Response to the draft Australian Dietary Guidelines

May 16, 2012 | Publisher: davy | Category: Health & Medical |  

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Page 1 of 18 Response to the draft Australian Dietary Guidelines February 2012 Author: Robert Davy BE(Hons), ME, MAppStat Canberra, ACT email: Executive summary The Australian Dietary Guidelines play a crucial role in determining the health of the population. They will influence what is thought to be healthy and culturally acceptable for decades to come, because they will be taught to students and medical practitioners, thereby influencing the decisions and eating habits of the population. However, in the production of these draft Guidelines there has been a number of crucial shortcomings in the Evidence Report and anomalies in the modelling. Additionally, clarity is needed in the Guide to Healthy Eating. These problems need to be corrected in order to guide the population’s eating habits to be more nutrient dense and healthy, and to avoid chronic disease. I write as someone who has lived healthily on a wholly plant-based diet for more than ten years. My comments mostly call into question the amount of animal foods prescribed for the Australian population, and the methods used to justify it. I have classified my findings into six main topics. These are summarised below.  Several of the Foundation Diets and Total Diets suggested in the Modelling document have saturated fat content that exceeds the NHMRC’s own recommended limit of 10 per cent of energy intake. Also, many of the prescribed diets that do not exceed 10 per cent saturated fat still go very close to this level. Even if someone followed the Guidelines closely, their saturated fat could easily climb above 10 per cent. This is important because saturated fat is linked to heart disease risk, and heart disease is the number one cause of death in this country. An estimated 18 per cent of people are displaying some symptoms of heart disease risk, and studies show that saturated fat at 11 per cent of energy may increase the risk of pancreatic cancer. Therefore, a lower saturated fat limit should be specified, and adhered to in the modelling.  There is a heavy emphasis on obtaining heme iron (iron from animal flesh), which could increase risk of heart disease. The Evidence Report did not consider the large body of evidence on this association. Heme iron is obtained only from animal products such as red meat, chicken, pork and seafood. Heme iron has been associated with increase in risk of heart disease in several large prospective studies. Iron from plant foods (non-heme iron) is not associated with increased risk of heart disease. Dietary iron needs can be met Page 2 of 18 sufficiently through plant foods. Its absorption can be improved with practices such as consuming adequate vitamin C with each meal.  There needs to be definitive statements about the risks associated with eating red meat. That red meat increases the risk of colon cancer is no longer seriously disputed. In addition to the heart disease risk from heme iron mentioned above, red meat has been associated with the development of type 2 diabetes in some very large cohort studies. As a minimum step, the 65 g daily limit on red meat articulated in the Modelling document should be included in the Guide to Healthy Eating, and the reasons for it should be highlighted. Given the heme iron association with heart disease however, this daily limit should be closer to zero.  There is much leeway within the Guidelines to adopt a high protein diet, which could increase risk of mortality. In large prospective studies, high protein diets have been associated with an increase in mortality risk, independently of saturated fat and other known mortality risks.  Dairy should not be emphasised above its plant-based “alternatives”. This can be argued on a number of grounds: a) The majority of the world’s adults, including Indigenous Australians, are lactose intolerant, thus an emphasis on dairy is Euro-centric and not representative of Australia’s cultural diversity. b) Calcium-fortified dairy “alternatives” such as soy, rice, almond and oat milk have much lower saturated fat. c) Good quality studies have shown that dairy increases the risk of prostate cancer (the most common cancer for Australian men) and ovarian cancer.  The immense nutritional value of green and brassica vegetables (and particularly leafy greens) is not recognised. a) In the Guide to Healthy Eating, green and brassica vegetables appear to be just one option along with other vegetables. The nutrient dense nature of green and brassica vegetables means that they really should have their own food group. They are also strongly protective against cancer. b) Why is only one serve per day of green vegetables prescribed in the modelling? It’s curious enough that green and brassica vegetables were limited to a maximum of two serves per day in the optimisation because of “cultural reasons”, but even under this constraint, why was the optimum number of daily serves of greens one, not two? Including more greens would be an opportunity to help meet a range of nutritional requirements such as calcium – but without the saturated fat associated with other sources of calcium. c) Within the green and brassica vegetable grouping, leafy green vegetables have been given insufficient weighting. Compared with green peas, leafy green vegetables are much denser in important nutrients such as iron, calcium and magnesium. Page 3 of 18 Saturated fat The NHMRC has set an upper limit of saturated fat at 10 per cent of energy intake (Nutrient Reference Values document). This contrasts with the USA’s Food and Nutrition Board which does not set a tolerable upper limit for saturated fat, recognising that any incremental increase in saturated fat is known to raise the risk of coronary heart disease. They recommend that individuals maintain their saturated fatty acid consumption as