Chronic Obstructive Pulmonary Disease
Manual of Clinical Nutrition Management III- 18 Copyright © 2013 Compass Group, Inc.
represents gas exchange and is defined as carbon dioxide produced divided by oxygen consumed. A lower
respiratory quotient indicates better gas exchange and an easier capacity for a patient to breathe. The type of
energy substrate (fat, protein, or carbohydrate) and how the body utilizes the substrates determine the
respiratory quotient (2). When oxidized for energy production, protein has a respiratory quotient of 0.8, fat
has an respiratory quotient of 0.7, and carbohydrate has an respiratory quotient of 1 (2). The clinical benefits
of altering fat-to-carbohydrate ratios in patients with COPD when the energy supplied is appropriate have not
been demonstrated (2,9,13). The respiratory quotient can be affected by a number of variables other than
substrate utilization (13,14). Current practice emphasizes the provision of measured or estimated energy
requirements with the emphasis of preventing overfeeding rather than altering substrate by providing high-
fat or low-carbohydrate formulations (13).
Omega-3 fatty acids: A review of studies on the influence of omega-3 fatty acids on airway responsiveness
demonstrated inconclusive findings regarding a relationship between overall fish intake and COPD mortality,
pulmonary function, and symptoms (Grade III) (9). In one study, dietary fish oil consumption by cigarette
smokers provided protective effects against COPD (Grade III) (9,15). Further investigation is required to assess
the relationship between omega-3 fatty acids and COPD. Currently, supplementation with fish oil is not
recommended (Grade III) (9).
Electrolytes and trace elements: Disturbances of electrolytes are common in critically ill patients with
COPD. Patients with cor pulmonale or pulmonary edema may require sodium and fluid restriction.
Hypophosphatemia, hypokalemia, hyperkalemia, hypocalcemia, and hypomagnesemia are associated with
diminished diaphragmatic function (8). Respiratory function improves with the repletion of these nutrients.
Phosphorus deficiency reduces the blood’s ability to deliver oxygen to tissues and decreases the contractility
of respiratory muscles. Magnesium deficiency compromises respiratory muscle strength. The dietary intake
of these key nutrients should be monitored (2). Reduced bone mass, as measured by dual-energy x-ray
absorptiometry, has been demonstrated in patients with COPD; this finding provides evidence for nutritional
concerns related to bone mineral density, fracture risk, and osteoporosis (Grade II) (9). The prevalence of
osteoporosis and/or vertebral fractures ranges from 25% to 60% in COPD patients (Grade II) (9). Patients who
are treated with steroids (greater than 1,000 mg/day of inhaled or oral steroids) are at an increased risk;
changes in biochemical bone markers, decreased bone mineral density, and increased fracture risk are
associated with higher steroid intake (Grade II) (9). Low body weight and low BMI are positively correlated with
decreased bone density in patients with COPD (Grade II) (9). Emerging research shows associations between
hypercapnia, vitamin D status, and bone mineral density (Grade II) (9). Until further research is available, the
dietitian should carefully assess the patient’s risk factors (eg, older age, corticosteroid use, low BMI, and
smoking) and dietary intake of calcium, phosphorus, and vitamin D. In consultation with the physician,
supplementation with these key vitamins and minerals should be considered based on the patient’s risk level
assessment or evidence of need.
Antioxidants: The effects of antioxidants (flavonoids and vitamins A, D, and E) on the pathogenesis and
exacerbation of COPD have recently been reviewed (9). Seven studies found reduced serum or tissue levels of
antioxidant vitamins in people with COPD (Grade III) (9). However, studies of supplementation report
insignificant effects (Grade III) (9). Ongoing studies are investigating the relationship between nutrients and lung
function and COPD (9). Food sources rich in antioxidants, vitamins, and minerals are currently recommended
in place of supplementation (2).
Mucus production and dairy consumption: Some patients with COPD perceive increased mucus
production after consuming milk and dairy products. However, a narrative review concluded that milk and
dairy product consumption does not significantly affect lung function parameters (Grade III) (9). More research
is needed on this topic (Grade III) (9).
*The Academy of Nutrition and Dietetics has assigned grades, ranging from Grade I (good/strong) to Grade V (insufficient evidence), to
evidence and conclusion statements. The grading system is described in Section III: Clinical Nutrition Management A Reference Guide,
page III-1.
References
- Snider GL. Nosology for our day: its application to chronic obstructive pulmonary disease. Am J Respir Crit Care Med.
2003;167:678-683. - Chronic obstructive pulmonary disease. In: Nutrition Care Manual. Academy of Nutrition and Dietetics; Updated annually. Available
at: http://www.http://nutritioncaremanual.org. Accessed February 5, 2013. - Bauldoff GS, Diaz PT. Improving outcomes for COPD patients. Nurse Pract. 2006;31:26-43.