High blood pressure, also known as hypertension, is one of the most common health complaints in the Western world. Approximately one in three adults are affected by high blood pressure; and as a result, it is one of the most extensively studied health conditions in the world today. Hypertension is commonly treated with medication, but there are natural methods that have been scientifically proven to be just as effective.
There are a wide range of dietary and lifestyle changes that are frequently recommended to help combat high blood pressure. In this article, we’ll be taking a look at some of the most common, and examining the evidence as to whether or not they can have a significant impact on high blood pressure.
Reducing hypertension through diet
Whilst approximately 1 in 3 adults in the UK today suffer from hypertension, research into traditional ‘hunter gatherer’ cultures suggest that this condition was a far less frequent occurrence; with less than 3% of adults that followed a traditional diet and lifestyle being affected 1,2. As a result, many experts firmly believe that hypertension is a disease brought about by poor dietary and lifestyle choices in the western world.
There are a number of dietary programmes that have been purported as having beneficial effects on hypertension, with one of the most common being the ‘Dietary Approaches to Stop Hypertension’ model – otherwise known as the DASH diet.
The original DASH diet, first delivered in the early 1990s, was built on much of the prevailing dietary wisdom of that decade; that is, reducing fat intake and prioritising vegetables, fruit, whole grains, beans, nuts and seeds. Studies into the effectiveness of the DASH diet have produced mixed results – in one study, the DASH diet was shown to reduce blood pressure in overweight and hypertensive individuals, however, DASH in combination with exercise resulted in greater reductions in BP than DASH alone – 11.2/7.5 mm (DASH alone) vs 16.1/9.9 mm (DASH + exercise).3 A separate study also found that when sodium, regular exercise, and weight loss goals were achieved in the subjects, the addition of the DASH diet had no beneficial effects in those younger than 50 years, but did have an impact in those over 50.4
One of the main criticisms of the DASH diet is the lack of healthy fats which may have a beneficial impact on blood pressure. Omega 3, for instance, has been shown to reduce the risk of hypertension in numerous studies5,6. Found primarily in oily fish, omega 3 intake may be below adequate in patients following the original DASH diet. Monounsaturated fats, such as those found in avocados, have also been shown to lower blood pressure in hypertensive individuals7. Adding avocado into the diet also improves cholesterol profile and triglycerides8,9, both of which are biomarkers for high blood pressure.
As a result, an ‘improved DASH diet’ has since been released, which incorporates more healthy plant fats such as nuts, seeds, oily fish, and extra virgin olive oil. The improved DASH diet has been likened by many to the typical Mediterranean diet, which has been shown in a randomised controlled trial to reduce blood pressure more significantly than a low fat diet10. The addition of extra virgin olive oil, a key component of the traditional Mediterranean diet, has been shown to have a significantly inverse association with both systolic and diastolic blood pressure11.
Are vegetables the answer?
In all of the studies we have come across, a common theme became clear – a high intake of fruits and vegetables correlated significantly with a reduction in blood pressure. This comes as no surprise, but it appears that fruits and vegetables rich in certain nutrients may be particularly beneficial. Take high nitrate foods, for example, which have been shown to improve vasodilation12 and may therefore reduce blood pressure. Leafy greens such as spinach, kale, rocket and cabbages are good sources of dietary nitrate, along with beetroot, which provides a significant source of this nutrient. In fact, beetroot juice has been studied in isolation for it’s potential to lower blood pressure, and significant evidence has shown that it can be effective in isolation on free living adults that do not already suffer from hypertension13,14.
There is also strong evidence to suggest the role of potassium in helping to prevent high blood pressure15. Found primarily in fruits and vegetables, good sources of potassium include potatoes, sweet potatoes, avocados, bananas and plantain. Increasing potassium intake by following a typical DASH or Mediterranean diet may well be another reason why these diets have been shown to have a beneficial impact on blood pressure.
Above sounds a bit contradictory to when you opened about dash diet producing mixed results.
Given the potential impact of fruits and vegetables on hypertension, is a vegetarian diet a sensible choice for those looking to lower their blood pressure? Perhaps, as suggested in a recent meta-analysis, which noted that a vegetarian diet reduces systolic and diastolic blood pressure more than omnivorous diets16.
