A high fat diet causes CHD. Discuss.

Coronary Heart Disease (CHD) refers to the damage to the heart as a consequence of reduced blood supply to the tissues of the heart itself.[1] The reduced blood supply is caused by the narrowing of the coronary arteries, otherwise referred to as coronary occlusion. This is due to a condition called atherosclerosis; a build-up of plaque in the arterial walls adjacent to the endothelium.[2] Low density lipoproteins containing fats and cholesterol accumulate, which causes phagocytes to migrate and grow large. Smooth muscle cells also migrate and build a tough cap over the atheroma, which bulges into the lumen impeding blood flow.[3] When the atheroma bursts, the resulting blood clots may block some parts of the coronary artery, which can cause myocardial infarction.

Risk factors for CHD include family history, hypertension, gender and many more.[4] However, one of the most significant is high blood cholesterol. Cholesterol is a lipid synthesised by the liver from the saturated fat in one’s diet[5], and is carried in two types of lipoprotein complexes; low-density lipoproteins (LDL) and high-density lipoproteins (HDL). The former carries cholesterol away from the liver to the cells, and the latter carries cholesterol away from the cells back to the liver to be broken down and excreted. Thus, HDLs reduce the level of cholesterol in the blood. Cholesterol is essential in the synthesis of cell membranes, but too much can lead to coronary occlusion through the process previous stated.

Cholesterol comes from two sources; food from animals, and the body itself. The cholesterol levels in food from animal sources are low, and reducing the amount of cholesterol intake does not have a significant impact on blood cholesterol levels, and consequently, on the rates of CHD.[6] Hence, one could suggest that cholesterol synthesised by the liver has a bigger impact on blood cholesterol levels. The raw materials in which cholesterol is synthesised from are saturated fats, which can be found in red meat, butter and cheese.[7]

Another type of fat that influences blood cholesterol levels are trans-unsaturated fatty acids, otherwise known as trans-fats. Typically referred to as “bad fats”, trans-fats lowers the level of HDLs and increases the level of LDLs in the blood.[8] These are known to affect the body even when ingested in small amounts and, hence, it is advisable to limit the amount of consumption. Trans-fats come from artificially hydrogenated foods like margarine, and foods that use partially hydrogenated vegetable fats, like deep-fried foods and baked foods.[9]

To conclude, not all types of fats are risk factors of CHD. What one should be weary of are trans-fats and saturated fats; monounsaturated and polyunsaturated fats (known as “good fats”) are actually beneficial for the body as they reduce blood pressure and can prevent heart diseases.[10] Hence, the statement “A high fat diet causes CHD” is a generalisation. One should look to consume “good fats”, and not replace all fat intake with carbohydrates, which in turn, can lead to a sudden rise in blood sugar levels and obesity.

Bibliography

Allott, A. and Mindorff, D. (n.d.). IB biology. Oxford: Oxford University Press

Nhlbi.nih.gov. (2016). What Are Coronary Heart Disease Risk Factors? - NHLBI, NIH. [online] Available at: https://www.nhlbi.nih.gov/health/health-topics/topics/hd [Accessed 30 Aug. 2016].

Nhs.uk. (2016). Coronary heart disease - Causes - NHS Choices. [online] Available at: http://www.nhs.uk/Conditions/Coronary-heart-disease/Pages/Causes.aspx [Accessed 28 Aug. 2016].

Hsph.harvard.edu. (2016). Fats and Cholesterol | The Nutrition Source | Harvard T.H. Chan School of Public Health. [online] Available at: https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/ [Accessed 30 Aug. 2016].

Foundation, T. (2016). Saturated and trans fats. [online] The Heart Foundation. Available at: http://heartfoundation.org.au/healthy-eating/food-and-nutrition/fats-and-cholesterol/saturated-and-trans-fat [Accessed 30 Aug. 2016].

Publications, H. (2016). The truth about fats: the good, the bad, and the in-between - Harvard Health. [online] Harvard Health. Available at: http://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good [Accessed 30 Aug. 2016].

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[1] Allott, A. and Mindorff, D. (n.d.). IB biology. Oxford: Oxford University Press, p.692.

[2] Allott, A. and Mindorff, D. (n.d.). IB biology. Oxford: Oxford University Press, p.297.

[3] Allott, A. and Mindorff, D. (n.d.). IB biology. Oxford: Oxford University Press, p.297.

[4] Nhlbi.nih.gov. (2016). What Are Coronary Heart Disease Risk Factors? - NHLBI, NIH. [online] Available at: https://www.nhlbi.nih.gov/health/health-topics/topics/hd [Accessed 30 Aug. 2016].

[5] Nhs.uk. (2016). Coronary heart disease - Causes - NHS Choices. [online] Available at: http://www.nhs.uk/Conditions/Coronary-heart-disease/Pages/Causes.aspx [Accessed 28 Aug. 2016].

[6] Allott, A. and Mindorff, D. (n.d.). IB biology. Oxford: Oxford University Press, p.669.

[7] Hsph.harvard.edu. (2016). Fats and Cholesterol | The Nutrition Source | Harvard T.H. Chan School of Public Health. [online] Available at: https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/ [Accessed 30 Aug. 2016].

[8] Foundation, T. (2016). Saturated and trans fats. [online] The Heart Foundation. Available at: http://heartfoundation.org.au/healthy-eating/food-and-nutrition/fats-and-cholesterol/saturated-and-trans-fat [Accessed 30 Aug. 2016].

[9] Foundation, T. (2016). Saturated and trans fats. [online] The Heart Foundation. Available at: http://heartfoundation.org.au/healthy-eating/food-and-nutrition/fats-and-cholesterol/saturated-and-trans-fat [Accessed 30 Aug. 2016].

[10] Publications, H. (2016). The truth about fats: the good, the bad, and the in-between - Harvard Health. [online] Harvard Health. Available at: http://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good [Accessed 30 Aug. 2016].