Olive Oil and Non-Alcoholic Fatty Liver

 

   The liver plays a crucial role in lipid metabolism, which involves the processes of synthesis, storage, and utilization of fats in the body. As we get older, the liver can undergo some changes. Blood flow to the liver might decrease, making it harder for liver cells to get oxygen and nutrients. The liver can also shrink in size, affecting its ability to process drugs and get rid of harmful substances. The liver's ability to repair itself may slow down, and changes in fat metabolism can increase the risk of liver disorders. Aging can also impact how the liver processes medications, potentially leading to more side effects. There is also a higher risk of liver fibrosis, where too much scar tissue forms in the liver due to inflammation, possibly leading to more severe liver problems.

 

    Non-alcoholic fatty liver disease is a fast-growing condition of the liver, where more than 5% of the liver is filled with fat. Non-alcoholic fatty liver disease is a condition that is commonly associated with aging, where excess fat accumulates in the liver of individuals who drink little to no alcohol. Mild cases are not life-threatening, but without treatment, they can progress to more severe stages like non-alcoholic steatohepatitis, leading to inflammation, liver injury, cirrhosis, and sometimes liver cancer. Non-alcoholic fatty liver disease is often associated with conditions such as obesity, type 2 diabetes, insulin resistance, and high blood fats.

 

    A lot of evidence, especially from studies on large groups of people, highlights the health benefits of the Mediterranean diet for health. Olive oil, a key part of this diet, is thought to be a functional food because it's rich in mono-unsaturated fatty acids and contains bioactive compounds like polyphenols, which are antioxidants with various health effects.

 

    Similar to the positive effects of the Mediterranean diet, studies show that consuming olive oil is linked to lower rates of cardio-metabolic diseases and certain cancers. It's been particularly noted for protecting against obesity, diabetes, cardiovascular issues, and other metabolic diseases. One group of researchers studied the impact of olive oil, canola oil, or soybean/safflower oil (as a control) on men with non-alcoholic fatty liver disease and found improvements in the severity of fatty liver, insulin resistance, and lipid profile (1).

 

    This randomized, double-blind, clinical trial was conducted on 66 patients with non-alcoholic fatty liver disease. Patients were divided to receive either olive or sunflower oil, each 20 g/day for 12 weeks. A hypocaloric diet (-500 kcal/day) was recommended to all participants (1).

 

    Fatty liver grade, weight, waist circumference, and blood pressure significantly decreased in both groups. Sunflower oil significantly reduced serum aspartate and alanine aminotransferases and olive oil only decreased serum aspartate aminotransferase. Fat-free mass and skeletal muscle mass significantly reduced after the consumption of sunflower oil and serum triglycerides and fat mass significantly declined after the ingestion of olive oil. Among these variables, only changes in fatty liver grade (-0.29 ± 0.46 in sunflower oil versus -0.75 ± 0.45 in olive oil; p < 0.001), skeletal muscle mass (-0.71 ± 1.36 in sunflower oil versus +0.45 ± 2.8 in olive oil; p = 0.04), and body fat percentage (+0.38 ± 5.2% in sunflower oil versus -3.4 ± 5.5% in olive oil; p = 0.04) were significantly different between the groups (1).

 

    This study showed that olive oil may reduce the severity of fatty liver. Low-calorie diets may benefit patients with non-alcoholic fatty liver disease additionally through mitigation of obesity, blood pressure, and liver enzymes (1).

 

    It is important to note from the results of this study (1) that olive oil led to a notable drop in body weight, waist circumference, fat mass, and body fat percentage. In contrast, sunflower oil caused a significant decrease in fat-free mass and skeletal muscle mass. This resulted in significant differences between the two groups in terms of skeletal muscle mass (p = 0.04) and body fat percentage (p = 0.05). Maintaining muscle mass can be a challenge in weight loss diets, so the fact that olive oil helps preserve muscles while promoting fat loss is quite valuable.

 

    Coronary artery disease is a major cause of death in people with non-alcoholic fatty liver disease. Studies have found a strong connection between increased aminotransferase levels and fat buildup in the liver, leading to heart complications. One study investigated how virgin olive oil affects liver enzymes and fat accumulation in non-alcoholic fatty liver disease patients on a weight-loss diet (2).

