Fibre helps protect against colorectal cancer

New World Cancer Research Fund Report supports dietary fibre for protection against colorectal cancer

 

The number of new cancer cases in Australia is rising each year. Data from 2007 (AIHW) indicates that bowel cancer (also known as colorectal cancer) is the second most common cancer in Australia and the second largest cause of cancer deaths in Australia, killing almost 80 people a week (Bowel Cancer Australia).

 

Rates of colorectal cancer increase with industrialisation and urbanisation and are generally more prevalent in high income countries, but now becoming increasingly more common in middle and low income countries. Somewhat more common in men than in women, colorectal cancer is fatal in just under half of all cases, however if detected early, it is actually one of the most curable cancers, with food and nutrition having an important role in its prevention and cause.

 

A new update to the Food, Nutrition, Physical Activity, and the Prevention of Colorectal Cancer Report by the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) as part of the Continuous Update Project (CUP) has just been published, including an additional 263 new articles from cohort studies and randomised controlled trials. The CUP provides a comprehensive and up-to-date systematic review of scientific developments on the relationship between diet, physical activity, obesity and cancer, with the panel consisting of leading scientists in these fields.

 

In this new report, the CUP panel agreed that the evidence for a protective effect from foods that contain dietary fibre had strengthened from probable in the previously completed Secondary Expert Report (SER) and therefore the evidence has been upgraded to ‘convincing’. This is highest level of evidence set by the WCRF and AICR, which identifies a causal relationship between a particular aspect of food, nutrition, physical activity or body composition, and cancer.

 

Twelve new papers were included in the review that investigated total dietary fibre and fibre from cereals, wholegrains, legumes, fruit and vegetables. The new report found that 13 of the 18 studies showed a decreased risk for colorectal cancer with increased intake of total dietary fibre.

 

The new meta-analyses showed a 10 per cent decreased risk for colorectal cancer and 11 per cent decreased risk for colon cancer with an increase in dietary fibre of 10g/day, which is a slightly better risk reduction than the 2007 report. The updated meta-analyses for rectal cancer, trended in the direction of decreased risk, but did not reach statistical significance.

 

Likewise, the updated reviews for sources of fibre and colorectal cancer showed a 10 per cent decreased risk for cereal fibre, but estimates for other sources of fibre were in the direction of decreased risk, but again did not reach statistical significance.

 

With 3 servings of wholegrains per day there was a 21 per cent decreased risk for colorectal cancer and 16 per cent decreased risk for colon cancer. There was also convincing evidence that physical activity protects against colon cancer. It is interesting to note the review concluded there is probable evidence that consumption of garlic, milk, and calcium may also protect from colorectal cancer.

 

The way in which fibre helps reduce the risk of colorectal cancer is due to several effects in the gastrointestinal tract, but the precise mechanism is still yet to be fully understood. Fibre dilutes faecal content, decreases transit time and increases stool weight whilst healthy gut bacteria from a wide range of dietary carbohydrates that reach the colon produce fermentation products, particularly short-chain fatty acids such as butyrate which helps to maintain healthy colon cells. Fibre intake is strongly correlated with intake of folate, however, adjusting for this does not often affect the risk reduction attributed to fibre.

 

The latest evidence from the WCRF review report also shows that consumption of red meat and processed meat, ethanol from alcoholic drinks (by men and probably by women), as well as body fatness and abdominal fatness, the factors that lead to greater adult attained height, or its consequences are convincing or probable causes of colorectal cancer.

 

Australian healthy eating guidelines recommend we eat at least 4 serves of core grain-based foods a day such as breads, breakfast cereals, rice, pasta and noodles, preferably wholegrain. One serve is equal to 2 slices of bread, approx 1 cup of breakfast cereal, 1 cup of cooked rice/noodles/pasta/oats. Don’t forget legumes are also a great source of fibre. Aim for at least 2 serves per week, 4 serves or more is even better for improved health outcomes. One serve is equal to half a cup of cooked dried beans, lentils, chickpeas etc.

