EDITORIAL

Providing expert nutrition advice: How do we knowwhat is best?ndi_1345 70..71

With nutrition playing such a pivotal role in the preventionof lifestyle-related diseases, having more detailed knowledgeon the effects of foods on health is a critical component ofmore effective practice. While analyses of reported dietarypatterns in populations provide evidence of relationshipsbetween dietary behaviours and disease risk, determiningthe best form of dietary intervention is perhaps not asstraightforward as it may seem.

Observational studies can provide details on specificdietary behaviours that are likely to have an impact onhealth. For example, an analysis of data on dietary patternsfrom the Health Professionals Follow-Up Study and theNurses Health Study found that more specific and compre-hensive dietary advice was warranted in reducing the risk ofdisease.1 However, changes to improve diet quality do notexist in isolation of other important health behaviours. Forexample, research has shown that in middle-aged women,substantial numbers of deaths could be avoided by notsmoking, maintaining a healthy weight and regular physicalactivity in addition to a healthy diet.2 Nevertheless, dietand physical activity appear to have benefits independentof reducing body fat.2 With increasing levels of obesity,however, the position and impact of lifestyle interventionbecome more relative. A recent review of anthropometricclassifications of obesity, for example, proposed a clinicalstaging system to aid in medical decision-making. Thissystem considered the clinical and functional staging ofobesity, moving from no apparent risk factors or functionallimitations through to severe disability and impairment ofwell-being.3 Lifestyle intervention, focusing on healthyeating habits and physical activity, plays a large role in theearly stages, but more aggressive management, such assurgery, may be required in the later stages.

Determining the specific dietary parameters for nutri-tional intervention is another area of concern. Dietarypattern analysis of observational data presents with substan-tial methodological challenges, and there are few ran-domised controlled trials on the effects of dietary patterns onlifestyle disease outcomes, such as coronary heart disease.4

Methodological challenges relate to arbitrary choices in foodgroups, problems with distortions in defining a patternbecause of correlated measurement error, and selective mis-classification of individuals.4 Where randomised controlledtrials are available, the published outcomes do little to clarifythe complex nature of dietary exposure. A recent trial of 811overweight adults found that reducing calories was the mostpotent variable on weight loss, with no difference found indietary treatments targeting varying macronutrient propor-

tions.5 It is important to note that an intention to treatanalysis was applied in the study, and that intakes at sixmonths and two years did not reach the macronutrienttargets, nor were reported energy intakes and physical activ-ity different between groups. Thus the study showed that afocus on behaviour rather than macronutrient intakes wasmore pertinent in terms of practice efficiency, but did littleto add to the knowledge on effect of various dietary macro-nutrient proportions.

Putting dietary intervention in a whole lifestyle contextand determining which food advice is best are just the begin-ning. Not surprisingly, a recent review by leading nutrition-ists found that controlling obesity and insulin resistancethrough activity and diet presented as the greatest challengefor nutrition in the next 30 years.6 Another challenge theynoted was the reductionist versus a food pattern approachused in nutrition science. This concept is gaining momen-tum as it is being more consistently argued that appreciatingthe synergy between the constituents in foods remainsan important consideration in exposing the relationshipbetween food and health.7 Focusing on food in its own rightis both pragmatic and scientifically defensible, with theconcept of food synergy further pointing to the value ofnutrient-rich foods.

Pragmatism is fundamental in developing processesfor evaluating the scientific literature to support practice.This also means defining systems of analysis that allowfor best judgements from the available information. Forexample, in the development of the US dietary guidelines,a process of evidence-based systematic reviews was appliedthat openly stated search rules and methods of study analy-sis.8 This analysis also focused on foods and food patterns,not just nutrients. Evidence was sought for dose–responserelationships, for example, to determine whether amountsof specific foods may be required to decrease the risk ofdisease. While systematic reviews are a rigorous and trans-parent approach serving evidence-based practice well, theyalso present with special challenges for nutrition.9 Thesehave been identified as considerations of baseline expo-sures, nutrient status, bioavailability, bioequivalence, mul-tiple and interrelated mechanisms of action, and dietarymethodology.9 Defining outcome measures for the effectsof food needs to be thought through carefully. In manycases, there are multiple outcomes and the effects may besubtle,10 making it difficult to discern the real effects inconventional terms. This means that we should not belimiting thinking to single food components and singleend-points.

Nutrition & Dietetics 2009; 66: 70–71 DOI: 10.1111/j.1747-0080.2009.01345.x

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Finally, determining what is best to say in providing nutri-tion advice does not occur in a policy vacuum. In this issueof the journal, Hewat writes on the situation in AustralianPrimary Health Care, which is most relevant to the practiceadvice issue.11 At the Public Health level, there are callsto consider the environmental and social consequences ofdietary advice,12 bearing in mind that food and agricultureare important considerations of nutrition policy. The respon-sibility of giving expert nutrition advice should not be takenlightly. There is a great need for scientific rigour and meth-odological development that is both sensitive and pragmaticin its approach to addressing the unique challenges of betterdelivery of nutrition for health.

Linda Tapsell, PhD, FDAADirector, Smart Foods Centre, University of Wollongong

Wollongong, New South Wales, Australia

REFERENCES

1 McCullough ML, Feskanich D, Stampfer MJ et al. Diet qualityand major chronic disease risk in men and women: movingtoward improved dietary guidance. Am J Clin Nutr 2002; 76:1261–71.

2 van Dam RM, Li T, Speigelman D, Franco OH, Hu FB. Com-bined impact of lifestyle factors on mortality: prospective cohortstudy in US women. BMJ 2008; 337: a1440. doi:10.1136/

bmj.a1440. (Accessed 1 Oct 2008.) Available from URL: http://bmj.com

3 Sharna AM, Kushner RF. A proposed clinical staging system forobesity. Int J Obes 2009; 33: 289–95.

4 Schulze MB, Hoffman K. Methodological approaches to studydietary patterns in relation to risk of coronary heart disease andstroke. BJN 2006; 95: 860–69.

5 Sacks FM, Bray GA, Carey VJ et al. Comparison of weight-lossdiets with different compositions of fat, protein, and carbohy-drates. NEJM 2009; 360: 859–73.

6 Katan MB, Boekschoten MV, Connor WE et al. Which are thegreatest recent discoveries and the greatest future challengesin nutrition? Eur J Clin Nutr 2009; 63: 2–10.

7 Jacobs DR, Gross MD, Tapsell LC. Food synergy: an operationalconcept for understanding nutrition. Am J Clin Nutr 2009; 89(Suppl.): 1S–6.

8 Lupton JR. The 2005 Dietary Guidelines Advisory CommitteeReport: from molecules to dietary patterns. Nutr Today 2005;40: 210–15.

9 Lichtenstein AH, Yetley EA, Lau J. Application of systematicreview methodology to the field of nutrition. J Nutr 2008; 138:2297–306.

10 Heaney RP. Nutrients, endpoints, and the problem of proof.2008 W O Atwater Memorial Lecture. J Nutr 2008; 138: 1591–5.

11 Hewat C. Primary health care: the new frontier. Are dietitians onthe front line or just bring up the rear? Nutr & Diet 2009; 66:72–73.

12 PHAA. A Future for Food. Canberra: Public Health Associationof Australia, 2009.

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