February 2009 Issue
Nutrition and COPD - Dietary Considerations for Better Breathing
By Ilaria St. Florian, MS, RD
Vol. 11 No. 2 P. 54
A recent survey conducted by the National Heart, Lung, and Blood Institute suggests that despite a growing awareness of chronic obstructive pulmonary disease (COPD), only 64% of respondents had ever heard of it. Yet, according to the Global Initiative for Chronic Obstructive Lung Disease, COPD “is the fourth leading cause of chronic morbidity and mortality in the United States” and an estimated 24 million Americans are affected.1
COPD is a progressive lung disease that makes breathing difficult due to partially obstructed airflow into and out of the lungs. It results from an inflammatory and destructive process in the lungs stimulated by exposure to toxins, primarily due to a history of smoking cigarettes.
Healthy people’s bronchial tubes and alveoli are elastic; thus, when they breathe in and out, they inflate and deflate much like a balloon. In contrast, patients with COPD experience limited airflow through their airways due to either a loss of elasticity and/or inflamed, damaged, or mucous-clogged airways. Because the airways are partially blocked or damaged, breathing becomes difficult, and the lungs begin to lose their ability to effectively take up oxygen and remove carbon dioxide.2,3 “Expiratory airflow limitation” is the hallmark of COPD, and the gold standard for diagnosis is spirometry, which is a simple lung function test that measures how well the lungs exhale.1
Symptoms of COPD include chronic cough, often referred to as “smoker’s cough”; excessive mucous production; wheezing; shortness of breath; tightness in the chest; and a decrease in exercise capacity.2,4 The leading cause of COPD is cigarette smoking; in fact, most patients with COPD are either current smokers or have a history of smoking. According to the American Lung Association, an estimated 80% to 90% of COPD deaths are attributed to smoking, and smoking cessation is the most effective means of disease prevention. Other causes include long-term exposure to indoor and outdoor air pollutants, occupational chemicals, fumes, dusts, and second-hand smoking. In rare cases, a genetic component may increase susceptibility.2
COPD is an umbrella term that includes both emphysema and chronic bronchitis. Patients with emphysema are referred to as “pink puffers” and experience shortness of breath due to a loss of elasticity and eventual damage to the air sac walls, leading to impaired exhalation and a buildup of gas in the lungs. These patients are typically thin, often exhibiting significant weight loss due to the increased energy requirements associated with labored breathing. In contrast, patients with chronic bronchitis are referred to as “blue bloaters” and are typically normal weight or overweight and edematous and experience persistent cough, increased mucous production, and shortness of breath due to inflammation, scarring, and eventual narrowing of the airways.3,5,6
The term COPD is used to refer to these two conditions because patients often exhibit features of both. As the disease progresses, the individual’s ability to breathe worsens, and some patients may require supplemental oxygen or mechanical ventilation. Although COPD is largely preventable, it is not curable, and lung damage is irreversible. Therefore, treatment focuses on smoking cessation, symptom management, improved conditioning, and increasing patients’ ability to lead an active life.3
Maintaining a Healthy Weight Is Vital
For most people, breathing is unconscious and perceived as effortless. Yet, for many patients with COPD, breathing requires a conscious effort. Because of this added effort, patients can increase their resting energy expenditure (REE) by up to 10% to 15%.4 As a result, if patients do not compensate for their increased energy needs by adding more calories to their diet, they will lose weight. Energy needs can be calculated using indirect calorimetry or the Harris-Benedict equation. The general recommendation is 1.2 to 1.3 X REE to provide adequate energy and avoid weight loss.6 Currently, an estimated 30% to 70% of patients experience unwanted weight loss.6
In addition to increased REE, patients lose weight due to decreased dietary intake as a result of an inherent inability to eat rather than a lack of appetite. Reasons for poor nutritional intake include the following:
• difficulty swallowing or chewing due to dyspnea;
• chronic mouth breathing, which can alter the taste of food;
• chronic mucous production;
• morning headache or confusion due to hypercapnia;
• depression; and
• side effect of medications.
The purpose of nutrition care for this population is to provide adequate energy to minimize the risk of unwanted weight loss, avoid loss of fat-free mass (FFM), prevent malnutrition, and improve pulmonary status. Research shows that COPD is a disease that not only affects the lungs but can also have systemic consequences, as well as result in severe weight loss and FFM depletion.7,8 Combined, loss of weight and FFM can adversely affect breathing by reducing the strength and function of respiratory and skeletal muscles. In addition, a low body mass index (BMI) is associated with a poor prognosis; therefore, patients must maintain energy balance in light of their increased caloric needs.