 

References:

WCRF/AICR World Cancer Research Fund / American Institute for Cancer Research.Continuous Update Project Interim Report Summary.Food, Nutrition, Physical Activity, and the Prevention of Colorectal Cancer. 2011

http://www.aihw.gov.au/

http://www.bowelcanceraustralia.org/

Draft Australian Dietary Guidelines:

Are the 2010 Dietary Guidelines for Americans a preview of our own?

Every 5 years the US government is required by federal law to review and update its dietary guidelines, which then guides all federal food programs in the US. The new 2010 Dietary Guidelines for Americans were released a couple of months ago, and with Australia’s draft guidelines currently under review, and a draft expected for consultation in April/May we can’t help but wonder if America’s Dietary Guidelines are a preview of our own.

The message from the 2010 Dietary Guidelines for Americans with regards to grains is “whenever possible, replace refined grains with whole grains." The 2005 message to "make at least half your grains whole" still holds true, however, this time the guidelines are full of reminders to replace refined grains with wholegrains. For most Americans the recommendation for grain-based foods is 6 serves a day (one American serve is equivalent to 1 slice of bread or ½ cup of cooked rice or pasta), with at least 3 of those wholegrain. This amount is equivalent to the 48g Daily Target Intake for wholegrains, as recommended by Go Grains Health & Nutrition.

A series of swap this for that options are promoted in the new 2010 Dietary Guidelines for Americans such as swapping white rice with brown rice, white pasta with whole wheat, cornflakes with oatmeal and doughnuts with wholegrain bagels. The concept is similar to that of the Australian Governments’ current “Swap it, Don’t stop it” campaign, where by Australians are urged to swap some of the things they are doing now for healthier choices - http://www.swapit.gov.au/

The current Australian Dietary Guidelines do not recommend a quantitative amount for wholegrains, instead stating ‘Australians should eat plenty of cereals (including bread, rice, pasta and noodles) preferably wholegrain’. If the new Australian Dietary Guidelines follow the US, it is likely the food industry will develop and manufacture more food products with wholegrains to promote the additional health benefits of these foods. If the US is a preview of our market, wholegrain foods may become the norm. The growth in popularity of wholegrain foods has been demonstrated recently in the US, as The Wholegrains Council’s wholegrain stamp reports a 25% growth over the past 9 months, now appearing on over 5000 wholegrain products in over 22 countries.

The Australian Dietary Guidelines provide evidence-based nutrition information and advice for health professionals and consumers. The National Health & Medical Research Council (NHMRC) is leading the review of Australia’s guidelines together with the Department of Health and Ageing.

The Australian Dietary Guideline review process started in April 2008, with a group of nutrition experts – The Dietary Guidelines Working Committee meeting to establish the terms of reference and review the latest scientific research to make recommendations for updates to the guidelines. The first review process for the Australian Dietary Guidelines is expected to be commence in April/May this year, with the final guidelines planned to be released at the end of the year. We are waiting with anticipation that a quantitative recommendation for wholegrains is included in the draft 2011 Australian Dietary Guidelines. A quantitative recommendation encourages consistency in wholegrain public health messages in the media and on product packs, ultimately helping consumers understand the actual amount of wholegrains they need for good health.

www.health.gov/dietaryguidelines
www.nhmrc.gov.au/publications/synopses/dietsyn.htm
http://www.swapit.gov.au/

We 'heart' legumes

Sound science supports legumes and cholesterol lowering for a healthier heart

There is consistent evidence from epidemiological studies showing that eating legumes can play a role in preventing some of our most serious chronic diseases, including cardiovascular disease, diabetes, as well as improving gut health and assisting with weight management. Despite this, Australians are not eating enough legumes. A consumption survey conducted by Go Grains Health & Nutrition in 2009 (which is currently in field again for 2011) found that not even a quarter of the 1700 Australians surveyed consumed legumes over the 2 day period food intake data was collected.

