Responses to a GP survey: current controversies in diet and cardiovascular disease

Background When advising patients on diet and health, the general practitioner (GP) makes judgements based on the evidence available. Since current evidence on diet and cardiovascular disease is conflicted and confusing, we surveyed the current consensus amongst GPs. The aim of this study was to determine the views of GPs on dietary saturated fat, carbohydrates and long chain omega-3 fatty acids in the management of cardiovascular disease. Method An online questionnaire inviting participants to comment on seven contentious statements on diet and cardiovascular disease. Questionnaire circulated to the 1800 members of South West Thames Faculty of the Royal College of General Practitioners (RCGP). Participants were invited to tick “Agree”, “Disagree” or “Not sure” and were encouraged to add comments for each question. The results were analysed with a combination of statistical analysis and thematic analysis of comments. Results There were 89 responses. Most GPs seem well aware that drug treatment alone is inadequate and that dietary advice is important. However, there was considerable disagreement about the roles of saturated fats and carbohydrates in cardiovascular disease and “Not sure” responses ranged from 12 to 40.7%. The 40.7% related to a statement on long chain omega-3 fatty acids. Analysis of comments revealed more opinions including an awareness of the need to warn patients about trans-fatty acids. Conclusions Although the GP response rate was poor, responders do seem to see dietary advice as part of their role but do not consider themselves as experts. Education in this area should have a higher priority. Electronic supplementary material The online version of this article (10.1186/s12875-018-0840-4) contains supplementary material, which is available to authorized users.


Background
The average general practitioner (GP) in the United Kingdom (UK) will have received very little education at medical school on the role of nutrition in health and disease [1][2][3], but should be well versed in Pharmacology as a prescribing doctor. In a recent survey [2], only 33% of medical school academics felt that they were providing adequate teaching on nutrition and health. Therefore, GPs may feel more confident in providing advice on drug therapy rather than diet for the prevention of cardiovascular disease (CVD). However, an experienced GP may have acquired information about diet and lifestyle through their professional experience. Current controversies over the relevance of free sugars (as opposed to endogenous sugars in fruit (fructose) and milk (lactose)) and fats to the aetiology of CVD [4][5][6] has caused confusion amongst the general public [7,8] and we wondered what the consensus was amongst GPs. Also, since 2013, the National Institute for Health and Care Excellence (NICE) clinical guidelines have de-emphasised the role of long chain omega-3 fatty acids in the management of CVD and advise against routine prescribing of omega-3 acid ethyl esters (Omacor) [9]. However, NICE continue to recommend an increase in dietary fish as part of a Mediterranean diet [9]. There is a substantial body of evidence for benefits to both primary and secondary cardiovascular health from long chain omega-3 [10][11][12][13], and an equally impressive body of evidence that has influenced NICE to be cautious [14][15][16]. A 2017 study lasting 19 years has shown a lower CVD death rate (hazard ratio 0.73) in subjects taking a long term regular daily dose of a long chain omega-3 fatty acid supplement [17].
The aim of our study was to assess the views of GPs on a range of issues relating to nutrition and cardiovascular disease by measuring their response to several emotive and contentious questions about diet and health.

Methods
A survey monkey questionnaire was sent by email to 1800 GPs in the SW Thames section of the RCGP. One follow-up reminder was sent with a link to the questionnaire as recommended by Pealer et al. [18]. This was followed by asking non-responders to complete the same questionnaire at an NHS Clinical Commissioning Group (CCG) meeting for all GPs in the Guildford and Waverly area of Surrey (approximately 6% of SW Thames GPs). The questions were framed as tests of opinion rather than tests of knowledge with tick box options "Agree", "Disagree" and "Not sure". Participants were also encouraged to add comments and the comments were analysed using thematic analysis. Questions: 1. Once you start a patient on a statin, diet isn't very important. 2. Omega 3 intake is key to recovery from a cardiac event. 3. LDL cholesterol is more important than HDL cholesterol when interpreting a lipid profile. 4. The latest evidence on dietary fat means that we can now advise that it is safe to consume saturated fat-rich foods. 5. Diet and dyslipidaemia are linked to dysfunction of the endothelium. 6. Non-alcoholic fatty liver disease is a major risk factor for cardiovascular disease. 7. Dietary carbohydrates are neutral with respect to cardiovascular disease.

Statistics
The completed questionnaires were analysed using chisquared foursome tables to determine differences between internet responders and non-responders and calculate p values. IBM SPSS Statistics software was used to analyse gender differences, significance of years in general practice using the student t-test and correlation coefficients to show any correlations between different components of the questionnaire and to calculate p values for this data. An analysis of respondents' comments was made for recurrent themes.

