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Novel dietary approach lowers cholesterol dramatically: the portfolio diet

Katherine E Paterson
BSc (Hons)

Specialist Community Dietitian
Norfolk and Norwich University Hospital

Training Officer
British Dietetic Association,
Heart Health and Thoracic Dietitians Specialist Group

Coronary heart disease (CHD) remains the leading cause of mortality in the UK causing over 100,000 deaths per year.(1) Around one in five deaths in men and one in six deaths in women are attributable to CHD. In 2003, CHD and stroke combined were estimated to cost the healthcare system £14,750m and 18% of this cost was associated with medications.(1)
Raised serum cholesterol, together with smoking and hypertension, are major risk factors for cardiovascular disease.(1,2) In the UK, nearly three quarters of adults have a total cholesterol level above that recommended by the National Service Framework for CHD.(1) Diet, physical activity and medication all have a role in reducing cholesterol levels.(1-3)
The consistency and size of cholesterol reduction found with statin therapy has moved the focus of treatment away from diet, even in primary prevention.(2,3) Dietary interventions altering dietary fat composition produce at best a 15% reduction in total cholesterol in metabolic studies, and between a 3% and 6% reduction in free living individuals with hyperlipidaemia.(4) This suggests that clinically meaningful interventions should move beyond fat modification.   
Nevertheless, lifestyle changes are recommended in combination with medication for those at high cardiovascular risk.(2,3) For those who are below the cut-off for pharmacological therapy and those who do not tolerate cholesterol-lowering medication, a new diet from Canada could be just what the doctor orders.

The Portfolio combination
Dr David Jenkins and his research team at the University of Toronto have been investigating a combined dietary approach to reducing blood cholesterol in hyperlipidaemic people. The dietary combination included components known individually to reduce cholesterol levels: almonds, soluble fibre, soya protein and sterols/stanols. See Box 1 for the role of the individual items.
Jenkins, who also invented the glycaemic index, wanted to know whether there was a combined effect of these foods already known individually to reduce cholesterol on their own. And there was. The hyper-cholesterolemia patients started on a low saturated fat and cholesterol diet before the study when they were supplied with the portfolio foods for a month.  
In these controlled metabolic studies reductions in low-density lipoprotein (LDL) or "bad" cholesterol of between 28% and 35% were found.(9)

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Dietary portfolio - in the long term
Jenkins and colleagues tested the approach over a year in 66 individuals with hypercholesterolaemia. Unlike the previous study, participants had to buy their food from local shops and supermarkets, although they did receive regular dietary support to help them meet their goals. The target diet aimed on average to include: 2 g plant sterols, 20 g soluble fibre, 45 g soya protein and 46 g almonds. Table 1 shows how one might include the portfolio constituents in the diet.

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The average reduction in LDL-cholesterol was 13% and this was maintained at one year. Interestingly though, a third of subjects achieved an LDL-cholesterol reduction of 20% or more, approaching the reduction levels seen with first generation statins. Compliance was more readily seen for the sterol and almond component of the diet. Adherence was less for the soya and fibre components mainly because the targets were very high. Generally, the most motivated patients were the most successful.  

The portfolio diet - who is likely to benefit?
The portfolio diet can be seen as an investment strategy - investing in a range of dietary approaches to reduce cholesterol and improve heart health, rather than just one approach, such as reducing saturated fat. The portfolio diet is not a replacement for other dietary approaches to reduce other risk factors. Nor is it a substitute for statin treatment. However, a small number of motivated patients who wish to remain statin-free - perhaps due to unwanted side-effects or who are unable to lower their cholesterol sufficiently despite medication, are the type of patients who may wish to consider the portfolio approach.  
But, it's not for everyone. Changes to dietary habits of a lifetime are difficult. A confident cook in the household is a prerequisite. A strong positive interest in dietary change is a must, coupled with enough time and money to make those changes sustainable. Those living on take-away and convenience foods need not apply.
Compliance on the other hand might be improved by starting with some of the easier investments and then building upon them gradually. Alternatively, moderate increases in the four investments may be appropriate for others.   

Conclusion
While the portfolio dietary approach improves blood lipid profile, it has yet to be proven to reduce clinical outcomes. Both larger studies and more research might be helpful here. Lipid-lowering drugs that have been proven to reduce CHD morbidity and mortality now cost the NHS more than any other kind of drug.(1)  
And this expenditure looks set to increase. Professor Roger Boyle, National Director for Heart Disease and Stroke, has called for a debate on whether all men over 50 and women over 60 should be offered statin treatment to prevent heart attacks and stroke.10 Now is an ideal time to consider what lifestyle approaches for cholesterol lowering and preventing CHD you have in your toolbox.

References

  1. Allender S, et al. Coronary heart disease statistics. 15th ed. London: BHF; 2007. Available from http://www.heartstats.org
  2. Department of Health. National service framework for coronary heart disease. Modern standards and service models. London: DH; 2000. Available from: http://www.dh.gov.uk
  3. Wood D, et al. Joint British Societies' Guidelines on prevention of cardiovascular disease in clinical practice. Heart 2005;91:v1-52.
  4. Tang L, et al. Systematic review of dietary intervention trials to lower blood total cholesterol in free-living subjects. BMJ 1998;316:1213-20.
  5. Jenkins DJA, et al. Assessment of the longer term effects of a dietary portfolio of cholesterol-lowering foods in hypercholesterolemia. Am J Clin Nutr 2006;83:582-91.
  6. Anderson JW, et al. Meta- analysis of the effects of soy protein intake on serum lipids. N Engl J Med 1995;333:276-82.
  7. Zhan S, Ho SC. Meta-analysis of the effects of soy protein containing isoflavones on the lipid profile. Am J Clin Nutr 2005;81:397-408.
  8. Law M. Plant sterol and stanol margarines and health. BMJ 2000;320:861-4
  9. Jenkins DJA, et al. The effect of combining plant sterols, soy protein, viscous fibres, and almonds in treating hypercholesterolaemia. Metabol 2003;52:1478-83.
  10. Rose D. A daily dose of statins would save lives says heart expert. The Times 28 July 2007.

Resources
Portfolio Eating Plan
W: http://portfolioeatingplan.com

Heart UK
W: www.heartuk.org.uk