While it is well known that high blood pressure increases the risk of cardiovascular events such as heart attacks and strokes, scientific evidence also suggests that excessively low blood pressure can be almost as harmful as high blood pressure.

A new study, presented at the American Society of Hypertension meeting in San Francisco this month, looked at how the risk of suffering a stroke or heart attack varied with blood pressure in a group of 10,001 coronary heart disease patients.

The researchers found that those with a systolic blood pressure below 110 mmHg were 3.1 times more likely to suffer a stroke or heart attack compared to those with a blood pressure of between 130 and 140 mmHg. Those with a diastolic blood pressure below 60 mmHg were 3.3 times more likely to suffer a heart attack or stroke compared to those with a diastolic blood pressure between 70 and 80 mmHg.

The blood pressure associated with the lowest overall risk of coronary heart disease was calculated to be 140.6/79.8 mmHg, significantly higher than the 120/80 mmHg level recommended by the American Heart Association.

The researchers noted that the findings did not necessarily mean that low blood pressure causes cardiovascular disease. It is possible that low blood pressure is caused by some other factor that is in turn responsible for increased cardiovascular disease risk. Congestive heart failure for example can lead to low blood pressure due to the inability of the heart to pump sufficient blood around the body.

The research backs up the findings of similar studies that have found an increased risk of cardiovascular events in patients with low blood pressure who are already suffering cardiovascular disease. On the other hand, healthy individuals with low blood pressure who are free from cardiovascular disease do not appear to be at an increased risk of heart disease and stroke.

A combination of cholesterol lowering foods can achieve similar cholesterol lowering results to statins according to a recent study published in the American Journal of Clinical Nutrition in 2005.

The research, conducted by Canadian scientists, involved the comparison of a diet rich in foods known to reduce cholesterol with a popular statin known as lovastatin.

34 participants who were suffering from high cholesterol completed the study which consisted of three one month phases. The first phase was a whole-wheat based diet (control diet), the second phases was the same whole-wheat diet plus 20mg per day of lovastatin, while the final phase consisted of a diet based on four cholesterol lowering components: 1g/1000kcal of plant sterols, 10g/1000kcal of soluble fiber which came from oats, barley, and psyllium, 21.4g/1000kcal of soy protein, and 14g/1000kcal of almonds.

The researchers found that LDL cholesterol was reduced by 29.6% for the cholesterol lowering diet compared to 33.3% for the statin diet. 27 of the 36 participants reduced their cholesterol levels to within the safe range on the statin compared to 24 participants on the cholesterol lowering diet. Nine of the participants achieved better results on the cholesterol lowering diet than from the statin alone. The researchers also calculated that participants dropped their 10 year risk of coronary heart disease from 11.4% to 8.4% on the cholesterol lowering diet and from 11.6% to 7.7% on the statin.

Cholesterol is thought to be one of the most important risk factors for coronary heart disease. Researchers have calculated that a 1% reduction in LDL cholesterol levels results in a 1.5% decrease in the risk of coronary heart disease.

Components of the cholesterol lowering diet were only included if they had a scientifically verified mechanism of action. Plant sterols reduce the absorption of cholesterol in the intestines. Soluble fiber increases the excretion of bile acids from the body leading to an increase in the production of bile acids in the liver. Bile acids are produced by the oxidation of cholesterol so an increase in bile acid production increases the rate of cholesterol metabolism. Soy protein increases the function of LDL receptors in hepatic cells leading to an increase in the uptake of LDL cholesterol by the liver. Almonds contain numerous cholesterol lowering substances including plant sterols, fiber, and mono-unsaturated fat which increases HDL cholesterol levels while lowering LDL cholesterol.

Rich sources of soluble fiber include peas, beans, oats, barley, pears, broccoli, Brussels sprouts, carrots, and psyllium. Sources of plant sterols include margarines, most vegetable oils, peanuts, blueberries, broccoli, Brussels sprouts, and cauliflower.

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Hypertension is one of the most significant risk factors for cardiovascular diseases such as heart disease and stroke. It is estimated that a blood pressure greater than 140/90 mmHg doubles an individuals risk of heart disease at a given age compared to a person with a normal blood pressure (115/75 mmHg).

More than 35% of adult Americans are known to suffer from hypertension and this figure rises to more than 60% in people older than 55.

Fortunately high blood pressure can largely be controlled through lifestyle and diet changes. Here are eight of the easier ways to lower blood pressure without the use of prescription medication.

1. Take A Fish Oil Or Omega 3 Supplement Daily

The largest study on the effect of fish oil on blood pressure was published in the journal Circulation which is published by the American Heart Association (AHA). The study found that 15 grams of fish oil a day lowered systolic blood pressure by 8.1 mmHg and diastolic blood pressure by 5.8 mmHg. Overall, the study found that each 1 gram per pay increase in fish oil lowered systolic blood pressure by 0.66 mmHg and diastolic blood pressure by 0.35 mmHg.

It is believed that the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found abundantly in fish oil, are responsible for its blood pressure lowering effects.

