The Mediterranean Diet - Benefits Beyond Heart Health

By Felicity Curtain, Accredited Practising Dietitian

A Mediterranean eating pattern has long been heralded as the diet of all diets: seemingly unrestrictive, uncomplicated in rules and with strong credentials for heart health benefits. However, recent research suggests there may be more to the story than just heart health. The Mediterranean diet first sparked interest in the 1960s, when it was discovered that people in countries bordering the Mediterranean Sea experienced significantly lower rates of chronic disease than those in western countries. While most research in the past has focussed heart health benefits, studies have recently started connecting the diet to reduced risk of Type 2 diabetes, cancer, and cognitive conditions.

The Diet
Over twenty countries border the Mediterranean Sea, and while types and amounts of foods eaten vary between nations, all are characterised by similar principles. This includes plenty of fruit and vegetables, olive oil, legumes, nuts and whole grains; moderate consumption of fish, and low-moderate amounts of dairy foods and red meat. Very few processed foods are consumed, and red wine is consumed in moderation with meals (1). While studies do not explicitly outline the types of whole grains consumed, varieties common to the Mediterranean include barley, buckwheat, bulgur, faro, oats, polenta, rice, bread, couscous, and pasta. The past century has included white pasta, though traditionally bread was stone-ground sourdough, made from whole wheat and barley (2).

The Health Effects
If you believe the media coverage of the diet, the benefits of a Mediterranean appear boundless. In reality, high quality evidence exists to indicate the eating pattern is protective against cardiovascular disease (CVD) and Type 2 diabetes, and mounting evidence points to a positive association with cancer and neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease (3,4,5).

The most recent research indicates that for those already exhibiting CVD risk factors, following a Mediterranean diet can halve the risk of diabetes development and reduce the risk of mortality from cardiovascular events by 30 percent (6). Observational evidence and limited experimental trials demonstrate that those adhering to the diet exhibit improved blood lipid profiles, a reduction in blood pressure, and insulin resistance, all risk factors for CVD (7,8). In fact, the cardiovascular benefits of the Mediterranean diet have been compared to pharmacological interventions, such as statins, aspirin, physical activity, and even anti-hypertensive drugs (9). In healthy populations, observational evidence suggests a 10 percent decrease in the risk of mortality and/or incidence of CVD (10).

Interestingly, few studies of the Mediterranean diet are designed to induce weight loss, but many participants do lose weight, a risk factor for chronic disease itself. It has been suggested that that may be due to the high ratio of plant to animal foods, and limited refined and processed foods, making the diet high in fibre and filling, without providing excess energy.

In recent years, a small pool of trials has shown preliminary evidence that the Mediterranean diet may slow the onset and/or progression of age-related cognitive decline, and promote healthy cognitive ageing. One such study found that greater adherence to a Mediterranean diet corresponded with lower decline in cognitive function over a five-year period. In younger adults, there is growing interest in the effects of the diet on mood and affective disorders, based on population data showing low depression rates in Mediterranean countries. Limited high-level evidence exists on the subject, however a number of Australian randomised control trials are currently being carried out to determine the link between the diet and mood disorders (11).

Considerable research has sought to understand the mechanisms behind the Mediterranean diet’s apparent link to health, with no single food or nutrient appearing to contribute in isolation. While the mechanisms are not fully understood, there is a general consensus among experts that it is based on the combination of protective nutrients and foods. The high ratio of plant to animal foods may be a contributing factor, particularly as foods like olive oil, herbs and spices, fruit, vegetables, whole grains and legumes are rich in phytochemicals, with antioxidant, anti-inflammatory effects.

These factors are also thought to relate to the emerging link between a Mediterranean diet and positive cognitive health. The combination of foods and nutrients are thought to protect against cognitive decline through reductions in oxidative stress, inflammation, and lowering insulin resistance. The diet may also help to increase cerebral blood flow, a factor that is inversely affected by a typical Western diet (12,13).