The research in support of legumes and health is not as extensive as that for cereal grains, mainly because there is generally a low intake of legumes in most free-living populations. Much of the legume research has focused on soy beans due to higher intakes of soy products such as tofu, soymilk, tempeh and textured soy protein; however, a meta-analysis just published has focused on non-soy legumes in relation to blood lipids. This is the second meta-analysis of this topic, is more vigorous in its methodology and includes four new studies since the 2002 review.

A total of 140 papers were retrieved from a search through MEDLINE, EMBASE and Cochrane databases through to July 2009. Ten randomised controlled trials were selected for analysis that compared a non-soy legume diet to a control diet. Each of the 10 studies lasted a minimum of 3 weeks duration, and reported blood lipid changes (in cholesterol, hypercholesterolemia or hypertriglyceridemia and/or cardiovascular disease) in intervention and control diets. The research included a total of 286 participants (70% males) from 5 countries with a mix of high, borderline high and normal baseline cholesterol levels.

The legume intake in the 10 studies ranged from 80-440g/day of peas, lentils, baked beans, pinto beans, lima beans or black eyed peas with a study length of 21 to 56 days. All studies reported net decreases in total cholesterol with a mean reduction of 11.76mg/dL (translating to around a 5% reduction). The combined results showed a significant decrease in unhealthy LDL cholesterol and triglycerides, however little effect on HDL cholesterol.

Although the number of participants was relatively small and majority were middle aged hypercholesterolemic men, the meta-analysis appears to be carried out very carefully. There was no publication bias or significant differences in the way the protocols were performed, and sensitivity analysis found no effect of study type, length or type of control on the results. The levels of legume intake in the studies are considerably above average legume consumption in Australia today, limiting the potential applicability in the findings, but also highlighting the potential health benefits if legume consumption can be increased amongst Australians, especially in those at higher risk of raised cholesterol and cardiovascular disease.

Non-soy legumes have a similar effect as soy-based supplementation on cholesterol lowering. The authors concluded this meta-analysis of randomised controlled trials provides the strongest evidence to date that non-soy legume consumption lowers serum total and LDL cholesterol and therefore may lower the risk of cardiovascular disease. This provides added weight to the body of scientific evidence supporting the role of legumes in the diets of Australians.

Bazzano et al 2011 Non-soy legume consumption lowers cholesterol levels: A meta-analysis of randomised controlled trials. Nutrition, Metabolism and Cardiovascular Disease (21) 94-103.
 http://www.ncbi.nlm.nih.gov/pubmed/19939654

Bread Matters

The impact of Folic Acid Fortification in Australia

Just over a year after the introduction of mandatory folic acid fortification in wheat flour for bread making, Australian researchers have set out to determine the impact it has had on the blood folate levels of Australians.

Research suggests an adequate intake of folate pre conception can reduce the incidence of neural tube defects in newborn infants. This has lead to the introduction of government sponsored health promotion campaigns encouraging women of child-bearing age to supplement with folic acid. In 1995, voluntary fortification was introduced and successfully increased the populations’ blood folate levels, and resulted in a reduction in neural tube defects between 1996 and 2006. In September 2009, fortification of 2-3mg of folic acid per kg of wheat flour for bread making was mandated under Standard 2.1.1 of the Food Standards Code, resulting in 0.135mg of folic acid per 100g of bread (approx 2-3 slices), or around half the recommended dietary intake (RDI) of folate. Note: the RDI is higher for woman of childbearing age.
 
Over 20,000 blood samples were used for the study between April 2009 and April 2010, as well as April 2007 and April 2008 (used as baseline). These samples tested for serum and red blood cell (RBC) folate levels in diagnostic pathology labs.

Between April 2009 and April 2010 the prevalence of low serum folate levels decreased by 77% (from 9.3% to 2.1%) and the prevalence of low RBC folate levels decreased by 85% (from 3.4% to 0.5%). The even better news is that while concerns were originally raised that women of child-bearing age may not be huge consumers of bread, the prevalence of low RBC folate levels amongst women of child-bearing age (15-50) was reduced to only one sample from 609 samples tested (0.16%). There was also a 31% increase in mean serum folate and a 22% increase in mean RBC folate levels for the samples tested.

