Nutrition for Healthy Blood Pressure
04 January 2019
In healthy individuals, the pressure of the blood in our arteries rises and falls throughout the day in order to meet the changing demands of the environment. Physical activity, stress and excitement, for example, cause blood pressure to rise so that more oxygen and nutrients are available to the brain and muscles to deal with such challenges. Blood pressure falls again once the body and mind return to a more restful state.
But if such environmental challenges remain throughout the coming weeks, months and years, blood pressure levels may stay elevated. Eventually, over the long term, the brain interprets this as the ‘new normal’, meaning that even when we think we’re relaxing, blood pressure levels may remain too high for optimal health.
This is a normal ‘allostatic’ adaptation to the environment. Sadly, it is an adaptation that can have devastating effects on many different organs, including the blood vessels, heart, brain, kidneys and eyes. Hypertension causes atherosclerosis, in which plaques accumulate on artery walls, causing blood vessels to narrow and inhibiting vital oxygen and nutrients to the brain and the heart. Persistent hypertension is a leading cause of heart attacks, strokes, kidney disease and vascular dementia.
Unfortunately, there are rarely any noticeable symptoms caused by abnormally high blood pressure. The only way to be sure it’s under control is to monitor it with a blood pressure machine, either at home or by going to see your GP, practice nurse or pharmacist.
It’s estimated that one in four adults in the UK has high blood pressure, many of whom are unaware. The NHS recommends that everyone over 40 years of age has their blood pressure monitored at least every 5 years.
Blood pressure values
Blood pressure is measured in millimetres of mercury (mmHg). There are two numbers in the reading. The upper number is the systolic pressure, which is the force at which the heart pumps the blood around the body. The lower number is the diastolic pressure, which is the level of blood vessels’ resistance to the blood flow.
For optimal health, blood pressure should be between 90/60mmHg and 120/80mmHg.
A reading of 140/90mmHg or above is considered hypertensive and unless you can make lifestyle changes to bring it down, your GP will likely offer you medication.
Risk factors for hypertension
Having a family member with hypertension can increase risk, as can advancing age and being of African or Caribbean decent. But there are also many risk factors that are modifiable. These include being overweight or obese; smoking; high stress levels; a diet high in processed foods, man-made fats like trans- and hydrogenated fats, salt, sugar and refined carbohydrates; drinking too much alcohol; getting insufficient sleep and/or physical activity; and exceeding your caffeine tolerance.
Making changes to diet and lifestyle, and supplementing particular key nutrients if indicated, can go a long way to keep blood pressure levels healthy.
The DASH diet (Dietary Approaches to Stop Hypertension) and the Mediterranean diet are the two most well-known diets used in hypertension. Personalised approaches in nutrition aim to tailor dietary interventions to the needs of the individual, rather than to the medical condition. But whatever diet you choose for helping a patient with blood pressure control, you can’t go wrong by increasing vegetable intake to 8-10 portions a day; and there are many reasons for this:
The more sodium we have in our bloodstream, the more water it binds, which may increase blood pressure. More veggies in the diet increases the potassium-to-sodium ratio. Although the results from many clinical trials indicate that reducing salt intake to the recommended level of 5-6 g/day lowers BP in both hypertensive and normotensive individuals, evidence points to the ratio between these two electrolytes being more important than either sodium or potassium alone. It’s also thought to be healthier to improve the ratio by increasing potassium, rather than simply by cutting sodium intake: a study of almost 29,000 high-risk individuals found that sodium insufficiency can be as harmful to health as eating too much, and that a moderate intake is best for all-round cardiovascular health.
Vegetables are also rich sources of magnesium, dietary fibre and nitrates, all of which have been shown to reduce blood pressure in clinical trials. Nitrates (found particularly in beetroot and dark green leaves like kale) are converted into endothelial nitric oxide that helps to relax the smooth muscle in blood vessels. What’s more, fruits and vegetables are also high in antioxidant vitamins and phytochemicals. These help to counteract inflammatory processes that can promote endothelial dysfunction and high blood pressure.
Most of our sodium comes from processed foods, including so-called staples like bread and breakfast cereals. Conversely, whole-food, Paleolithic-type diets (with the main dietary fat type being monounsaturated) are naturally low in sodium and high in the beneficial nutrients above, and have been found to lower blood pressure in human trials.
Such wholefood diets tend to be lower in concentrated carbohydrates and this may also be important for blood pressure control because insulin tells the kidneys to hold onto sodium. Lower-starch diets keep insulin levels low and this, in turn, allows excess sodium to be excreted, rather than building up and contributing to high blood pressure. A prospective analysis of 810 adults found that blood pressure was reduced in line with reductions in the consumption of sugar, especially sugar-sweetened drinks.
Thus the best strategy may be to stick to a wholefood, low-starch, high-vegetable diet, adding a little salt to taste if desired, but without getting too hung-up on the exact level of daily sodium intake.
- Manage stress and support adrenal gland function. An overactive sympathetic nervous system causes blood vessels to constrict.
- Get to a healthy weight, as blood pressure tends to rise incrementally with weight gain.
- Stick well within the government guidelines for alcohol intake. These are no more than 3–4 units a day for men and no more than 2–3 for women. And have at least two alcohol-free days a week.