low as possible, while consuming a nutritionally adequate diet (National Academy of Sciences 2006). Dietary saturated fat has also been linked to increased risk of other adverse health outcomes such as pancreatic cancer, and it has no known role in prevention of chronic disease. It is concerning that several of the sample diets in the draft Dietary Guidelines have saturated fat content which exceeds the NHMRC’s own limit of 10 per cent. Heart disease and saturated fat—still the main issue Heart disease is still the number one cause of death in Australia. In a recent survey, 18 per cent of Australians reported having symptoms relating to heart disease risk factors, and this percentage increased with age (Australian Bureau of Statistics 2006). Mean cholesterol levels as of a few years ago have been estimated to be 5.1 and 5.2 mmol/L for men and women respectively (Farzadfar et al. 2011). This is still among the highest in the world – similar to North America. A meta-analysis of 61 prospective studies showed conclusively that total serum cholesterol is related to heart disease risk (Lewington et al. 2007). Modelling of experimental data predicts that decreasing saturated fat content by 5 per cent would lower serum cholesterol by about 0.3 mmol/L (Hegsted et al. 1993). Using the data from these articles, it is clear that a 5 per cent further reduction in saturated fat content of the diet would achieve a substantial reduction in heart disease risk among the general population. Pancreatic cancer and saturated fat A large prospective study (Thiébaut et al. 2009) showed that a group with median intake of 11 per cent saturated fat had a 21 per cent increase in risk of pancreatic cancer when compared to lower saturated fat intake, after adjusting for other variables. The association was strongest for saturated fat of animal origin. This is one of the best designed studies to date on pancreatic cancer and fat intake, with 1337 cancer cases and a wide range of observed fat intakes. NHMRC’s sample diets exceed saturated fat limit Several of the Foundation Diets and Total Diets have saturated fat content exceeding the NHMRC’s own recommended limit of 10 per cent of energy intake (see Tables 1 to 3 below). Many of the other prescribed diets that do not exceed 10 per cent saturated fat still go very close to this level, posing the real risk of the recommended limit easily being exceeded, even by the most discerning eater. Even if the Guidelines were followed precisely, many people would exceed 10 per cent saturated fat, just due to natural variation from person to person and the lack of precise knowledge about fat content in their diets. Very few people would be able to estimate their saturated fat intake to within one per cent. Calculations readily show that an extra serve of dairy milk could raise saturated fat from 10 to 11.5 per cent of energy, and an extra 40 g serve of cheese could increase it from 10 to 12 per cent. Clearly, then, it is unwise to prescribe diets with saturated fat above 9 per cent. A lower target should be aimed for in the Page 4 of 18 diets, simply to ensure that the majority of people who follow the Guidelines will actually come under 10 per cent. Reducing the recommended serves of meat and dairy is an easy way of reducing saturated fat intake. Additional calculations I used the data for energy and saturated fat in grams from the Tables in Appendix A of the Modelling document. The percentage energy from saturated fat was calculated using the accepted figure of 37.6 kJ per gram of fat. When applied to the Foundation Diets in Tables A11.1 and A11.2, the following results were obtained, showing levels of saturated fat exceeding or coming very close to the recommended upper limit. Table 1 Saturated fat content of Foundation Diets for women Women, from Table A11.1, Foundation Diets Age 19-30 31-50 51-70 70+ Energy (kJ) 7383.98 7561.16 7214.27 6586.64 Saturated fat (g) 17.81 17.74 19.44 19.11 Saturated fat (% energy)* 9.1 8.8 10.1 10.9 *NHMRC’s recommended upper limit of saturated fat is 10% of energy intake Table 2 Saturated fat content of Foundation Diets for men Men, from Table A11.2, Foundation Diets Age 19-30 31-50 51-70 70+ Energy (kJ) 8943.91 8894.29 8286.49 7304.92 Saturated fat (g) 22.39 22.96 21.94 19.93 Saturated fat (% energy)* 9.4 9.7 10.0 10.3 *NHMRC’s recommended upper limit of saturated fat is 10% of energy intake While these tables represent a low physical activity level, I found a similar pattern among the 7-day simulations listed in Appendix 15 of the Modelling document where higher activity levels are assumed. Using the tables in Appendix 15, I calculated the mean percentage saturated fat for each grouping of gender, height/activity level and age. For average height/ light to moderate activity, the diets in Table 3 were found to exceed 10 per cent saturated fat on average. Page 5 of 18 Table 3 Mean saturated fat content for diet simulations in Appendix 15 of modelling document – average height, light- moderate physical activity Gender/Age Saturated fat (% energy)* Boys 12 to 13 10.5 Girls 12 to 13 10.7 Men 70 plus 10.2 Women 51 to 70 10.5 Women 70 plus 10.6 *NHMRC’s recommended upper limit of saturated fat is 10% of energy intake Again, while several of the sample diets do not exceed 10 per cent saturated fat, a number of them lie in the range between 9 and 10 per cent, which is very close to the limit. Summary  The modelling system used to inform the Guide to Healthy Eating is flawed because the fraction of energy from saturated fat frequently exceeds 10 per cent, the limit set by the NHMRC.  Because many of the modelled diets go close to or exceed 10 per cent of energy from saturated fat, and there is a strong reliance on animal products, it is to be expected that many people will go over 10 per cent saturated fat without being aware of it.  At these levels of saturated fat it can be expected that there will be additional increases in the risk of heart disease and pancreatic cancer.  