Results
A total of 89 GPs responded to the initial questionnaire and a further 19 non-responders completed the questionnaire at the CCG meeting. The total sample was 108, which was 6% of the targeted GPs. There were 74 (68.5%) female GPs and 33 (30.5%) male GPs. Although age was not recorded for participants the number of years in general practice was recorded. The significance of age and experience was reflected in this data (Additional file 1: Appendix 1). The mean number of years in general practice was 13.7 yrs. (range 0.5-42) and for male GPs average was 17.6 yrs. (range 2-42) and for female GPs average was 12 yrs. (range 0.5-33). This data was similar to regional data for age and gender for GPs in South England although there was a slight bias in favour of female GPs responding to the questionnare which failed to reach statistical significance (Additional file 2: Appendix 2).
The combined results are summarised in Table 1. There was no statistically significant difference between internet responders and non-responders. However there was a trend for Question 2 with a greater proportion of non-responders disagreeing with the statement "Omega 3 intake is key to recovery from a cardiac event": Responders disagreed 30/89 (33.7%) Non responders disagreed 10/19 (52.6%), p = 0.076. Responders were twice as likely to respond "Not sure" than non-responders: Responders "not sure" 40/89 (44.9%) and non-responders "not sure" 4/19 (21.1%), p = 0.054. There was a trend for female GPs to be more likely to chose "Not sure" responses ( Table 2), but this was only statistically significant for Question 4 which suggested that dietary saturated fat is now considered "safe". 78.8% of male GPs disagreed with this statement, whereas only 41.9% of female GPs disagreed and 35% were "Not sure." There was a trend for years in practice as a GP to be a factor in responses to the statements about omega-3 and cardiac events, interpretation of lipid profiles and nonalcoholic fatty liver disease with responses from younger GPs reflecting their lack of experience (Table 3). There was a degree of overlap between questions which did not reach statistical significance: 42.6% disagreed that dietary carbohydrates are neutral for CVD and disagreed that it is now safe to advise saturated fat rich food and 42.6% agreed that diet & dyslipidaemia are linked to endothelial dysfunction and were of the opinion that dietary saturated fat is not safe.
Although there was an even split for statement 3 on the relative importance of HDL and LDL cholesterol with 15.7% of respondents opting for "not sure" (Table 1), 5.6% added the comment that the HDL/cholesterol ratio is more significant.
Subjects were invited to add comments to all questions and at the end of the questionnaire. There were 37 comments that varied from very brief such as "in moderation" for the question on safety of saturated fats, to longer detailed comments on the role of nutrition science in primary care. Comments of 4 words or less that conveyed little or no meaning, were excluded (5/37). Comments that could be classified thematically (32/37) tended to come from respondents who had been GPs a little longer (Table 4).
From a total of 32 such comments, the commonest comment (10/32) was an acknowledgement that a wide range of nutrients are important to cardiovascular health, and that a pharmacological approach alone is inadequate. Comments that are representative examples of each type of response are summarised in Table 5.

Summary
Comments by participants (Table 5) seem to show a genuine interest in dietary factors that influence cardiovascular disease (CVD). Most GPs (97%) were well aware that diet is of crucial importance in the control of CVD (Tables 1 and  5). However, there was considerable confusion about certain aspects of this topic with 44% being "Not sure" about the role of omega-3 in recovery from cardiovascular events, and 33% being unsure what advice they should be giving on the safety of saturated fats in the diet (35% for female GPs). The lack of teaching on nutritional science in medical schools is illustrated by some responses from new recruits to general practice (Tables 3 and 4).
The uncertainty and doubts about the evidence regarding the heart and long chain omega-3 supplementation is illustrated by a response to the Question 2; "Omega-3 is key to recovery from a cardiac event" with the comment: "If it was, why was it taken off prescriptions?", whereas others were impressed with the evidence for the anti-arrhythmic and anti-thrombotic activity of dietary long chain omega-3 fatty acids. Although controversial, there is good evidence for the anti-arrhythmic and anti-thrombotic properties of   long chain omega-3 fatty acids [10][11][12][13]. However, there was an impression of general confusion rather than an informed consensus on this issue amongst these GPs. While dietary trans-fatty acids were not mentioned in the questionnaire, six GPs commented on the importance of these fatty acids as a risk factor for CVD. There was some agreement on the role of dietary free sugars and saturated fats in CVD with 42.6% of GPs disagreeing with both the statement that dietary saturated fat is safe (Q4), and that dietary carbohydrates are neutral for CVD (Q7). Several comments highlighted the importance of the differences between free sugars (as a CVD risk factor) and complex carbohydrates, with the latter being generally viewed as being beneficial to cardiovascular health.
The split vote on the relative importance of LDL cholesterol and HDL cholesterol, probably reflects the current state of knowledge and confusion over the questionable clinical relevance of raised HDL cholesterol. However one participant suggested that the circulating level of VLDL (very low density lipoprotein) is more significant than either LDL or HDL. This may well be relevant to patients with cardiometabolic risk factors who are at risk of developing metabolic syndrome and type 2 diabetes mellitus and in whom serum LDL cholesterol is unremarkable. Although VLDL is not generally available for testing in primary care, estimation of 12 h fasting triacylglycerol (also termed triglycerides) is available and would be as reliable as VLDL as an indicator of cardiometabolic risk [19].
The overall outcome of this survey provides evidence of a body of professional doctors who have vested interest in diet and health. However, as several GPs indicated, their knowledge of the topic is inadequate and this may apply especially in the early stages of their career.

Strengths and limitations
Strengths of this study include canvassing of grass roots GPs who are dealing with the issue of diet and CVD regularly. The main weakness of the study is the poor response rate to the initial e-mailed online survey monkey with only 89 (5.9% of targeted group) responding. However, this response rate is fairly typical for mailings to members of the RCGP. A recent election for places on the college council got an 8.4% response (personal communication from Professor Kamila Hawthorne). While these responders may represent a select group of GPs with a greater interest in nutrition, there was very little difference between the responders and the 19 non-responders. An exception was that more responders disagreed about the value of long chain omega-3 fatty acids for recovery from a cardiac event than non-responders (52.6% versus 33.7%, p = 0.076). Responders were twice as likely to opt for "Not sure" for this statement. The main source of fats should be plant rather than animal derived.
High homocysteine is a risk factor for CVD 1 Final comments Excess protein in the diet is an important risk factor, especially excess methionine from cheese. It leads to high homocysteine levels.
VLDL cholesterol is an important risk factor 1 Q3 LDL is more important than HDL but VLDL cholesterol is even more so.
Role of omega-3 in prevent ing CVD deaths 1 Q2 Omega 3 is anti-thrombotic and anti-arrhythmic. Synthetic supplements have been disappointing.