NAFLD is the most common cause of liver disease worldwide and research suggests the number of cases will climb given an increasing trend toward higher fat diets, obesity, decreased physical activity, and a rise in diabetes. Past studies indicate that more than 30 million Americans have NAFLD and approximately 8 million may have nonalcoholic steatohepatitis (NASH).
In the first study, Ramón Bataller, M.D., and colleagues from the Hospital Clínic in Barcelona, Spain investigated the effects of cigarette smoking (CS) in obese rats. Rats were divided into 4 groups (n=12 per group): obese smokers, obese non-smokers, control smokers and control non-smokers. Smoker rats were exposed to 2 cigarettes/day, 5 days/week for 4 weeks. Researchers found that obese rats exposed to CS showed a significant increase in ALT serum levels (indicating liver disease), while this effect was not observed in control rats.
“Our results show that CS causes oxidative stress and worsens the severity of NAFLD in obese rats,” said Dr. Bataller. “Further studies should investigate longer exposures to CS, and assess whether this finding also occurs in patients with obesity and NAFLD.”
In her editorial, also published in Hepatology this month, Claudia Zein, M.D., from the Cleveland Clinic, noted that “the importance of these results is that taken together with other experimental and clinical data, they support that cigarette smoking appears to aggravate liver injury in patients with liver disease.” Dr. Zein added, “Studies characterizing the effects of cigarette smoking in human NAFLD will be crucial because of the vast number of patients that may benefit from modification of this risk factor.”
Additionally, prior studies suggest an over consumption of high fructose corn syrup (HFCS), primarily in the form of soft-drinks, have contributed to weight gain and the rise in obesity, particularly in children and adolescents. Table sugar (sucrose) and HFCS are the two major dietary sources of fructose. Over the past 40 years, consumption of dietary fructose has increased 1,000% according to Bray et al, and doctors believe it to be a major cause of NAFLD.
Researchers from Duke University studied 341 adults enrolled in the NASH Clinical Research Network who responded to a Block food questionnaire within 3 months of a liver biopsy. Fructose consumption was estimated conservatively by including that found in beverages, which accounts for 50% of dietary fructose intake. Results showed that 27.9% of participants consumed at least 1 fructose-containing beverage per day, 52.5% had 1 to 6 beverages with fructose per week, and 19.7% drank no beverages with fructose.
“In patients with NAFLD, daily fructose ingestion was associated with reduced fatty liver (steatosis), but we found increased fibrosis,” noted Manal Abdelmalek, M.D., M.P.H, and lead author of the study. “Further dietary intervention studies are needed to evaluate whether a low-fructose diet improves metabolic disturbances associated with NAFLD and improves patient outcomes for those at risk of disease progression,” concluded Dr. Abdelmalek.
A second fructose study led by Ling-Dong Kong, M.D., from Nanjing University in China investigated the effects of curcumin on fructose-induced hypertriglyceridemia and fatty liver in rats. Curcumin, a compound derived from turmeric (curcuma root), is sold as an herbal supplement and is believed to have anti-inflammatory, anti-tumor, and anti-viral properties. Researchers observed a hyperactivity of hepatic protein tyrosine phosphatase 1B (PTP1B), which is associated with defective insulin and leptin signaling, in fructose-fed rats.
For the first time this study demonstrated that curcumin inhibited hepatic PTP1B expression and activity in fructose-fed rats. “Our results provide novel insights into the potential therapeutic mechanisms of curcumin on fructose-induced hepatic steatosis associated with insulin and leptin resistance,” said Dr. Kong.
These studies indicate modifying risks such as smoking and fructose consumption offer potential benefits for those with liver diseases. Further studies are needed to explore these benefits in preventing the progression of liver disease.
Q: What evidence is there that diet can make a difference?
A: As an Accredited Practising Dietitian the advice I give has to be scientifically based. Recommended dietary allowances are set for a population group and includes sub-sectors like infants, children and the elderly.
Dietary advice is often based on epidemiological research that is carried out by public health scientists. It is this kind of research, for example that has suggested the value of the Mediterranean diet in reducing the risk of heart disease and cancer. Another example is selenium. Research suggests that this is a mineral influential in improving our immune systems but also indicates that, given its toxicity level, taking a selenium supplement can’t normally be recommended.