Saturated fat intake can easily be much lower than 10 per cent of energy while meeting nutrient requirements. This is achieved through consumption of nutrient-rich plant foods. Page 6 of 18 Red meat risks Unprocessed red meat remains central to the Australian diet and is still recommended in the new draft Dietary Guidelines, despite evidence showing serious adverse health effects. Evidence is accumulating on the potential association with gastric cancer (González et al. 2006, Cross et al. 2011), liver disease (Freedman et al. 2010) and renal cancer (Daniel et al. 2012). The evidence for the link between colorectal cancer and unprocessed red meat is convincing and uncontroversial. There also exists a large amount of data on the positive association between unprocessed red meat and type 2 diabetes. Further discussion on the latter two diseases follows below. Colorectal cancer Every meta-analysis of prospective studies published in the international peer-reviewed literature in the last ten years has found a statistically significant positive association between red meat and colorectal cancer (Sandhu et al. 2001, Norat et al. 2002, Larsson & Wolk 2006, Chan et al. 2011, Alexander et al. 2011 and World Cancer Research Fund / American Institute for Cancer Research 2007). Only Alexander et al. (2011) downplayed their result due to heterogeneity of studies; however, heterogeneity generally makes it harder to detect an underlying association. This only confirms the robustness of the finding. Two of these studies existed prior to the release of the previous edition of the Dietary Guidelines, however they appear to have escaped the notice of the authors at the time. The previous version of the Guide to Healthy Eating (1998), which is still current, suggests that up to 200 g daily serves of red meat is healthy. As a result, many people erroneously believe this to be the case – with potentially tragic health outcomes. The document “A review of the evidence to address targeted questions to inform the revision of the Australian Dietary Guidelines” (the Evidence Report) states that the evidence linking red meat to colorectal cancer is in Grade B (probable). Given the history of investigation stated above, it is not clear why the evidence is not Grade A (convincing association). The disease burden associated with colorectal cancer is significant and every effort is needed to reduce it. Type 2 diabetes In recent years there have been a number of large prospective studies on the link between red meat and diabetes. Of three recent meta-analyses conducted, two returned a statistically significant link between red meat and type 2 diabetes (Aune et al. 2009, Pan et al. 2011). The latter of these (and the most up-to-date) included 28,228 cases of type 2 diabetes. Their estimate of the effect is a 19 per cent increase in risk of type 2 diabetes per 100 g of unprocessed red meat. The meta-analysis by Micha et al. (2010) did not return a statistically significant result; however, a number of large cohort studies appeared just after that paper was written, such as Steinbrecher et al. (2011) which included 8587 incident cases of type 2 diabetes. This alone would increase the number of cases in that meta- analysis by 80 per cent. In Australia, around 1.7 million people have type 2 diabetes and a further 2 million people have a pre- diabetes condition (source: http://www.diabetesvic.org.au). This is about one person in six. Therefore, including red meat in the Dietary Guidelines is particularly inappropriate for at least one in six people in Australia on account of diabetes risk. Page 7 of 18 Getting iron and zinc It is often suggested that iron from animal flesh is the most reliable way to avoid iron deficiency anemia. Yet, the majority of the population’s iron intake comes from plants (Australian Bureau of Statistics 1998). The bioavailability of non-heme iron (mostly from plants) can be improved markedly by simple practices such as consuming vitamin C-rich food with a meal and avoiding tea with a meal (Thankachan et al. 2008). Some studies of young women among well-nourished populations have shown little relationship between iron intake and the incidence of anemia (Pynaert et al. 2007, Asakura et al. 2009). Also, it has been found that the rate of iron deficiency anemia is not markedly different between vegetarians and non-vegetarians (Ball & Bartlett 1999). Good sources of iron from plant sources include legumes, whole grains, dried fruits, leafy green vegetables, nuts and seeds. The recommended daily intake of zinc for Australian men is set at 14 mg per day, with up to 50 per cent extra said to be required in the case of plant-based diets (Nutrient Reference Values document). This recommended daily intake for zinc is one of the highest in the world, despite there being little evidence of zinc deficiency in Australia. In Canada and the USA the recommended daily intake is 11 mg per day. The World Health Organization set a recommended nutrient intake of 14 mg per day only for the extreme case of high phytate diets with very low bioavailability. Zinc is readily available from foods across the plant kingdom, including grains, legumes, seeds, nuts and vegetables. Examples include peanut butter, green beans, zucchini, chick peas, pumpkin seeds, whole wheat, rice and oats. Bioavailability is improved substantially by practices that are already common in food preparation which reduce the phytate content. This includes using yeast in bread making, soaking or sprouting (in the case of legumes), and roasting (of nuts and seeds). It is not hard to obtain iron and zinc from a plant-based diet. Summary  The Modelling document placed serve limits on red meat at 65 g per day. The previous version of the Guide to Healthy Eating suggested that 200 g per day was acceptable, so this is a major change. This change, and the reasons for it, has not been communicated clearly enough in the new Guide to Healthy Eating. There is nothing in the Guide to Healthy Eating to indicate that when people eat red meat they are taking on additional risk for chronic disease depending on their level of intake.  