High Blood Pressure
Blood pressure is the force exerted on your arteries by the circulating blood. When the heart beats the blood pressure increases in the arteries, this is the systolic pressure. Between beats the heart rests and there is less force on the arteries, this is the diastolic pressure. Although the systolic blood pressure reading is important, the diastolic blood pressure reading is probably more important as this is the minimum pressure which is exerted on the arteries at any time. Blood pressure is recorded using the systolic and diastolic blood pressures, systolic/diastolic, e.g. 120/80 mmHg (millimetres of mercury).
Blood pressure fluctuates throughout the day, it is lower when resting and higher with activity and stress. The average resting blood pressure for a healthy adult is 120/80. There may be health implications if your blood pressure is consistently higher or lower than this.
High blood pressure, or hypertension is considered to be 140/90 or higher. If someone has hypertension their blood pressure remains high even at rest. It has been estimated that in the UK 16 million people have high blood pressure, and that one third of those people may be unaware that their blood pressure is high. Having high blood pressure is considered to be a major risk factor for heart disease and stroke.
Symptoms of high blood pressure
High blood pressure is usually symptomless, which is why high blood pressure is often called the ‘silent killer’. If the blood pressure is extremely high, symptoms such as dull headaches, dizziness, fatigue, confusion, numbness, shortness of breath, coughing blood and nose bleeds have been reported.
Causes of high blood pressure
Blood pressure increases when the heart pumps with more force, when there is a greater volume of blood due to water retention, when the blood has greater viscosity, when the arteries lose flexibility (atherosclerosis) and are unable to expand or when the smallest arteries constrict, known as vasoconstriction, which increases peripheral resistance. In most cases the cause of the high blood pressure is unknown and may be due to a combination of these factors. When the cause of the high blood pressure is unknown, it is called primary hypertension.
In a small percentage of cases the cause can be found, and this is called secondary hypertension. In these cases increased peripheral resistance is often the cause. Kidney disease can be a cause of high blood pressure as the kidneys remove excess fluids from the body, if they are not functioning properly fluids build up causing increased blood volume and blood pressure.
Risk factors for high blood pressure
There are a number of factors which are known to increase the risk of developing high blood pressure. Some factors we can do nothing about such as a family history, ethnic origin and increasing age, however other factors, such as lifestyle play a part and can be modified in order to reduce blood pressure.
Being overweight increases the chances of developing high blood pressure, because the heart has to work harder to circulate the blood. Obesity is also often related to insulin resistance which may cause an increase blood sugar levels and hyperinsulinaemia which can damage arteries.
Smoking increases blood pressure because it increases free radicals in the blood, causes hardening of the arteries (atherosclerosis) and narrows blood vessels.
Excess intake of alcohol and binge drinking increase blood pressure as the resulting rises in blood sugar and free radical production damage the arteries.
Diet especially salt intake affect blood pressure, excess salt causes retained fluid leading to greater blood volume. Blood pressure can also increase during pregnancy.
Stress contributes to high blood pressure although the effects are often temporary while the person is under stress and then resolves when the stress is over, for example white coat hypertension.
Prescription medications such as some antidepressants, steroids and the oral contraceptive pill can also increase blood pressure.
Diet and high blood pressure
Most people with high blood pressure will have mild to moderate high blood pressure, and often their blood pressure can be brought under control with diet and lifestyle changes. For mild hypertension 140/90 to 160/104 the following dietary and lifestyle measures may help:
Excess salt (sodium chloride) consumption is known to increase the chances of developing high blood pressure. Processed foods are generally high in salt. Instead of adding salt while cooking try using herbs and spices to flavour food. However salt restriction may not be enough to bring down high blood pressure. Salt restriction needs to be accompanied by increased intake of potassium.
Eating more plant based foods, such as vegetables, fruits, beans and pulses, nuts and seeds, can increase the potassium to sodium ratio in the body and so help bring down high blood pressure. Leafy green vegetables not only contain potassium but are rich sources of other minerals such as magnesium and calcium. Magnesium works with potassium to help the body’s cells expel sodium. Some research suggests that certain vegetables with a high nitrate content, such as beetroot, may help to lower blood pressure via a different mechanism. The study below showed a significant decrease in blood pressure and it was suggested that this may be due to the nitrates being a source of vasoprotective nitric oxide.
Eat a diet with a low glycaemic load (GL). This sort of diet is based on eating certain carbohydrates as part of a healthy diet. Eating a low GL diet helps keep blood sugar levels stable and reduces insulin resistance. High blood sugar and hyperinsulinaemia (high levels of insulin in the blood) cause damage to blood vessels which can contribute to high blood pressure. Instead of processed grains, white flour and products made from these, choose wholegrains and wholegrain products such as brown rice, wholewheat pasta, oats, pearl barley, rye and bulgar wheat. There is evidence to suggest that for some people eating a low carbohydrate diet may be preferable to a low fat diet.