However, it should not be forgotten that the good health of Mediterranean populations may also relate to lifestyle and cultural elements central to their traditions. Cooking, socialising, regular physical activity and rest are all important factors to consider in a balanced lifestyle.

Incorporating Mediterranean Eating Habits into Australian Diets
Interestingly the macronutrient distribution of the Mediterranean diet is not that dissimilar to the average Australian diet (Table 1). The Mediterranean diet is slightly lower in protein and carbohydrate and higher in fats, largely from the free consumption of olive oil, nuts, and seeds. The Mediterranean diet is significantly higher in fibre than the average Australian diet (33g/day compared to 22- 23g/day), a reflection of the higher intake of fibre rich foods including vegetables, legumes, whole grains and nuts.

Table 1. Average macronutrient contribution to energy and total fibre intake of Australians average intakes compared to estimated Mediterranean diet macronutrient distribution ranges and fibre intakes.

 

	Mediterranean Diet	Australian Average(14)
Protein	10-15%	16%
Carbohydrate	43%	45%
Fat	30-40%	31%
Fibre	33g/day	22g (F) 23g (M)

Comparing the diets from in terms of foods, a noteworthy distinction between the Mediterranean Diet Pyramid and the Australian Dietary Guidelines is the former does not detail serve sizes, instead emphasizing overall food quality according to dietary patterns.

Table 2. The Mediterranean Diet Pyramid compared to the Australian Dietary Guidelines

Food Group	Mediterranean Diet Pyramid	Australian Dietary Guidelines (men and women 19-50).
Vegetables	2 or more serves per meal (6+ per day)	5 serves per day
Fruit	1-2 serves per meal (3+ per day)	2 serves per day
Breads & Cereals	1-2 serves per meal (3+ per day)	6 serves per day
Dairy	2 serves per day	2 ½ - 3 serves per day
Meat & Alternatives	2 serves of red/white meat per week, 2 or more serves of fish/seafood, and legumes per week, 2-4 serves of eggs per week, 1 or fewer serves of processed meat per week.	2 ½ - 3 serves per day (inclusive of red meat, poultry, fish, legumes, nuts, seeds).
Oils	Olive oil in unspecified amounts daily	4 serves per day
Olives, nuts, and seeds	1-2 serves daily	-
Discretionary Foods	2 or fewer serves daily	0-3 serves per day

In reality we know that Australian diets do not reflect the guidelines, with an average of one third of total daily energy stemming from discretionary foods, and less than seven percent of the population meeting the recommendations for vegetable intake (14).

A simple way for Australian to adjust their diets and reap the benefits of the Mediterranean diet is to increase the amount of vegetables, nuts, whole grains and legumes eaten each day. This can be coupled with including small amounts of red meat a few times a week and increasing consumption of fish, using olive oil and as the main fat source, and using fresh herbs and spices to add flavour to meals in place of salt.

References
1. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92:1189-96
2. D'Alessandro A, De Pergola G. Mediterranean Diet Pyramid: A Proposal for Italian People. Nutrients. 2014;6(10):4302-4316.
3. Itsiopoulos C. The Mediterranean Diet. Melbourne: Pan Macmillan Australia; 2013.
4. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92:1189-96
5. Trichopolou A, et al. Definitions and potential health benefits of the Mediterranean diet: views from experts around the world. BMC Medicine. 2014; 12:1121-16.
6. Estruch R, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. N Engl J Med. 2013; DOI: 10.1056/NEJMoa1200303
7. Kastorini C, Milionis H, Esposito K, Giugliano D, Goudevenos J, Panagiotakos D. The Effect of Mediterranean Diet on Metabolic Syndrome and its Components. Journal of the American College of Cardiology. 2011;57(11):1299-1313.
8. Grosso G, Mistretta A, Frigiola A, Gruttadauria S, Biondi A, Basile F et al. Mediterranean Diet and Cardiovascular Risk Factors: A Systematic Review. Critical Reviews in Food Science and Nutrition. 2013;54(5):593-610.
9. Trichopolou A, et al. Definitions and potential health benefits of the Mediterranean diet: views from experts around the world. BMC Medicine. 2014; 12:1121-16.
10. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92:1189-96
11. Preedy V, Watson R. The Mediterranean diet. USA: Elsevier; 2015.
12. Knight A, Bryan J, Wilson C, Hodgson J, Murphy K. A randomised controlled intervention trial evaluating the efficacy of a Mediterranean dietary pattern on cognitive function and psychological wellbeing in healthy older adults: the MedLey study. BMC Geriatric. 2015;15:55
13. Keast R, Parkinson L. 2016. Available from: http://eds.a.ebscohost.com.ezproxy-b.deakin.edu.au/eds/pdfviewer/pdfviewer?sid=e44b952b-b40c-49f5-8c2d-2a746edcb669@sessionmgr4001&vid=5&hid=4103
14. Australian Bureau of Statistics. Australian Health Survey: Nutrition First Results. 2015. Available from: http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/4364.0.55.007~2011-12~Main%20Features~Cereals%20and%20cereal%20products~720