The risk of malnutrition, which the American Dietetic Association (ADA) defines as a BMI of less than 20 kilograms per square meter, is a common concern among patients with COPD who lose an excessive amount of weight and FFM. Malnutrition can impair pulmonary function, increase susceptibility to infection, lower exercise capacity, and increase the risk for mortality and morbidity.6,9 According to the American Thoracic Society, criteria for initiating caloric supplementation is a BMI of less than 21 kilograms per meter squared, involuntary weight loss of more than 10% during the previous six months or more than 5% in the previous month, or depletion in FFM or lean body mass. FFM depletion is defined as below 16 kilograms per meter squared for men and 15 kilograms per meter squared for women based on the FFM index (FFM divided by height squared). For those patients who are overweight, added pressure on the lungs can increase the effort required to breathe, so encouraging patients to safely lose excess weight is important.
Antioxidant, Vitamin, and Mineral Considerations
Research indicates that cigarette smoke contains free radicals and other oxidants that can lead to oxidative stress, subsequent inflammation, and reduced airflow to the lungs. For this reason, antioxidant therapy has been proposed for its ability to minimize free radical damage and reduce inflammation.8 In fact, studies have shown that patients who continue to smoke have low concentrations of serum vitamin C, and according to findings from the National Health and Nutrition Examination Survey I published in the American Journal of Clinical Nutrition, a positive relationship exists between an increased dietary intake of vitamin C and pulmonary function. Researchers have found that smokers, as well as patients experiencing acute exacerbations, had lower plasma levels of certain antioxidants (eg, ascorbic acid, vitamin E, beta-carotene, selenium) and that this imbalance between oxidants and antioxidants leads to oxidative stress and inflammation and could be a significant contributing factor to the systemic effects characterized by the disease.8,10
Although the research is not sufficient to conclude that antioxidant therapy can slow COPD’s rate of progression, findings indicate that the consumption of fresh fruits and vegetables is positively associated with improved pulmonary function, fewer symptoms, and possibly reduced oxidative stress.8 Keeping in mind that patients may develop vitamin and mineral deficiencies due to reduced dietary intake is also important.
Many patients with COPD are prescribed glucocorticoids to help reduce airway inflammation and improve breathing. However, one of the side effects of glucocorticoid use is bone mass loss and eventual osteoporosis, leading to an increased risk of fractures. There are several risk factors that can cause osteoporosis, and patients with COPD typically have many of them, such as the use of glucocorticoids, smoking, vitamin D deficiency, low BMI, malnutrition, and decreased mobility.
According to a study in the February 2002 issue of Chest that examined the impact of COPD on osteoporosis development, 36% to 60% of patients with COPD eventually develop osteoporosis. For this reason, patients who are starting a long-term inhaled or oral glucocorticoid therapy are encouraged to supplement it with calcium and vitamin D, since bone loss occurs rapidly upon initiating treatment. According to the ADA’s 2008 practice guidelines for COPD, at-risk patients should take at least 1,200 milligrams of calcium and 800 to 1,000 international units of vitamin D daily to minimize bone loss.
A healthy diet for patients with COPD can lead to better breathing and possibly facilitate weaning from mechanical ventilation by providing the calories necessary to meet metabolic needs, restore FFM, and reduce hypercapnia. Carbon dioxide is a waste product of metabolism and is normally expelled via the lungs. However, patients with COPD who have limited and obstructed airflow have a compromised ability to take in oxygen and eliminate carbon dioxide. In patients with COPD, this impaired gas exchange increases patients’ ventilatory demands, as the lungs must work harder to clear excess carbon dioxide. In healthy individuals, increased carbon dioxide levels are easily eliminated.7
The Importance of Proper Nutrition
Proper nutrition can help reduce carbon dioxide levels and improve breathing. Specifically, it is important to focus on the percentages of total carbohydrate, fat, and protein that patients consume to see how their diet composition impacts their respiratory quotient (RQ), which is defined as the ratio of carbon dioxide produced to oxygen consumed. To put it simply, following metabolism, carbohydrate, fat, and protein are all converted to carbon dioxide and water in the presence of oxygen. However, the ratio of carbon dioxide produced to oxygen consumed differs per macronutrient; the RQ for carbohydrate is 1, fat is 0.7, and protein is 0.8. From a nutritional standpoint, this means that eating carbohydrates will yield the most carbon dioxide, while eating fats will yield the least carbon dioxide. That said, prescribing a high-fat, low-carbohydrate diet would reduce patient RQ levels and carbon dioxide production. In fact, patients who have difficulty increasing ventilation following a carbohydrate load or patients with severe dyspnea or hypercapnia may benefit from a high-fat diet.6
A July 1993 study in Chest found that a high-fat diet (55% fat) would be more beneficial to patients with COPD than a high-carbohydrate diet (55% carbohydrate) because it would decrease carbon dioxide production, oxygen consumption, and RQ, as well as improve ventilation. However, there is not a general consensus in the literature to universally recommend a high-fat, low-carbohydrate diet, as it may not be necessary for stable patients and not all patients may be able to tolerate the potential side effects (eg, gastrointestinal and abdominal discomfort, belching, diarrhea). In addition, some patients may have a coexisting heart condition, which could make a high-fat diet contraindicated.6 In fact, 25% of COPD patients develop pulmonary hypertension due to low oxygen levels, which results in enlargement and thickening of the right ventricle of the heart, a condition known as cor pulmonale.
