Dietary fats found in both animal and plant foods, meats, regular-fat dairy products, butter, margarine, and plant oils have been linked to brain functioning and deficiencies in these may cause depression. Reducing fat and cholesterol in the diet (to prevent cardiac disorders) may deplete brain serotonin levels, causing mood changes, anger, and aggressive behavior.

Alcoholic beverages provide energy but virtually no vitamins or minerals. Alcoholism is one of the most common causes of nutritional deficiencies. Extra amounts of certain vitamins, such as Thiamine, are needed to break down alcohol in the body, further contributing to nutrient deficiencies. Contrary to popular belief a high alcohol intake can interfere with normal sleep patterns, and affect mood and functioning of the mind.

Vitamin B-12 found in foods of animal origin like milk, meat, or eggs, is needed to maintain the outer coating, called the myelin sheath, on nerve cells. Inadequate myelin results in nerve damage and impaired brain function. Strict vegans who consume no animal-based foods need to supplement their diet with vitamin B-12 to meet the body's need for this nutrient. Chronic vitamin B-12 deficiency can cause irreversible nerve damage, dementia , and brain atrophy.

Folic acid, found in liver, yeast, asparagus, fried beans and peas, wheat, broccoli, and some nuts,  is involved in protein metabolism in the body and in the metabolism of some amino acids, particularly the amino acid methionine. Low folic acid levels result in  methionine not being metabolized properly. This can cause levels of another chemical, homocysteine, building up in the blood. Folic acid deficiency can lower levels of serotonin in the brain. All these can lead to a range of mental disorders, including depression.

Vitamin B-6, (Pyridoxine), found in many plant and animal foods, including chicken, fish, pork, whole wheat products, brown rice, and some fruits and vegetables,  is needed by the body to produce most of the brain's neurotransmitters. It is also involved in hormone production. Vitamin B-6 deficiency can result in mental changes such as fatigue , nervousness, irritability, depression, insomnia , dizziness, and nerve changes.

Vitamin A, is found in meats, fish and eggs, and in orange and green leafy vegetables such as carrots, yellow squash, and spinach. Excess of Vit A can cause headache, fatigue, irritability, and loss of appetite.

Magnesium, found in green leafy vegetables, whole grains, nuts, seeds, and bananas, and hard water, aids in the transmission of nerve impulses. Deficiency of Magnesium can cause restlessness, nervousness, and apathy.