Issue 128 nafld nutrition and lifestyle choice

CONDITIONS & DISORDERS

NON-ALCOHOLIC FATTY LIVER DISEASE (NAFLD): NUTRITION AND LIFESTYLE ADVICE Dr Laura Wyness Registered Nutritionist Laura is a Nutrition Consultant providing research and communication services to a variety of sectors, including charities, commercial companies and local authorities. www. laurawyness.com

For full article references please email info@ networkhealth group.co.uk

Until recently, NAFLD was considered to be quite rare and harmless. For most people, a fatty liver can remain free of inflammation and asymptomatic.

However, there seems to be an increasing number of people with NAFLD due to the rising obesity figures.

Individuals who have had a fatty liver for some time are more likely to develop inflammation causing scarring (or fibrosis). In these people, this can progress to potentially life-threatening liver cirrhosis. So, how prevalent is NAFLD? Who is at risk? What diet and lifestyle advice is appropriate?

WHAT DOES THE LIVER DO?

The liver is involved in around 500 different reactions in the body. These include filtering and cleaning the blood; fighting infections; producing bile which helps digest fats; storing glycogen and some vitamins and minerals; producing and maintaining the balance of hormones, enzymes and proteins; and getting rid of waste substances from the body. It has the unique ability to repair itself, although it can sometimes be damaged beyond repair.

WHAT IS FATTY LIVER?

Fatty liver occurs when too much fat builds up in liver cells. Although it is normal for liver cells to contain a small amount of fat, more than about 5% fat is considered too much. Liver disease is often associated with drinking too much alcohol. Excessive alcohol can result in a build-up of fat in the liver. However, fatty liver in people who drink within the alcohol guidelines is known as nonalcoholic fatty liver disease (NAFLD).

This is a disease that is quietly becoming more prevalent and poses an increasing threat to public health.

It is estimated that NAFLD affects 25% of people globally.1 The UK NICE

guidelines state that about two to three people in every 10 have NAFLD.2 Prevalence has doubled over the past 20 years due to the rise in obesity levels, mainly as a result of sedentary lifestyle and poor diet.3,4 NAFLD is now the commonest cause of abnormal liver function test results in the UK and the commonest cause of liver disease in western countries.3 NAFLD develops in four stages (see Table 1) with the first being simple fatty liver or steatosis. Too much fat in lever cells is caused by an accumulation of triglycerides. There are few, if any, symptoms in the early stages of NAFLD, so it often goes unnoticed. For many people, fatty liver does not develop further and can be reversed with a healthy diet and lifestyle. However, for some, fatty liver develops into nonalcoholic steatohepatitis (NASH) or fibrosis. The cause of progression from NAFLD to NASH remains unclear and researchers have estimated that approximately 20% of those with prolonged simple fatty liver will go on to develop NASH and fibrosis.5 NASH, which is thought to affect up to 5% of the UK population,6 occurs when the build-up of fat in the liver cells is accompanied with inflammation.

Inflammation occurs as part of the process of repairing damaged tissue. If left unchecked, the liver may eventually not be able to regenerate fast enough and the inflammation tissue can remain as a scar. This is known as fibrosis and can take a variable amount of time, sometimes several years, to develop. www.NHDmag.com October 2017 - Issue 128

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CONDITIONS AND DISORDERS Table 1: The four stages of NAFLD Stages

Description

Steatosis or simple fatty liver

Fat accumulation in the liver cells, although there is no inflammation or scarring. As symptoms are often not present, fatty liver remains undetected in many people.

NASH (nonalcoholic steatohepatitis)

The liver becomes inflamed. Symptoms often do not occur, but if they do, they can include a dull ache or discomfort over the lower right side of the ribs, fatigue, unexplained weight loss and weakness.

Fibrosis

Persistent inflammation causes scar tissue around the liver and nearby blood vessels.

The liver still functions normally.

Cirrhosis

The liver shrinks and becomes scarred and lumpy. The damage is permanent and can lead to liver failure and liver cancer. Symptoms include yellowing of the skin and whites of the eyes, itchy skin and swelling in the legs, ankles, feet or stomach.