Department of Health - Healthy Weight Guide

The Department of Health has released the Healthy Weight Guide (the Guide). The Guide consists of a website as well as supporting resources that have been developed to help Australians achieve and maintain a healthy weight. 

The Healthy Weight Guide website contains information and tools that will guide users to:

1. Set goals and plan healthy meals and physical activity
2. Monitor what they do and manage challenges
3. Find information and support that will guide them along the way.

The primary audience for the Guide is the Australian general public. However, organisations and health professionals may also find the Guide useful as a resource for gaining background information on healthy weight issues or for suggesting to consumers as a practical tool to assist them in achieving and maintaining a healthy weight.

The Guide includes links to a variety of relevant sources and a page is included for each state and territory that provides links to state and territory specific programmes and resources.

Latest Look at Legumes

Legumes are trending. They’re featuring on restaurant menus, in glossy magazines and even in lunch-time salad bars. Research is mirroring the interest with new research emerging to strengthen the evidence for a range of health benefits of legumes.

A review published in Asia Pacific Journal of Clinical Nutrition in March by Australian researchers Antigone Kouris-Blazos and Regina Belski outlines the latest evidence for the nutrition and health benefits of legumes. This extensive review considers the evidence for the effect of legumes, and in particular Australian Sweet Lupin, on longevity, diabetes, cardiovascular disease, cancer and weight management. In addition, the review considers the content of both nutrients and anti-nutrients in legumes as well as comparing current intakes with recommendations.

While most people would think of heart health as the first benefit of legumes, the authors in fact suggest the strongest evidence is for links between eating legumes and reduced risk of colorectal cancer. The World Cancer Research Report in 2006 concluded that there was limited evidence on legume consumption and reduced risk of cancer. However, it appears the evidence for legumes maybe strengthening. Three meta-analyses in the last 7 years have found eating legumes is associated with a reduced risk of bowel cancer. The bulk of this research has been conducted on the effect of soy intake.

In addition to colorectal cancer, this review outlines the evidence of benefits of eating legumes regularly for longevity, as well as reduced risk of and management of diabetes, cardiovascular disease and obesity. The authors suggest that one of the key factors for the benefits of legumes may be via favourable effects on the gut microbiome.

Australian Sweet Lupin is a crop grown predominantly in Western Australia but is not well known by many Australians. The review puts of focus on this little-known legume and suggests these are unique with one of the highest combined amounts of digestible plant protein (38%) and dietary fibre (30%). The authors note that low levels of anti-nutritional factors means they do not need to be soaked, or even cooked so can be eaten raw. Initial evidence suggests sweet lupins may lower blood pressure, improve blood lipids and insulin sensitivity and favourably alter the gut microbiome.

Kouris A, Belski R. Health benefits of legumes and pulses with a focus on Australian sweet lupins. Asia Pac J Clin Nutr. 2016;25(1):1-17.