It is a concern that the Guidelines recommend eating red meat at all given that it has been convincingly associated with cancer and other chronic disease.  Red meat is particularly inappropriate for at least one in six people in Australia on account of diabetes risk.  Iron and zinc can be obtained from plant foods by following some simple guidelines. Page 8 of 18 Coronary heart disease and cardiovascular disease: the link with heme iron from meat Dietary iron comes in two forms: heme and non-heme. Plants contain only non-heme iron. Heme iron is only obtained from animal products, the main ones being red meat, chicken, turkey and seafood. Dietary heme iron has been shown to be associated with coronary heart disease or cardiovascular disease in several large prospective studies (Ascherio et al. 1994, Klipstein-Grobusch et al. 1999, Lee et al. 2005, van der A et al. 2005 and Qi et al. 2007). These studies included several tens of thousands of people. The latter study found that a high dietary heme intake was associated with a 50 per cent increase in risk of heart disease. Recently, a large cohort study with over 21,000 participants found an association between red meat consumption and coronary heart disease (Ashaye et al. 2011). This may also be due to the heme iron mechanism. A similar finding was documented in Kelemen et al. (2005), where a study of 29,017 women showed a 44 per cent increase in coronary heart disease risk for the highest versus lowest red meat intake. It is surprising that the Evidence Report did not examine the evidence linking heme iron and heart disease. Heart disease is still the number one cause of death in this country. The evidence on heme iron and heart disease risk should be comprehensively examined and dietary advice should be modified accordingly. Plant foods can meet dietary iron needs adequately. Therefore, heme iron from animal flesh should be avoided, resulting in lower heart disease risk. Summary  Heme iron, obtained from animal flesh, has been associated with an increased risk of heart disease in a number of large cohort studies.  This increase in risk is especially important since heart disease remains the number one cause of death in Australia. The evidence suggests that wherever possible, heme iron (derived from meat products) should be avoided.  Non-heme iron from plants can meet iron needs adequately. Page 9 of 18 High protein diets Since the release of the previous Dietary Guidelines there has been an increase in the number of books and programs advocating a high protein diet. Data is beginning to emerge on the long-term adverse consequences of these diets. In a large prospective study of more than 40,000 women over a 12-year period, protein intake was associated with cardiovascular mortality. Among women aged 40—49 at enrolment, the increase in cardiovascular mortality risk was 16 per cent per decile of protein intake (Lagiou et al. 2007). The study corrected for saturated fat intake and other factors. This increase in mortality risk could be due partially to heme iron (derived from animal flesh), as already mentioned. Another study of 43,960 men found that among healthy men, there was a 21 per cent increase in risk in ischemic heart disease for the highest versus lowest quintiles of total protein intake (Preis et al. 2010). This result was due almost entirely to animal protein; no association was found for vegetable protein. The Nutrient Reference Values document sets an upper limit for protein at 25 per cent of total energy. This upper limit of protein has been reduced from 35 per cent in the previous Dietary Guidelines. High protein diets, such as the one in Noakes et al. (2005) that led to a popular diet book1, are no longer valid within the Dietary Guidelines – not only because of the extreme protein level, but also because of the large daily serves of red meat which are known to raise colorectal cancer risk. However, a diet with 25 per cent protein is still well within the high range of those long-term cohort studies mentioned above. These protein amounts are excessive: the population mean is around 16—17 per cent. The available data indicates an increase in mortality risk at protein levels of 25 per cent of total energy. Summary The draft Dietary Guidelines and Guide to Healthy Eating do not rule out the possibility of high protein diets which have been shown to be associated with chronic disease and mortality risk in the long term. 1 http://www.themainmeal.com.au/Red+meat+and+nutrition/Red+meat+and+nutrition.htm Page 10 of 18 Dairy The Guide to Healthy Eating emphasises dairy intake and effectively gives dairy a food group of its own, albeit with “alternatives” that are not clearly defined. However, in addition to its saturated fat content, the intake of dairy has been shown to be associated with chronic diseases and other adverse conditions. Lactose intolerance The ability of humans to digest dairy milk is a relatively recent genetic adaptation. The condition known as lactase persistence is the ability to digest lactose from milk as an adult. Worldwide, the majority of the population (approximately 65 per cent) does not have this ability, and is lactose intolerant. Within certain ethnic groups the prevalence of lactose intolerance is very much higher. This includes Aboriginal Australia, southern Africa, China, Japan, south-east Asia, Indonesia and Papua New Guinea (Itan et al. 2010). Clearly, an emphasis on dairy milk to obtain calcium represents a limited Euro-centric viewpoint. While the Guidelines make some suggestions for people who are lactose intolerant, these are not backed up by model results. None of the diets in the Modelling document reflect a lactose intolerant diet; hence, the draft Dietary Guidelines do not