 

    This study involved 50 non-alcoholic fatty liver disease patients (average age 45.91 ± 9.61 years, average BMI 29.7 ± 0.58 Kg/m2). They were randomly divided into two groups: the olive oil group (received 20% of their daily energy from olive oil) and the control group (normal oil consumption) for 12 weeks. All patients followed a reduced-calorie diet. ALT and AST enzyme levels and liver fat were measured at the beginning and end of the study (2).

 

    The control group showed a significant decrease in ALT levels at the end of the study (p = 0.004). In the olive oil group, both enzymes decreased compared to the start (p < 0.01). There were significant differences in ALT and AST levels between the two groups (p < 0.02). The severity of liver fat did not change significantly during the study. This study showed that a low-calorie diet enriched with olive oil, combined with modest weight loss, enhances the positive effects of weight loss by improving hepatic enzyme levels (2).

 

    One study investigated the effects of dietary intervention with canola or olive oil in comparison with commonly used refined oil in Asian Indians with non-alcoholic fatty liver disease. This 6-month intervention study included 93 males with non-alcoholic fatty liver disease, matched for age and body mass index (BMI). Subjects were randomized into three groups to receive olive oil (n=30), canola oil (n=33), and commonly used soybean/safflower oil (control; n=30) as cooking medium (not exceeding 20 g/day) along with counseling for therapeutic lifestyle changes. Various health indicators were measured before and after the 6-month intervention (3).

 

    Results showed that olive oil led to a significant decrease in weight (77.8± 7.9 to 72.8± 7.5 kg) and BMI (27.3± 2.4 to 25.6 ± 2.3) compared to the control oil group (weight: 79.8 ± 9.1 to 78.2 ± 8.3 kg, and BMI: 27.4 ± 2.7 to 27.4 ± 2.5, p <0.05). When comparing olive and canola oil, olive oil showed a significant decrease in insulin levels (8.1± 2.0 to 3.0 ± 1.8  mcU/ml), insulin resistance, and other related measures. Canola oil, on the other hand, led to a significant increase in high-density lipoprotein (HDL) and decreases in fasting blood glucose (91.9 ± 13.7 to 84.0 ±11.7 mg/dL) and triglyceride levels (186.6 ± 58.2 to 154.6 ± 48.7 mg/dL) (3).

 

    In the olive and canola oil groups, post-intervention grading of fatty liver was reduced significantly (grade I, from 73.3% to 23.3% and from 60.5% to 20%, respectively [p<0.01]; grade II, from 20% to 10% and from 33.4% to 3.3%, respectively [p<0.01]; and grade III, from 6.7% to none and from 6.1% to none, respectively). In contrast, in the control oil group, no significant change was observed. These results suggested significant improvements in a reduction in fatty liver grading, liver span, insulin resistance, and lipids with the use of canola and olive oil compared with control oils in Asian Indians with non-alcoholic fatty liver disease (3).

 

    One study showed that 12 weeks of high mono-unsaturated fatty acid or fiber-rich weight-maintenance diet could lower hepatic fat content and improve glucose tolerance in people with prediabetes. The subjects (n=43) were randomized into three isocaloric weight-maintaining diets containing mono-unsaturated fatty acid (olive oil), extra fiber, and standard US food (control-habitual diet). Body weight was maintained constant in all groups during the intervention. Glucose and hormonal concentrations were similar in all groups before, and unchanged after, 12 weeks of intervention (4).

 

    The liver fat fraction was significantly lower after intervention in the mono-unsaturated fatty acid group (9.7% ± 2.8% vs 8.0% ± 2.5%; p < 0.0003), but remained unchanged in the fiber group (6.9% ± 1.1% vs 6.3% ± 1.0%; p = 0.25) and the control group (11.2% ± 2.5% vs 11.9% ± 2.7%; p = 0.45). After 12 weeks, the liver fat fraction was significantly lower in the mono-unsaturated fatty acid group than in the control group (p = 0.01), but fiber and control groups did not differ (p = 0.41). Indices of insulin action and secretion were not significantly different between the mono-unsaturated fatty acid group and control groups after the intervention, but within-group comparison showed higher hepatic (p = 0.01) and total insulin sensitivity (p < 0.04) with mono-unsaturated fatty acid (4).