That said, there are some notable nutrient deficiencies that can arise from a vegetarian diet, and may in fact worsen blood pressure. An example of this is vitamin B12, found almost exclusively in animal foods, which has been linked to lower blood pressure17. Vitamin B12 is notoriously difficult to consume on a vegetarian diet, with blue-green algae such as spirulina and chlorella one of the only known plant based sources. Vegan diets are also notably absent in vitamin K2, which could also help prevent hypertension by reducing arterial calcification and vascular stiffness18,19. Vitamin K2 is found primarily in the fat of grass fed animals and raw, unpasteurised dairy. It can, however, also be found in fermented foods such as sauerkraut and kvass.
The impact of protein consumption of blood pressure
In a meta-analysis on dietary protein intake and blood pressure, researchers found that dietary protein intake had a significant effect on blood pressure reduction when compared with carbohydrate intake20. One study conducted by Boston University Medical Center was of particular interest, found that participants consuming the highest amount of protein (an average of 100g per day) had a 40 percent lower risk of hypertension than the adults with the lowest protein intake21.
This evidence suggests that paying attention to protein consumption, particularly in replacement for refined carbohydrates, could be beneficial for those suffering from hypertension. This is another potential drawback for a vegetarian or vegan diet, which make consuming enough high quality protein more challenging. That said, it is certainly not impossible in a balanced vegetarian diet that includes plenty of nuts, seeds and legumes. Again, we come back to spirulina – an algae which contains an average of 60% protein.
I have added the above. We need to elaborate on this after spirulina product description complete.
What is the right diet for hypertension?
Although there are numerous studies to digest and some conflicting information to consider, if we take into account the common themes that are present in all of the diet programmes that have been shown to improve hypertension, we can start to get an idea as to what the ideal diet for hypertension would look like.
Similar to both the DASH and Mediterranean diets, the ideal diet for hypertension would be rich in vegetables and fruits of all shapes, sizes and colours. Particular attention should be paid to vegetables rich in nitrate and potassium. Also like the Mediterranean diet but unlike the original DASH diet, the ideal diet for hypertension would also be rich in monounsaturated fats from foods such as extra virgin olive oil and avocados, as well as Omega 3 from oily fish.
The ideal diet for hypertension would be higher in protein and lower in refined carbohydrates. Meat and dairy would be consumed, if desired, to allow for adequate intake of protein and vitamins B12 and K2. If the patient were vegan or vegetarian, particular attention would be paid to these two nutrients to ensure nutrient deficiencies that may cause high blood pressure do not arise. High quality protein sources such as hemp, lentils and chick peas *spirulina would also be highly recommended on a vegetarian or vegan diet, as would omega 3 rich seeds such as flax and chia.
It is important to remember that new studies are emerging all the time, so we can never consider any diet to be the definitive prevention or cure for any given illness. At this time, however, there is strong evidence to suggest that the above diet could be considerably beneficial to anyone suffering from high blood pressure.
Should you give up the salt?
One of the most common recommendations for reducing blood pressure is to lower your salt intake. Some experts even recommend eliminating it completely – but is this a sensible approach?
Whilst salt intake has long been theorised as a contributing factor to hypertension, as you will see below, eliminating salt completely may not be the appropriate solution. Indeed, whilst too little salt is certainly better than too much salt, it appears that some salt is also better than no salt at all.
Whether it is in the form of sea salt, rock salt, or common table salt, salt is made almost entirely of sodium chloride and by weight is 40 % sodium and 60% chloride. Sodium is an essential nutrient, vital in maintaining fluid balance and normal cellular metabolism. We need sodium to survive, and although many people consuming a standard Western diet undoubtedly consume too much, cutting it out entirely could do more harm than good.
Salt and hypertension – a tenuous link?
The theory that salt causes hypertension (otherwise known as the salt – hypertension hypothesis) was originally established in 1972, when Dr Lewis Dahl attempted to prove a link between high sodium intake and high blood pressure. Crucially, however, this study was not conducted on humans – rather, laboratory rats, which were fed the human equivalent (based on total sodium intake per gram of body weight) of 500 grams of salt per day22. Considering the typical human in the Western world consumes an average of ten grams of salt per day, the rats were being fed 50 times the salt equivalent of the standard human23,24! What society now quantifies as a ‘high salt diet’ pales to insignificance in comparison with what the rats were consuming in this particular test.
