NEW YORK – Fish oil supplementation, in daily doses of 2 g or more, may mitigate weight loss, increase appetite, and improve overall quality of life in people with lung cancer, according to a systematic review presented by Dr. Heidi Fritz, at the annual meeting of the Society for Integrative Oncology.
Fish oil supplementation may also have a small but significant impact on survival at higher doses of 18 g/day, said Dr. Fritz, a naturopathic physician at the Canadian College of Naturopathic Medicine in Toronto.
Dr. Fritz and her colleagues have undertaken a comprehensive effort to gather the best available data on the benefits and risks of various popular nutritional supplements in the management of lung cancer, among them vitamin A, green tea, selenium, and fish oils.
The Canadian team searched six medical literature databases, finding 50 papers including 6 randomized controlled trials, 11 observational studies, and 30 preclinical studies on the use of fish oil supplements as an adjunctive or supportive treatment for lung cancer.
For the most part, these studies focused on fish oil’s effects on cancer-associated cachexia or – in the case of the human clinical studies – on its use as a supportive therapy to improve quality of life. However, one phase II study looked at the impact on survival of supplementation with eicosapentaenoic acid (EPA), an omega-3 polyunsaturated fatty acid.
Dr. Fritz said that although the conclusions of individual studies varied, overall "modest clinical benefit from the use of fish oil and/or EPA alone was seen on parameters associated with cachexia – notably weight loss, appetite, and physical function – and there were also modest improvements seen in quality of life."
She added that one of the clinical trials showed a "significant benefit on survival with high-dose fish oil using 18 g/day." The generally recommended dose is 2 g/day.
No significant adverse effects were associated with the use of fish oils at any dosage in the human clinical studies in this systematic review, and no thromboembolic events – the biggest potentially life-threatening adverse effect associated with intensive omega-3 fatty acid supplementation – were reported.
"Fish oil, particularly EPA, appears safe and may be effective in the treatment of cachexia and related symptoms," Dr. Fritz concluded. "Use of EPA as part of a multifaceted approach to the treatment of cachexia may be advantageous in a clinical setting."
The Canadian team’s systematic review of 66 published studies on green tea and lung cancer concluded that although there is some evidence that compounds in green tea do have antitumor properties, there is no strong evidence that drinking green tea, even in large quantities, will prevent lung cancer or substantially improve treatment outcomes.
Their vitamin A/retinoids systematic review, based on 232 papers including 5 randomized controlled trials, does not support the use of this vitamin for either prevention or treatment of lung cancer. The available data indicate that beta-carotene should not be given to smokers; however, Dr. Fritz added, vitamin A and the retinoids deserve further study in other types of cancer, as the negative findings for lung cancer do not necessarily apply to all cancers.
Their analysis of selenium in the context of lung cancer was inconclusive. Available studies are conflicting in terms of both safety and efficacy, and there is little consensus about the appropriate form of supplemental selenium, the dosage, and the optimal level in humans.
"There may be potential benefit from selenium supplementation in populations with low baseline status, but increased risk of cancer and diabetes associated with supplementation in populations with higher baseline status," she said. Currently the evidence is insufficient to support a recommendation for routine use of selenium to prevent or treat lung cancer.