It’s important to note the samples are not necessarily representative of the whole Australian population as they were obtained unexpectedly from those for whom a blood folate test was requested for the investigation of a possible folate deficiency, and are therefore likely to be biased towards low folate levels. Another limitation is that different patients were studied pre and during the mandatory fortification period and both samples would have included blood samples from those patients with coeliac disease or others on wheat free diets. Lastly, the authors stated they do not know the number of patients that might have already been taking a folate supplement.

Although no evaluation has been made to date on the impact of mandatory folic acid fortification of wheat flour for bread making on the incidence of neural tube defects, the results of this study are somewhat impressive in relation to the reduction of folate deficiency in the Australian population.

Already one of the leading sources of fibre in the diets of Australians, low in fat, a source of protein, thiamin, niacin and folic acid, there are plenty of reasons to enjoy the goodness of bread!

Reference:

Brown et al. The impact of mandatory fortification of flour with folic acid on the blood folate levels of an Australian Population. MJA (2011) 194: 65-67

Food or Physical Activity?

Picking sides in the energy balance equation

As the holidays draw to a close and children start heading back to school its is vital to get yourself and the kids back into the school routine, organising after school sport, switching computer game time with homework time, limiting TV time, and producing quick, easy and healthy family dinners at the table.

With unpleasant stats on childhood obesity and the fact many families are becoming increasingly squeezed for time it’s worth entering the debate on what is more effective - food intake or physical activity?

We know the stats are unpleasant with one in four children overweight or obese in Australia. But with our busy lifestyles and often not enough hours in the day, Dietitian’s are often asked, what is the easiest way to help kids maintain a healthy weight? One of the main causes of obesity is energy imbalance, with epidemiological studies indicating that children’s habitual energy expenditure has declined and their energy intake has increased. However, the underlying cause cannot be related to just one factor. A combination of everything that makes tasty, tempting, energy dense, nutrient-lacking food items easily available, convenient, cheap and marketable is one major contributor, along with every technological advance that results in us doing less physical work; washing machines, dryers, mix masters, cars and the endless list continues all which makes us more prone to excessive energy intake and inadequate physical activity than any previous generation.

The science suggests that there is little evidence dietary composition or macronutrient distribution has a meaningful influence on weight management independent of energy intake. However, it has been established that diet can affect satiety and is likely to influence weight indirectly by affecting the quantity of kilojoules eaten.

A recent review of the research completed in the US set out to understand the relative importance of overconsumption and physical inactivity to excess weight gain. The researchers found that there is wide variation in data quality and in the accuracy of measures of energy intake, and based on the available evidence there was no consensus on whether overconsumption or physical inactivity was the main driver for weight gain among US children and teens.

Despite this conclusion, intervention studies usually report that dietary modifications can be effective at weight loss on their own, whereas exercise based interventions do not, although a combination of the two works better than either on its own. From a practical perspective it is important to think about the most efficient ways to lose weight, and whilst we always, and will continue to recommend physical activity which has powerful influences on weight and health, we have to accept the challenge of getting an increasingly sedentary generation to participate in physical activity, all which could be undone by an unhealthy food or drink choice.

If you think about the 1000kJ a child might burn during 1 hour of bike riding per day and then consider the 2500kJ++ in a Happy Meal that takes less than 5 mins to eat, it’s easy to understand how hard it is becoming to maintain a healthy weight. This example emphasises the challenge we will continue to face unless we improve the quantity and quality of children’s diets. A study just published has found that that detailed representation of fast food and soft drink brands (developed via experience and advertising) has higher scores on an ‘added flavour’ sugar/fat/salt liking palate, fundamentally changing children's taste palates to increase their liking of highly processed and less nutritious foods. The researchers concluded early food-related behaviours are important and if we want to intervene we need to start when children are young.

