The SA Journal Diabetes & Vascular Disease Vol 12 No 1 (July 2015)

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4 VOLUME 12 NUMBER 1 • JULY 2015
EDITORIAL SA JOURNAL OF DIABETES & VASCULAR DISEASE
The cardioprotective diet – carbohydrates versus fat
FJ RAAL
Correspondence to: FJ Raal
Division of Endocrinology and Metabolism, Department of Medicine,
Johannesburg Hospital, Parktown, Johannesburg, South Africa
e-mail:
Previously published in Cardiovasc J Afr 2014; 25(6): 302
S Afr J Diabetes Vasc Dis 2015; 12: 4
The global burdens of cardiovascular disease, obesity and
type 2 diabetes mellitus continue to rise in both developed
and developing countries.1 Much of these burdens are
preventable as they are the result of sub-optimal lifestyle, which
includes poor diet, excess calorie intake, physical inactivity and
cigarette smoking.2
As discussed by Lionel Opie (page 5), several diets, such as
the new Adkins diet, the Noakes diet and the Dukan diet, which
encourage the restriction of carbohydrates rather that the restriction
of fat, has recently been introduced and many more are likely to
follow.3 Each claim to be better that the next at addressing this
global health burden. However one has to consider what these
diets are trying to achieve. Are they trying to achieve weight loss
and prevention of the onset of type 2 diabetes, or are they trying to
achieve cardiovascular protection?
It is correct that excessive carbohydrate intake, particularly
refined carbohydrate as found in sugary drinks and energy snacks,
is contributing to the global epidemic of obesity and type 2 diabetes
mellitus but it is wrong to conclude that a high-carbohydrate
intake is the major cause of atherosclerosis, the leading cause of
cardiovascular disease worldwide. Atherosclerosis, particularly
coronary artery disease, is not a disease of carbohydrate metabolism
and there is little evidence to show that a low-carbohydrate diet
will prevent atherosclerosis.
Restriction of refined carbohydrates, being our major energy
source, will assist with weight reduction in the short term. However
in terms of prevention of atherosclerosis and cardiovascular disease
in the longer term, restriction of saturated fat is more important. It
is therefore incorrect, and in fact it may be harmful, to advocate the
substitution of refined carbohydrates with saturated fats.
Increasing the intake of saturated fats raises serum low-density
lipoprotein (LDL) cholesterol levels.4 Innumerable epidemiological
studies have shown a positive relationship between serum LDL
cholesterol levels and risk for cardiovascular disease, particularly
coronary artery disease. In fact the link between LDL cholesterol and
coronary artery disease is one of the most thoroughly researched
in all of medicine.5
There is overwhelming evidence, accumulated over more than
three decades, to show that the more you lower LDL cholesterol the
lower your cardiovascular risk. For every 1 mmol/l reduction in LDL
cholesterol using statins, there is approximately a 12% reduction
in total mortality and a 21% reduction in major vascular events.6
We have not yet identified a threshold below which LDL cholesterol
reduction is no longer beneficial but harmful.7
So what should we be advising our patients at risk for
cardiovascular disease? Obesity is not so much about diet but
about energy balance – calories consumed versus those expended.
Appropriate restriction of calorie intake whether it be carbohydrate,
protein or fat is important for weight maintenance and prevention
of obesity and type 2 diabetes. However in terms of achieving
cardiovascular protection or maintaining a low LDL level, cholesterol
is pivotal.
As Lionel Opie emphasises, we need to encourage and promote
a healthy lifestyle with regular exercise, non-smoking and a healthy
diet consisting of moderate portions of all three of the major
components of our diet, namely carbohydrate, protein and fat.3
If LDL cholesterol levels remain elevated or if the individual has
established cardiovascular disease or diabetes, or is considered
at high cardiovascular risk, international guidelines worldwide
recommend that statin therapy should be initiated.8,9 This will be
much more beneficial for long-term cardiovascular protection than
the short-term benefit of weight reduction achieved with marked
carbohydrate restriction.
References
1. Murray CJ, Lozano R, Naghavi M, et al. Disability adjusted life years (DALYs) for
291 diseases and injuries in 21 regions, 1990–2010: a systematic analysis for the
Global Burden of Disease 2010 study. Lancet 2012; 380: 2197–2223.
2. Moran AE, Forouzanfar MH, Roth G, et al. Temporal trends in ischaemic heart
disease mortality in 21 world regions, 1980–2010: the Global Burden of Disease
2010 study. Circulation 2014; 129: 1483–1492.
3. Opie L. Lifestyle and diet. Cardiovasc J Afr 2014; 25: 00–00.
4. Keys A. Seven Countries: A Multivariate Analysis of Death and Coronary Artery
Disease. Cambridge, Ma: Harvard University Press, 1980.
5. Grundy SM. Is lowering low-density lipoprotein an effective strategy to reduce
cardiac risk? Circulation 2008; 117: 569–573.
6. Cholesterol Treatment Trialists’ (CTT) collaborators. Efficacy and safety of
cholesterol-lowering treatment: prospective meta-analysis of data from 90 056
participants in 14 randomised trials of statins. Lancet 2005; 366: 1267–1278.
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intensive lowering of LDL cholesterol: A meta-analysis of data from 170 000
participants in 26 randomised trials. Lancet 2010; 376: 1670–1681.
8. Reiner Z, Cataplano AL, DeBacker G, et al. ESC/EAS guidelines for themanagement
of dyslipidaemias: the Task Force for the management of dyslipidaemias of the
European Society of Cardiology (ESC) and the European Atherosclerosis Society
(EAS). Eur Heart J 2011; 32: 1769–1818.
9. Stone NJ, Robinson JG, Lichtenstein AH, et al. 2013 ACC/AHA guideline on
the treatment of blood cholesterol to reduce atherosclerotic cardiovascular
risk in adults: a report of the American College of Cardiology/American Heart
Association Task Force on practice guidelines. Circulation 2014; 129: S1–S45.