Fibre - The Hallmark of a Healthy Diet

The most recent National Nutrition Survey showed that grain foods are the leading source of fibre in the diets of young Australian women delivering a whopping 42.4% ⁽¹⁾. However, despite this important link between grain foods and fibre, many young women fall short of their core grain intake recommendation⁽²⁾. But why is this? Despite being the hallmark of healthy eating, dietary fibre rarely captivates the attention of young women, however the results of a new study⁽³⁾ have bolstered the case for fibre to be recognised as a, if not the, leading health promoting component of food. This has raised concern that young women may be missing the benefits of a high fibre diet, of which high fibre grain and whole grain foods play an important role. Here we have summarised the results of this recent study in light of the dietary fibre and core grain intakes of young Australian women.

PhD candidate, young woman and lead author of the new review on dietary fibre⁽³⁾ Stacey Fuller said, “The evidence has shown time and time again that people who eat higher fibre diets experience greater digestive wellbeing and reduced risk of specific cancers, heart disease, diabetes and obesity – some of the biggest causes of death and disability in Australia. Despite the overwhelming body of evidence emphasising the importance of a high fibre diet for wellbeing, Australians are falling short of fibre recommendations, particularly young women aged 19-30 years, who on average consume around 20g of dietary fibre per day (25g recommendation)⁽¹⁾.

Co-author, Associate Professor Eleanor Beck of the University of Wollongong stated, “While people generally understand that fibre is important for digestive health, there is a lack of understanding of the additional and wide ranging benefits of fibres for disease risk reduction and as a result, there is a lack of appreciation of the importance of eating a variety of high fibre foods as part of a balanced diet.”

What many people don’t realise is that fibre is not a single nutrient but rather a range of complex components found in a variety of foods including grains, legumes, fruits, vegetables, nuts and seeds. Pectin, which is found in a range of plant-based foods, including legumes, fruit, vegetables, nuts and seeds, has been shown to reduce cholesterol reabsorption and improve bowel health. Other types of fibre such as β-Glucan, a type of cereal fibre, is found more exclusively in grain foods such as barley and oats. Cereal fibre has been shown to offer the greatest protection against risk of early death, compared with other types of fibre⁽⁵⁾. Just 10g of cereal fibre per day can reduce future risk of heart disease by 10%(4) and type 2 diabetes by 35%⁽⁶⁾.

Whilst core grain foods are the major source of fibre in all Australian’s diets, the 2014 GLNC Consumption and Attitudinal Survey showed that people are much less likely to identify grains (and legumes) as sources of dietary fibre compared to fruit and vegetables⁽²⁾. On top of this, many young women believe that grain foods, including those that are high in fibre (e.g. wholemeal pasta, whole grain bread), are not an important part of a healthy diet⁽²⁾. What they don’t understand is that by limiting their intake of core grains, they not only compromising their fibre intake but also their consumption of a wide range of other essential nutrients and protective components found in fibre rich grain foods.

This recent review highlights the need for a greater understanding that when it comes to fibre, variety is essential, and all Australians should be encouraged to eat a variety of fibre-rich plant foods including grains, legumes, fruits, vegetables, nuts and seeds as part of a balanced diet. To help meet dietary fibre recommendations and achieve fibre intakes associated with wellbeing in the short term and reduced risk of chronic disease in the long term, young women should aim to enjoy core grains foods three to four times each day, choosing at least half as whole grain and/or high fibre grain foods, within a balanced diet rich in other source of dietary fibre. This could be as easy as having a bowl of porridge with fruit for breakfast, a whole grain salad sandwich for lunch and a vegetable stir-fry with brown rice or barley for dinner.

For a range of fibre rich recipes, cooking tips and snack ideas with grains and legumes visit the GLNC website.

References

1.         ABS. National Health Survey: First Results, 2014-15. Australian Bureau of Statistics, 2014-15.

2.         GLNC. 2014 Australian Grains and Legumes Consumption and Attitudinal Report. Unpublished: 2014.

3.         Fuller S, Beck E, Salman H, Tapsell L. New Horizons for the Study of Dietary Fiber and Health: A Review. Plant foods for human nutrition. 2016.