Therefore, according to the ADA’s Manual of Clinical Dietetics, it is best to replete energy needs but avoid overfeeding as “excess calories are more significant in the production of carbon dioxide than the carbohydrate to fat ratio.” Because both overfeeding and carbohydrate metabolism produce high carbon dioxide levels and expelling excess carbon dioxide puts an enormous burden on the already-stressed lungs, it is best to meet but not exceed energy needs to keep both carbon dioxide and RQ levels in check.
Protein needs should be assessed on an individual basis. Intake should be high enough to stimulate protein synthesis, prevent muscle atrophy, and maintain lung strength but should not contribute excess calories to the diet. The general rule of thumb is about 1.2 to 1.7 grams per kilogram of protein daily or approximately 20% of total caloric intake. As for fluids, patients who are not on a fluid-restricted diet should be encouraged to drink liquids (2 to 3 liters per day) to keep mucous thin and help clear the airways.
There is still debate as to the effectiveness of nutrition therapy in improving anthropometric measurements, lung function, and exercise capacity in patients with COPD.9 According to the Global Initiative for Chronic Obstructive Lung Disease, nutrition supplementation coupled with exercise may increase efficacy. Although exercise is probably the last thing most patients with breathing problems want to think about, engaging in regular exercise has been shown to improve overall strength and endurance, reduce symptoms of dyspnea and fatigue, improve cardiovascular function, and contribute to stronger respiratory muscles and improved breathing.1,3 In addition, well-conditioned muscles use less energy, which can help stabilize REE levels.
Dietary Tips for Better Breathing
To help increase patients’ dietary intake and ensure a healthy diet, the following are some nutritional tips for better breathing:
• Eat meals when energy levels are at their highest, which is usually in the morning.
• Eat several small, nutrient-rich meals to avoid becoming breathless while eating.
• Eat slowly and chew foods thoroughly to avoid swallowing air while eating.
• Choose foods that are easy to chew. Modify food consistency if mastication seems to increase fatigue while eating.
• Choose foods that are easy to prepare to conserve energy for eating.
• Limit salt. Consuming too much can cause the body to retain water and can make breathing more difficult.
• Eat calcium- and vitamin D-rich foods to support bone health.
• Prepare meals that appear palatable and well presented.
• Avoid foods that cause gas or bloating. A full abdomen can make breathing uncomfortable.
• Eat while sitting up to ease lung pressure.
• Drink liquids at the end of the meal to avoid feeling full while eating.
• Wear a cannula while eating if continuous oxygen is prescribed. Eating and digestion require oxygen, so the body will need the extra oxygen.
• Limit caffeinated beverages, as caffeine can interfere with some medications and cause nervousness or restlessness.
• Make the meal more enjoyable by engaging in social interaction while dining.
• Avoid aspiration by breathing carefully, swallowing, and sitting properly and with good posture while eating.
• Rest before meals.
— Ilaria St. Florian, MS, RD, is a freelance food and nutrition writer currently based in Martinique. She holds a master’s degree in nutrition education from Teachers College, Columbia University.
1. Pauwels RA, Buist AS, Calverley PM, Jenkins CR, Hurd SS. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. NHLBI/WHO Global Initiative for Chronic Obstructive Lung Disease (GOLD) Workshop summary. Am J Respir Crit Care Med. 2001;163(5):1256-1276.
2. National Heart, Lung, and Blood Institute. What is COPD? Available at: http://www.nhlbi.nih.gov/health/dci/Diseases/Copd/Copd_WhatIs.html
3. Mayo Clinic. COPD definition. Available at: http://www.mayoclinic.com/health/copd/DS00916
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