Table 2: Risk factors for NAFLD Overweight or obese Visceral adiposity (excess belly fat) Rapid weight loss (e.g. following gastric bypass surgery) Type 2 diabetes or family history of Type 2 diabetes Aged over 50 years High blood pressure High cholesterol Smoking Poor diet Sedentary lifestyle

Cirrhosis is the most severe stage of NAFLD. This occurs when the persistent inflammation and scaring causes permanent damage and reduced function of the liver. This can lead to liver failure and liver cancer.

RICK FACTORS OF NAFLD

As NAFLD is often asymptomatic in the early stages, diagnosis is often a result of routine blood tests for liver function. Although NAFLD can be found in non-obese individuals, obesity is a major risk factor for developing NAFLD.7 Estimates suggest that 30-90% of obese adults have NAFLD.8 NAFLD is increasingly prevalent amongst children, with over a fifth of four- to five-year-olds and a third of 10- to 11-year-olds being overweight or obese.9 Visceral adiposity, or excess belly fat, is also a recognised risk factor.10 Some of the main risk factors for NAFLD are shown in Table 2. In terms of diet, a high intake of refined carbohydrates and sugar-sweetened drinks can contribute to

the development of fatty liver.11 Recent research also suggests that poor gut health may also contribute to the development of NAFLD.12,13 DIETARY ADVICE

As there is no effective drug therapy for NAFLD, diet and lifestyle modifications are the main prevention and treatment options. Dietary advice for NAFLD is generally similar to the advice for obesity and metabolic syndrome. For overweight and obese individuals, gradual weight loss along with increased physical activity can help reduce the amount of fat in the liver. A rapid weight loss, using a very low calorie diet, should be avoided due to the risk of worsening liver inflammation.3 The Mediterranean diet has shown to be particularly beneficial in NAFLD patients. The main beneficial factors of this diet includes plenty of plant-based foods and wholegrains, beneficial fatty acids and polyphenols.14 The classic Mediterranean diet consists of plenty of fruits, vegetables, grains, nuts, moderate www.NHDmag.com October 2017 - Issue 128

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CONDITIONS & DISORDERS

There is a need for more awareness and understanding of NAFLD amongst both healthcare professionals and the general public.

amounts of dairy and fish, small amounts of meat, and predominantly unsaturated fats rather than saturated fats. Evidence shows that this dietary pattern can reduce fatty liver and improve insulin sensitivity in insulin-resistant individuals with NAFLD.15 A recent meta-analysis that examined the evidence on the optimal diet composition, reported that both moderate-carbohydrate (<45% of daily energy intake) and low/moderate fat (<30% of daily energy intake) diets can equally improve liver function.16

the body. Excess fructose is associated with hepatic steatosis, cellular stress and inflammation.19 Fructose syrups or sugar containing fructose and glucose is widely added to fizzy drinks, fruit juices, jams and sweets. A recent study of 271 obese children found that fructose consumption was independently associated with non-alcoholic steatohepatitis (NASH).20 Fructose also increases serum uric acid concentrations which is linked with the development of gout, coronary artery disease, Type 2 diabetes metabolic syndrome and NAFLD.21

FAT

PROTEIN

In terms of fat, including foods high in monounsaturated fatty acids (such as olive oil, rapeseed oil, nuts and avocados) may be particularly beneficial in promoting liver fat loss.4 Long-chain omega-3 fatty acids are known for their beneficial effects in cardiovascular disease, stroke and diabetes and evidence has also shown reductions in lipid accumulation, improved insulin sensitivity and anti-inflammatory effects,17,18 which has increased interest in the benefits of omega-3 in treating NAFLD. The optimal dose of omega-3 supplementation or oily fish consumption for managing NAFLD is uncertain, as further high quality, and larger RCTs are required. Consuming the recommended two portions of fish a week, one of which is an oily fish, will help provide the beneficial long-chain omega-3 fatty acids.

CARBOHYDRATE

Carbohydrates are an important part of a healthy diet as they provide energy, fibre and a range of nutrients essential for the body. There is good evidence to show that diets low in refined carbohydrates can help reverse NAFLD. Excess carbohydrates in the diet are converted into fat and accumulate in the liver. This occurs at a higher rate with high intakes of dietary fructose.

