene (very common: 40% of the population) reduce folate methylation: methylated forms of folate and B12 (methylfolate, methylcobalamin) have better bioavailability.

Circadian rhythms, food, and bipolar disorder

Circadian rhythms (the 24-hour biological cycle that regulates sleep, body temperature, cortisol, and hunger) are profoundly disrupted in bipolar disorder: circadian rhythm disruptions are both a cause and consequence of episodes. Diet is one of the primary zeitgebers (biological clock synchronizers) alongside sunlight. Regular meal timing is a powerful zeitgeber: eating at the same time each day helps synchronize circadian rhythms, and synchronization is associated with greater mood stability in BD. Nutritional chronotherapy (meal timing as rhythmic therapy) is an emerging concept in BD management. Irregular meals (skipping breakfast, eating late in the evening, variable schedules) contribute to circadian desynchronization. Time-restricted eating (TRE: eating within an 8–10 hour window of the day) is associated with improved circadian rhythms in animal models of bipolar disorder. Research in humans with BD is still preliminary, but TRE during morning/afternoon hours (breakfast at 7 a.m., dinner at 3–5 p.m., fasting until the next day) is the most studied model for restoring circadian rhythms. Real-world practice: difficult for many people for social reasons (family dinners, workplace meals). A realistic goal is regular meal timing (same time each day) even if extreme TRE is not practiced.

Drug-nutrient interactions in bipolar disorder

Interactions between mood-stabilizing medications and diet are clinically important and often inadequately communicated to patients. Lithium and dietary sodium: this is the most critical interaction. The kidneys manage lithium and sodium through the same reabsorption pathway: when sodium intake drops (low-sodium diet, excessive sweating, diarrhea, diuretics), the kidneys reabsorb more lithium to compensate, increasing plasma levels with risk of toxicity (nausea, tremor, confusion, in severe cases: kidney damage). Practical rule: maintain stable sodium intake. Do not start low-sodium diets or very restrictive diets without consulting your psychiatrist. Always report events that can reduce sodium (fever with heavy sweating, gastroenteritis, summer heat). Valproate and carnitine: valproate can reduce carnitine levels (which transports fatty acids into mitochondria). L-carnitine supplementation is often recommended in prolonged valproate therapy. Food sources: red meat, fish, dairy products. Lamotrigine and folate: folate influences lamotrigine metabolism (can reduce its plasma levels). This is not a critical interaction but explains why folate should be monitored. MAOIs and tyramine: see the article on depression. If therapy includes MAOIs (rarely used in BD but possible), dietary restrictions on tyramine are mandatory.

Body weight in bipolar disorder: a real challenge

Overweight and obesity are much more common in people with bipolar disorder than in the general population. The causes are multiple: many mood-stabilizing medications cause weight gain (valproate, lithium, quetiapine, olanzapine are most associated with weight gain), the depressive phase is often associated with hyperphagia (overeating) and reduced physical activity, the manic phase can lead to impulsive eating behaviors, remission periods don't always see recovery of weight lost and gained during episodes. Excess weight worsens bipolar disorder: through inflammation, through worsening sleep quality (sleep apnea), through metabolic complications (diabetes, metabolic syndrome) that add to the disease burden. Strategies for managing weight in BD: weight intervention should be discussed with the psychiatrist (changing a medication for weight gain without supervision is dangerous), drastic restrictive diets are discouraged (cognitive load and frustration can destabilize mood), regular moderate physical activity (walking, swimming, yoga) is the most effective and safest intervention for weight in BD, regular dietetic follow-up (every 3–6 months) allows monitoring and correcting trends before they become serious problems.

Alcohol and bipolar disorder: a complicated relationship

Alcohol abuse is much more common in people with bipolar disorder (lifetime prevalence: 40–60% according to National Comorbidity Survey data) than in the general population. The reasons: alcohol is used for self-medication of dysphoria, depression, insomnia, but structurally worsens the course of bipolar disorder. The effects of alcohol in BD: during depressive episodes: alcohol amplifies depression in the medium term despite acute reduction of distress. During the manic or hypomanic phase: alcohol further lowers inhibitions and impulse control, amplifying the risky behaviors typical of mania. Interaction with medications: alcohol interacts with almost all mood-stabilizing medications, reducing their effectiveness (enzyme induction) or potentiating sedative effects (dangerous with benzodiazepines, quetiapine, lithium). The practical message: the goal is abstinence or maximum possible reduction of alcohol in bipolar disorder. Not for moralistic reasons: for reasons of therapeutic effectiveness. The psychiatrist managing BD should include assessment of alcohol consumption as part of the follow-up visit.