An update on cardiovascular disease

Mei Wan assesses the latest evidence surrounding nutrition and cardiovascular disease.

Cardiovascular disease (CVD) is an umbrella term for diseases relating to the heart and blood vessels. The four main types of CVD are coronary heart disease (CHD), stroke, peripheral arterial disease and aortic disease. According to NHS England, CVD affects an estimated seven million people in the UK and causes one in four premature deaths.

Depending on the type of CVD, the symptoms may vary and may present as chest pain, weakness of limbs, feeling dizzy, shortness of breath and/or a slow heartbeat. According to the National Institute for Health and Care Excellence (NICE),¹ there are four non-modifiable risk factors:

1. Age: There is a greater risk of developing CVD with age; it primarily affects people aged over 50 years.
2. Gender: At all ages, men have a higher risk of CVD than women, and on average develop CVD about ten years earlier.
3. Family history of CVD: This may reflect a shared environment, genetic factors or both. There is an increased risk of early and lifetime CVD if there is a family history of premature CVD death.
4. Ethnic background: People of South Asian or Sub-Saharan African origin have an increased risk of CVD, while people of South American or Chinese origin have a lower risk compared with people of European origin.

What are the current nutritional guidelines?

According to NICE,¹ there are five modifiable risk factors in the prevention and management of cardiovascular diseases.

1. Healthy diet

Aim for a daily total fat intake of 30% or less of total energy intake. Specifically, saturated fatty acids (SFA) should make up 7% or less of total energy intake and should be replaced by monounsaturated and polyunsaturated fatty acids (MUFA; PUFA) such as olive oil, rapeseed oil or spreads based on these oils. Avoid or minimise trans-fat intake.² However, a pooled analysis of 11 cohort studies suggested that replacing SFA intake with PUFA intake rather than MUFA intake prevents CHD over a wide range of intakes and among all middle-aged and older women and men.³

Include at least five portions of fruits and vegetables daily, that contain minerals, vitamins, fibre and antioxidants that help to protect heart health.²

Be mindful that salt intake does not exceed six grams (about one teaspoon) a day.² Instead of adding salt to cooking and/or for taste, try adding dried/fresh herbs and spices (the latter will help to increase your overall fibre intake too).

Limit refined sugar by eating fewer biscuits, chocolates, cakes and products with added sugar, and drinking less sugary soft drinks. Aim for no more than 30 grams (two tablespoons) of refined sugar a day.²

Increasing fibre intake helps lower heart disease risk, lowers cholesterol and may help with maintaining a healthy weight and weight loss, as fibre keeps you full for longer. Alongside vegetables, include wholegrains, pulses, wholemeal or granary breads, oats, brown rice and wholegrain breakfast cereals.²

Aim to have two portions of fish a week including one serving of oily fish, as the latter is rich in omega-3 polyunsaturated fats that have benefits for heart health.²

2. Physical activity

General physical activity recommendations are also heart-healthy recommendations. Adults should aim for 150 minutes of moderate-intensity activities (for example cycling, brisk walking, swimming) and/or a combination of 75 minutes of vigorous-intensity exercise activities (for example running, team sports, high-intensity interval training) a week. In addition, two days a week of muscle-strengthening activities are recommended. For individuals unable to perform moderate-intensity physical activities, encourage them to exercise at their maximum safe capacity.⁴

3. Smoking cessation

Advise and support all people to stop smoking by signposting to local services.

4. Weight management

Aim for a healthy weight through individualised behaviour change techniques and dietary approaches whilst taking into consideration any other pre-existing medical conditions, mental health and social support.

5. Alcohol consumption

For men and women who drink regularly or frequently (i.e. most weeks), do not drink more than 14 units a week. It is best to spread 14 units of drinking evenly over three or more days. Alternatively, to help reduce alcohol consumption, aim for several alcohol-free days each week.⁵

Is there a link between CVD and omega-3 intake?

Fish oil supplements have been a topic of discussion regarding their potential benefits for heart health. While some studies suggest fish oil supplements benefit specific heart conditions in certain individuals, others haven’t found conclusive evidence. It’s challenging to have robust data as there are limitations with interpretation using statistical methods and, often, an observed effect is not based on actual dietary changes.

In addition, intervention studies are poorly suited for investigating dietary interventions and outcomes that require a long follow-up period, such as mortality. Furthermore, participants generally self-report dietary intake, which is prone to error and unlikely to be precise which means changes in diet or covariates are likely not captured over time.