Another contributor to the salt / hypertension hypothesis was the INTERSALT study, first published in 1988, which examined the impact of salt consumption on blood pressure across different populations around the world. Researchers brought forward observational studies of populations that had a low salt intake and low incidences of hypertension, in order to support the hypothesis that salt contributes to high blood pressure. One example often cited are the Yanomami Indians of the Amazon rainforest, who at the time of research, had both low salt intake and low blood pressure25. This particular correlation lends weight to the salt / hypertension hypothesis and led researchers to theorise that salt intake can have a direct relationship on high blood pressure.
However, this was an observational study, which as we know from our previous article***, is far less reliable than an experimental study as it does not take into account the impact of other variables on the given result. And although the Yanomami Indians did have a lower sodium intake, researchers also found that they had a low body mass index with almost no occurrences of obesity, high ingestion of fibres, high physical activity, and the absence of the physiological stressors that come with a job and living in a financial economy. The same can be said for other regions where low salt intake correlated with low blood pressure, such as areas in rural Africa, where a high intake of fibres and regular exercise were a common factor in all of the populations assessed26.
Furthermore, the INTERSALT study as a whole did not produce any clear pattern between the total salt intake and blood pressure in the countries studied. Interestingly, the study did show that higher salt consumption correlates with higher life expectancy amongst the countries studies27.
The INTERSALT study certainly doesn’t rule out salt as a contributing factor to high blood pressure – but as with all observational studies, it should be, as they say, taken with a pinch of sodium chloride. Good!
Further evidence against complete salt restriction
Since Dr Lewis Dahl’s original study on laboratory rats, dietary guidelines around the world have continually and consistently advised us to reduce our salt intake. This comes despite a 2011 study in the Journal of the American Medical Association, that documented how a low salt diet can increase the risk of stroke, heart attack, and overall mortality28,29. Unlike Dr. Dahl’s study on lab rats, and the observational studies of INTERSALT, this particular study was a controlled, double blind trial.
A further study conducted in 2012 for the American Journal of Hypertension found a slight blood pressure reduction in patients on a low salt diet, but they also found that these patients developed higher plasma levels of triglycerides, LDL cholesterol, and total blood cholesterol30. The researchers concluded that the positive impact of the small reduction in blood pressure was overshadowed by these negative effects, and that excessive sodium restriction may actually have an undesirable impact at a human level.
We discussed the potential benefits of potassium earlier, and evidence also suggests that maintaining a better balance of potassium and sodium is more beneficial than simply reducing sodium31,32. These studies indicate that rather than actively reducing our sodium intake, it may be more beneficial to actively increase our intake of foods rich in potassium.
To salt or not to salt?
On the whole, the evidence that supports the salt-hypertension hypothesis is weak, and does little to suggest that reducing one’s salt intake will lower the risk of hypertension in an otherwise healthy individual, or indeed, reduce blood pressure in an individual already suffering from hypertension. This is certainly not to be interpreted as a ‘free pass’ to sprinkle salt liberally over your meals, but there are undoubtedly other dietary factors that have been proven to have a more substantial effect on blood pressure and overall cardiovascular health. Until further evidence proves otherwise, there appears to be little benefit in lowering your sodium consumption to less than the typical dietary recommendations, which currently stand at 6 grams of salt per day (approximately one teaspoon), which equates to 2.4g of sodium per day. Keep in mind that this recommendation is for total sodium intake, which includes sodium that naturally occurs in foods, additional sodium added to processed foods, and the salt that you use to impart flavour to your meals.
You put 6g of sodium which is equal to 15g of salt per day. Limit is 6g of salt. Please clarify the paragrpaph that comes after it. This salt vs sodium issue needs to be clear
Given the widespread use of salt in processed foods such as bread, breakfast cereals, crisps and convenience foods; the lower your intake of processed foods, the more liberal you can afford to be with the salt.
75% of our salt intake is processed food, only small amount from salt we put on ourselves. Above needs to be rephrased inline witht his.
With a contentious issue like this with some studies saying salt increases bp, and others saying it doesn’t we need to remain as impartial as possible, representign both sides. In this case yes point out the recent studies saying salt may not affect bp but it also appears peoples response is different with some a specific subset of people who may suffer from increased bp with salt intake – this is missing.
Exercise and blood pressure
There is extremely strong evidence to suggest that exercise, in all of it’s guises, can have a highly beneficial impact on blood pressure. Both aerobic33,34 and anaerobic34,35 exercise have been shown to have a statistically significant impact on blood pressure; but if you can’t hit the gym, fear not. Simply incorporating more regular movement into your day has also been proven to have profound effects on both hypertensive and non-hypertensive patients36,37,38.