meaningfully consider large sections of the diverse Australian population. Prostate cancer and dairy Studies show an increased risk of prostate cancer with dairy consumption. The Evidence Report cites only the “poor quality” literature review by Alvarez-León et al. (2006). This review doesn’t consider the findings in the meta-analysis by Gao et al. (2005) which was conducted on prospective studies and found that high intake of both dairy and calcium was related to increased risk of prostate cancer. They found a 33 per cent increase in risk of prostate cancer for the highest versus the lowest categories of dairy intake. A similar association was observed in a subsequent prospective study of 43,435 men over 7.5 years (Kurahashi et al. 2008). On what basis were these two publications excluded from the NHMRC’s Evidence Report? The link between dairy and prostate cancer is also seen in case-control studies (Qin et al. 2004) and ecological studies across many countries (Ganmaa et al. 2002). More recently, a large prospective study of 27,111 participants found that intake of phytanic acid (found in dairy products and meat) was related to an increased risk of prostate cancer (Wright et al. 2011). Laboratory tests have shown that dairy milk stimulated the growth of prostate cancer cells in culture, increasing the growth rate by over 30 per cent, while almond milk decreased the growth rate by 30 per cent (Tate et al. 2011). Within the 7-day sample diets that form the basis of the Dietary Guidelines, adult men have average calcium values ranging from about 1340 to 1780 mg per day, depending on age group and activity level. Sample diets for boys aged 14–18 with high activity level have average calcium nearly 1900 mg per day. The recommended daily intake already has a considerable safety margin, and exceeding the recommended daily intake to this extent (by 40 to 60 per cent) is unnecessary. The large amounts of dairy used to deliver these quantities of calcium are likely to be enhancing lifetime prostate cancer risk. Page 11 of 18 Prostate cancer is the most common cancer for men in Australia. One in nine men will develop the disease in their lifetime (source: http://www.prostate.org.au). Given this disease burden, the advice on dairy intake should be reconsidered urgently. Ovarian cancer and dairy Over time, a number of studies have reported a suggestive association of ovarian cancer risk with the intake of lactose. Two meta-analyses published in 2006 independently reported a statistically significant increase in cancer risk for higher lactose intake (Larsson et al. 2006, Genkinger et al. 2006). The former of these studies reported a 13 per cent increase in risk of ovarian cancer for each 10 g increase in lactose. In addition, suggestive associations have been found between the risk of ovarian cancer and the intake of fat from animal sources. Recently, in a very large study of 151,552 women over a period of 9 years, 695 cases of ovarian cancer were observed, and the risk of ovarian cancer was found to be related to the intake of animal fat (Blank et al. 2012). Dairy and severe acne Acne is not considered to be a chronic disease, however it is a major concern for many young people and can leave lifelong scars. Large prospective studies have shown that dairy intake increases the risk of severe acne in a dose-dependent manner (Adebamowo et al. 2005, Adebamowo et al. 2006). The risk was found to be higher for low fat milk. This is a particular concern because the Guide to Healthy Eating places an emphasis on low fat dairy products. Alternative sources of calcium The draft Dietary Guidelines and Guide to Healthy Eating do not devote much space to discussing the “alternatives” within the dairy grouping. Due to the high saturated fat content and the diseases associated with dairy (i.e. milk, yoghurt and cheese), the calcium-fortified “alternatives” are almost invariably a better choice. A serving of calcium-fortified soy milk typically has less than one quarter of the amount of saturated fat as dairy milk. There are other choices available, such as oat, rice and almond milk. There are many other foods that can contribute to daily calcium requirements. From the nuts and seeds group, tahini (sesame seed paste) and ground flax seed have about the same calcium content per gram of saturated fat as whole milk. Also, compared with whole milk, chia seeds contain about 3 times the amount of calcium per gram of saturated fat. Chia seeds are grown in Australia and are readily available in supermarkets nowadays. Within the legumes group, certain kinds of beans have more bioavailable calcium and can contribute a substantial fraction of daily needs. These include white beans and chick peas (Sahuquillo et al. 2003). These legumes can also contribute useful amounts of iron and zinc. The nutrient density of leafy green vegetables places them in a category of their own. They differ markedly from other vegetables, even green peas. This is shown in Figure 1, where it can be seen that leafy greens have much higher calcium for the energy content. They are also more calcium-dense than dairy milk. They can be a significant source of calcium without the saturated fat. My own experiments with linear programming and the AUSNUT07 database indicate that calcium requirements can be met by generous consumption of leafy greens along with other plant foods. Page 12 of 18 While calcium bioavailability does vary between foods, it can be seen that a wide variety of foods can be used to meet daily calcium needs. Figure 1 Calcium content per unit energy (mg/kcal) of selected foods, USDA Nutrient Database Summary  The draft Dietary Guidelines’ emphasis on dairy neglects the prevalence of lactose intolerance in the Australian community.  There are chronic disease associations with dairy intake (prostate cancer, ovarian cancer). The sample diets that form the basis of the Guidelines exceed the recommended daily intake of calcium by up to 60 per cent. The amount of recommended dairy is excessive and is likely to be enhancing cancer risk.  