In summary, as a population, we are still not eating enough fish (as food). Whilst supplements may help, we require better quality research to fully understand dosing given that many LCn3 trials at moderate to high risk of bias appear to be inflating any protective effects and that small trial bias is also inflating any protective effects; in simple terms, there are some protective effects, but they are small.⁸

What is the debate around saturated fat?

For decades, saturated fat has been linked to increased LDL (‘bad’) cholesterol levels, a major risk factor for heart disease. This evidence underlies current dietary recommendations to limit saturated fat. However, as with any dietary modification, there’s a potential for unintended consequences – for example, replacing saturated fat with other unhealthy options with added salt or added sugars. Therefore, focusing solely on villainising specific components of food might be less effective than actively promoting a more desirable dietary approach, such as the Mediterranean diet.

A systematic review and network meta-analysis of 40 randomised control trials (RCTs) (involving 35,548 adults with CVD or with at least two cardiovascular risk factors), compared seven named dietary programmes: low fat (18 studies); Mediterranean (12); very low fat (six); modified fat (four); combined low fat and low sodium (three); Ornish (three); Pritikin (one). It suggested that moderate certainty evidence shows that the Mediterranean and low-fat diets, with or without physical activity or other interventions, reduce all-cause mortality and non-fatal myocardial infarction in adults with increased cardiovascular risk. In addition, the Mediterranean diet data suggested it could likely reduce stroke risk.⁹

The Mediterranean diet is known to promote a low saturated fat intake but one that is rich in fatty fish. A Cochrane review of 15 studies with over 56,000 adult participants (aged 18 years or older) suggested that reducing SFA and replacing it with PUFA intake for a minimum of two years leads to a reduction in cardiovascular events. Furthermore, the greater reduction in SFA caused greater reductions in cardiovascular events. However, the effects of replacement with MUFA remain unclear.¹⁰

What about coconut oil, which is high in saturated fat?

A systematic review and meta-analysis of 16 trials suggested that coconut oil consumption results in significantly higher LDL-C than vegetable oils low in SFA and trans-fat. The participants were a mix of healthy subjects and hypercholesterolemic males and females aged between 20 and 60. Even though high-density lipoprotein cholesterol (HDL-C) concentrations increased, it was not enough to reduce cardiovascular disease risk. Furthermore, coconut oil did not have superior benefits for improved adiposity or glycaemic and inflammatory markers. Therefore, it is suggested that coconut oil consumption is limited due to the high SFA content and lack of evidence to support cardiovascular disease risk reduction.¹¹

The take-home message is that numerous studies have documented that a high saturated intake is associated with increased CVD risk, and encouraging a Mediterranean diet will reduce cardiovascular disease risk, promote healthy weight management and improve overall wellbeing.

Is there a link between CVD and gut health?

In healthy adults, the two bacterial phyla Firmicutes and Bacteroidetes dominate the gut microbiota, making up more than 90% of the total gut bacterial population.¹² A systematic review and meta-analysis of 11 studies (with 960 subjects) of Chinese and Japanese populations showed that patients with CVD had higher levels of gut Firmicutes and gut microbial dysbiosis when compared with healthy controls.¹³

Furthermore, the Firmicutes to Bacteroidetes ratio (F/B ratio) plays an important role in maintaining normal intestinal homeostasis;¹⁴ specifically, the increase of F/B ratio will increase the risk of cardiovascular disease.¹⁵ A systematic review and meta-analysis of 19 studies (adult subjects with hypertension and healthy controls) found hypertensive patients may have an imbalance of gut microbiota. Faecalibacterium was significantly decreased while, at the genus level, Streptococcus and Enterococcus were significantly increased.¹⁶

In addition, a systematic review and meta-analysis of 26 RCTs (involving 1,720 adults) suggested that probiotics consumption may help improve body adiposity and some CVD risk markers in individuals with overweight and obesity. Reduction in body adiposity was only observed in studies using a probiotic dose of ≥ 1,010 colony-forming units (CFU) and for eight weeks or more.¹⁷ However, in terms of a direct association between CVD and gut health, it still needs further validation by large sample size studies of high quality.

Final thoughts

Alongside the five modifiable risk factors, it seems the Mediterranean diet, omega-3 intake from fish and supplements may reduce CVD risk. A high intake of saturated fat, including coconut oil, is not recommended and is likely to increase CVD risk. Gut health may play a role in CVD development, but further research is needed.

