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The CSIRO Diet – "Trust me, I'm a Scientist" –
Part 2 So we come to the main bone of contention, which is the sudden flip in nutritional advice from the CSIRO. In 1991, the CSIRO first published its nutritionally assessed food guidance plan, the "12345+" pyramid, where it recommended a daily intake of no less than five serves of cereal grains, four serves of vegetables, three serves of fruit, two serves of dairy and one serve of meat (or eggs, or legumes).[1] Now, in an about-turn, CSIRO is telling us to replace the cereals with meat, reduce our fruit from three serves to one serve daily, and lower our vegetable intake from four to two serves daily. Clearly, animal protein has won the day. This has brought a backlash from nutritionists who are raising concerns on the links between high protein intake and cancer, and are warning that we could face an increase in colorectal, prostate and breast cancer if people switch to a high-protein diet. However, Peter Clifton, co-author of The CSIRO Total Wellbeing Diet,[2] is quick to assert that "the evidence [which links red meat to cancer] is contradictory",[3] and also states that "losing 10 or 12 kilos in weight will overwhelm any risk – if there is any – from the high meat diet".[4] The truth is that risk factors may never be scientifically proven as causative factors, but they invariably supersede and have greater relevance than scientific proof. For example, the biggest risk factor for lung cancer is smoking, but has this ever been scientifically proved? So while scientists argue about the pros and cons of meat and try to tally up the risk–benefit trade-off, the consumer is left not knowing which way to turn. It’s like a game of "whoever has the most scientific proof wins". Fibre's anticancer benefits While they argue, let's switch our attention from meat to fibre. Fibre is a big protector of health and it could be the missing link. It's also found in carbohydrate-rich foods. All fibre is resistant to digestion. Some fibre, such as wheat bran, absorbs water in the large colon and guards against constipation. Some fibre, such as the pectins and gels from fruits and vegetables, binds with bile acids (more about this later) and is digested by the bowel flora to produce valuable sugar acids which act as immune system modulators. Other fibre, known as resistant starch, found in cereal grains and legumes, is fermented by colonic bacteria to produce short-chain fatty acids. These fatty acids not only stimulate the colonisation of beneficial bacteria (Bifidobacterium), but are also the preferred fuel of colonic mucosal cells. These cells maintain a healthy mucosal interface which protects against the risk of bowel cancer. The role of fibre and bile acids is also interesting. Bile acids are produced by the liver and assist in the digestion of fat. The more fat you eat, the more bile acids you secrete. However, once they reach the large intestine, they act as cancer-promoters. This means that while they don't cause cancer, they will promote it if conditions prevail – much like oestrogen, while not a direct cause of oestrogen-sensitive cancers, can stimulate cancer cell growth. So it's important to make sure that the bile acids don't hang around for too long. A high-fibre diet offers a twofold protective effect: it ensures that bile acids rapidly clear the bowel (i.e., promote bowel movement), while the pectins and gels bind the bile acids. Bile acids, in their bound form, not only inhibit the digestion and absorption of fat and cholesterol but ensure their safe clearance via the bowel. So fibre lowers cholesterol and fats, and minimises the risk of bowel cancer. You may wonder how a low-fibre diet is related to breast and prostate cancer. Both conditions are negatively affected by oestrogens. Normally, oestrogen is bound and inactivated by the liver and eliminated via the bile through the colon. How efficiently we do this is related to our fibre intake. Quite simply, if bound oestrogen remains in the colon too long, or if unfavourable bacteria "unbind" the oestrogen, then biologically active oestrogen will be reabsorbed. Diets high in fat and protein encourage the colonisation of unfavourable bacteria that produce enzymes which liberate oestrogen from its bound state, while high-fibre diets reduce such colonisation. Scientific studies have shown a positive correlation between high-fat diets, increased recycling of oestrogens and breast cancer, and high dietary fibre, increased faecal oestrogen elimination and low incidence of breast cancer.[5] Fibre versus protein intake So, focusing only on protein intake is simplistic. Maybe we should be looking at fibre intake in relation to protein intake. I think that David Topping, who authored the material in The CSIRO Total Wellbeing Diet explaining the role of resistant starch, would agree with me – particularly in light of the latest study he co-authored.[6] This study refers to the authors' previous research which showed that: "...high levels of dietary protein (as casein) result in increased levels of colonic DNA damage, measured by the comet assay, and thinning of the colonic mucus layer in rats when dietary resistant starch (RS) is negligible. Feeding RS abolishes these effects." The new study, which tests red meat, supports these findings. The authors conclude: "Because DNA damage is an early step in the initiation of cancer, these findings suggest that increased DNA damage due to high dietary protein as cooked red meat or casein could increase colorectal cancer risk but inclusion of resistant starch in the diet could significantly reduce that risk." So how much fibre and how much resistant starch are the authors (including David Topping) of the Total Wellbeing Diet advocating? Here's the loophole: there's no government-recommended daily intake (RDI) for fibre, so technically the authors are not "in the wrong" for indicating that 20 grams per day is adequate. However, there is a general consensus based on population studies that indicates we should be aiming for 30–40 grams daily. So how much fibre are you actually getting on this high-protein diet? By my calculations, if you opt for three slices of wholegrain bread, you will get 8 g; 40 g of high-bran cereal, 7 g; a piece of fruit, 3 g; and two cups of vegetables, 5 g – making an average total of 23 grams of fibre. If you were to swap one of your pieces of bread for a potato, then you'd reduce your fibre intake to the bare minimum. However, in the book you are told to "keep regular with dietary fibre" and that "an adequate intake of dietary fibre becomes even more important when you are on a weight-loss diet".[7] The authors recommend you to increase your fibre intake if need be. But then, if you were to do this, you wouldn't be doing the diet, you wouldn't be following the rules and you wouldn't be inducing ketosis – which is the basis of the "scientifically proven" weight-loss program. To "expert patients" who may want weight loss and wellbeing, the odds may not stack up. With no long-term studies to support the claims, we are asked to act in blind faith, trust that scientists know best and disregard all other risk factors. This is a tall order. However, all is not lost. There is more than one way to lose weight. You don't have to take the risk of a high-protein, ketone-producing diet – as was demonstrated in the CSIRO's own trial. On a reduced-calorie diet including fibre-rich foods such as wholegrains and legumes, you can still effectively lose weight, lower your blood pressure and cholesterol, and protect against heart disease, diabetes, cancer, inflammatory bowel disease, arthritis and osteoporosis. I think I'll go and stir the beans! Endnotes
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