Studies show that dairy intake may increase the risk of severe acne.  Calcium can be obtained from a wide variety of plant sources with less saturated fat than dairy.  Due to the chronic disease risk associated with dairy consumption, and to reduce the saturated fat content of the diet, it would be prudent to promote calcium-rich plant foods and calcium-fortified alternatives to dairy. Green peas Broccoli Milk (whole fat) Milk (low fat) Parsley Chinese cabbage (pak choy) milligrams of calcium per kilocalorie 0 2 4 6 8 0 2 4 6 8 Page 13 of 18 Green vegetables The Foundation Diets and many of the sample Total Diets include only one serve of green and brassica vegetables per day. Also, the modelled composite serve of greens has a large proportion of green peas and beans, which are less dense in calcium and magnesium than leafy greens (although they are extremely good sources of zinc). A further complication is that the Guide to Healthy Eating effectively groups green and brassica vegetables with all other vegetables, which could be taken to mean that they are in some way equivalent. This may stem from some of the modelling work, where a severe limit was placed on the green vegetable grouping. Modelling questions The Modelling document states that the number of daily serves of green and brassica vegetables was limited to two in the optimisation (Table 4). The stated reason for this was that the nutrient-dense nature of green vegetables caused them to become too dominant, and that any more serves would not be culturally acceptable. It is disappointing that this arbitrary suboptimal constraint was imposed. At least three serves are achievable by anyone, and some people may choose to eat more if they knew about the benefits. Culturally, we are not homogenous – for example, people of Asian background tend to eat more leafy green vegetables (Butler et al. 2010). Eating more green vegetables (and especially leafy greens) should be encouraged, not stifled. Limiting green vegetables in this way not only denies the opportunity for healthier diets but also ignores Australia’s diverse cultural makeup. Nevertheless, given the upper constraint of two serves per day, it is unclear why the Foundation Diets and many of the sample Total Diets only prescribe one serve per day (as shown in Tables 11 and 12 of the Modelling document). Why wasn’t the optimal number of green vegetables two serves per day? Green and brassica vegetables have potent anti-carcinogenic properties (Boivin et al. 2009). There is an opportunity here to improve health outcomes, simply by allowing these nutrient-dense foods to take their proper place in the diet. Summary  Leafy green vegetables are more nutrient dense in calcium, magnesium and iron than full-fat and low-fat dairy.  The decision by the modellers to severely restrict the amount of green and brassica vegetables in their model means that their nutrient density (particularly calcium density) will not be seen for what it is.  In the Guide to Healthy Eating, green and brassica vegetables appear to be just one option amongst all other vegetables. A reader could take this to mean that all vegetables are essentially equivalent— they are not.  In terms of public education, the best way to communicate the benefits of green and brassica vegetables is to give them a food group of their own, with a strong emphasis on leafy greens. Page 14 of 18 Concluding remarks Many statements in the Modelling document stress “cultural acceptability”. These Guidelines will be influencing what is culturally acceptable for decades to come, because they will be taught to students and medical practitioners, thereby influencing the eating habits of the population. Some questionable modelling decisions were taken that essentially reinforce the status quo of high saturated fat intake. The continued reliance on animal products, and the trivial amounts of green and brassica vegetables in these diets, means that high saturated fat will remain firmly entrenched. It appears that these modelling decisions were made so as not to overly challenge the average person as measured by a survey of eating habits in 1995. Saturated fat, and its association with heart disease, is still the main issue in the Australian diet. Nevertheless, it appears that the modelling did not explicitly attempt to cap the saturated fat content. This means that in practice, many people with good dietary intentions will have saturated fat intake well above 10 per cent of energy. Few people can accurately estimate the saturated fat content of their own diet. The exhortations to choose low-fat dairy are ineffective because the marketing of low fat and fat reduced products bears little relationship to the actual fat content. Also, low fat products often have added sugar to entice the consumer. This, along with “discretionary” serves of sausages, bacon, eggs, cream and so on, is likely to lead to a poor result. The Evidence Report failed to examine some chronic disease links for which there is a large amount of evidence. Heme iron from animal flesh contributes to heart disease independently of the saturated fat link. In addition, continued reliance on animal products for many people is likely to lead to chronic disease such as cancer (pancreatic, colon, prostate, ovarian) and type 2 diabetes. Final remark: getting vitamin B12 Vitamin B12 is made from bacteria and is not reliably available from plants. This is often cited as a reason not to abandon eating meat, dairy and eggs. However, the prevalence of B12 deficiency is very high in older Australians: 23 per cent of people aged 50 or over (Flood et al. 2006). Clearly, it is not the lack of animal products in the diet that has caused this high rate of deficiency. Supplementation is a very good idea for omnivores, vegetarians and vegans. Page 15 of 18 References Adebamowo, C. A., Spiegelman, D., Berkey, C. S., Danby, F. W., Rockett, H. H., Colditz, G. A., Willett, W. C. & Holmes, M. D. (2006), ‘Milk consumption and acne in adolescent girls.’, Dermatol. Online J. 12(4), 1. Adebamowo, C. A., Spiegelman, D., Danby, F. W., Frazier, A. L., Willett, W. C. & Holmes, M. D. (2005), ‘High school dietary dairy intake and teenage acne.’, J. Am. Acad. Dermatol. 