Can a Lack of Vitamin D Cause You to be Fatigued?

Your body can absorb vitamin D from the ultraviolet rays of the sun.

Vitamin D, also known as the sunshine vitamin, contributes to balancing mood and fatigue. Vitamin D is found in a small number of foods. The majority of the average person's vitamin D comes from the body's ability to produce vitamin D from sunlight. Certain interactions between vitamin D and energy-related hormones may help increase your energy, but not getting enough vitamin D can leave you feeling tired and lacking energy.

Vitamin D Deficiency and Fatigue

According to the Vitamin D Council, a vitamin D deficiency may cause a lack of energy, including depression and chronic fatigue. A vitamin D deficiency is characterized as levels that fall below 50 nanograms per milliliter of vitamin D.

Vitamin D and Melatonin

A lack of vitamin D may contribute to fatigue by its interaction with melatonin. Melatonin is a mood regulator, decreasing your energy at the sign of darkness to help you sleep. Your melatonin levels are inversely related to your levels of vitamin D. In other words, increased vitamin D means lower levels of melatonin. The reverse is also true, less vitamin D means increased melatonin and increased fatigue.

Seasonal Affective Disorder

Seasonal affective disorder occurs during certain seasons of the year, specifically the fall and winter, and is characterized by feelings of depression, fatigue and sleepiness. It is believed that a lack of sunlight and a deficiency of vitamin D may be the cause of this disorder. A lack of sunlight reduces absorption of vitamin D and affects internal melatonin levels. When the winter months lose sunlight, you may begin to lack vitamin D, which increases melatonin and fatigue.

Sources and Recommendations

Vitamin D can be ingested through dietary sources and can also be absorbed through sunlight. Absorption of ultraviolet light on your skin allows your body to produce vitamin D. Dietary sources include milk, eggs, cereals, bread and fish. Intake recommendations for vitamin D vary by age. Beginning at birth through 12 months, your need for vitamin D is 400 IU per day. From the age of one to 70, the National Institutes of Health recommends taking in 600 IU of vitamin D each day. After age 70, your needs increase to 800 IU per day.