The liver is the only organ that can metabolise fructose, whereas glucose is metabolised widely in 40

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The impact of the amount and type of protein on the development and treatment of NAFLD is not clear. Some animal studies have suggested that supplementation with the amino acids tryptophan, glutamine or L-carnitine may have a protective effect against developing NAFLD, but further studies conducted in humans is required.22 VITAMIN E

The antioxidant activity of vitamin E is thought to be particularly beneficial in protecting against oxidative stress apparent in fatty liver disease progression.

American Gastroenterological Association guidelines suggest the use of 800IU/ day of vitamin E in non-diabetic patients with NASH.6 However, the evidence is not strong enough to support the use of vitamin E to treat NASH in diabetic patients, NASH cirrhosis or in NAFLD. COFFEE

Coffee appears to confer a number of protective effects relating to liver disease. A meta-analysis of nine studies investigating coffee consumption and cirrhosis concluded that an increase in daily coffee consumption of two cups is associated with almost halving the risk of cirrhosis.23 A recent systematic review and meta-analysis investigating the effect of coffee on NAFLD found a significantly decreased risk of NAFLD among

The incidence of NAFLD has significantly increased in recent years with around one in four people in the UK currently living with NAFLD.

coffee drinkers and a significantly decreased risk of liver fibrosis among patients with NAFLD who drank coffee on a regular basis.24 It is unclear whether such benefits to the liver are due to the caffeine or the other constituents found in coffee, such as cafestol and kahweol, or the range of antioxidants. Consuming regular and moderate amounts (three to five cups a day) of filtered unsweetened coffee, along with following other recommended diet and lifestyle advice, appears to be beneficial for those with NAFLD. Measureable benefits to the liver were also recently found in frequent coffee drinkers in the general population in the large Rotterdam cohort study.25 POTENTIALLY BENEFICIAL DIETARY FACTORS

Current evidence suggests that gut microbiota plays an important role in fatty liver, fibrosis and insulin resistance. A systematic review of three randomised controlled trials investigating the effects of different probiotic and/or prebiotic formulations in adults with NAFLD, did not find sufficient evidence to support their use in treating NAFLD.26 Further research is needed to explore the links between gut microbiota and NAFLD. Several medicinal herbs may have potential benefits for the management of NAFLD. These include milk thistle and Tamarindus indica Linn. A Cochrane review of 77 RCTs with a total of 6,753 participants with fatty liver disease explored evidence relating to 75 different herbal products. The reviewers concluded that herbal medicines may have beneficial effects on fatty liver disease, but the evidence is insufficient to recommend them to individuals with NAFLD.27 GENERAL LIFESTYLE ADVICE

A recent meta-analysis of 20 RCTs found that exercise alone, or in combination with dietary intervention, improves serum levels of liver enzymes and liver fat.16 For the greatest benefit, a healthy diet needs to be coupled with regular physical activity. A combination of aerobic

activity and strength exercises as set out in the UK Governmentâ&#x20AC;&#x2122;s physical activity guidelines is likely to benefit liver health.

The liver works hard to rid the body of toxins.

Smoking is thought to have a detrimental effect on the liver through a variety of mechanistic pathways, including insulin resistance, cell death and oxygen deficiency. Evidence suggests that both active and passive smoking is likely to put extra stress on the liver and may aggravate and accelerate the progression of NAFLD.28,29 Although NAFLD is not caused by alcohol, drinking may make the condition worse. For example, alcohol can increase the progression of liver damage in individuals with NASH. Advice related to NAFLD from the NHS is to cut down or stop drinking alcohol.30 SUMMARY

There is a need for more awareness and understanding of NAFLD amongst both healthcare professionals and the general public.

The incidence of NAFLD has significantly increased in recent years with around one in four people in the UK currently living with NAFLD. The main reason for this increase is the rise in obesity, which is mainly due to the populationâ&#x20AC;&#x2122;s sedentary lifestyle and poor diet.

There is currently no specific drug treatment for NAFLD. However, a combination of dietary modifications and increased physical activity can be effective in reducing the risk and slowing the development of NAFLD. NAFLD is largely preventable and in the early stages, it can be reversed. Therefore, it is important that the general public are more aware of the impact that diet and lifestyle has on their liver health.

Relevant advice from healthcare professionals on healthy eating, as described in this article, along with advice on maintaining a healthy weight, exercising regularly, cutting down or not drinking alcohol and not smoking will help reduce the prevalence of NAFLD amongst the population. www.NHDmag.com October 2017 - Issue 128

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