People who consume a varied diet tend to have a wider nutritional profile, and therefore are more likely to achieve recommended nutrient intakes. It is important that no foods are portrayed as good or bad, all foods can be consumed in moderation and food choices should be put in context with an individual’s lifestyle.
Whatever condition you’re treating a patient for, once their basic nutritional needs have been met, research suggests that the biggest difference diet can make will be in relation to weight control. It’s down to mathematics. However, what we need can differ. If you’re in your 20s you may have a different level of physical activity from when you’re in your fifties and therefore your requirements will be different. Normal body weight with a slight increase with age appears to be the most beneficial to health and longevity.
Q: Is there any new evidence emerging, which doctors should be aware of?
A: Because diet is part of the treatment programme for diabetes it is sometimes assumed that diet (sugar intake) causes diabetes. However the idea that sugar causes diabetes/heart disease was dismissed as long ago as 1989. A number of more recent, international expert committees have come to the same conclusion. A very recent report shows no association of sugars or total carbohydrate intake on the risk of cardiovascular disease. Obesity and lack of exercise appear to be the main risk factors.
Modest intakes of alcohol have been shown to increase protective HDL cholesterol levels. Those with an increased risk of CHD are recommended to consume alcohol regularly in small quantities, 1-2 units a day for men and women. However, binge drinking is certainly not recommended. Only modest amounts of alcohol should be included in the diets of patients with hypertriglyceridaemia and sometimes-total alcohol avoidance is advised.
Epidemiological evidence is quite clear that communities with a higher intake of fruit and vegetables have a lower incidence of heart disease and cancer.
Pregnant women need a supplement of folic acid before and throughout pregnancy to reduce the risk of neural tube defects.
Prospective cohort studies have shown that a high consumption of plant-based foods is associated with significantly lower risk of coronary artery disease and stroke. The protective effects are thought to be due to beneficial nutrients within the foods, for example, n-3 fatty acids. A healthy plant-based diet should include unsaturated fat as the predominant form of dietary fat. Animal products may be included, such as fish, poultry and low-fat dairy.
Q: Doctors are busy professionals, usually with a range of commitments. What are the things they are most likely to miss out on, as far as diet is concerned?
A: Lack of regular meals is probably the most important factor here. If you eat three meals a day you’ll normally eat a wider variety of foods and will be less likely to graze on fatty foods.
One meal you commonly miss out on if you’re busy is breakfast. Research here is absolutely clear – people who have breakfast cereal tend to be thinner and have a higher nutritional intake.
If you’re very busy you may also end up eating late at night, so have less control over what you eat because you’re hungry. You’ll eat pretty much anything.
If there’s a canteen at work you could end up eating two dinners a day and over consuming.
You may eat more convenience foods and miss out on fruit and vegetables and women doctors may not eat enough calcium and iron rich foods.
Q: What would you suggest to counteract this?
A: Breakfast is the most important meal of the day. Healthy breakfast options include wholemeal bread/toast, breakfast cereal with low fat milk, fresh fruit, fruit juice, tea or coffee.
Research suggests a higher intake of cereals and grains, such as whole wheat and rye, are associated with a lower incidence of cardiovascular disease. People who eat breakfast are also less likely to be overweight.
Fortified cereals can be a significant source of minerals and vitamins – for instance calcium which is essential for bone development. Folic acid is highly recommended to pregnant women or women planning a pregnancy, as it is proven to prevent neural tube defects. And iron which is particularly important for women of menstruation age.
No matter how busy you are, aim to eat three meals a day and have fruit or juice with each meal. Avoid high density energy snacks.
Contrary to popular belief, carbohydrates are not fattening and in general are either fat free or very low in fat. Recent research has shown that a higher cereal fibre intake in adults aged 65 years and over is associated with lower risk of CVD with the lowest risk appearing to be related to intake of dark breads, such as whole wheat, rye and pumpernickel. Meals should therefore be based around carbohydrate foods. This would include the use of high fibre breakfast cereals especially porridge, brown breads, potatoes, pasta, rice, noodles and pitta bread.
