Mediterranean diet helps NAFLD

A recent review assessed the role of the Mediterranean diet for those with nonalcoholic fatty liver disease (NAFLD), finding that this diet decreased hepatic steatosis even without weight loss (see DOI: 10.1111/liv.13435​). For detailed prior assessments of NAFLD, see the array of blogs at http://blogs.bmj.com/bmjebmspotlight/?s=NAFLD&submit=Search .

Details:
-- NAFLD is remarkably common and the potential cause of significant liver-related morbidity and mortality. Also increase in overall mortality as well as risk of developing type II diabetes and cardiovascular disease
-- the main treatment of NAFLD at this point is through lifestyle interventions, especially weight loss in those overweight (though http://gmodestmedblogs.blogspot.com/2017/06/nature-vs-nurture-studies-on-lipids-and.html  highlights the significant incidence of NAFLD in lean individuals as well)
-- the Mediterranean diet (MD), one that has relatively high intake of plant-based foods (vegetables, fruits and nuts, legumes, whole grains, fish and seafood); low intake of dairy products, meat and meat products; moderate intake of alcohol; and a high ratio of monounsaturated saturated fats (especially with the high intake of olive oil is the main source of fat). This diet is in sharp contradistinction to the typical Western diet (e.g. fast foods, high fructose intake) which is associated with weight gain, insulin resistance, increased hepatic triglycerides, NAFLD, …
--Studies have found that the DASH diet, in many ways similar to MD, is associated with decreases in blood pressure, especially for those minimizing their salt intake. Of note, there are studies suggesting that blood pressure reduction itself decreases liver disease aggression in NAFLD, and salt intake is associated with increased risk for NAFLD. Also, the MD does encourage adequate rest and family meals, and NAFLD is also related to short sleep duration, poor sleep quality, and a tendency to OSA symptoms.
-- Adherence to MD is associated with lower serum ALT levels, insulin, severity of steatosis, and higher serum adiponectin levels (which also reflects higher insulin sensitivity). In addition, adherence to MD for 6 months is associated with improvement in the amount of liver fat on ultrasound, though there was no change in the serum ALT levels.
-- in terms of the individual components of the MD, and their potential effect on NAFLD:
    -- fish and seafood: omega-3 fatty acids have been shown to decrease lipid accumulation and liver enzyme levels, improve insulin sensitivity, and have anti-inflammatory effects; it been shown to decrease liver fat accumulation (the studies are a bit mixed on this), though has not been found to decrease nonalcoholic steatohepatitis or fibrosis. A Japanese study found a decrease in developing hepatocellular carcinoma.
    --olive oil: adding extra virgin olive oil (EV00) to a Mediterranean diet, vs adding corn oil, decreases blood glucose levels, DPP-4 activity and LDL levels, and increases GLP-1 and gastric inhibitory polypeptide levels. EVOO also leads to decreased oxidative stress through down-regulation of nitric oxide activation. It is not clear whether this action is mediated largely through monounsaturated fats (for which olive oil seems to be the prototype) or through the fact that the EVOO has higher amounts of polyphenols (over 30 of them have been identified in EV00), antioxidants, and phytochemicals that are lost when olive oil is refined
    -- fruits and vegetables: many studies have suggested benefit in prevention of cardiovascular disease, type II diabetes, and reducing all-cause and cardiovascular mortality. These are basically been observational studies where it is hard to tease out the exact role of diet conclusively (i.e., those eating more fruits and vegetables may be having other more healthful lifestyles as well). Fruits and vegetables also seem to be beneficial for weight loss, lower liver fat deposition, increased insulin sensitivity, and decreased visceral adiposity. Part of the benefit may be the decreased energy density of these foods, part by the array of antioxidants (polyphenols, carotenoids) in them. As noted in the innumerable blogs on the microbiome (see http://gmodestmedblogs.blogspot.com/search/label/microbiome , and in particular: http://gmodestmedblogs.blogspot.com/2016/03/microbiome-changes-and-severity-of-nafld.html ), diets high in vegetables create a more healthful gut microbiome, which in and of itself may be protective against NAFLD
    -- whole grains: there are many phytochemicals in whole grains as well as more fiber, which lead to reduced energy intake (being less energy dense than refined grains), modulation of the gut microbiota (prebiotic effects on the beneficial Bifidobacteria and Lactobacilli strains), increase some short chain fatty acids (e.g. butyrate, propionate) which have anti-inflammatory properties and insulin sensitizing effects, and increase some protective phytochemicals (e.g. betaine). No clinical data showing clear benefit, however.
    -- Red and processed meats: there are several observational studies suggesting that increased red or processed meat consumption is associated with NAFLD. Other studies have suggested increased risk of diabetes, cardiovascular and all-cause mortality, though more evident with processed meats. Part of this association may be related to higher levels of sodium, especially in processed meats, and its effect on blood pressure. Part of it may be related to saturated fats, advanced glycation end products, nitrates/nitrates, heme iron, and branched-chain amino acids. As an aside, see blog http://gmodestmedblogs.blogspot.com/2014/08/lung-microbiome.html /  which found that eating red meat leads to changes in the microbiome, so that the red meat in the presence of this altered microbiome produces TMAO, a well-documented atherogen.
    -- alcoholic beverages: one component of the MD is moderate alcohol consumption (one glass per day for women and 2 glasses per day for men, with meals). Studies have found that episodic heavy drinking is associated with fibrosis progression in patients with NAFLD. Some studies have shown a protective effect of moderate alcohol consumption in NAFLD. However, see blog http://gmodestmedblogs.blogspot.com/2015/02/moderate-alcohol-and-cardioprotection.html  ,which suggests that there might be important confounders, and that there may be no real "protective effect" of moderate alcohol consumption.

So,
--The Mediterranean diet overall seems to be a reasonable one, and has been recommended by several European agencies for NAFLD (eg, it is promoted by the EASL-EASD-EASO Clinical Practice Guidelines). There are suggestive data finding that this diet decreases NAFLD comorbidities, and limited data on prevention of type II diabetes, and cardiovascular disease. Overall, I think it is important to avoid too much reductionism here: it may well be that the effects of a Mediterranean diet overall is different from the effects of its individual components. For example, the fact that increasing omega-3 fatty acids does not seem to have a profound effect by itself on NAFLD does not necessarily mean that it has minimal or no effect in its combination with other components of the Mediterranean diet….
-- One of the big challenges in nutrition counseling is trying to promote healthful diets which are congruent with the cultural background and eating habits of the patient. My guess is that simply giving the patient a Mediterranean diet handout probably does nothing. The real issue with diet, as well as other lifestyle changes, is the motivational interviewing/patient-centered approach of understanding specifically what the patient eats and then assessing the potential for modification in ways that are more congruent with a Mediterranean diet.