Alan R. Gaby, MD
Olive Oil and Mortality: Virgin Versus Refined Oil
The association between olive oil consumption and all-cause and cause-specific mortality was examined in a prospective cohort study of 12,161 Spanish adults (mean age, 47 years). After a mean follow-up period of 10.7 years, 143 cardiovascular deaths and 146 cancer deaths occurred. The hazard ratio (HR) for all-cause mortality in the highest tertile of refined olive oil consumption was 0.96 (not significant). In contrast, the HR for all-cause mortality in the highest tertile of virgin olive oil was 0.66 (p for trend = 0.04). Virgin olive oil consumption was also inversely associated with cardiovascular mortality, with a HR of 0.43 (p for trend < 0.02), but the inverse association with refined olive oil was not statistically significant (HR = 0.88; p for trend = 0.24). No variety of olive oil was associated with cancer mortality.
The authors concluded that daily consumption of about 1.5 tablespoons of virgin olive oil was associated with a one-third lower risk of all-cause mortality and half the risk of cardiovascular mortality. These effects were not seen with refined olive oil.
Comment: All forms of olive oil are high monounsaturated fatty acids (MUFAs), which are thought to protect against the development of cardiovascular disease. However, according to the results of this observational study, this protective effect was small and not statistically significant. Virgin olive oil also contains substantial amounts of four phenolic compounds – hydroxytyrosol, tyrosol, oleuropein, caffeic acid – the vast majority of which are lost in the refining process. These phenolic compounds have antioxidant activity, and some inhibit platelet aggregation and have anti-inflammatory effects. Each of these actions might be expected to help prevent cardiovascular disease and possibly some other chronic diseases as well. Thus, the beneficial effects of virgin olive oil appear to be more pronounced than those of refined olive oil.
Donat-Vargas C, et al. Only virgin type of olive oil consumption reduces the risk of mortality. Results from a Mediterranean population-based cohort. Eur J Clin Nutr. 2023;77:226-234.
Mediterranean Diet for Cardiovascular Disease
Patients (n = 1,002) in Cordoba, Spain (aged 20-75 years; mean, 59.5 years) with coronary heart disease were randomly assigned to consume a Mediterranean diet or a diet low in fat and high in complex carbohydrates (low-fat diet) for 7 years. The Mediterranean diet contained at least 35% of calories as fat (22% monounsaturated, 6% polyunsaturated, less than 10% saturated), 15% protein, and a maximum of 50% carbohydrates. The low-fat diet contained less than 30% total fat (less than 10% saturated, 12-14% monounsaturated, and 6-8% polyunsaturated), 15% protein, and at least 55% carbohydrates. The Mediterranean diet contained more nuts and more oily fish than the low-fat diet. The researchers were blinded to which diet the participants were consuming. The primary outcome was a composite of major cardiovascular events, including myocardial infarction, revascularization, ischemic stroke, peripheral artery disease, and cardiovascular death. The primary endpoint occurred in 198 participants: 87 in the Mediterranean diet group and 111 in the low-fat group (p < 0.04). The protective effect of the Mediterranean diet was seen in men but not in women.
Comment: The “Mediterranean diet” refers to the diet of olive-growing regions of the Mediterranean. In addition to olive oil, the diet emphasizes salads, legumes, wheat, fruit, nuts, and garlic. In Italy a lot of pasta is consumed, whereas in Spain fish consumption is high. Total fat intake is around 30-40% of total energy. As mentioned above, virgin olive oil may have cardioprotective effects because of its high content of monounsaturated fatty acids and phenolic antioxidants.
In the present study a Mediterranean diet was more effective than a diet low in fat and high in complex carbohydrates for preventing major cardiovascular events.
Delgado-Lista J, et al. Long-term secondary prevention of cardiovascular disease with a Mediterranean diet and a low-fat diet (CORDIOPREV): a randomised controlled trial. Lancet. 2022;399:1876-1885.
Coffee Gets Things Moving After Intestinal Surgery
Seventy-nine patients who had undergone small-bowel resection were randomly assigned to consume 100 ml of caffeinated coffee or water 3 times per day (at 8 a.m., noon, and 4 p.m.). Treatment was started no later than the day after surgery and was continued until the time of first flatus or first bowel movement, whichever came first. The median time until the nasogastric tube was removed (3.4 vs. 4.0 days; p = 0.002) and the median time until hospital discharge (6.7 vs. 7.7 days; p = 0.01) was significantly shorter in the coffee group than in the water group.
Comment: Prolonged ileus occurs in 10-24% of patients undergoing abdominal surgery. Several studies have found that coffee consumption reduces postoperative ileus, but this has not been evaluated for small bowel resection. In the present study, consumption of coffee decreased time to nasogastric tube removal and decreased length of hospital stay in patients undergoing small bowel resection.