If you eat at the canteen then have a wrap or sandwich at lunch and dinner in the evening, or vice versa.
If you live on your own, plan ahead. Online supermarket shopping can be very helpful here. You can plan a balanced diet for the week ahead, order it online and get it all delivered at one go. Also consider bulk cooking and freezing individual portions to ensure healthy options are readily available especially on those particularly busy, stressful days.
Q: So what is a balanced diet?
A: A well balanced diet is one that provides the body with enough energy, and all the nutrients required in their correct amounts to prevent illness and disease. However, how you translate this into food terms is quite difficult.
The biggest difference diet makes to health is through weight control. If you are maintaining your weight over a period of time then your energy intake is matching your energy output. However, if your weight is increasing slowly over a period of a year then you are eating more than your body actually needs. In reverse, if you are underweight then you are not eating enough food to meet your body’s needs. Most diet related problems are associated with weight, either the risk factors associated with obesity, or the health factors associated with anorexia.
People who consume a varied diet tend to have a wider nutritional profile, and therefore are more likely to achieve recommended nutrient intakes.
A diet high in saturated fat will raise blood cholesterol levels in individuals who have a genetic predisposition for raised cholesterol and most people won’t know whether or not they are genetically predisposed. In some individuals, a low saturated diet is sufficient to control blood cholesterol levels. In others, medication is required.
A low fibre diet is associated with cancer of the bowel, constipation and other bowel disorders
Low intake of fruit and veg is associated with higher incidence of cancer and heart disease.
It is important that no foods are portrayed as good or bad, all foods can be consumed in moderation and food choices should be put in context with an individual’s lifestyle.
The main keys to good health are:
- Be a good weight. Obesity is a major risk factor for type 2 diabetes and can also induce raised blood pressure. Combined with type 2 diabetes this would become a major risk factor for heart disease.
- Exercise regularly. Epidemiological evidence shows that people who are physically fit have fewer medical problems and a longer life span that people who dont do any exercise at all. Daily activity, like walking or cycling to work is potentially beneficial to health, especially in terms of type 2 diabetes prevention.
- Don’t smoke.
- Drink alcohol but in moderation.
Q: From a dietary perspective what are the three most useful things doctors can do themselves and advise their patients to do, to reduce the risk of a heart attack?
A key dietary message is the value of fish in preventing heart disease. Omega-3 fatty acids found in oily fish are beneficial for blood clotting and platelet aggregation, having an anti-thrombotic and anti-inflammatory effect. Omega-3 fatty acids also reduce plasma triglyceride levels, but have minimal effects on LDL and HDL cholesterol levels.
Oil rich fish include herrings, kippers, salmon, sardines, mackerel, trout, tuna and swordfish. These contain much higher levels of Omega-3 than white fish.
Try to include three or more portions of oily fish a week. Those unwilling to do this should use a fish oil supplement (fish body oil not fish liver oil) that contains 0.5-1.0g of omega-3 fatty acids (DHA and EPA).
Epidemiological evidence has shown that diets rich in fruit and vegetables are protective against CVD, including CHD and stroke. These foods contain many important nutrients. Potassium can help reduce blood pressure, folic acid limits homocysteine formation and soluble fibre helps reduce LDL cholesterol and improves HDL cholesterol. In addition, fruit and vegetables contain anti-oxidants as well as bioactive compounds with anti-oxidant activity such as carotenoids and flavonoids. However, anti-oxidant supplements in whatever form are not recommended to replace fruit and vegetable.
Avoid high intakes of total fat, saturated fat and trans fatty acids, as these are linked to raised blood cholesterol levels especially LDL cholesterol. This means limiting how much cream, butter, mayonnaise, cheese, chocolate and biscuits you eat. Products like biscuits are often produced using cheap vegetable oils, which change their chemical composition when cooked, creating trans fatty acids, which are more damaging than even cholesterol.