Back to school lunch box tips

• Pat wet ingredients dry with a paper towel and layer lettuce between wet ingredients and bread to prevent moisture from spreading. Prepare sandwiches as close to lunchtime as possible to ensure freshness.
• Older students might go for something a little more gourmet. Tempt teen tastebuds with roast vegies on Turkish bread or a wholemeal wrap. 
• If the kids keep throwing out their crusts, beat them to it. Try using breads with no crust, such as wraps or Turkish bread. Alternatively, cut the crust of regular bread and use the left over crusts to make croutons or breadcrumbs.
• Wholegrain dinner rolls with healthy fillings can be used instead of larger bread rolls for younger kids. Cutting sliced bread into different shapes or creating a face by adding a grape cut in half for the eyes, a piece of carrot for the nose and a capsicum mouth can make lunches fun.
• Get kids involved with a best filling competition or a naming competition for sandwiches. Encourage the school canteen to have a reduced price or a meal deal with a free apple or yoghurt.
• Introduce wholegrain breads into the kids’ diet with ‘zebra’ sandwiches by using one slice of wholegrain and one white slice. Wholegrain crispbreads and rice cakes are a good alternative for kids who don’t like bread.

References:

Katz DL. Unfattening our children: Forks over feet. International Journal of Obesity (2011) 35, 33-37.
 Bleich SN et al. Relative contribution of energy intake and energy expenditure to childhood obesity: a review of the literature and directions for future research. International Journal of Obesity (2011) 35, 1-15.
 Cornwell TB et al. Alternative thinking about starting points of obesity. Development of child taste preferences. Appetite (2011) Published online ahead of print.

Carbohydrates may be linked to hearing loss

Age related hearing loss effected by quality of carbohydrate nutrition.

A new Australian study suggests that age-related hearing loss could potentially be reduced by decreasing the amount of lower quality carbohydrate in the diet and increasing the intake of cereal fibre

Age-related hearing loss is the most prevalent form of hearing loss worldwide. Research suggests that nutrition is a modifiable risk factor that could play a role in the development of age-related hearing loss. The Blue Mountains Hearing Study investigated whether a cross-sectional or longitudinal relationship exists between carbohydrate nutrition, starch, cereal and total fibre, and age-related hearing loss in a large group of adults aged 50 years and older. Of the total 2448 participants 32.1% had hearing loss and more than two thirds (67.9%), had no hearing loss over the 5 year follow up period. Those with hearing loss had a significant change between baseline and the follow up period.

In this group of older adults the higher Glycaemic Index (GI) of foods eaten are associated with an increased risk of hearing loss. However, this association is reduced when there is an increase in dietary intake of cereal fibre. This suggests that the effect of cereal fibre may override the effects of other components of carbohydrate and may have a protective effect on the hearing function, possibly by improving insulin sensitivity or by reducing blood glucose levels after eating.

The incidence of hearing loss in this 5 year period was predicted by a high Glycaemic Load* (GL). A high GL diet at baseline is found to increase the risk of developing age-related hearing loss by 76% among older adults. This is regardless of other potential variables such as education, smoking, previous history of diagnosed stroke and diabetes, family history of hearing loss and exposure to noise at work.

The association with GL and hearing loss suggests that both the quantity and quality of carbohydrate may play a role in the development of age-related hearing loss. The underlying causes for these findings are unknown, however long term higher dietary Glycaemic Load (GL) brings on abnormally high blood sugar levels and excess levels of insulin circulating in the blood. This can lead to diabetes, hypertension, and/or dislipidemia in individuals who are at risk. Other studies show a relationship between hearing and diabetes mellitus, stroke, and vascular risk factors such as high blood pressure and serum lipids. Therefore, dietary GL could potentially influence hearing function through its adverse effects on vascular health. The current study speculates oxidative damage as the underlying mechanism between carbohydrate and hearing loss.

The authors however, conclude that in order to confirm this theory and replicate findings, large high quality randomised controlled trials of long duration are needed to investigate any potential links between carbohydrate nutrition and hearing.