Holland C, et al. Coffee administration to promote return of bowel function after small bowel resection: A randomized, controlled trial. Am J Surg. 2023;226:156-160.
Melatonin for Chronic Obstructive Pulmonary Disease
Thirty-nine Brazilian patients (mean age, 67 years) with chronic obstructive pulmonary disease (COPD) were randomly assigned to receive, in double-blind fashion, 3 mg of melatonin or placebo 2 hours before bedtime for 12 weeks. All patients underwent a 12-week pulmonary rehabilitation program consisting of 60-minute sessions 3 times a week that included aerobic exercise, resistance exercises, and stretching. After 12 weeks, the mean distance covered in the 6-minute walk test was significantly greater in the melatonin group than in the placebo group (71 vs. 25 m; p < 0.01). The mean score on scales that measured health status and health-related quality of life were also significantly better in the melatonin group than in the placebo group (p < 0.01 for each).
Comment: This study demonstrated that melatonin supplementation during 12 weeks of pulmonary rehabilitation improved functional capacity, health status, and quality of life in patients with COPD. The authors suggested that the mechanism of action of melatonin may involve enhancement of muscle regeneration.
Viana SM, et al. Melatonin supplementation enhances pulmonary rehabilitation outcomes in COPD: a randomized, double-blind, placebo-controlled study. Respir Med. 2023;220:107441.
Low-FODMAPs Diet Improves Symptoms in Some Patients with Celiac Disease
Seventy adults with celiac disease who had persistent gastrointestinal symptoms despite being on a gluten-free diet for at least 12 months and being in remission (both serologically and by small-intestinal biopsy) were randomly assigned to continue their current diet (control) or to consume a low-FODMAPs gluten-free diet for 4 weeks. Compared with the control diet, the low-FODMAPs diet resulted in significant improvements in the mean score on the Gastrointestinal Symptom Rating Scale, as well as subscales for pain, bloating, and diarrhea. Significant differences between groups were evident after the first week.
Comment: “FODMAPs” is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. FODMAPs include fructose, lactose, sorbitol, fructans (fructooligosaccharides, inulin), and galactans (also called galactooligosaccharides; e.g., raffinose). Foods restricted on a low-FODMAPs diet include lactose-containing foods, foods with added fructose, foods which naturally contain fructose in excess of glucose (e.g., apples, pears), fructans-containing foods (e.g., wheat, artichokes, onions, garlic, leeks), sorbitol-containing foods (e.g., stone fruits), and raffinose-containing foods (e.g., legumes, lentils, cabbage, and Brussels sprouts). In clinical trials, consumption of a low-FODMAPs diet improved symptoms in patients with irritable bowel syndrome.
In the present study, a low-FODMAPs diet significantly reduced gastrointestinal symptoms in patients with celiac disease who had persistent gastrointestinal symptoms while on a gluten-free diet. The likely explanation for this improvement is that some of the patients had irritable bowel syndrome in addition to celiac disease.
van Megen F, et al. A low FODMAP diet reduces symptoms in treated celiac patients with ongoing symptoms – a randomized controlled trial. Clin Gastroenterol Hepatol. 2022;20:2258-2266.e3.
Krill Oil for Osteoarthritis
Two hundred thirty-five individuals (aged 40-65 years) with mild-to-moderate osteoarthritis of the knee were randomly assigned to receive, in double-blind fashion, 4 g per day of krill oil (daily, 0.6 g of eicosapentaenoic acid [EPA], 0.28 g of docosahexaenoic acid [DHA], and 0.45 mg of astaxanthin) or placebo (mixed vegetable oil) for 6 months. The mean WOMAC (Western Ontario and McMaster Universities Arthritis Index) pain score improved by 44% in the krill oil group and by 30% in the placebo group (p = 0.04 for the difference in the change between groups). Knee stiffness and physical function also improved to a greater extent in the krill oil group than in the placebo group.
Comment: Like fish oil, krill oil contains the omega-3 fatty acids, EPA and DHA, which have anti-inflammatory activity. In addition, krill oil contains astaxanthin, which has also demonstrated anti-inflammatory activity. In the present study, administration of krill oil resulted in modest improvement in pain, stiffness, and physical function in adults with mild-to-moderate osteoarthritis of the knee.
Stonehouse W, et al. Krill oil improved osteoarthritic knee pain in adults with mild to moderate knee osteoarthritis: a 6-month multicenter, randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2022;116:672-685.
Iron Deficiency and Heart Failure
Phosphorus magnetic resonance spectroscopy was used to quantify the phosphocreatine (PCr) to ATP (PCr/ATP) ratio, an index of cardiac energetics, in heart failure patients and healthy volunteers. Because PCr degradation maintains ATP levels when ATP supply does not meet demand, the PCr/ATP ratio is a marker of cellular energetic status. It is decreased when ATP demand is excessive or when ATP supply is decreased. Patients with (n = 27) and without (n = 12) iron deficiency and healthy volunteers (n = 11) were similar with respect to age and gender. The median PCr/ATP ratio was lower in heart failure patients with than in those without iron deficiency (1.03 vs. 1.72; p < 0.01) and healthy volunteers (1.39; p < 0.05). This difference persisted after adjustment for the presence of anemia, hemoglobin levels, and New York Heart Association (NYHA) class. In the total heart failure cohort, the PCr/ATP ratio correlated with ferritin levels (p < 0.01) and was higher in NYHA class I than class II or III patients (p = 0.02).