A high fat intake is also linked with excess weight and obesity. Women should limit fat intake to 60-70g per day with a maximum of 20g coming from saturated fat. Men should limit fat to 80-90g per day with a limit of 25g saturated fat. If the patient needs to lose weight then fat levels should be cut by half.
Potassium will help reduce blood pressure. Good dietary sources are bananas, orange juice and potatoes.
Cholesterol lowering spreads containing plant sterols or stanols have been shown to lower LDL cholesterol by up to 15%
Consuming alcohol three or more times a week even in small to moderate amounts was associated with reduced risk of coronary heart disease and myocardial infarction.
So, in summary, eat:
- Three or more portions of oily fish a week
- Less fat, especially saturated fat
- More fruit and vegetables
Q: One in three people is diagnosed with cancer at some stage in their lifetime. What changes should doctors be thinking of, in their own diet and that of their patients, to try to reduce the risk of cancer?
The association between diet and cancer is still only in its infancy. Most studies are epidemiological in origin and research trials are sometimes hard to replicate.
The evidence is currently suggesting that isoflavones, which are phytoestrogens present in high quantities in soy products, may play a preventative role in breast cancer.
An abundance of data suggests that consuming diets high in fruit and vegetables and thus anti-oxidants, results in a decreased risk for many cancers including colorectal and lung.
Vitamin C has been associated with a decreased risk of many types of cancers especially stomach cancer.
Selenium supplementation has been associated with a decreased risk of prostate cancer (but given its toxicity levels need to be regulated by the GP).
Resveratrol , a polyphenolic phytoalexin found in grapes is an anti-oxidant that has been shown to exhibit strong anti-inflammatory, cell growth-modulatory and anti carcinogenic effects so can be helpful if there is genetic predisposition.
Some evidence has shown a protective effect of tea on the incidence of stomach and rectal cancers. There is little to associate coffee drinking with cancer. Decaffeinated coffee may be worse for you than ordinary coffee, as a result of the decaffeinating process.
Diets rich in cruciferous vegetables like broccoli, cabbage, cauliflower, horseradish and mustard seed appear to reduce the risk of cancer of the colon and rectum.
Allium vegetables like garlic and onions appear to be preventative against stomach cancer.
High alcohol intakes are associated with cancers of the mouth, pharynx, larynx, oesophagus and liver.
Based on the most recent evidence, the recommendations to prevent cancer are, that the diet should contain foods of plant origin, they should be varied and nutritionally adequate, 7% of energy should come from fruits and veg and 45-60% from starch and protein foods of plant origin. In addition, the diet should maintain a normal BMI (body mass index) and active lifestyle.
Excess intakes of salt, alcohol, heavily cooked meats and hydrogenated fats should be avoided. To achieve this cut down on barbequed food and cheaper manufactured foods, for instance.
Q: Is there anything diet can do to help boost our immune system?
A: Unknown to many people is the role that vitamin A plays in our immune system. Mild vitamin A deficiency leads to an increased susceptibility to a variety of infectious diseases. However, because it is a fat-soluble vitamin that can be stored in the body, supplements should be used with caution. It is far better to improve the sources in the diet, such as fortified milk with vitamins A and D added to it.
Liver is such a rich source of vitamin A that pregnant women should actually avoid it. Many margarines have vitamin A added to them. Carotenes, which are precursors of vitamin A are found in green, yellow and red fruits and vegetables, and these are also a great source of antioxidants.
Selenium (a mineral) and also an antioxidant plays a major role in immunity. Selenium deficiency is accompanied by loss of immunocompetence. Covert suboptimal selenium status may be widespread in human populations. However, there is a narrow margin between beneficial and harmful intakes of selenium so be careful of supplements. Brazil nuts are a rich source of selenium. Fish, shellfish, liver and kidney as well as milk and eggs are also good sources of selenium.
Zinc deficiency causes increased susceptibility to infections. Meat, (beef and lamb being higher than pork and chicken) seafood (especially oysters and crab) and liver are the main sources of bioavailable zinc.
Q: For doctors working long hours, do you have any diet tips to help maintain energy?
A: A high carbohydrate diet is the only way to maintain energy levels. It depends where you are.