References

1. The National Institute for Health and Care Excellence (NICE). 2023. Cardiovascular disease: risk assessment and reduction, including lipid modification [NICE guideline No. 238] https://www.nice.org.uk/guidance/ng238
2. The Association of UK Dietitians (BDA). 2020. Heart health (fact sheet). https://www.bda.uk.com/resource/heart-health.html
3. Jakobsen MU, O’Reilly EJ, Heitmann BL, Pereira MA, Bälter K, Fraser GE, Goldbourt U, Hallmans G, Knekt P, Liu S, Pietinen P, Spiegelman D, Stevens J, Virtamo J, Willett WC, Ascherio A. Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies. Am J Clin Nutr. 2009 May;89(5):1425-32. doi: 10.3945/ajcn.2008.27124. Epub 2009 Feb 11. PMID: 19211817; PMCID: PMC2676998. https://pubmed.ncbi.nlm.nih.gov/19211817/
4. UK Chief Medical Officer. 2019. Physical activity for adults and older adults (infographic). https://assets.publishing.service.gov.uk/media/620a2b0c8fa8f549142bf221/physical-activity-for-adults-andolder-adults.pdf
5. UK Chief Medical Officer. 2016. Low risk drinking guidelines. https://assets.publishing.service.gov.uk/media/5a80b7ed40f0b623026951db/UK_CMOs__report.pdf
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7. Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, Deane KH, Summerbell CD, Worthington HV, Song F, Hooper L. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020 Feb 29;3(3):CD003177. doi: 10.1002/14651858.CD003177.pub5. PMID: 32114706; PMCID: PMC7049091. https://pubmed.ncbi.nlm.nih.gov/32114706/
8. Hu Y, Hu FB, Manson JE. Marine Omega-3 Supplementation and Cardiovascular Disease: An Updated Meta-Analysis of 13 Randomized Controlled Trials Involving 127 477 Participants. J Am Heart Assoc. 2019 Oct;8(19):e013543. doi: 10.1161/JAHA.119.013543. Epub 2019 Sep 30. PMID: 31567003; PMCID:PMC6806028 https://pubmed.ncbi.nlm.nih.gov/31567003/
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10. Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database of Systematic Reviews 2020, Issue 8. Art. No.: CD011737. DOI: 10.1002/14651858.CD011737.pub3. Accessed 19 January 2024. https://pubmed.ncbi.nlm.nih.gov/32428300/
11. Neelakantan N, Seah JYH, van Dam RM. The Effect of Coconut Oil Consumption on Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Clinical Trials. Circulation. 2020 Mar 10;141(10):803-814. doi: 10.1161/CIRCULATIONAHA.119.043052. Epub 2020 Jan 13. PMID: 31928080. https://pubmed.ncbi.nlm.nih.gov/31928080/
12. Jandhyala SM, Talukdar R, Subramanyam C, Vuyyuru H, Sasikala M, Nageshwar Reddy D. Role of the normal gut microbiota. World J Gastroenterol. 2015 Aug 7;21(29):8787-803. doi:10.3748/wjg.v21.i29.8787. PMID:26269668; PMCID: PMC4528021. https://pubmed.ncbi.nlm.nih.gov/26269668/
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14. Stojanov S, Berlec A, Štrukelj B. The Influence of Probiotics on the Firmicutes/Bacteroidetes Ratio in the Treatment of Obesity and Inflammatory Bowel disease. Microorganisms. 2020 Nov 1;8(11):1715. doi: 10.3390/microorganisms8111715. PMID:33139627; PMCID: PMC7692443. https://pubmed.ncbi.nlm.nih.gov/33139627/
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16. Cai M, Lin L, Jiang F, Peng Y, Li S, Chen L, Lin Y. Gut microbiota changes in patients with hypertension: A systematic review and meta-analysis. J Clin Hypertens (Greenwich). 2023 Dec;25(12):1053-1068. doi: 10.1111/jch.14722. Epub 2023 Oct 18. PMID:37853925; PMCID: PMC10710550. https://pubmed.ncbi.nlm.nih.gov/37853925/
17. Pontes KSDS, Guedes MR, Cunha MRD, Mattos SS, Barreto Silva MI, Neves MF, Marques BCAA, Klein MRST. Effects of probiotics on body adiposity and cardiovascular risk markers in individuals with overweight and obesity: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2021 Aug;40(8):4915-4931. doi: 10.1016/j. clnu.2021.06.023. Epub 2021 Jul 3. PMID: 34358838. https://pubmed.ncbi.nlm.nih.gov/34358838/