Nutritional Factors - What Causes Fatigue: Chronic Fatigue

Content provided by the Faculty of the Harvard Medical School

Nutritional factors

What you eat or drink can influence how energetic you feel, but unless you're malnourished, the impact of food is minor compared with stress, depression, or other causes described thus far. Nevertheless, nutritional factors can contribute to fatigue in several ways.

Not eating often enough. Eating small meals and snacks throughout the day maintains your energy level better than eating one or two large meals, even if they provide the same calorie intake. Eating frequently creates a steadier level of sugar in the blood with less pronounced peaks and valleys. Steadier levels may help people whose brains are particularly sensitive to drops in blood sugar during the valleys. Without some adjustment in eating patterns, these people can have trouble concentrating or may feel mentally foggy. For most people, the ideal eating pattern is breakfast, lunch, and dinner, with light snacks in between.

Overeating. Ever wonder why you feel tired after a big meal? One reason is that it floods the blood with sugar, temporarily giving you a lift of energy. But the ensuing surge of insulin, the hormone that carries sugar to the cells, can pull too much sugar from the blood and into the muscle cells for storage. This leaves too little sugar available for immediate energy. The result is a feeling of lethargy. Overeating on a regular basis can also make you overweight, which promotes fatigue by forcing you to expend more energy in everything you do.

Lack of fluids. As important as eating enough food is getting enough water and other fluids. Fatigue is one of the first signs of dehydration. In the typical man, water constitutes 60% of body weight; in women, it accounts for about 50%. Not only is water the major component of most cells, it carries nutrients to your cells and takes away waste products, and it helps regulate your body temperature. But your body continually loses water, through perspiration, excretion, and breathing (the air you exhale contains microscopically small drops of water). Drink when you're thirsty to replenish what you lose. Drink extra water if you've consumed coffee, tea, cola, or alcohol, which draw water out of your body. Even more important is drinking plenty of water before and during exercise.

Vitamin and mineral deficiencies. Although there's no evidence that taking extra vitamins and minerals will give you extra energy, being deficient in certain of these substances can cause fatigue. In prosperous societies, probably the most common deficiencies are of iron and vitamin B₁₂. Women, who lose a lot of iron-containing blood in their monthly menstrual flow, are at greatest risk for becoming iron-deficient. Vitamin B₁₂ deficiency can be a problem for vegetarians — particularly vegans, who consume no animal or dairy products, the main dietary sources of vitamin B₁₂ — although it can occur in others besides vegans. Like iron deficiency, vitamin B₁₂ deficiency can cause a form of anemia (see "Anemia"). Both iron and vitamin B₁₂ deficiencies are easy to diagnose and, for most people, simple to remedy with supplements.

Fatigue-inducing foods. Certain foods can have a calming effect. Milk, turkey, corn, brown rice, and legumes contain the amino acid tryptophan. The brain converts tryptophan into serotonin, a neuro­transmitter that, among various actions, helps you feel relaxed and possibly fatigued. Not everyone will feel sleepy after having a turkey sandwich or a glass of milk. But if you're prone to fatigue, to be on the safe side, you might want to avoid these foods in the middle of the day. It's also a good idea to limit your intake of caffeine, which can interfere with sleep.

Last updated:	January 23, 2007