2. Reduce Salt Intake

Scientific evidence suggests that a 2.3 gram per day reduction in sodium intake can cut systolic blood pressure by 6-10 mmHg and diastolic blood pressure by 3-5 mmHg.

The current maximum recommended intake of sodium is 2.4 grams of sodium per day which is the equivalent of a teaspoon of table salt. The average daily intake of salt in the United States is more than twice this amount. Around 12% of sodium in the average American diet is due to salt being directly added to food while more than three-quarters of sodium intake is through the consumption of processed foods which tend to be high in salt.

3. Consume A Diet Rich In Potassium

Potassium appears to reduce blood pressure levels, particularly in those who consume a high sodium diet or who suffer from hypertension. Studies indicate a reduction in systolic blood pressure of up to 6 mmHg and diastolic blood pressure of up to 4 mmHg in people who consume a potassium rich diet. Potassium appears to work by increasing the rate that sodium is excreted from the body.

The recommended daily intake of potassium is 4.7 grams per day however the average daily intake in the United States is just 2.5 grams per day. Potassium is found abundantly in fresh fruits and vegetables. Potassium rich foods include (potassium per serving in brackets): bananas (0.6g), tomatoes (0.5g), cucumbers (0.4g), pears (0.3g), baked potatoes (0.9g), and orange juice (0.5g).

4. Reduce Intake Of Caffeine

A high intake of caffeine is associated with a significant increase in blood pressure. Interestingly, when caffeine is consumed through natural sources such as coffee, tea, and chocolate the effect on blood pressure appears to be much smaller. The amount of caffeine in three cups of coffee is enough to increase short term systolic blood pressure by 8mm Hg and diastolic blood pressure by 5 mm Hg.

Caffeine has a relatively short half life of 3 to 4 hours meaning its effects on blood pressure are relatively short lived although regular caffeine consumption throughout the day can result in a sustained increase in blood pressure. People looking to reduce their blood pressure levels should limit their intake of caffeine, particularly from sources where caffeine is not naturally present such as energy drinks and caffeine pills.

5. Reduce Abdominal Fat Levels

Body fat, particularly around the abdominal area, is strongly correlated with blood pressure. One study, published in the Journal of Human Hypertension in 1999, found that waist size, a measure of central obesity, was strongly correlated with the risk of developing hypertension. Individuals in the highest quartile for waist size were almost six times more likely to have hypertension than individuals in the lowest quartile for waist size.

6. Increase Intake Of Dietary Fiber

A study, published in the Archives of Internal Medicine in 2005, found that an increase in fiber of 11.5 grams per day resulted in a reduction in systolic blood pressure of 1.13 mmHg and a reduction in diastolic blood pressure of 1.26 mmHg. The effect was greatest amongst people aged over 40 years and in those with hypertension.

7. Increase Intake Of Vitamin C

A high intake of vitamin C appears to reduce blood pressure in hypertensive individuals. A study, published in the journal Lancet in 1999, found that taking 500mg of vitamin C a day for a month reduced overall blood pressure by 9% in hypertensive individuals.

8. Increase Intake Of Magnesium And Calcium

Both magnesium and calcium appear to reduce blood pressure by a small, but statistically significant amount. Magnesium rich foods include beans, broccoli, fish, prunes, almonds, brazil nuts, tofu, and spinach. Calcium is found abundantly in dairy products, fish with edible bones, tofu, peas, broccoli, spinach, and almonds.

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A study, published in the Archives of Internal Medicine in 2004 has found that high total cholesterol levels can double an individuals remaining lifetime risk of developing coronary heart disease.

The researchers used data from the Framingham Heart Study (FHS) to determine how total cholesterol levels influence overall heart disease risk. More than 7,000 men and women were studied of which 1,120 developed coronary heart disease during the 25 year study period.

The researchers calculated that at the age of 40, men in the highest group for total cholesterol (greater than 240mg/dL) had a 57% probability of developing coronary heart disease by age 80. In contrast, men in the lowest group for total cholesterol (less than 200mg/dL) had a 31% probability of developing coronary heart disease. In women, the risks of developing coronary heart disease by age 80 were 33% and 15% for the high and low cholesterol groups respectively.

The full results of the study are presented in the graph below.

The American Heart Association (AHA) recommends individuals maintain a total cholesterol level below 200mg/dL. Total cholesterol is made up of two components: LDL and HDL. LDL makes up the larger proportion of of total cholesterol and is the type that is detrimental to heart health. An LDL cholesterol level of 100mg/dL or lower is considered optimal however further reductions in heart disease risk are seen at levels as low as 60mg/dL. HDL cholesterol is the other component of total cholesterol and is considered to be beneficial to heart health. It is recommended that an individual aims for a HDL to total cholesterol ratio of 5:1 with a ratio lower than 3.5:1 considered ideal.

The percentage of Americans with high cholesterol is currently decreasing with just 16% of men and 18% of women having total cholesterol levels greater than 240mg/dL. In 1975 the numbers were 26% and 28% for men and women respectively.