For immediate energy, that is fat free, go for something that is sugar-based like tea or coffee with two spoons of sugar added or a soft drink or sweets like pastilles or wine gums. This is so much better than eating biscuits, chocolate or crisps, which are all high in fat.
If you have time and you can get it, white bread is absorbed the quickest so a bread roll will give you instant energy and is also fat-free. Nutritious energy snacks would include fruit juices, a smoothie, a fruit or wholemeal scone, a wholemeal cereal bar, a piece of fruit or even just a couple of slices of toast.
Q: Do dietary supplements have any value or is the main benefit from what we eat and drink?
A: The aim should be to get all the nutrients that your body needs from your diet. However, this is not always practical. There is a role for supplements but in special situations, not for the general population.
Women who do not eat dairy products should take a calcium supplement. Vegetarians should take an Iron and vitamin B12 supplement. Vitamin D requirements increase in the elderly so a vitamin D supplement could be necessary here. If someone has been ill then a short course of a vitamin supplement would be useful.
Most important of course is folic acid for women who are planning a pregnancy.
But for the rest of us, they really are not necessary.
One other point to bear in mind is the value of the sun, within reason, as a source of vitamin D. We are now hearing of an increase in rickets in children, as a result of very high levels of sunscreen use.
Q: The word diet sometimes conjures up the idea of weight loss and every year seems to bring the latest celebrity diet. What would your advice be for someone looking to lose weight?
A: There’s no mystery to dieting. It is simply a question of mathematics. Bigger portions contain more calories, which can contribute to weight gain. So to lose weight, or maintain body weight, reduce portion sizes.
Don’t skip breakfast. Have three regular meals a day – just keep the portion sizes down. If you’re eating in, a smaller plate is an easy way of achieving this.
Q: For doctors studying for examinations is there anything they should include in their diet or avoid to help their concentration?
A: The brain is one of the smallest organs in the body yet it uses up 20% of our daily energy. Keeping a constant supply of glucose to the brain will ensure concentration so, again, don’t skip breakfast. Lack of glucose will reduce your ability to recall and concentrate.
High fire carbohydrate foods will ensure a slow but sustained release of glucose. Foods like high fibre breakfast cereal, brown bread, fruit and vegetables are all recommended.
Q: Would you give different advice to doctors at different stages in their lives and careers? For instance, how might your advice differ, talking to a recently qualified doctor compared with a doctor approaching retirement?
A: The basic nutritional requirements will be pretty much the same throughout your life and career. What is more likely to change is your requirement for energy.
There was probably a time when the pace of life earlier in your career was more frantic but changes in Medicare mean you may now be experiencing a hectic pace throughout most of your career. In the past too, many male medical careers were partly built on having a wife at home looking after the home and children and doing the cooking. With both men and women now having careers, pressures outside work may be growing, hence increasing concerns about achieving a work/life balance.
However, physical activity may still be more likely when you are younger, for instance if looking after young children compared with after they have left home.
Other factors will also be age related. As we grow older our appetite may be reducing, there may be a slight loss of taste and smell, we may be getting a bit bored with and losing interest in the food we have traditionally eaten. All this suggests the value of planning our diet to ensure we continue to eat regularly and enjoy a varied diet as we grow older. I’ve already explained the value of higher cereal fibre intake in adults aged 65 years and over.
Also, as you grow older, if your weight goes up your blood pressure tends to rise, so the diet and exercise advice I mentioned earlier becomes increasingly important.
Q: Food allergies seem to be an increasing problem. Is there anything we can do, through choice of diet, to reduce the risk of developing food allergies?
A: Food allergy is a reaction by the body to a dietary protein like milk, egg or nut. This allergic response produces a lot of IgE antibodies and will make you ill immediately after eating the food. 1 – 2% of the population is believed to have a food allergy.
Food intolerance causes symptoms hours/days after eating the offending food. This response may or may not involve the immune system. Foods like soya, milk, eggs, and wheat; chocolate, caffeine and wine can all be listed as offenders. There is no scientific test to prove food intolerance. Advice is usually to avoid the offending food. If you think you have a food intolerance seek advice from an Accredited Practising Dietitian like myself.