Some research suggests a low carbohydrate diet may be more effective at reducing blood pressure than weight loss medication, see the BBC article, Low carb diets like Atkins 'better for blood pressure'; here
Eat oily fish such as mackerel, salmon, fresh tuna and trout. These are rich in long chain omega-3 fatty acids. There are many clinical trials showing long chain omega-3 fatty acids have cardioprotective effects. These effects relate to improvements in blood pressure, heart function, arterial flexibility and vascular function, helping to maintain a regular heartbeat as well as reducing blood viscosity and ‘stickiness’. Flaxseed and flaxseed oil may offer the same benefits because they also contain short chain omega-3 fatty acids, however these must be transformed in the body into the long chain fatty acids that occur in oily fish, and in some people the transformation into these longer chain omega-3 fatty acids is blocked due to a lack of the necessary enzyme.
Garlic has been shown to reduce blood pressure in people with high blood pressure, without affecting the blood pressure if it is not elevated. Include garlic in your diet or take a supplement.
Other ways to reduce high blood pressure
Stress is known to raise blood pressure. Stress reduction techniques have been shown to significantly decrease high blood pressure. Suggested methods include meditation, yoga, stretching and walking. See a local qualified herbalist for help with reducing stress levels.
Caffeine is a stimulant which promotes the fight or flight stress response, raising blood pressure. Try switching to relaxing herbal teas such as chamomile, passion flower or limeflower.
If smoking may a factor a local qualified herbalist can help with quitting. Herbal medicines are effective for reducing the anxiety and cravings during this time.
Moderate exercise for 30 mins, done five times a week has been shown to help lower blood pressure.
Herbal remedies for high blood pressure
Hawthorn has traditionally been used as a heart tonic. Herbalists use hawthorn leaves, flowers or berries in addition to other herbs to protect and strengthen the heart muscle and its blood supply. In addition to mildly lowering blood pressure, hawthorn has been found to reduce symptoms of congestive heart failure, improve myocardial and coronary circulation and reduce abnormal cardiac rhythms. Although hawthorn is safe to use long term, it should not be used at the same time as other high blood pressure medication without professional supervision, as hawthorn may potentiate the effect of the medication.
The medicinal properties of garlic have been known for thousands of years. It has found use in the treatment of many conditions. Garlic contains many active compounds including sulphur compounds, vitamins and minerals. Research shows garlic slightly lowers high blood pressure and so can be used in mild hypertension. Though it's hypotensive effects may not be great, garlic also has beneficial effects on other cardiovascular factors such as thinning the blood by inhibiting platelet aggregation, improving triglyceride levels and lowering LDL cholesterol and total cholesterol levels. Garlic has also been shown to reduce atherosclerotic plaques in arteries. Although the fresh raw cloves of garlic provide the maximum health giving benefits, it has been shown that garlic also has beneficial effects on the cardiovascular system in dried form and even odourless garlic products.
To get the maximum benefit from garlic, chop or crush the garlic and leave it ten minutes before cooking lightly, or preferably adding to food raw. The chopping or crushing allows the enzymatic breakdown of the sulphur compound alliin into allicin, one of garlic's most active ingredients. Allicin is responsible for the odour of garlic, and can be destroyed by cooking.
Research on high blood pressure
Joint Effects of Sodium and Potassium Intake on Subsequent Cardiovascular Disease: The Trials of Hypertension Prevention (TOHP) Follow-up Study: full article
Potassium, magnesium, and calcium: their role in both the cause and treatment of hypertension; abstract
Acute Blood Pressure Lowering, Vasoprotective, and Antiplatelet Properties of Dietary Nitrate via Bioconversion to Nitrite; full text PDF
Omega-3 fatty acids and hypertension in humans; abstract
Omega-3 polyunsaturated fatty acids: their potential role in blood pressure prevention and management; abstract
Dietary protein level interacts with omega-3 polyunsaturated fatty acid deficiency to induce hypertension; abstract
Primary and secondary prevention of Cardiovascular Diseases: A Practical Evidence-Based Approach;
full text PDF
Hypertension prevention: from nutrients to (fortified) foods to dietary patterns. Focus on fatty acids; abstract
Association between trans-fatty acids in erythrocytes and pro-atherogenic lipid profiles among Canadian Inuit of Nunavik: possible influences of sex and age; abstract
The preventable causes of death in the United States: comparative risk assessment of dietary, lifestyle, and metabolic risk factors; abstract full text PDF
Effects of garlic on blood pressure in patients with and without systolic hypertension: a meta-analysis; abstract
A meta-analysis of the effect of garlic on blood pressure; abstract
Effects of garlic on blood pressure in patients with and without systolic hypertension: a meta-analysis; abstract
The effects of [omega]3 fatty acids and coenzyme Q10 on blood pressure and heart rate in chronic kidney disease: a randomised controlled trial; abstract
Blood pressure lowering efficacy of coenzyme Q10 for primary hypertension; abstract
Hypotensive effects of hawthorn for patients with diabetes taking prescription drugs: a randomised controlled trial; full text PDF
Low carbohydrate diets, pro: time to rethink our current strategies; abstract
High-sugar diets increase cardiac dysfunction and mortality in hypertension compared to low-carbohydrate or high-starch diets; abstract
Low Carbohydrate/High Fat Diet Attenuates Pressure Overload Induced Ventricular Remodeling and Dysfunction; full text
Nutritional effects on blood pressure; abstract
Effect of garlic on blood pressure: A systematic review and meta-analysis; full text PDF
Garlic: nature's protection against physiological threats; abstract
More information on high blood pressure
BBC Health pages - hypertension (high blood pressure)