I have been having trouble tracking down the original studies, that showed that saturated fat causes increased heart
disease, and that identified dyslipidaemia as a cause of heart disease and therefore needing treating rather than just
an indicator of risk. I understand that recent study has shown statins mechanism in reducing second heart attacks comes
more from its influence on vascular smooth muscle rather than its cholesterol lowering ability.
I am currently feeling a little high and dry on evidence to support my recommendations to patients to lower their cholesterol
and reduce the saturated fat in their diet. I would be grateful if you could provide some references to this effect and
would be interested in your comment.
The so-called “Cholesterol Myth” is the real myth. It has been promulgated by journalists and other writers seeking
controversy where there is none, in order to sell newspapers and books. The “false flames” of controversy have probably
also been fanned by industries with vested interests in saturated fat production and these are powerful industries with
huge propaganda resources. Unfortunately there is little money to be made from the truth, which is that almost everything
new that has been learnt about saturated fat, blood cholesterol and congestive heart failure (CHD) in the last 30 years
supports what we already knew back then, which is simply that “a diet high in saturated fat causes an increase in blood
cholesterol which causes an increase in CHD”.
With regards to local data, Jim Mann and colleagues undertook a great little trial randomising people to butter or
margarine and showed clear evidence of worsening lipid profiles in those given butter which reversed when they were
changed to margarine.1 This evidence was unsurprisingly consistent with a huge body of international trial
evidence from many decades of research demonstrating that saturated fat consumption increases blood cholesterol levels.
The New Zealand diet has changed significantly over the last 30 years and in particular there has been a significant
reduction in saturated fat consumption. For example butter consumption – which alone accounts for one-fifth of our total
saturated fat consumption – has fallen from a high of almost 20 kg/head in the late 1950s to about 10 kg/head this decade
(www.fao.org). Also the increasing range of low fat milk and other
dairy products has had an important impact on our saturated fat consumption. Most of these products were not available
until the 1970s and 1980s.
This change in diet has been associated with a substantial reduction in blood cholesterol levels. Since the early
1980s a fall in blood cholesterol of about 0.5 mmol/L on average has been documented. During the same period CHD mortality
has fallen by 2–3% per year in New Zealand – more than two-thirds reduction in CHD mortality in New Zealand since the
late 1960s! It has been estimated that the decline in blood cholesterol levels between the early 1980s and early 2000s
account for about one-third of this decline in CHD mortality.2
However the best evidence comes from systematic reviews of the literature that avoid the peculiarities and random
error in single studies. An international meta-analysis of cohort studies published in the Lancet in 2007 described
a ten year follow-up of almost one million people and demonstrated beyond doubt that blood lipids are strongly associated
with CHD mortality.3
Almost every trial of statins, of which there are now many, support the cohort data described above. Moreover it exposes
the other cholesterol myth that statins work primarily by their influence on smooth muscle rather than their cholesterol-lowering
ability. While statins may well work indirectly on smooth muscle, it is almost certainly secondary to their cholesterol-lowering
ability because the different declines observed in CHD risk in the different statin trials, can be explained by their
effect on lipid levels. This has been demonstrated in another international meta-analysis of almost 100,000 people in
randomised trials of statins versus placebos, published in the Lancet in 2005.4 The meta-analysis clearly
shows a strong and consistent relationship between changes in blood lipids and changes in CHD risk.
The cholesterol myths are generated by people who cherry pick individual studies or parts of studies to support their
need for controversy. The boring headline one never gets to read, based on a more systematic approach to the huge range
of evidence, is that: “We continue to confirm with almost every new study, that what we knew 30 years ago about saturated
fat, cholesterol and CHD is still true – they are strongly related and the effects are reversible.” The proof is also
in the (low saturated fat) pudding. In New Zealand saturated fat consumption has been falling for over 30 years, blood
cholesterol levels have been falling over the same period (it started before statins were invented), and so has CHD.
Professor Rod Jackson, School of Population Health, Faculty of Medical and Health Sciences, Auckland
- Chisholm A, Mann J, Sutherland W, et al. Effect on lipoprotein profile of replacing butter with margarine in a low
fat diet: randomised crossover study with hypercholesterolaemic subjects. BMJ 1996;312:931-4.
- Tobias M, Taylor R, Ken Huang L-C, et al. Did it fall or was it pushed? The contribution of trends in established
risk factors to the decline in premature coronary heart disease mortality in New Zealand. Aust N Z J Public Health
- Prospective Studies Collaboration. Blood cholesterol and vascular mortality by age, sex, and blood pressure: a meta-analysis
of individual data from 61 prospective studies with 55 000 vascular deaths. Lancet 2007; 370: 1829–39
- 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: 1267–78.