4.         Pereira MA, O'Reilly E, Augustsson K, Fraser GE, Goldbourt U, Heitmann BL, et al. Dietary fiber and risk of coronary heart disease: a pooled analysis of cohort studies. Arch Intern Med. 2004;164(4):370-6.

5.         Kim Y, Je Y. Dietary Fiber Intake and Total Mortality: A Meta-Analysis of Prospective Cohort Studies. American journal of epidemiology. 2014;180(6):565-73.

6.         Yao B, Fang H, Xu W, Yan Y, Xu H, Liu Y, et al. Dietary fiber intake and risk of type 2 diabetes: a dose-response analysis of prospective studies. European journal of epidemiology. 2014;29(2):79-88.

Healthy Ageing with Grains and Legumes

By Julie Christy, Accredited Practising Dietitian

As Australia faces an ageing population, addressing health issues associated with ageing is becoming increasingly important. While most older Australians may understand they should be eating more fruit and vegetables for better health, many may not also recognise that higher intakes of core grain foods (mostly whole grain and high fibre) and legumes can be an effective strategy for preventing and managing chronic disease as well as for promoting longevity. With older Australians’ intakes of core grains and legumes falling below recommended intakes, many are missing out on the benefits these foods offer for healthy ageing.

How can grains and legumes benefit older Australians?

With older Australians experiencing the highest incidence of diet related chronic diseases – including heart disease, type 2 diabetes, obesity and cancers, such as bowel cancer – understanding the most powerful dietary strategies to reduce the risk of such diseases can help older Australians to make the best choices for themselves.

While many are aware that plant based foods offer the greatest protection against diet related diseases, it may come as a surprise that a recent comprehensive review, the first of its kind which included a pooled analysis of over 300 meta-analyses and systematic reviews, found that whole grain/high fibre grain foods appear to offer the greatest protection against diet related disease out of all plant based foods.⁽¹⁾ This is not the first study to highlight the potential that whole grain and high fibre foods can play against diet related diseases, as evidence based dietary guidelines from around the world widely recommend a balanced diet, with core grain foods (mostly whole grain and high fibre) and legumes being key components in such recommendations. ^(2-8)

At the recent Oldways “Finding Common Ground” Conference, a team of leading nutrition experts from a range of dietary research backgrounds reached a consensus on the fundamental principles of healthy eating. According to the OldwaysCommon Ground Consensus Statement, a healthy dietary pattern is one that is high in plant based foods such as whole grains and legumes, along with fruits, vegetables and nuts.⁽⁹⁾ As part of this dietary pattern, grains and legumes represent a rich source of nutrients such as fibre, folate, thiamine, iron, magnesium and iodine⁽¹⁰⁾ as well as protective components like phytonutrients that are important for wellbeing over the lifespan.

Not surprisingly, the benefits of incorporating grains and legumes into your diet extend beyond simply reducing the risk of disease but also help to promote longevity. A study from Harvard researchers found that people with the highest whole grain intakes had a 17% lower risk of death from all causes and an 11–48% lower risk of disease-specific mortality compared to people with the lowest intakes of whole grain.⁽¹¹⁾ Meanwhile, the role of legumes in contributing to a long life has been observed in the diets of long-lived cultures such as the Japanese, who regularly eat soy foods such as tofu, natto, and miso, and people from the Mediterranean, where lentils, chickpeas, and white beans are important components of the traditional diet.⁽¹²⁾

Despite these benefits, older Australians do not appear to be achieving recommendations. The GLNC 2014 Consumption Study found that on average, both men and women aged 51-70 years fell short of the daily core grain serves recommended by the Australian Dietary Guidelines and they also fell short of their 48g whole grain Daily Target Intake. Worryingly, the study also found that only 25% of 51-70 year old Australians overall reported legume consumption on one or both days of the survey. This suggests that older Australians are at risk of missing out on key nutrients important for good health and longevity.