52(2), 207–214. Alexander, D. D., Weed, D. L., Cushing, C. A. & Lowe, K. A. (2011), ‘Meta-analysis of prospective studies of red meat consumption and colorectal cancer.’, Eur. J. Cancer Prev. 20(4), 293–307. Alvarez-León, E.-E., Román-Viñas, B. & Serra-Majem, L. (2006), ‘Dairy products and health: a review of the epidemiological evidence.’, Br. J. Nutr. 96 Suppl 1, S94–S99. Asakura, K., Sasaki, S., Murakami, K., Takahashi, Y., Uenishi, K., Yamakawa, M., Nishiwaki, Y., Kikuchi, Y. & Takebayashi, T. (2009), ‘Iron intake does not significantly correlate with iron deficiency among young Japanese women: a cross-sectional study.’, Public Health Nutr. 12(9), 1373–1383. Ascherio, A., Willett, W. C., Rimm, E. B., Giovannucci, E. L. & Stampfer, M. J. (1994), ‘Dietary iron intake and risk of coronary disease among men’, Circulation pp. 969–974. Ashaye, A., Gaziano, J. & Djoussé, L. (2011), ‘Red meat consumption and risk of heart failure in male physicians.’, Nutrition, metabolism, and cardiovascular diseases : NMCD 21(12), 941–6. Aune, D., Ursin, G. & Veierød, M. B. (2009), ‘Meat consumption and the risk of type 2 diabetes: a systematic review and meta-analysis of cohort studies.’, Diabetologia 52(11), 2277–2287. Australian Bureau of Statistics (1998), ‘National Nutrition Survey: Nutrient Intakes and Physical Measurements, 1995’, Catalogue No. 4805.0. Australian Bureau of Statistics (2006), ‘Cardiovascular Disease in Australia: A Snapshot, 2004-05’, Cat. 4821.0.55.001. Ball, M. J. & Bartlett, M. A. (1999), ‘Dietary intake and iron status of Australian vegetarian women.’, Am. J. Clin. Nutr. 70(3), 353–8. Blank, M. M., Wentzensen, N., Murphy, M. A., Hollenbeck, A. & Park, Y. (2012), ‘Dietary fat intake and risk of ovarian cancer in the NIH-AARP Diet and Health Study.’, Br. J. Cancer . Boivin, D., Lamy, S., Lord-Dufour, S., Jackson, J., Beaulieu, E., Côté, M., Moghrabi, A., Barrette, S., Gingras, D. & Béliveau, R. (2009), ‘Antiproliferative and antioxidant activities of common vegetables: A comparative study’, Food Chemistry 112(2), 374–380. Butler, L. M., Wong, A. S., Koh, W.-P., Wang, R., Yuan, J.-M. & Yu, M. C. (2010), ‘Calcium intake increases risk of prostate cancer among Singapore Chinese.’, Cancer Res. 70(12), 4941–4948. Chan, D. S. M., Lau, R., Aune, D., Vieira, R., Greenwood, D. C., Kampman, E. & Norat, T. (2011), ‘Red and processed meat and colorectal cancer incidence: meta-analysis of prospective studies.’, PLoS One 6(6), e20456. Page 16 of 18 Cross, A. J., Freedman, N. D., Ren, J., Ward, M. H., Hollenbeck, A. R., Schatzkin, A., Sinha, R. & Abnet, C. C. (2011), ‘Meat consumption and risk of esophageal and gastric cancer in a large prospective study.’, Am. J. Gastroenterol. 106(3), 432–442. Daniel, C. R., Cross, A. J., Graubard, B. I., Park, Y., Ward, M. H., Rothman, N., Hollenbeck, A. R., Chow, W.-H. & Sinha, R. (2012), ‘Large prospective investigation of meat intake, related mutagens, and risk of renal cell carcinoma.’, Am. J. Clin. Nutr. 95(1), 155–162. Farzadfar, F., Finucane, M. M., Danaei, G., Pelizzari, P. M., Cowan, M. J., Paciorek, C. J., Singh, G. M., Lin, J. K., Stevens, G. A., Riley, L. M. & Ezzati, M. (2011), ‘National, regional, and global trends in serum total cholesterol since 1980: systematic analysis of health examination surveys and epidemiological studies with 321 country-years and 3·0 million participants.’, Lancet 377(9765), 578–586. Flood, V. M., Smith, W. T., Webb, K. L., Rochtchina, E., Anderson, V. E. & Mitchell, P. (2006), ‘Prevalence of low serum folate and vitamin B12 in an older Australian population.’, Aust. NZ J. Public Health 30(1), 38–41. Freedman, N. D., Cross, A. J., McGlynn, K. A., Abnet, C. C., Park, Y., Hollenbeck, A. R., Schatzkin, A., Everhart, J. E. & Sinha, R. (2010), ‘Association of meat and fat intake with liver disease and hepatocellular carcinoma in the NIH-AARP cohort.’, J. Natl Cancer Inst. 102(17), 1354–1365. Ganmaa, D., Li, X.-M., Wang, J., Qin, L.-Q., Wang, P.-Y. & Sato, A. (2002), ‘Incidence and mortality of testicular and prostatic cancers in relation to world dietary practices.’, Int. J. Cancer 98(2), 262–267. Gao, X., LaValley, M. P. & Tucker, K. L. (2005), ‘Prospective studies of dairy product and calcium intakes and prostate cancer risk: a meta-analysis.’, J. Natl Cancer Inst. 97(23), 1768–77. Genkinger, J. M., Hunter, D. J., Spiegelman, D., Anderson, K. E., Arslan, A., Beeson, W. L., Buring, J. E., Fraser, G. E., Freudenheim, J. L., Goldbohm, R. A., Hankinson, S. E., Jacobs, Jr, D. R., Koushik, A., Lacey, Jr, J. V., Larsson, S. C., Leitzmann, M., McCullough, M. L., Miller, A. B., Rodriguez, C., Rohan, T. E., Schouten, L. J., Shore, R., Smit, E., Wolk, A., Zhang, S. M. & Smith-Warner, S. A. (2006), ‘Dairy products and ovarian cancer: a pooled analysis of 12 cohort studies.’, Cancer Epidemiol. Biomarkers Prev. 15(2), 364–372. González, C. A., Jakszyn, P., Pera, G., Agudo, A., Bingham, S., Palli, D., Ferrari, P., Boeing, H., del Giudice, G., Plebani, M., Carneiro, F., Nesi, G., Berrino, F., Sacerdote, C., Tumino, R., Panico, S., Berglund, G., Simán, H., Nyrén, O., Hallmans, G., Martinez, C., Dorronsoro, M., Barricarte, A., Navarro, C., Quirós, J. R., Allen, N., Key, T. J., Day, N. E., Linseisen, J., Nagel, G., Bergmann, M. M., Overvad, K., Jensen, M. K., Tjonneland, A., Olsen, A., Bueno-de Mesquita, H. B., Ocke, M., Peeters, P. H. M., Numans, M. E., Clavel-Chapelon, F., Boutron- Ruault, M.