The bottom line is that we should all certainly be moving more, and a variety of movement and exercise seems to be the key in reducing blood pressure39. Simply walking for an extra 30 minutes per day has been shown to lower both systolic and diastolic blood pressure in hypertensive adults40, whilst regular exercise in all forms has been shown to lower the risk of hypertension in non-hypertensive patients41. Whether you are currently hypertensive or not, incorporating regular exercise into your life is undoubtedly of benefit.
Interestingly, recent research appears to suggest that short bursts of high intensity exercise appear to have the most profound impact on blood pressure. In a study conducted on over 55s, high intensity exercise was shown to have a greater impact on blood pressure reduction, whilst at the same time positively impacting other cardiovascular biomarkers such as plasma triglycerides and oxidised low density lipoprotein42.
In additional studies on both hypertensive and non-hypertensive individuals of all ages, evidence has suggested that high intensity interval training (HIIT), which consists of several bouts of intense exercise (1 to 4 minute bouts at 85% to 95% of max heart rate with intervals of rest or active recovery) has demonstrated a more profound impact on several factors involved in the pathophysiology of hypertension, including cardiorespiratory fitness, endothelial function and its markers, insulin sensitivity, markers of sympathetic activity and arterial stiffness; than continuous moderate intensity exercise43,44,45.
Furthermore, in a 2012 review published in the American Journal of Cardiovascular Disease concluded that high intensity interval training may have an important role in preventing and controlling hypertension, as shown by the greater benefits for reversing key alterations in the physiopathology of high blood pressure in both hypertensive patients and normotensive subjects at high familial for hypertension when compared with continuous moderate intensity exercise46. The study also outlined future intentions to establish the optimal dose of high intensity interval training, in order to establish the best relation between exercise quantity (frequency and duration) and blood pressure reduction.
In conclusion, there is compelling evidence to suggest that exercise, in all of it’s forms, can have a highly beneficial impact on blood pressure. However, for those with limited time, high intensity interval training (HIIT) may well be the most favourable option.
Other lifestyle factors
There are many other lifestyle factors that can contribute to hypertension. Often, it is a combination of numerous contributory factors that cause an individual to suffer from high blood pressure, but it is interesting to examine the independent relationship between individual lifestyle factors and hypertension in controlled trials.
Alcohol: Alcohol consumption has long been linked with high blood pressure, and there is notable evidence to suggest a relationship between the two. In the short term, alcohol intake appears to have a slight blood pressure lowering effect47,48,49 due to the vasodilative impact whereby blood vessels relax to allow greater blood flow. Over a longer term period, however, regular consumption of alcohol has been shown to demonstrate blood pressure increasing effects and increase risk of hypertension50,51, 52.
In a 2008 meta-analysis of ten studies examining the relationship between alcohol intake and blood pressure, researchers found that patients who drank the most alcohol were 2.42 times more likely to suffer from hypertension than the group who had the lowest alcohol intake53. These studies were, however, all epidemiological studies.
Nonetheless, various experimental studies have proven the same relationship and led researchers to draw strong conclusions about alcohol and blood pressure. A meta-analysis of 15 randomised, controlled trials (which totalled 2234 participants), in which alcohol reduction was the only intervention difference between active and control treatment groups, showed a significant mean reduction in blood pressure when alcohol consumption was reduced54. A dose-response relationship was observed, whereby the greater the reduction in alcohol, the greater reduction in mean blood pressure. Effects of intervention were also enhanced in those with higher blood pressure, suggesting that patients suffering from existing hypertension can benefit further from alcohol reduction than non-hypertensive patients.
Caffeine: Caffeine has been shown, in many different studies, to impart an acute increase in blood pressure (at greater than or equal to three hours) on both hypertensive and non-hypertensive individuals55, 56, 57, 58. In a 2005 meta-analysis of randomised, controlled trials, a long term increased risk of hypertension was also noted in regular caffeine drinkers59. Interestingly though, patients who consumed their caffeine through coffee saw less of an increase in blood pressure than those consuming their caffeine through other beverages. There is also evidence that caffeine affects people to a progressively greater degree according to their current blood pressure classification60.
Smoking: Cigarette smoking is a strong cardiovascular risk factor, and exerts an acute hypertensive effect in the period immediately after smoking by stimulating the sympathetic nervous system61. Smoking also causes arterial stiffness, a major risk factor for high blood pressure62. It is quite paradoxical, therefore, that there is little evidence to suggest that chronic smoking can increase blood pressure; in fact, some evidence even suggests that smokers may be at a lower risk of hypertension than non-smokers63,64.
