Carbohydrates are sugars found in a diverse array of foods. Bread, pasta, rice, fruit and veggies are all rich sources of carbs, which your body breaks down into the simple sugar glucose. When you overdo it on carbs, especially refined varieties, your waistline is likely to increase. On the other hand, a severe lack of dietary carbs is likely to increase moodiness and irritability because your brain needs glucose to function normally.
Importance of Glucose
Glucose is the simplest sugar that your body uses to produce energy and do work. With the help of enzymes, carbohydrates are metabolized to glucose, which is readily absorbed into your bloodstream and transported around your body. One of the main destinations of blood glucose is your brain, which is powered entirely by the simple sugar. In fact, although your brain is only about 2 percent of your body’s weight, it uses approximately 20 percent of your daily calories -- almost completely from dietary carbohydrates. Only in extreme and dire circumstances will your brain use substances other than glucose for fuel.
Low Blood Glucose
Not eating enough carbohydrates leads to hypoglycemia, which is a lack of circulating blood glucose. Blood glucose levels below 70 milligrams per deciliter trigger a variety of symptoms in your body, although the ones related to your brain are usually first to be noticed. For example, hypoglycemia can quickly trigger confusion, dizziness, irritability, moodiness, anxiety, depression and headaches. Brain functions related to cognition and mood are quickly affected because the frontal cortex is especially sensitive to low blood glucose levels. In contrast, the brain regions responsible for more vital functions -- such as breathing -- are more resistant to dietary factors. Other symptoms of hypoglycemia include extreme fatigue, muscle weakness and tremors.
Serotonin and Insulin
Aside from glucose, neurotransmitters in your brain are also responsible for mood. Serotonin, for example, lifts mood and makes you feel happier when it’s released within your brain. In general, eating carbohydrates increases serotonin production, whereas a severe lack of carbs can have the opposite effect. On the other hand, low-carb diets can help regulate mood because they tend not to cause spikes in insulin release -- the hormone that regulates glucose uptake into cells. For example, eating too many carbs, especially refined types that are easily metabolized, quickly increases blood sugar levels, which triggers lots of insulin release. When lots of insulin is secreted, blood glucose levels tend to “crash” and hypoglycemia develops.
Dietary factors affect everyone a little differently. However, eating a combination of carbohydrates, protein and fat in small meals spread throughout the day is probably best for keeping your mood even. Focusing on eating natural carbs combined with fiber -- found in whole grains and fibrous fruit, veggies and legumes -- feeds your body the glucose it needs without spiking insulin release. In contrast, binging on candy, desserts and other sweets may lead to mood swings due to the sugar high and inevitable crash.
- Human Biochemistry; Charles Dreiling
- Human Metabolism: Functional Diversity and Integration; J. Ramsey Bronk
- Biochemical Pathways; Gerhard Michal
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.