June 8, 2015 | by Michelle Muller
Non-Alcoholic Fatty Liver Disease Epidemic?
The CBC recently reported that very few people are aware of the current non-alcoholic fatty liver disease (NAFLD) epidemic in our society, and many may unknowingly have it. Most people remain asymptomatic, unaware of the disease until it becomes symptomatic at the later stages. NAFLD comprises a spectrum of liver damage, from steatosis to steatohepatitis, advanced fibrosis and cirrhosis, and can result in liver disease, cancer, transplantation, death. NAFLD is a risk factor for metabolic syndromes, such as type 2 diabetes, and cardiovascular disease. A review in the World Journal of Hepatology describes it as the most frequent chronic liver disease and is prevalent in 20-40% of the population in western countries and 5-40% of the population across the Asia-Pacific region. NAFLD was first identified in the 1980s and the exact cause is still unknown.
The leading cause of NAFLD is believed to be due to poor diet and lack of movement/exercise, which has also been recently reported in The Guardian. Dr. Quentin Anstee, a consultant hepatologist at Newcastle University in the UK, explains how “there has been a shift in the entire population. The truth is that the man in the street is carrying a few more pounds than a decade ago. The rate of liver disease has increased 400% since the 1970s.”
The most effective treatment method is promoting lifestyle changes, including dietary modifications, weight loss, and exercise. A variety of drugs or supplements are used to address risk factors and metabolic disorders, and liver transplantation is an option for those with end-stage liver disease.
However, the high prevalence of NAFLD in the general population makes it difficult to even locate a donated liver organ that doesn’t already have this condition. This has prompted a team of doctors in Halifax to establish methods to “de-fat” a fatty liver after it is donated and before being transplanted. They are working on building a pump system to store organs and help them flush out fat through the bile ducts or blood vessels.
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Link to Other Diseases?
The increase of NAFLD and associated metabolic abnormalities correlates with increasing rates of obesity, diabetes, and cognitive impairment such as Alzheimer’s disease. The exact causes of Alzheimer’s are unknown, but growing evidence supports an association with metabolic and immune dysfunctions in the brain, such as diabetes and other peripheral insulin resistance disorders. Some researchers believe these disorders can cause brain insulin resistance via a liver-brain axis of neurodegeneration.
Researchers at Washington University School of Medicine recently uncovered a connection between Alzheimer’s and diabetes, describing a correlation between elevated blood sugar and increasing levels of amyloid beta, a key component of brain plaques in Alzheimer’s. Diabetes and other metabolic drugs are continuing to be researched to explore this connection further, which may lead to identifying drugs that can help alleviate some risk factors in NAFLD.
So Why the Major Increase in NAFLD?
Although no direct mechanism has been found, NAFLD has a high correlation with obesity, occurring in approximately 74% of obese individuals, but also occurs in 29% of lean individuals. Metabolic abnormalities associated with obesity also exist in up to 40% of individuals with normal body mass index – including symptoms of hypertension, hyperlipidaemia, NAFLD, visceral adiposity, and cardiovascular disease. NAFLD is associated with insulin resistance in 75% of patients and with diabetes in up to 50% of patients, not to mention an association with other metabolic and immune system dysregulations.
Previously this year, the Academy of Medical Royal Colleges published a “medical cure” that consists of doing moderate physical exercise for 30 minutes, five times a week. Although physical activity has enormous benefits, other medical professionals argue that physical activity levels haven’t changed significantly over the past 30 years, during which we have seen a dramatic increase in levels of obesity. These medical professionals believe the emphasis should be placed on the quality of food we consume and that “you cannot outrun a bad diet”.
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Considering the increasing prevalence of NAFLD and other metabolic and immune disorders, some medical professionals believe examining broader cultural and environmental influences may provide insight into the origins of these disorders.
Consumption of fructose has increased as much as 25% over the past 30 years, much of it “hidden” in processed goods. It is estimated that around 10% of dietary intake is fructose consumption for the average American, as high as 15% in at least one fourth of adolescents, and 10% of adults consume as much as 25% of their daily calories from added sugar. This March, the WHO has called on all countries to reduce sugar intake among adults and children to less than 10% of their total energy intake, even aiming for below 5% for additional health benefits. These recommendations were also made in 1989 and 2002 by the WHO Study Group.
Dietary sugar, including fructose and sucrose, is implicated as a factor driving the metabolic dysregulation underlying many metabolic syndromes associated with obesity, including coronary heart diseases, diabetes, and metabolic syndromes. The sugar intake in children and adolescents is of particular concern and regulating healthy energy intake has been shown to important in the prevention of NAFLD.
Studies in rats that assess the impact of high-fructose Western diets have found this promotes liver responses and gene expression pathways of NAFLD spectrum symptoms – even without any necessary weight gain. Overfeeding on carbohydrates has also been suggested as a risk factor for NAFLD, since carbohydrates stimulate lipogenesis, the conversion of acetyl-CoA to fatty acids in simple sugar metabolism.
Although there has been a well-established correlation of health disorders with increased sugar intake, there has been little to no policy addressing interventions of sugar consumption, though Mexico is the first country introduced a tax on sugar-filled beverages and the UK is also considering this policy.
Global policy solutions are being suggested by medical professionals and researchers that would address the obesity and diabetes pandemic on a macrolevel, and promote the building of wholesome living spaces and communities. This May, an article published in the Journal of the American Medical Association suggests policy strategies for food, nutrition, and agricultural sectors. These include: financial incentives for production and consumption of healthy foods and taxing unhealthy foods, marketing regulations to children, labelling policies, restricting sale of unhealthy foods in public spaces, making water more available, incentives to support supermarkets in low-income regions, and nutrition standards in food assistance programs and schools. Policies that change physical landscapes to promote physical activity are also recommended, especially for early child care settings, schools, and urban and rural community design.
Addressing socioecological factors and environmental forces that influence our culture and behavior are likely to have long term improvements in the overall health of individuals and prevent metabolic diseases such as NAFLD. However, prevention and treatment of widespread disease and cultural habits are beyond the scope of any one health care system, and will require participation from: research, government, food industry, health professionals, urban planners, media, nongovernmental organizations, communities, and individuals.
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Keywords: Cardiovascular Disease
, Alzheimer Disease
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