Cultivating good health with grains and legumes

Making just a few small changes can make a big difference to the health of older Australians – eating 2-3 serves of whole grains daily can reduce the risk of developing chronic disease by 20-30%,⁽¹³⁾ whilst just a 20g increase in daily legume intake can reduce the risk of death by 7-8%.⁽¹⁴⁾ GLNC recommends that all Australians, including older men and women, enjoy grain foods 3-4 times a day, choosing at least half as whole grain or high fibre, and also aim to enjoy legumes at least 2-3 times each week.

Overall, making healthy choices with core grains and legumes as a priority in your diet is important to leading a long and healthy life. Simple changes older Australians could make to improve their grain and legumes choices toward meeting recommendations include:

• Choosing whole grain crispbreads, unsalted air-popped popcorn, or wholemeal fruit toast as snacks over discretionary choices such as sweet biscuits, cakes or muffins
• Adding barley, brown rice or other whole grains to soups, stews and casseroles
• Swapping pastries and pies for a sandwich, made with whole grain or high fibre bread, at lunch
•  Looking for breakfast cereals that are high in whole grain or fibre
• Substituting serves of legumes into your favourite dishes such as kidney beans in casseroles, red lentils in spaghetti bolognaise or chickpeas into any salad.

For more information on the impact of grain and legumes on health and for lots of tasty recipe ideas visit GLNC’s website.

References

1.            Fardet A, Boirie Y. Associations between food and beverage groups and major diet-related chronic diseases: an exhaustive review of pooled/meta-analyses and systematic reviews. Nutrition Reviews. 2014 Dec;72(12):741-62.

2.            Mellen PB, Walsh TF, Herrington DM. Whole grain intake and cardiovascular disease: a meta-analysis. Nutrition, metabolism, and cardiovascular diseases. NMCD. 2008;18(4):283-90.

3.            NHMRC. Australian Dietary Guidelines - Providing the scientific evidence for healthier Australian diets. 2013. Accessed online January 2014.

4.            Priebe MG, van Binsbergen JJ, de Vos R, Vonk RJ. Whole grain foods for the prevention of type 2 diabetes mellitus. The Cochrane Database of Systematic Reviews.2008(1):Cd006061.

5.            Aune D NT, Romundstad P, Vatten LJ. Whole grain and refined grain consumption and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies. European Journal of Epidemiology. 2013;28(11):845-58.

6.            Kushi LH, Meyer KA, Jacobs DR J. Cereals, legumes, and chronic disease risk reduction: evidence from epidemiologic studies. The American Journal of Clinical Nutrition. 1999;70(3 Suppl):451s-8s.

7.            Afshin A, Micha R, Khatibzadeh S, D M. Consumption of nuts and legumes and risk of incident ischemic heart disease, stroke, and diabetes: a systematic review and meta-analysis. The American Journal of Clinical Nutrition. 2014 Jul;100(1):278-88.

8.            Food and Agriculture Organization of the United Nations. Food-based dietary guidelines [cited 2016 January]. Available from: http://www.fao.org/nutrition/education/food-dietary-guidelines/regions/en/.

9.            Oldways. Oldways Common Ground Consensus Statement on Healthy Eating [cited 2016 January]. Available from: http://oldwayspt.org/common-ground-consensus.

10.          Australian Bureau of Statistics. Australian Health Survey: Nutrition First Results - Food and Nutrients, 2011-12. Canberra: Commonwealth of Australia; 2014.

11.          Tao Huang MX, Albert Lee, Susan Cho, Lu Qiu. Consumption of whole grains and cereal fiber and total and cause-specific mortality: prospective analysis of 367,442 individuals. BMC Med. 2015;13(59).

12.          WHO. Life expectancy: Life expectancy by country [cited 2013 July]. Available from: http://apps.who.int/gho/data/node.main.688?lang=en.

