Reducing the risks of Cardiovascular Disease, AS Biology, Edexcel

Antioxidants

• During reactions in the body, unstable radicals result when an atom has an unpaired electron.
• Radicals (free radicals) are highly reactive and can damage many cell components including enzymes and genetic material.
• This type of cellular damage has been implicated in the development of some types of cancer, heart disease and premature aging.
• Some vitamins including vitamin C, beta-carotene and vitamin E, can protect against radical damage.
• They provide hydrogen atoms that stabilise the radical by pairing up with its unpaired electron.
• High levels of antioxidants seem to protect against heart disease (MONICA study)
• Recommended 5 portions of fruit and vegetables per day.
• Wine and some fruit juices contain chemicals which have antioxidant properties and also help stop platelets sticking together.

Slide 2

• The risk of CVD can be reduced by:
• stopping smoking
• maintaining resting blood pressure below 140/85 mmHg
• maintaining low blood cholesterol level
• maintaining a normal BMI/low waist to hip ratio
• taking more physical exercise
• moderate or no use of alcohol

Reducing High Blood Pressure

• If someone is diagnosed with HBP, changes in diet and lifestyle are recommended.
• For people with a sustained blood pressure above 160/100, medications can be prescribed.
• There are 3 main types of drugs to treat HBP:
• ACE inhibitors
• Calcium channel blockers
• Diuretics
• ACE inhibitors and calcium channel blockers are antihypertensives.

ACE inhibitors

• (angiotensin converting enzyme inhibitors) These are effective antihypertensive drugs.
• They reduce the synthesis of angiotensin II.
• Angiotensin II is a hormone that causes vasoconstriction of blood vessels.
• The ACE inhibitors prevent the hormone being produced from inactive angiotensin I which reduces vasoconstriction and reduces blood pressure.
• Side Effects: dry cough, dizziness due to hypotension,abnormal heart rhythms and a reduction in the function of the kidney
• For anyone with kidney disease, the drug may reduce the risk of kidney failure.

Calcium Channel Blockers

• Antihypertensive drugs that block the calcium channels in the muscle cells in the lining of the arteries.
• For the muscle to contract, calcium must pass through the channels into the muscle cells.
• Failure of calcium to enter the cell prevents contraction of the muscle so the blood vessels don't constrict which reduces blood pressure.
• Side Effects: headaches, dizziness, swollen ankles (oedema), abnormal heart rhythms, flushing red in the face and constipation.
• This isn't prescribed to those who've had a heart attack (myocardial infarction)

Diuretics

• Increase volume of urine produced by the kidneys which therefore rids the body of excess fluid and salt.
• It leads to a decrease in blood plasma volume and cardiac output which lowers blood pressure.
• Side Effects: dizziness, nausea, muscle cramps.
• Too much salt in food counteracts the effect.

Reducing blood cholesterol levels

• A low fat diet can help with this however dietary advice often has little effect on blood cholesterol levels so medication can be prescribed such as statins.

Statins

• Cholesterol-lowering drug
• Works by inhibiting an enzyme involved in the production of LDL cholesterol by the liver.
• Side Effects: tiredness, disturbed sleep, feeling sick, vomiting, diarrhoea, headache and muscle weakness.

A diet to reduce the risk of CVD

• Energy balanced
• Reduced saturated fat
• More polyunsaturated fat
• Reduced cholesterol
• Reduced salt
• More non-starch polysaccharides such as pectins and guar gum: these are soluble fibre which have been found to lower blood cholesterol. They're only partially digested, forming a gel that traps cholesterol and prevents its absorption.
• Includes oily fish: contain omega-3 fatty acids (polyunsaturated). These fatty acids are essential for cell functioning and have been linked to a reduction in heart disease and joint inflammation. (Japan and Inuit people)
• More fruits and vegetables: contain antioxidants and often non-starch polysaccharides.
• Include functional foods containing sterols and stanols: these are naturally produced substances in plants, similar to cholesterol. Stanols are saturated. Both sterols and stanols compete with cholesterol during its absorption in the intestine. Margarine contains them.

Anticoagulant & platelet inhibitory drugs

• If someone has had a heart attack or stoke, or is identifies as being at high risk of one, in addition to the lifestyle changes and drug treatments to reduce blood pressure and blood cholesterol, they may be given drugs to prevent formation of a blood clot in an artery.
• The tendency for platelet aggregation and clotting is reduced by platelet inhibitory and anticoagulant drugs.
• Aspirin
• Reduces stickiness of platelets and the likelihood of clot formation.
• Some people are allergic.
• For others it's not effective or only partially effective.
• Clopidogrel
• High risk of gastrointestinal bleeding when used in combination with aspirin.
• Warfarin
• Interferes with the production of vitamin K and affects the synthesis of clotting factors.