Despite these reductions in total cholesterol, heart disease remains the most common health problem facing the western world. In the United States, 49% of men and 32% of women will develop heart disease during their lifetimes. By comparison, cancer carries a 44% and 37% lifetime risk for men and women respectively, diabetes carries a 33% and 39% lifetime risk for men and women, while the lifetime risks for Alzheimer’s disease are 7% for men and 13% for women.

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There are numerous lifestyle, dietary, and genetic factors believed to play a part in heart disease and it can be difficult to determine which of these factors are the most important ones. According to a report published in the journal Lancet in 2004, there are just nine risk factors that account for the overwhelming majority of heart attacks. The good news is that each of the risk factors identified is preventable.

The study, conducted by Canadian scientists, involved analyzing 262 previous studies on heart disease involving a combined 29,000 individuals from 52 countries. The researchers attempted to isolate the risk factors thought to have the greatest impact on an individuals probability of suffering a heart attack.

The researchers found that nine modifiable risk factors accounted for more than 90% of all heart attack cases. The risk factors were (in descending order to importance):

• A high ApoB/ApoA-1 ratio
• Current smoking
• Psychosocial factors (e.g work stress)
• Diabetes
• Hypertension (high blood pressure)
• Abdominal obesity
• Poor fruit and vegetable intake
• Lack of physical activity
• Little or no consumption of alcohol

The ApoB/ApoA-1 ratio is similar to the LDL/HDL ratio but is thought to be a better overall predictor of heart disease. The odds of suffering a heart attack were 3.25 times greater for individuals with an ApoB/ApoA-1 ratio in the top 20% compared to the bottom 20% and were 2.87 times greater for current smokers compared to former or non smokers. The full odds ratios for each of the factors are shown in the graph below (an odds ratio greater than one indicates an increased risk of heart attack while an odds ratio less than one indicates a reduction in heart attack risk).

The two greatest risk factors, a high ApoB/ApoA-1 ratio and smoking, were calculated to be responsible for a massive 67.3% of all heart attacks worldwide. The nine factors combined were responsible for 90% of all heart attacks in men and 94% of heart attacks in women.

According to lead researcher Dr. Salim Yusuf of the Michael DeGroote School of Medicine in Ontario, Canada: “…most people believe that only half the risk of heart attacks can be predicted. This study convincingly shows that 90% of the global risk is preventable.”

The researchers added that while obesity was an established heart attack predictor, it was not included as one of the risk factors because it performed relatively poorly compared to abdominal obesity. This is because fat located around the central organs appears to be much more problematic for the heart than fat located in other areas. The authors recommend people place less emphasis on BMI and instead use  a measure of central obesity such as waist size or the waist to hip ratio to more accurately gauge heart disease risk.

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Many people believe that diets high in fat will lead to a greater risk of heart disease in later life however this is not necessarily the case. Countries such as Spain, Greece, Italy, and France all have remarkably low rates of heart disease while consume a Mediterranean style diet that is relatively high in fat.

Recent scientific studies point instead to two specific types of fat, trans fats and saturated fats, which are thought to increase the risk of cardiovascular disease.

The largest study on the effects of fat intake on heart disease was published in The New England Journal of Medicine in 1998. The research was conducted at the Harvard Medical School and involved more than 80,000 women from the Nurses’ Health Study (NHS) who were followed over a 14 year period.

Over the course of the study, 939 of the women developed heart disease. The researchers found that both saturated and trans fats led to an increase in the risk of heart disease while polyunsaturated and mono-unsaturated fats both reduced heart disease risk.

The researchers calculated that a 5% increase in calories increased heart disease risk by 17% (relative to carbohydrate calories). A 2% increase in energy due to trans fats was calculated to increase heart disease risk by 93%. This means calorie for calorie, trans fats have almost ten times the impact on heart disease compared to saturated fats.

In contrast, a 5% increase in energy due to mono-unsaturated fat and poly-unsaturated fat was found to decrease heart disease risk by 19% and 38% respectively.

The authors also found that animal fats as a whole increased heart disease risk while fat from plant sources reduced risk slightly. A small positive trend was observed between dietary cholesterol and heart disease however the relationship was not statistically significant.

Trans fats are produced in an industrial process where unsaturated fats are partially hydrogenated in order to increase their melting point. Both saturated and trans fats are thought to increase heart disease risk by increasing levels of LDL cholesterol. Trans fats are further thought to lower levels of the beneficial HDL cholesterol. It is thought that trans fats are responsible for more than 35,000 heart disease deaths each year in the United States.

Trans fats are not widely found in natural foods but are common in processed goods such as french fries, spreads, dips, biscuits, pies, and other snack foods. A small amount of trans fat is also present in animal milk and fat. Foods high in saturated fat include beef, pork, coconut oil, palm oil, full-fat milk, butter, cream, eggs, and bacon.

Mono-unsaturated and poly-unsaturated fats on the other hand are thought to increase HDL cholesterol while decreasing LDL cholesterol levels. Rich sources of unsaturated fats include avocados, seeds, nuts, soybean oil, canola oil, olive oil, and most varieties of oily fish.

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