Comment: Mitochondrial oxidative phosphorylation provides over 90% of the heart’s adenosine triphosphate (ATP), and iron is essential for oxidative phosphorylation. The present study demonstrated that iron deficiency is associated with greater cardiac energetic impairment in patients with heart failure, irrespective of anemia. Suppression of cardiac mitochondrial function might therefore be a mechanism by which iron deficiency worsens heart failure.
Patients with heart failure are at risk for iron deficiency for at least 3 reasons. First, heart failure may be associated with poor appetite, which can lead to multiple nutritional deficiencies. Second, gastric acid plays a role in iron absorption, and a large proportion of heart failure patients have hypochlorhydria,[1] either due to their age or to the use of acid-suppressive medications. Third, bowel wall edema (secondary to the backup of fluid from the heart) can impair nutrient absorption.
Previous randomized controlled trials have demonstrated that correction of iron deficiency in patients with heart failure improves functional capacity and decreases the number of hospitalizations for worsening heart failure.
Papalia F, et al. Cardiac energetics in patients with chronic heart failure and iron deficiency: an in-vivo 31P magnetic resonance spectroscopy study. Eur J Heart Fail. 2022;24:716-723.
Plant-Based, Whole-Foods Diet for Cardiovascular Disease
Case report: An 82-year-old man on multiple medications for coronary artery disease, previous myocardial infarction, ischemic cardiomyopathy, hyperlipidemia, hypertension, and persistent atrial fibrillation presented with memory loss, cognitive impairment, fatigue, lightheadedness, and weakness. His medications were 40 mg per day of atorvastatin, 75 mg per day of clopidogrel, 40 mg per day of furosemide, 81 mg per day of aspirin, and 6.25 mg of carvedilol (a beta and alpha blocker) twice a day. His treatment plan included an exclusively plant-based, whole-foods diet with no animal foods, added sugar, salt, or oils, and no processed food; and moderate physical activity. Progressive improvement occurred over a period of 4.5 months. His physician was able to taper and discontinue atorvastatin, furosemide, and carvedilol. Four months after the start of the treatment program, the patient reported he had no chest pain, shortness of breath, fatigue, weakness, lightheadedness, or mental fog. One week later he reported increased fatigue, which improved by increasing his caloric intake. At his visit to the cardiologist 4.5 months after starting the program, blood pressure was 110/70 without medication, and his heart was in sinus rhythm.
Comment: This case report illustrates the potential for a plant-based, whole-foods diet to produced marked symptomatic and clinical improvement in patients with cardiovascular disease. The conversion of persistent atrial fibrillation to normal sinus rhythm is particularly noteworthy. It is possible that the improvement in some symptoms (such as fatigue and cognitive impairment) was due at least in part to a reduction and eventual discontinuation of medications. However, changes in his medication regimen were apparently possible only because of the initiation of the diet.
Beauchesne AB, et al. Exclusively plant, whole-food diet for polypharmacy due to persistent atrial fibrillation, ischaemic cardiomyopathy, hyperlipidaemia and hypertension in an octogenarian. BMJ Case Rep. 2018;11:e227059.
- Furbetta D, et al. Behavior of hydrochloric acid secretion in cardiopathies. JAMA. 1951;146:1615.
Published May 18, 2024
About the Author
Alan R. Gaby, MD, is the author of the textbook, Nutritional Medicine, which is now in its third edition (doctorgaby.com). He received his undergraduate degree from Yale University, his M.S. in biochemistry from Emory University, and his M.D. from the University of Maryland. He was in private practice for 19 years, specializing in nutritional medicine. Over the past 43 years, Dr. Gaby has developed a computerized database of more than 29,000 individually chosen medical journal articles related to the field of natural medicine. He was professor of nutrition and a member of the clinical faculty at Bastyr University in Kenmore, Washington, from 1995 to 2002.
He is past president of the American Holistic Medical Association and gave expert testimony to the White House Commission on Complementary and Alternative Medicine on the cost-effectiveness of nutritional supplements. He is the author of Preventing and Reversing Osteoporosis (Prima, 1994), The Doctor’s Guide to Vitamin B6 (Rodale Press, 1984), and co-author of The Patient’s Book of Natural Healing (Prima, 1999). He was Chief Science Editor for Aisle 7 (formerly Healthnotes, Inc.) and has appeared on the CBS Evening News and the Donahue Show.