13.          GLNC. The Grains & Legumes Health Report. Grains & Legumes Nutrition Council: 2010.

14.          Darmadi-Blackberry I, Wahlqvist ML, Kouris-Blazos A, Steen B, Lukito W, Horie Y, et al. Legumes: the most important dietary predictor of survival in older people of different ethnicities. Asia Pacific Journal of Clinical Nutrition. 2004;13(2):217-20.

Update On Carbohydrate Recommendations for Type 2 Diabetes

Some people are calling for low-carbohydrate diets to be recommended for people with diabetes but what does the evidence show? Dr Alan Barclay APD, GI Foundation Chief Scientific Officer, looks at the issue.

Type 2 diabetes is increasing rapidly around the globe, due to a large number of factors including our ageing population, decreased physical activity and changes to the foods we eat and drink, amongst many others. While all factors are undoubtedly important, food and nutrition seem to gain a disproportionate amount of attention and generate the most debate. Hardly a week goes by without a new “diet” that self-proclaims it will help people prevent or manage their diabetes better than all preceding diets. Food faddism not only creates confusion and angst for people with diabetes, it also inadvertently affects their families, friends and carers who they share their food with. Low carbohydrate diets are becoming the latest fad, having last been popular in the 1970’s.

To help put healthy eating into perspective, the American Diabetes Association⁽¹⁾ has crafted a number of food and nutrition management goals that summarise all of the main points that need to be considered about healthy eating for diabetes:

1) Achieve and maintain

* Blood glucose levels in the recommended range or as close to recommended as is safely possible

* Blood pressure levels in the recommended range or as close to recommended as is safely possible

* A blood cholesterol and triglyceride profile that reduces the risk of vascular (e.g., heart attack, stroke, retinopathy, kidney and peripheral vascular) diseases

2) Prevent, or at least slow, the rate of development of the chronic complications of diabetes by modifying food and nutrient intakes and lifestyle (e.g., physical activity, drinking, sleep, smoking habits, etc…)

3) Consider individual nutrition needs, taking into account personal and cultural preferences and willingness to make changes

4) Maintain the pleasure of eating by only limiting food choices when indicated by scientific evidence

While points 1 and 2 are self-evident and the focus of most health professionals that work with people with diabetes, points 3 and 4 are arguably just as important, as ultimately they determine how well an individual will be adhere to a dietary regimen in the long-term.

What scientific evidence is there for recommending low carbohydrate diets over other dietary patterns? To answer this, we first need to define what a low carbohydrate diet is. The following definitions have recently been recommended⁽²⁾:

• Very low-carbohydrate diets provide 20-50 g/carbohydrate/day or less than 10% of a 8,400 kJ diet.
•  Low-carbohydrate diets provide less than 130 g/carbohydrate/day or less than 26% of energy from a 8,400 kJ diet.
• Moderate-carbohydrate diets provide 130-230 g/carbohydrate/day, or 26 - 45% of energy from a 8,400 kJ diet. 
• High-carbohydrate diets provide greater than 230 g/carbohydrate/day or 45% of energy from a 8,400 kJ diet.

It is also important to consider how much carbohydrate the average Australian, and person with diabetes, is eating at present. The most recent national nutrition survey⁽³⁾ estimates that the average adult consumed 222 g/carbohydrate/day in 2011/12, and the most recent study of people with diabetes⁽⁴⁾ estimates that they consumed 214 g/carbohydrate/day in the 1990’s. In other words, the average Australian consumes a moderate amount of carbohydrate, and it’s likely that people with diabetes consume less.

The American Diabetes Association⁽¹⁾, Canadian Diabetes Association⁽⁵⁾ and Diabetes UK⁽⁶⁾ have all recently conducted independent systematic reviews of the scientific evidence for the management of diabetes and are all in agreement that there is no evidence for strict macronutrient recommendations for people with diabetes. Instead, there are a variety of healthy eating patterns that may be suitable, based on the individual’s personal and cultural preferences and willingness to change. These may include, but are not limited to Mediterranean style, vegetarian/vegan, low-fat and low-carbohydrate patterns of eating⁽¹⁾.

