Chronic obstructive pulmonary diseasePatient friendly summary

  • Severity of COPD may be higher in winter. Sunlight levels are lower, and the rate of respiratory infections are higher.
  • There is limited evidence that vitamin D reduces the severity of COPD.

Chronic obstructive pulmonary disease (COPD) is one of the most common lung diseases.

There are two main forms of COPD:

  • Chronic bronchitis is identified by a long-term cough with mucus.
  • Emphysema is a slow destruction of the lungs over time.
Most people with COPD have a combination of both conditions.

Symptoms include cough with mucus, shortness of breath that worsens with mild activity, fatigue, frequent respiratory infections, and wheezing. Symptoms vary and become worse at times. This is known as flare-ups or acute attacks.

Risk factors

Risk factors for COPD include:

  • Smoking
  • Gases or fumes in workplaces
  • Exposure to secondhand smoke and air pollution
  • Cooking over flames without proper ventilation

Sunlight exposure and COPD risk

In Finland, people hospitalized for an acute attack of COPD had higher death rates between December and May. Rates of viral respiratory infections are highest at that time because there is less sunlight.

Ultraviolet-B (UVB) light and vitamin D may reduce the risk of COPD flare-ups. Two studies reported that farmers had lower rates of COPD attacks. However, farmers in general have higher rates of COPD, possibly because they are exposed to more organic matter and chemicals.

Vitamin D and COPD

Vitamin D levels

According to U.S. studies, there is a strong relationship between vitamin D levels and forced air capacity. This includes the total amount of air forced from the lungs after taking the deepest breath possible. It also includes the amount of air forced during the first second of exhalation.

Vitamin D deficiency occurs frequently in COPD. This is shown in a few studies:

  • Former smokers in the Netherlands with low levels of vitamin D had more severe COPD.  Rates of those with less than 20 ng/ml (50 nmol/l) increased from 30% for ex-smokers with normal lung function to 75% for those with the most advanced COPD.
  • In Japan during a six-year study, baseline vitamin D levels did not predict lung function decline. However, vitamin D levels change with time. That may have affected the findings.

How vitamin D works

Vitamin D may protect against COPD flare-ups by:

  • Protecting the body against viral and bacterial infections. These infections often trigger COPD attacks.
  • Reducing compounds in the body that destroy tissues. This includes matrix metalloprotease-9 (MMP-9). MM-9 may contribute to COPD.


There is little evidence that vitamin D reduces the risk of developing COPD. However, this possibility cannot be ruled out.

Vitamin D and calcium

Those with COPD have an increased risk of osteoporosis. Vitamin D can reduce the risk of osteoporosis. People with COPD should supplement with vitamin D and calcium. Doses of 800 international units (IU) (20 mcg)/day of vitamin D plus calcium have been shown to provide some protection against osteoporosis.


Based on the evidence, vitamin D levels above 30–40 ng/mL (75-–100 nmol/L) may reduce the risk of COPD. To reach these levels, most people need to take 1000–5000 international units (IU) (25–125 mcg)/day of vitamin D3. This is the active form of vitamin D produced under the skin. However, there is considerable variation from person to person. To determine proper dosage, vitamin D blood levels should be measured before and several months after taking vitamin D3 supplements or increasing UVB exposure.

Find out more...

Do you want to find out more and see the research upon which this summary is based?  Read our detailed evidence summary on Chronic obstructive pulmonary disease (COPD).

Page last edited: 04 May 2011