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bmj.com: Ben Goldacre

Posted Jan 06 2010 8:09am
bmj.com: Just found this lovely response to The Bitch Doctor from Dr John Briffa on the BMJ website ........ it's old but worth revisiting.


John P Briffa,
Doctor and health writer
Woolaston House, 
25 Southwood Lane, 
Highgate, 
London 
N6 5ED




Dr Goldacre’s opinion piece [1] takes a broad swipe at media nutritionists by focusing on some silly thinking and the ‘pseudoscience’ that undoubtedly can sometimes be found in the area. The author takes particular exception to Gillian McKeith’s claim that chlorophyll is rich in oxygen and that eating plenty of it will help to oxygenate the blood. In respect to this, Dr Goldacre comments “as any 14 year old biology student could tell you, plants only make oxygen in light: it's very dark in your bowel; and even if, to prove a point, you put a searchlight up your bottom, you probably wouldn't absorb too much oxygen through the gut wall.”
Fair enough, but I wonder how many of us (doctors included) have beliefs and, where relevant, employ clinical approaches that in their entirely would stand up to scrutiny. Take, for example, Dr Goldacre’s own suggestion to test the oxygen-producing capacity of chlorophyll in the gut by illuminating the large bowel: this hypothetical test, albeit tongue-in- cheek, is flawed because the process of digestion would render chlorophyll biologically inactive by the time it reaches the colon. On the face of it, some of Dr Goldacre’s own musings here might be regarded as nonsensical at those of McKeith.
Dr Goldacre appears to give the impression that much what media nutritionists do is unvalidated mumbo-jumbo. Yet, many nutritionists do refer to the research and scientifically reference their work. The accusations of misinterpretation, cherry-picking, inappropriate extrapolation of data and conflict of interest can be made, but these can also be levelled at the medical and scientific establishments too: The widespread promotion of statins despite there being no evidence that these are effective in reducing mortality in the primary prevention setting is a case in point [2,3].
The area of nutrition is an emerging field, and thus many nutritionists will advocate approaches that may not have been formally studied, but do seem to be of broad benefit in practice. It seems that for Dr Goldacre such clinical experience does not count for much. Is he of the mind, then, that everything health professionals do be properly studied and validated before implementation. If that’s the case, we doctors should pack up and go home now: only 15 per cent of medical practice has been proven effective, and most of what we do is of unknown effectiveness, is unlikely to be beneficial, or has been shown to be positively harmful [4].
Dr Goldacre expresses his belief that nutritionists have deliberately over-complicated their approaches and adds, “Basic, uncomplicated dietary advice is effective and promotes health.” Given his attachment to scientific rigour, it seems appropriate to ask Dr Goldacre what evidence there is for this assertion.
If anything, the evidence is to the contrary. For example, the perhaps most pervasive nutritional message that has sunk deep into the population’s psyche is certainly a simple one: that we should eat a diet low in fat and high in carbohydrate. And despite this easy-to-understand piece of advice, rates of chronic conditions such as obesity and Type 2 diabetes in the UK continue to soar.
And the evidence for the ineffectiveness of low-fat eating is not merely anecdotal. Studies show that this oft-touted ‘healthy’ way of eating is, for instance, thoroughly ineffective for the purposes of weight loss in the long term [5,6]. It is perhaps worth bearing in mind that the ‘low-fat high-carb’ dictum is not generally popularised by media nutritionists, but instead by dieticians and the professional bodies to which they are affiliated, notably the British Dietetic Association (BDA).
Other dietetic ‘gems’ that come from the dietetic establishment include the notion that plenty of calcium and dairy products in the diet are somehow ‘essential’ to bone health in children and adults [7-9], that artificial sweeteners are preferred to sugar for those seeking to lose weight (not one single randomised, placebo-controlled study assessing the effects of artificial sweeteners on weight is to be found in the scientific literature), that diabetics should make starchy carbohydrates a cornerstone of their diet (many of these release sugar relatively quickly into the bloodstream and tend to disrupt glycaemic control, and eating less of such foods has been shown to improve biochemical markers including those of glycaemic control) [10-17], and that taking dietary steps to reduce cholesterol saves lives [18].
I accept that media ‘nutritionists’ may get it wrong sometimes (myself included) and some make a tidy living from their efforts. But if Dr Goldacre’s cry is for more accountability in the area, I reckon he should put the spotlight of scrutiny less on media nutritionists, and more on dieticians and the BDA.
References:
1. Goldacre B. Tell us the truth about nutritionists. BMJ 2007;334:292
2. Abramson J, Wright JM. Are lipid-lowering guidelines evidence- based? Lancet 2007;369:168-169
3. Jauca C, Wright JM. Therapuetics letter: update on statin therapy. Int Soc Drug Bull Newsletter. 2003;17:7-9
4. http://www.clinicalevidence.com/ceweb/about/knowledge.jsp
5. Pirozzo S, et al. Advice on low-fat diets for obesity. Cochrane Database Syst Rev. 2002;(2):CD003640
6. Willett C, et al. Dietary fat is not a major determinant of body fat. Am J Med. 2002;113(9B):47S-59S
7. Lanou AJ, et al. Calcium, dairy products, and bone health in children and young adults: a reevaluation of the evidence. Pediatrics. 2005;115(3):736-43
8. Winzenberg T, et al. Effects of calcium supplementation on bone density in healthy children: meta-analysis of randomised controlled trials. BMJ 2006;333:775-778
9. Feskanich D, et al. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. American Journal of Clinical Nutrition 2003 77(2):504-511
10. Collier GR, et al. Low glycemic index starchy foods improve glucose control and lower serum cholesterol in diabetic children. Diabetes Nutr Metab 1988;1:11-19
11. Fontvieille AM, et al. A moderate switch from high to low glycemic-index foods for 3 weeks improves metabolic control of type I (IDDM) diabetic subjects. Diabetes Nutr Metab 1988;1:139-43
12. Jenkins DJ, et al. Low-glycemic-index starchy foods in the diabetic diet. Am J Clin Nutr 1988;48:248–54
13. Wolever TM, et al. Beneficial effect of a low glycaemic index diet in type 2 diabetes. Diabet Med 1992;9:451–8
14. Wolever TM, et al. Beneficial effect of low-glycemic index diet in overweight NIDDM subjects. Diabetes Care 1992;15:562–4
15. Brand JC, et al. Low-glycemic index foods improve long-term glycemic control in NIDDM. Diabetes Care 1991;14:95–101
16. Fontvieille AM, et al. The use of low glycaemic index foods improves metabolic control of diabetic patients over five weeks. Diabet Med 1992;9:444–50
17. Frost G, et al. Dietary advice based on the glycaemic index improves dietary profile and metabolic control in type 2 diabetic patients. Diabet Med 1994;11:397–401
18. Studer M, et al. Effect of different antilipidemic agents and diets on mortality. Archives of Internal Medicine. 2005;165:725-730
19. Email communication (available on request)
contact: john@drbriffa.com
Competing interests: I am a private-practising doctor and health writer with a special interest in nutrition
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