Systematic reviews and meta-analyses⁽⁷⁾ have shown that over the medium-term, all of these different patterns of eating can lead to decreases in HbA1c between 0.12-0.47% points, with low-carbohydrate diets being the least effective (0.12% reduction) and Mediterranean style (0.47% reduction) and vegetarian (0.39% reduction)⁽⁸⁾ being the most effective. Unfortunately no long-term (> 2 years) studies have been published to-date.

Since these systematic reviews were conducted, Australia’s CSIRO investigated the effect of a very low-carbohydrate (50 g / day), high fibre (24.7 g / day) and low saturated fat diet versus a moderate carbohydrate (205 g / day), low GI diet in people with diabetes over 12 months⁽⁹⁾. Both patterns achieved similar decreases in body weight (~10 kg), BMI (~3.3 kg/m²), waist circumference (~9.5 cm), fasting glucose (-0.7 (low carb) vs -1.5, P=0.1), HbA1c (-1% in both), BP, total and LDL cholesterol. Medication score, glycemic variability, HDL (0.1 vs 0.06 mmol/L) and TG (-0.4 vs -0.01 mmol/L) improved modestly on the very low CHO diet compared to the moderate carbohydrate diet. These results would therefore not materially affect the conclusions of the earlier systematic reviews.

Dietary patterns with widely differing carbohydrate composition may produce similar outcomes due to differences in glycemic index (GI), glycemic load (GL) and insulin responses. It’s important to note that while the amount and type of carbohydrate are the most powerful predictors of the effect of foods on blood glucose⁽¹⁰⁾ and insulin levels⁽¹¹⁾, protein and fat also have an independent effect^(12;13).

Glycemic index values are frequently found on the labels of carbohydrate-containing foods in Australia (e.g. foods with the GI Symbol (see below) and online and total carbohydrate is a mandatory component of the Nutrition Information panel, so people with diabetes can easily calculate the glycemic load (GL = GI Í Carbohydrate per serve ÷ 100) of commonly consumed foods and beverages.

The best way to use the GI is to swap from regular high GI to low GI alternatives within a food group, and this approach also typically identifies the lower GL choices. The insulin response of a food is highly correlated with its glycemic load⁽¹⁴⁾ and for common foods and meals may be used as a surrogate at present. Table 1 lists commonly consumed low GI foods in Australia.

Table 1: Low GI foods

Dense wholegrain bread Authentic sourdough bread Barley Quinoa Pasta and noodles Pearl cous cous Doongara rice Legumes Bran Traditional oats Natural muesli Most fruits and vegies (except melons and most potatoes) Milk Yoghurt

Reducing the amount of carbohydrate is therefore simply one method of reducing blood glucose and insulin levels, but it is not the only way, nor necessarily the best way – that depends on the individual. Every person with diabetes should see an Accredited Practicing Dietitian for personalised advice.

References

1.               Evert AB, Boucher JL, Cypress M, Dunbar SA, Franz MJ, Mayer-Davis EJ, et al. Nutrition therapy recommendations for the management of adults with diabetes. Diabetes Care 2014 Jan;37 Suppl 1:S120-43. doi: 10.2337/dc14-S120.:S120-S143.

2.               Feinman RD, Pogozelski WK, Astrup A, Bernstein RK, Fine EJ, Westman EC, et al. Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base. Nutrition 2015 Jan;31(1):1-13.

3.               Australian Bureau of Statistics. Australian Health Survey: Nutrition First Results – Foods and Nutrients, 2011–12 — Australia.  9-5-2014. Canberra, Australia, Australian Bureau of Statistics.

4.               Barclay AW, Brand-Miller JC, Mitchell P. Macronutrient intake, glycaemic index and glycaemic load of older Australian subjects with and without diabetes: baseline data from the Blue Mountains Eye study. Br J Nutr 2006 Jul;96(1):117-23.

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