Cardiovascular Health – is cutting saturated fat still the
answer…………….?
By Linda Main, Dietetic Adviser at HEART UK – The Cholesterol Charity
In the last couple of years a number of studies in the Media have reported that saturated fat intakes
do not influence cardiovascular risk. This is contrary to:
a) the body of science supporting saturated fat reduction
b) clinical guidelines supporting saturated fat reduction
c) population dietary reference values supporting saturated fat reduction
SACN (Scientific Advisory Committee on Nutrition) a UK advisory body that reports to Government is
currently reviewing the evidence and is expected to report late 2017 or early 2018.
In the meantime here are some key points that might help you when speaking to patients and
colleagues about saturated fat.
UK Dietary Recommendations for fats – what are they and are we
achieving them?
Below (table 1) are the population targets for fat intake in the UK as a percentage of Total
Energy (% Food energy in brackets). In table 2 actual UK intakes from the National Diet and
Nutrition Surveys are stated – Red indicates that targets are not being met, Green indicates
targets are met.
Table 1 – UK population Dietary Reference Values for Fat (COMA 1991, SACN 2004)
Fat
SFA = Saturated fat, MUFA = Monounsaturated fat, PUFA = Polyunsaturated fat, Trans = Trans fat
Table 2 UK fat intakes (NDNS 2016 – Years 5 and 6 combined)
2016 WHO systematic reviews and regression analysis – effect on
lipids and lipoproteins
Two excellent documents have reviewed the effect of dietary fats on blood lipids. These are
available on the WHO website with open access. The main points are set out below:
SATURATED FAT
• The report emphasises that there is strong
evidence from RCT’s covering a wide range of
saturated fat intakes
• That it is important to think about replacement
calories when reducing saturated fat
• Reducing SFA and replacing with a mixture of
MUFA and PUFA is more favourable on blood
lipids than replacing with a mixture of
carbohydrates (or background westernised
diet)
• Replacement of saturated fat with PUFA brings
about the biggest reduction in total Cholesterol,
LDL cholesterol and triglycerides, followed by
replacement with MUFA
• Not all saturated fatty acids have the same
effect – C12, C14, C16 are cholesterol raising
• Saturated fats of less than 12 carbons or more
than 18 carbons cannot be estimated due to
lack of information but effects may be neutral
• More studies needed with myristic (C14) and
Lauric (C12) acids
• No differences between genders, or baseline
lipid levels
TRANS FAT
• Replacement of industrial trans fats with cis
PUFA, MUFA or Carbohydrate leads to
improvements in lipids and lipoproteins
• PUFA most favourable
• Limited data on trans fats from ruminant
sources so outcomes less conclusive but were
largely in the same direction as for industrial
trans fats
• Ruminant fats provide only small amounts of
trans fats in the UK
The effects of dietary fatty acids on LDL
cholesterol
This slide shows the effect on LDL cholesterol of
replacing carbohydrate calories with equal calories
from




TFA – trans fats
SFA – saturated fat
MUFA – monounsaturated fat
PUFA – polyunsaturated fat
And
The effect on LDL cholesterol of replacing
carbohydrate calories with equal calories from
saturated fatty acids of various chain lengths – It
demonstrates that saturated fats C12, C14 and C16
are all cholesterol raising.
Micha & Mozzafarin (2010) Lipids 45, 893-905
Results from prospective longitudinal studies and dietary fat
Two large studies – the Nurse’s Health Study (73,147) and Health Professional Follow Up Study
(42,635) can be used to illustrate the effects of long term dietary patterns. These studies are very
large and have 28 & 24 years of follow up respectively.
The main conclusion (in an open access paper from Zong et al - BMJ 2016; 355:i5796) are:
• Dietary intakes of lauric (C12:0) myristic (C14:0) palmitic (C16:0) and stearic (C18:0) fatty
acids were positively associated with risk of CHD
• Replacement of 1% Energy from combined C12-C18 saturated fats resulted in 6-8% reduced
risk of CHD
• Replacement of 1% Energy from C16:0 (palmitic acid) was associated with a 10-12%
reduction in risk
There are limitations with such studies. The main ones are that they are usually based on food
frequency questionnaires. Secondly it can be difficult to disentangle the associations with
intakes of individuals saturated fatty acids that are highly correlated with each other.
Negative studies – the following studies failed to demonstrate any benefits from saturated fat
reduction:
The main reasons for this are:


the lack of control over what saturated fat calories were replaced by – often this was just
background westernised diet which is high in refined carbohydrates
inclusion of very old studies using spreads with a high trans fats content which skewed the
results – this was before we were aware of the problems associated with trans fats
Problems with Chowdhury et al 2014
The Chowdhury paper has a number of problems and a critique can be found here
http://wphna.org/wp-content/uploads/2014/08/201403_Annals_of_Int_Med_Chowdhury_et_al_Fat_and_CHD_+_responses.pdf
The authors had never published a diet study before and were unfamiliar with how such data
should be interpreted. The main points of the critique are:
• Big errors when transcribing data from original papers
• Omitted important studies – especially on PUFA (e.g. de Goede 2012, Dolecek
1997, Jakobsen 2009)
• Issues with data interpretation e.g. no account taken of the source of nutrients e.g.
MUFA from meat or nuts
• They included the Sidney Diet Heart study which used a margarine high in trans fats
– this significantly influenced the results
• Their recommendations fail to take into account nutrient substitutions
• They also choose to ignore strong primary data that shows there is an effect