Whilst current evidence may rule out smoking as a risk factor for hypertension, possibly due to it’s antithrombotic effects, smoking is a major contributor to numerous other cardiovascular risk factors; including cardiac hypertrophy65, vascular disease66, and coronary heart disease67, 68, 69. Smoking also significantly increases the risk of heart failure and overall mortality70, so despite there being no apparent long term relationship between smoking and hypertension, there is still overwhelming evidence to suggest that giving up smoking is a wise choice for your overall health.
Stress: It is difficult to observe the direct impact of stress on blood pressure, given that stress in itself is somewhat hard to quantify. That said, studies have shown a direct relationship between an increase in cortisol production (the body’s stress hormone) and an increase in blood pressure on both a short and long term level71. There are several studies that suggest a beneficial impact of anti-stress therapies such as meditation, yoga and deep breathing on blood pressure72.
Sleep: Lack of sleep has been shown to acutely increase blood pressure over a 24 hour period, and prolonged short sleep durations are theorised to contribute to hypertension by consistently exposing the patient to increased blood pressure and elevated heart rate73. In a study on mild to moderate hypertensive patients, blood pressure significantly increased the morning after a sleepless night74. Both lack of total sleep and lack of sleep quality have been shown to increase blood pressure and risk of hypertension amongst otherwise healthy individuals75. Chronic insomnia has also been shown to increase both incidence and prevalence of hypertension76, whilst correcting sleep apnea has been shown to lower blood pressure77.
In a ten year longitudinal study conducted between the years of 1982 and 1992 subjects who slept less than five hours per night were associated with a significantly increased risk of hypertension78. There is undoubtedly strong evidence to suggest that sleep loss may be a major contributing factor to hypertension.
Choosing the right supplements
There are numerous herbs and supplements that have been clinically studied for their potential to treat hypertension, with several displaying extremely promising effects. For a more in depth look at some of these supplements, take a look at our previous article ‘The best herbs for reducing blood pressure.’
To give a brief synopsis of some of the most effective herbs and supplements for blood pressure, we have compiled a list below:
Hibiscus: Numerous human studies have indicated that hibiscus can have a significant impact on blood pressure in both hypertensive and prehypertensive patients79.80,81,82. These studies suggest that both hibiscus tea and powdered hibiscus extract can be effective, and on average, hibiscus supplementation facilitated a decrease in blood pressure by 15.34 points systolic (the first number on a blood pressure reading) and 6.59 points diastolic (the second).
Garlic: There are two main forms of garlic supplement available; traditional garlic, and aged garlic extract. Despite facilitating numerous positive changes on various cardiovascular risk factors including arterial elasticity, blood flow, and protection against oxidative stress, there is currently little evidence that points to the potential of traditional garlic to lower blood pressure in non-hypertensive patients83, 84. There is, however, evidence to suggest that garlic supplementation may be beneficial to hypertensive patients85. There is also evidence to support the impact of Aged Garlic Extract on hypertension86,87. In one particular study, doses of between 600 and 1500mg of aged garlic extract were shown to be just as effective as the drug Atenolol over a 24 week period87.
Further research is required into both traditional garlic and aged garlic extract to be able to draw more reliable conclusions.
Olive leaf extract: Two clinical studies using a standardised olive leaf formulation, at doses of 500mg and 1000mg respectively, reduced blood pressure in hypertensive patients by an average of 11 points systolic and 4 points diastolic88,89. Much like garlic, however, current evidence suggests that olive leaf extract only demonstrates a significant blood pressure lowering impact on patients who currently suffer from hypertension90.
Spirulina: There is encouraging evidence that spirulina has the capacity to reduce blood pressure in both hypertensive and non-hypertensive individuals, whilst also improving other cardiovascular biomarkers such as blood cholesterol and triglycerides91,92. This evidence suggests an effective dosage of spirulina at between 3.5mg and 4.5mg per day. Further research into spirulina is required to draw more accurate conclusions.
Magnesium: There is notable evidence to suggest that magnesium supplementation may impart a significant benefit on blood pressure, providing that the patient is either currently suffering from hypertension93, 94 or from an existing magnesium deficiency95, 96. Evidence suggest an effective dose of magnesium for hypertension to be approximately 400 – 500mg.
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