-C., Trichopoulou, A., Psaltopoulou, T., Roukos, D., Lund, E., Hemon, B., Kaaks, R., Norat, T. & Riboli, E. (2006), ‘Meat intake and risk of stomach and esophageal adenocarcinoma within the European Prospective Investigation Into Cancer and Nutrition (EPIC).’, J. Natl Cancer Inst. 98(5), 345–354. Hegsted, D. M., Ausman, L. M., Johnson, J. A. & Dallal, G. E. (1993), ‘Dietary fat and serum lipids: an evaluation of the experimental data.’, Am. J. Clin. Nutr. 57(6), 875–883. Itan, Y., Jones, B. L., Ingram, C. J. E., Swallow, D. M. & Thomas, M. G. (2010), ‘A worldwide correlation of lactase persistence phenotype and genotypes.’, BMC Evol. Biol. 10, 36. Kelemen, L. E., Kushi, L. H., Jacobs, D. R. & Cerhan, J. R. (2005), ‘Associations of dietary protein with disease and mortality in a prospective study of postmenopausal women.’, Am. J. Epidemiol. 161(3), 239–49. Page 17 of 18 Klipstein-Grobusch, K., Grobbee, D. E., den Breeijen, J. H., Boeing, H., Hofman, A. & Witteman, J. C. (1999), ‘Dietary iron and risk of myocardial infarction in the Rotterdam Study.’, Am. J. Epidemiol. 149(5), 421–8. Kurahashi, N., Inoue, M., Iwasaki, M., Sasazuki, S. & Tsugane, A.S. (2008), ‘Dairy product, saturated fatty acid, and calcium intake and prostate cancer in a prospective cohort of Japanese men.’, Cancer Epidemiol. Biomarkers Prev. 17(4), 930–937. Lagiou, P., Sandin, S., Weiderpass, E., Lagiou, a., Mucci, L., Trichopoulos, D. & Adami, H.-O. (2007), ‘Low carbohydrate-high protein diet and mortality in a cohort of Swedish women.’, J. Intern. Med. 261(4), 366–74. Larsson, S. C., Orsini, N. & Wolk, A. (2006), ‘Milk, milk products and lactose intake and ovarian cancer risk: a meta-analysis of epidemiological studies.’, Int. J. Cancer 118(2), 431–441. Larsson, S. C. & Wolk, A. (2006), ‘Meat consumption and risk of colorectal cancer: a meta-analysis of prospective studies.’, Int. J. Cancer 119(11), 2657–64. Lee, D.-h., Folsom, A. R. & Jacobs, D. R. Jr. (2005), ‘Iron , zinc , and alcohol consumption and mortality from cardiovascular diseases : the Iowa Women’s Health Study’, Am. J. Clin. Nutr. pp. 787–791. Lewington, S., Whitlock, G., Clarke, R., Sherliker, P., Emberson, J., Halsey, J., Qizilbash, N., Peto, R. & Collins, R. (2007), ‘Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta-analysis of individual data from 61 prospective studies with 55,000 vascular deaths.’, Lancet 370(9602), 1829–1839. Micha, R., Wallace, S. K. & Mozaffarian, D. (2010), ‘Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes mellitus: a systematic review and meta-analysis.’, Circulation 121(21), 2271–2283. National Academy of Sciences (2006), ‘Dietary reference intakes : the essential guide to nutrient requirements’, National Academies Press. Noakes, M., Keogh, J. B., Foster, P. R. & Clifton, P. M. (2005), ‘Effect of an energy-restricted, high-protein, low-fat diet relative to a conventional high-carbohydrate, low-fat diet on weight loss, body composition, nutritional status, and markers of cardiovascular health in obese women.’, Am. J. Clin. Nutr. 81(6), 1298– 1306. Norat, T., Lukanova, A., Ferrari, P. & Riboli, E. (2002), ‘Meat consumption and colorectal cancer risk: dose- response meta-analysis of epidemiological studies.’, Int. J. Cancer 98(2), 241–256. Pan, A., Sun, Q., Bernstein, A. M., Schulze, M. B., Manson, J. E., Willett, W. C. & Hu, F. B. (2011), ‘Red meat consumption and risk of type 2 diabetes: 3 cohorts of US adults and an updated meta-analysis.’, Am. J. Clin. Nutr. 94(4), 1088–1096. Preis, S. R., Stampfer, M. J., Spiegelman, D., Willett, W. C. & Rimm, E. B. (2010), ‘Dietary protein and risk of ischemic heart disease in middle-aged men.’, Am. J. Clin. Nutr. 92(5), 1265–1272. Pynaert, I., Delanghe, J., Temmerman, M. & De Henauw, S. (2007), ‘Iron intake in relation to diet and iron status of young adult women.’, Ann. Nutr. Metab. 51(2), 172–181. Qi, L., van Dam, R. M., Rexrode, K. & Hu, F. B. (2007), ‘Heme iron from diet as a risk factor for coronary heart disease in women with type 2 diabetes.’, Diabetes Care 30(1), 101–106. Page 18 of 18 Qin, L.-Q., Xu, J.-Y., Wang, P.-Y., Kaneko, T., Hoshi, K. & Sato, A. (2004), ‘Milk consumption is a risk factor for prostate cancer: meta-analysis of case-control studies.’, Nutr. Cancer 48(1), 22–27. Sahuquillo, A., Barberá, R. & Farré, R. (2003), ‘Bioaccessibility of calcium, iron and zinc from three legume samples.’, Die Nahrung 47(6), 438–41. Sandhu, M. S., White, I. R. & McPherson, K. (2001), ‘Systematic review of the prospective cohort studies on meat consumption and colorectal cancer risk: a meta-analytical approach.’, Cancer Epidemiol. Biomarkers Prev. 10(5), 439–446. Steinbrecher, A., Erber, E., Grandinetti, A., Kolonel, L. N. & Maskarinec, G. (2011), ‘Meat consumption and risk of type 2 diabetes: the multiethnic cohort.’, Public Health Nutr. 14(4), 568–574. Tate, P. L., Bibb, R. & Larcom, L. L. (2011), ‘Milk stimulates growth of prostate cancer cells in culture.’, Nutr. Cancer 63(8), 1361–1366. Thankachan, P., Walczyk, T., Muthayya, S., Kurpad, A. V. & Hurrell, R. F. (2008), ‘Iron absorption in young Indian women: the interaction of iron status with the influence of tea and ascorbic acid.’, Am. J. Clin. Nutr. 87(4), 881–886. Thiébaut, A. C. M., Jiao, L., Silverman, D. T., Cross, A. J., Thompson, F. E., Subar, A. F., Hollenbeck, A. R., Schatzkin, A. & Stolzenberg-Solomon, R. Z. (2009), ‘Dietary fatty acids and pancreatic cancer in the NIH-AARP diet and health study.’, J. Natl Cancer Inst. 101(14), 1001–1011. van der A, D. L., Peeters, P. H. M., Grobbee, D. E., Marx, J. J. M. & van der Schouw, Y. T. (2005), ‘Dietary haem iron and coronary heart disease in women.’, European Heart Journal 26(3), 257–62. World Cancer Research Fund / American Institute for Cancer Research. (2007), ‘Food, nutrition, physical activity, and the prevention of cancer: a global perspective.’, Washington DC: AICR. Wright, M. E., Bowen, P., Virtamo, J., Albanes, D. & Gann, P. H. (2011), ‘Estimated phytanic acid intake and prostate cancer risk: A prospective cohort study.’, Int. J. Cancer . http://dx.doi.org/10.1002/ijc.27372

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