 

    Researchers studied the impact of three diets on liver fat in individuals at high cardiovascular risk. The diets included a Mediterranean diet with extra-virgin olive oil, a Mediterranean diet with nuts, and a control diet advising to reduce all dietary fat. No weight loss or increased physical activity recommendations were given (5).

 

    The study involved 100 men and women with an average age of 64, and 62% had type 2 diabetes. After three years, liver steatosis (accumulation of fat in the liver) was present in 8.8%, 33.3%, and 33.3% of participants in the Mediterranean diet with extra-virgin olive oil, Mediterranean diet with nuts, and control diet groups, respectively (p=0.027). The corresponding mean values of liver fat content were 1.2%, 2.7%, and 4.1% (p=0.07). The Mediterranean diet with the extra-virgin olive oil group showed a tendency toward significance in reducing liver fat compared to the control group (5).

 

    The study concluded that a Mediterranean diet supplemented with extra-virgin olive oil, known for its antioxidant and anti-inflammatory properties, was associated with a lower prevalence of liver steatosis in older individuals at high cardiovascular risk (5).

 

    Olive oil is often considered a healthy fat, and it can have positive effects on liver health. It contains monounsaturated fats, and it is rich in antioxidants, such as vitamin E and polyphenols, which can help protect the liver from oxidative stress. The anti-inflammatory properties of olive oil may also contribute to its positive impact on liver health.

 

    These studies have suggested that consuming olive oil may help prevent or manage non-alcoholic fatty liver disease. Olive oil could reduce the grade of fat accumulation in the liver and liver enzyme levels and improve insulin sensitivity, and it was associated with reducing the risk of liver disease and other health conditions such as obesity, diabetes, and cardiovascular disease. Consuming olive oil in moderation can be part of a balanced diet for better liver health.

 

References:

1. Rezaei S, Akhlaghi M, Sasani MR, Barati Boldaji R. Olive oil lessened fatty liver severity independent of cardiometabolic correction in patients with non-alcoholic fatty liver disease: A randomized clinical trial. Nutrition. 2019 Jan;57:154-161. doi: 10.1016/j.nut.2018.02.021. Epub 2018 Mar 23. PMID: 30170304.

2. Shidfar F, Bahrololumi SS, Doaei S, Mohammadzadeh A, Gholamalizadeh M, Mohammadimanesh A. The Effects of Extra Virgin Olive Oil on Alanine Aminotransferase, Aspartate Aminotransferase, and Ultrasonographic Indices of Hepatic Steatosis in Nonalcoholic Fatty Liver Disease Patients Undergoing Low Calorie Diet. Can J Gastroenterol Hepatol. 2018 Apr 17;2018:1053710. doi: 10.1155/2018/1053710. PMID: 29850450; PMCID: PMC5932499.

3. Nigam P, Bhatt S, Misra A, Chadha DS, Vaidya M, Dasgupta J, Pasha QM. Effect of a 6-month intervention with cooking oils containing a high concentration of monounsaturated fatty acids (olive and canola oils) compared with control oil in male Asian Indians with nonalcoholic fatty liver disease. Diabetes Technol Ther. 2014 Apr;16(4):255-61. doi: 10.1089/dia.2013.0178. PMID: 24625239.

4. Errazuriz I, Dube S, Slama M, Visentin R, Nayar S, O'Connor H, Cobelli C, Das SK, Basu A, Kremers WK, Port J, Basu R. Randomized Controlled Trial of a MUFA or Fiber-Rich Diet on Hepatic Fat in Prediabetes. J Clin Endocrinol Metab. 2017 May 1;102(5):1765-1774. doi: 10.1210/jc.2016-3722. PMID: 28323952; PMCID: PMC5443322.

5. Pintó X, Fanlo-Maresma M, Corbella E, Corbella X, Mitjavila MT, Moreno JJ, Casas R, Estruch R, Corella D, Bulló M, Ruiz-Canela M, Castañer O, Martinez JA, Ros E; PREDIMED Study Investigators. A Mediterranean Diet Rich in Extra-Virgin Olive Oil Is Associated with a Reduced Prevalence of Nonalcoholic Fatty Liver Disease in Older Individuals at High Cardiovascular Risk. J Nutr. 2019 Nov 1;149(11):1920-1929. doi: 10.1093/jn/nxz147. PMID: 31334554.

 

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