Key:
Glycaemic Load* - the product of a food’s glycaemic index and total available carbohydrate content, and represents both the quantity and quality of carbohydrates.

Source:

Gopinath B et al. Dietary Glycemic Load is a Predictor of Age-Related Hearing Loss in Older Adults. J. Nutr. 140: 2207-2212, 2010.

New year, new diet?

Wholegrains, legumes and refined grains in weight loss...

If you are gearing up for a healthy summer eating plan and are not sure what to include, consider the results of some new research that has just been published. Over one hundred people participated in an 18 month weight loss trial with advice to either follow a control diet based on the National Heart Foundation of New Zealand guidelines, or a diet that emphasised wholegrains and legumes.

The first 6 months involved 2-weekly counselling sessions, cooking classes, supermarket tours, and recipe ideas, in the following 12 months participants had monthly contact with the investigators. Participants in the (very healthy) control group were instructed to follow the guidelines published by the National Heart Foundation of New Zealand which included recommendations to eat at least 3 servings of vegetables and 2 serving of fruit, at least 6 servings of breads and cereals (where 1 serve is equivalent to 1 slice of bread),at least 2 servings of reduced fat milk and milk products, 1-2 small servings of protein-rich foods (meat, poultry, fish, seafood and legumes) and 1-2 tablespoons of monounsaturated or polyunsaturated fats and oil products and a small amount of nuts and seeds. The intervention group was given similar advice, except they were specifically instructed to consume 2 servings of legumes as a substitute for 2 serving of breads and cereals, and all other breads and cereals were to be wholegrain.

Key foods were provided to the participants for the first 6 months of the study to encourage consumption of the ‘suitable foods’ for their group. For example, participants assigned to the control group received cornflakes, cans of fruits and veggies white bread and cereals with a medium to high glycaemic index. The intervention group received rolled oats and rye, canned legumes, wholegrain and rye bread. Providing key foods seems to have played a role in the participant’s weight loss, as after 6 months when less support was provided many people re-gained some of the weight they had lost.

Data from weighed food records showed that most people in the intervention group complied reasonably well with the substitution of legumes into their diet, with the median legume intake over the first 6 months almost reaching the advised 2 serves/day. This declined to just under 1 serve/day in the last 6 months of the study. Wholegrain intake remained stable in the intervention group over the 18 months at around 1.5 serves/day. Wholegrain intake was slightly higher in the intervention vs the control group at 2 and 6 months, but no different at 12 months, therefore, it is likely that poor compliance after 6 months could have diminished the difference between diets.

The great thing about this study for the participants is that both groups lost a significant amount of weight – approximately 7kg at 6months, and 5kg at 18 months, compared to their weight when they started the weight loss program. Due to the overall similar decrease in energy intake and similar weight loss in both groups it is more difficult to see differences between the two interventions. Overall, there was a small difference in wholegrain intakes between both groups and significantly noticeable differences between legume intakes. Both groups decreased blood pressure, triglycerides and glycaemic load resulting in significant weight loss in both intervention groups, but there was no significant difference between the groups. Despite a small difference in the glycaemic index (GI) between the two diets, there was no relationship of GI to weight loss, consistent with other trials. The group that ate more wholegrains and legumes had a significantly lower waist circumference by 2.8cm after 18 months of the weight loss program. This group also had a lower Total cholesterol and a lower LDL cholesterol at the end of the study.

From a practical perspective, 81% of people stuck out the complete 18 months of the weight loss program, giving a good indication that people were willing to incorporate wholegrains and legumes in their diet over this period. Overall, all participants found the diets easy to follow and did not report any decrease in dietary satisfaction. The researchers concluded that their data provides strong evidence in support of national guidelines for healthy eating that recommend the inclusion of wholegrains and legumes in the diet. This research also shows that although wholegrain foods are a better choice, core refined grain foods such as white bread, white pasta, and white rice can be included as part of a successful weight loss program.

Venn BJ et al, 2010. The effect of increasing consumption of pulses and wholegrains in obese people – a randomised controlled trial. JACN