Cardiovascular disease Flashcards
Cardiovascular disease (CVD)
diseases and injuries of the heart and blood vessels (in the heart, brain and throughout the body)
Atherosclerosis
build up of plaque in arteries, narrowing arteries and limiting blood flow
Coronary heart disease
build up of plaque in coronary arteries, which may lead to heart attack
Heart attack
Myocardial infarction: loss of blood flow to the heart
What causes artherosclerosis?
LDL “bad cholesterol” transport cholesterol to cells. If LDL is not taken by cells - keeps circulating in blood. The longer LDL circulates in blood, the more likely it is oxidized (becomes heavy;micro-injury accumulates)
- uptake by macrophage
- foam cell formation
- fatty plaques
- atherosclerosis
Development of atherosclerosis
- Arterial endothelial cell injury
- Entry of LDL cholesterol and phagocytic cells
- Phagocytes engorges LDL -> Foam cells
- Formation of fatty plaques; narrowing of blood vessel (MI); Rapture (Thrombus)
Un-modifiable risk factors
Age
Biological sex (male>female)
Family history
Ethnicity
Modifiable risk factors
High blood cholesterol
High blood pressure
Diabetes
Overweight/obesity
Excessive alcohol use
Physical inactivity
Smoking
Stress
“Unhealthy” diet (Poor diet)
Classic Diet-Heart Hypothesis
Dietary characterisitics: highly saturated fat, high cholesterol, low PUFA
Elevated serum cholesterol
Atheromatous plaque
Coronary arteries narrow
Myocardial infraction
What is the history of “Diet-heart” hypothesis from early studies in animal studies?
- Dietary cholesterol is transported in bloodstream
- Cholesterol deposits in arteries supplying heart can lead to heart attack
- Coronary heart disease identified as early as 1930
Measuring Serum Cholesterol
Lipid profile: Blood test FASTING state that report:
Total cholesterol
LDL cholesterol
HDL cholesterol
Triacylglycerols
Ratio of total cholesterol/HDL cholesterol or LDL/HDL appears to be most predictive of CHD risk
Main apolipoproteins:
HDL - apoA
LDL - apoB
- HDL is higher than LDL
Ratio of apoB/apoA also used
Looking at ratios is of greater validity and significance in clinical diagnostic
than measuring total cholesterol only
Dietary Fat & Serum Cholesterol
Dietary cholesterol does not seem to have a major influence on serum cholesterol
Dietary fat does seem to modify serum cholesterol
* Replacing saturated fats or carbohydrate with monounsaturated or polyunsaturated fats (PUFA) decreases total cholesterol to HDL cholesterol ratio
Based on the previous figure, from Micha & Mozzafarian 2010, replacing carbohydrate with which fatty acid would be predicted to give the least favorable serum cholesterol profile (i.e. which would be predicted to be the worst for CHD risk?)
A) Saturated
B) Monounsaturated
C) Polyunsaturated
D) Trans
D) Trans
What are the current recommendations for dietary cholesterol?
Dietary Reference Intakes:
* Minimize intakes of saturated and trans fats
* AMDR: n-6 PUFA 5-10% energy
* AMDR: n-3 PUFA 0.6-1.2% energy
No recommendations for MUFA
AMDR: Fat = 20-35% energy
Why is epidemiological studies evidence conflicting?
Epidemiological studies are difficult to interpret
* Difficult to separate effects of nutrients from dietary patterns or lifestyle factors
* Studies may be done on secondary prevention
* Difficulties in conducting “good” observational and experimental nutrition studies
What replaces saturated fat is important!
What is the latest evidence?
- Lowered intake of dietary saturated fat and replacement with polyunsaturated vegetable oil reduced CVD by ≈30% (RCTs)
- Benefits from lower intake of saturated fat coupled with higher intake of polyunsaturated and monounsaturated fat (prospective cohort studies)
- NO benefits: replacement of saturated fat with mostly refined carbohydrates and sugars (clinical trials)
Is the “Diet-Heart” Hypothesis too simplistic?
Most inter-individual variation in serum cholesterol is NOT related to dietary fat/cholesterol intake.
Factors other than blood cholesterol are important in the etiology of CHD
- types of fats replaced SF matters
Lipoproteins (a)
-similar to LDL particle with covalently linked glycoprotein: apolipoprotein(a)
- may have prothrombotic (blood clotting) properties in addition to atherosclerotic properties of LDL
- appears to be positively correlated with CHD risk
What are dietary factors that may influence CHD?
