Eating for Different Needs

• Eat regular meals with some protein and fiber, which helps keep blood sugar steadier.
• Drink enough water. Mild dehydration may affect attention and mood, although studies are not consistent (Liska et al., 2019).
• If you drink caffeine, up to about 400 milligrams a day (roughly four cups of coffee) is considered safe for most healthy adults (FDA, EFSA). People who are pregnant are advised to keep to about 200 milligrams a day or less. Caffeine can affect sleep, so many people do better with less.

• A Mediterranean-style way of eating (vegetables, fruit, whole grains, beans, nuts, olive oil, fish) helped some adults with depression when added to their usual care in the SMILES trial (Jacka et al., 2017). It was a small trial that used dietitian support.
• Studies of omega-3 supplements that are mostly EPA, at about 1 gram a day or less, show a small average benefit for depression, but the evidence is mixed (Mocking et al., 2016; Liao et al., 2019). Products made mostly of DHA did not show a clear benefit. Ask your doctor before starting supplements. Eating fish about twice a week is a common recommendation for heart health.
• Diets high in ultra-processed foods are linked to higher odds of depression in observational studies (Lane et al., 2022).

• Caffeine can cut sleep time and deep sleep. A review suggests that a standard cup of coffee is best finished at least about 9 hours before bed, and more caffeine may need longer (Gardiner et al., 2023).
• Even a small amount of alcohol can reduce REM sleep, and more alcohol disrupts it more (Gardiner et al., 2025).
• In a small lab study, eating more fiber was linked to more deep sleep, while more saturated fat and sugar were linked to lighter, more broken sleep. These were associations in 26 people (St-Onge et al., 2016).

• No food calms anxiety on its own, but regular meals help. Low blood sugar can cause shakiness and a racing heart that may feel like anxiety.
• Too much caffeine can add to jitteriness and a fast heartbeat.
• Gut-friendly foods, such as fiber and fermented foods, may support the gut–brain connection. See Gut Bacteria and What They Eat.
• Slow breathing and other calming practices can help in the moment. See our Tools.

• Add fiber slowly and drink water to avoid gas and bloating.
• Try small servings of fermented foods such as yogurt, kefir, kimchi, or sauerkraut.
• See a doctor for blood in your stool, severe pain, unexplained weight loss, or changes in bowel habits that last.

Learn more in The Gut–Brain Connection.

Low iron or low vitamin B12 can contribute to tiredness, brain fog, and low mood. Evidence for vitamin D and mood is less clear. Vitamin B12 is found mainly in animal foods, so people who eat little or no animal food should ask a doctor about it.

Because symptoms overlap with many conditions, a blood test is the reliable way to find out if you are low. Please do not start high-dose supplements on your own.

• Liska, D., et al. (2019). Narrative review of hydration and selected health outcomes in the general population. Nutrients, 11(1), 70.
• Jacka, F. N., et al. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the SMILES trial). BMC Medicine, 15.
• Mocking, R. J. T., et al. (2016). Meta-analysis and meta-regression of omega-3 polyunsaturated fatty acid supplementation for major depressive disorder. Translational Psychiatry, 6.
• Liao, Y., et al. (2019). Efficacy of omega-3 PUFAs in depression: A meta-analysis. Translational Psychiatry, 9, 190.
• Lane, M. M., et al. (2022). Ultra-processed food consumption and mental health: A systematic review and meta-analysis of observational studies. Nutrients, 14(13).
• Gardiner, C., et al. (2023). The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Medicine Reviews, 69.
• Gardiner, C., et al. (2025). The effect of alcohol on subsequent sleep in healthy adults: A systematic review and meta-analysis. Sleep Medicine Reviews, 80.
• St-Onge, M.-P., et al. (2016). Fiber and saturated fat are associated with sleep arousals and slow wave sleep. Journal of Clinical Sleep Medicine, 12(1), 19–24.
• U.S. Food and Drug Administration guidance on caffeine (up to about 400 mg per day for most healthy adults).