- Saturated fats/PUFA/n-3 fatty acids (fish oils)
- Glycemic index
- Whole grains/Fiber
- Anti-oxidants
- Phytochemicals
- Vitamin D
- Magnesium
- Alcohol
- B vitamins- folate, B6, B12
Omega-3 Fatty Acids
- Hypothesis generated from observation of
lower rates of CHD in populations with very high intake of fish such as Greenland & Japan
Possible mechanisms: - Effects on blood lipids (triacylglycerol lowering)
- Anti-arrhythmic effects
- Anti (less)-inflammatory effects
- Anti-thrombotic effects
Fiber
- May reduce serum cholesterol by binding to bile acids in the gut
- Major pathway of cholesterol excretion in the body; to produce new ble need CH from blood
- May also improve glycemic control, insulin resistance and weight control
- Whole grains: source of fiber,
phytochemicals, magnesium.
Anti-Oxidants
- Eg. Vit E, Vit C, beta-carotene, selenium
- Hypothesis that anti-oxidants may protect the arterial wall and prevent LDL oxidation
- Oxidation of LDL particles is an important step in progression of atherosclerosis
Phytochemical
E.g. Flavonoids, stilbenoids, and others
* Have anti-oxidant properties
* Stilbenoids (e.g., resveratrol from grapes and pterostilbene from blueberries) modify gene expression through epigenetic mechanisms which may explain their anti-oxidant and anti-inflammatory properties
Vitamin D
Low vit D associated with higher risk for CHD:
* Decreasing inflammation
* Endothelial function
* Reducing vascular stiffness
Possible mechanisms:
* Vitamin D receptor (VDR) and VDR responsive elements in DNA
* Regulation of gene expression
* Epigenetic mechanisms
Magnesium
- Low magnesium associated with higher risk for CHD
Possible mechanisms:
* modulating vascular smooth muscle tone
* endothelial cell function
* myocardial excitability
B-Vitamins
Facilitate the synthesis methionine synthase (folic acid, B-12)
- high levels of homocysteine can damage the inside of arteries and inc. risk of forming blood clots.
- Possible risk factor for CHD
Is red wine protective?
Possibly in moderation (1-2 drinks/day) ?
* Contains
– Resveratrol
– Other polyphenolic compounds (antioxidants)
– Alcohol
Excess alcohol is harmful
No evidence that “non-drinkers” should drink alcohol
The safest level: zero
drinks per week
Key FInding:
- Low-volume alcohol drinking was not associated with protection against death from all causes
- For adults of 40 and older without any underlying health conditions, drinking a small amount of alcohol was linked to some health benefits, such as reducing the risk of ischaemic heart disease, stroke and diabetes
Dietary Patterns vs. Nutrients
We eat foods, not nutrients, therefore it may be more useful to determine which dietary patterns (foods) relate to CVD risk rather than nutrients
Dietary Patterns
Dietary patterns associated with reduced CVD risk:
“Prudent diet”
* a high intake of vegetables, fruit, legumes, whole grains, and fish and lean meats (poultry)
“Mediterranean diet”
* high intake of vegetables, legumes, fruits, nuts, olive oil (monounsaturated fats), fish and seafood
In contrast a “Western diet” is associated with increased CHD risk
* higher intakes of red and processed meats, sweets and
desserts, high fat dairy, refined grains
Mediterranean Diet
Evidence: A Mediterranean diet with olive oil or nuts significantly reduced CVD risk compared to a low fat diet
- dec. inflammation
- inc. cardioprotective lipid profiles
- inc. glucose metabolism
What are current recommendations for prevention of heart disease?
Balanced diet
* Emphasizes veg & fruit, whole grains, minimizes saturated fat, encourages fish for omega-3 fatty acids
High Fat Dairy
Dairy Fat:
- Saturated FA do not all have the same effect; saturated fatty
acids from dairy may not increase LDL in a clinically
significant way
- Medium-chain fatty acids (8-22%) may lead to better weight
management
- MUFA/PUFA increase HDL and lower total cholesterol
- Oleic acid (MUFA; 20-30%)
Other ingredients in dairy:
- calcium, iodine, potassium, vit D, bioactive peptides, vit A
Evidence: Whole-fat dairy does not raise cardiovascular risk. Conversely, some fats presnet in certain dairy products might even keep stroke and heart disease at bay
American Heart Association (AHA) Diet & Lifestyle Recommendations
Use up at least as many calories as you take in:
* Aim for at least 150 minutes of moderate physical activity or 75 minutes of vigorous physical activity– or an equal combination of both – each week
Eat a variety of nutritious foods from all the food groups:
* Eat an overall healthy dietary pattern that emphasizes:
* a variety of fruits and vegetables, whole grains, low-fat dairy products, skinless poultry and fish, nuts and
legumes, non-tropical vegetable oils
* Limit saturated fat, trans fat, sodium, red meat, sweets and
sugar-sweetened beverages. If you choose to eat red meat,
compare labels and select the leanest cuts available.
* One of the diets that fits this pattern is the DASH (Dietary
Approaches to Stop Hypertension) eating plan or the Mediterranean diet.