- Get regular exercise: the government recommends 2.5 hours a week of moderate intensity activity. But this is the bare minimum - more would be better. Some find it helpful to aim to walk 10,000 steps a day, as well as engaging in an aerobic and weight bearing activity for at least half an hour three times a week. Even children with more sedentary behaviour tend to have higher blood pressure.
- Stop smoking.
- Reduce coffee, tea, chocolate, energy drinks and other forms of caffeine as much as possible.
- Spend time outdoors: exposing the skin to sunlight helps to control blood pressure because it stimulates nitric oxide production, relaxing blood vessels.
- Get at least 7 hours’ sleep a night. Short sleep duration is a significant independent risk factor for hypertension.
Magnesium is an essential mineral for many aspects of cardiovascular health yet dietary intake is typically low, due to modern food processing practices and dietary habits. Government surveys indicate that the median intake for magnesium in the UK is only 223mg/day, which is far lower than the recommended daily allowance (RDA) of 375mg.
Magnesium has various anti-hypertensive mechanisms: it acts as a natural calcium channel blocker, increases nitric oxide, improves endothelial dysfunction and induces vasodilation. Studies have found supplements of 500mg – 1,000mg/day to significantly reduce both systolic and diastolic pressure; and the effect is even greater when combined with increased potassium and reduced sodium intake.
For optimal absorption, magnesium is best supplemented in two or more divided doses throughout the day and in an organic form like magnesium citrate, as this is more bioavailable and has less chance of causing bowel disturbance. And it’s worth knowing that oral supplements carry far more evidence for raising blood magnesium levels than do transdermal solutions.
The beneficial components of fish oil are the two omega-3 fatty acids EPA and DHA.
A large meta-analysis of 70 RCTs concluded that EPA+DHA can reduce systolic pressure, and at higher doses, also diastolic pressure, with the greatest effects being in untreated hypertensive patients. Another review showed it to reduce arterial stiffness.
Fish oil may work via various different mechanisms, such as through activating nitric oxide; producing vasodilatory prostaglandins; reducing insulin resistance; stimulating the parasympathetic nervous system; and inhibiting the renin–angiotensin–aldosterone system.
Government guidelines are to eat oily fish twice a week. But this may not provide enough EPA+DHA for a therapeutic effect as some of the trials used up to 2,000mg/day. So it may be worth supplementing if hypertension is a concern.
Hypertensive patients appear to have lower blood levels of both vitamins C and D.
Supplementing vitamin C (500-1,000mg/day) has been found to lower blood pressure in many clinical trials of hypertensive patients. It may also improve the efficacy of certain types of blood pressure medications.
Vitamin C may work by increasing nitric oxide, reducing angiotensin, acting as a diuretic, helping to normalize the adrenal stress response and helping to protect blood vessel integrity through both its antioxidant and collagen-supporting effects.
Garlic has a tradition of use for cardiovascular health and is a popular choice for supporting healthy cholesterol and blood pressure levels.
Recent analyses of clinical trials have reported garlic to be effective for lowering both systolic and diastolic pressure in patients with hypertension and in those with normal blood pressure. A range of garlic preparations and dosages have been used across studies.
Garlic’s many sulphur-containing compounds are what makes garlic so special. One of these, alliin, is converted to allicin when chewed or crushed, giving garlic its characteristic smell. Allicin is responsible for many of the health benefits of garlic.
CoQ10 is a fat-soluble antioxidant found in raw red meat and fish. In the human body it is made in the liver but its synthesis can be compromised by age and particularly by the use of cholesterol-lowering statin medications. Some studies indicate that statins can reduce CoQ10 synthesis by as much as 40% within the first few weeks of use.
CoQ10 is used throughout the body but particularly in the cardiovascular system to scavenge free radicals; regenerate other antioxidants; help prevent the oxidation of low‐density lipoprotein; and support mitochondrial energy production. Hypertensive patients are often found deficient.
In a meta-analysis of RCTs, CoQ10 (100mg or more) was found to reduce both systolic and diastolic BP in hypertensive patients. Other studies have also reported improved blood pressure at 50-100mg twice daily, alone or with antihypertensive medications.
Ubiquinone is the form of CoQ10 most widely studied and this will be appropriate for most individuals. But in ageing or severely health compromised patients, it may be helpful to start with ubiquinol, as this form of CoQ10 has been pre-converted into the active molecule. The most bioavailable supplements present CoQ10 in an oil base.
The amino acid L-arginine is crucial for the production of nitric oxide that relaxes the arteries.
A meta‐analysis of 11 RCTs (387 participants) reported that L-arginine supplementation significantly reduced both diastolic and systolic blood pressure and suggested that effects could be seen after approximately 4 weeks.
It may be worthwhile considering supplementation because although L-arginine is found in animal proteins, grains, beans and nuts, more may be needed at certain times of life, such as following injury or surgery; and also because the trials used quite significant doses of 4g-24g/day.
L-theanine is an amino acid well-known for reducing anxiety by calming the sympathetic nervous system response, thereby reducing adrenal gland stimulation. There is evidence from a small human study that it also attenuates increases in blood pressure normally caused by stressful mental tasks.
Another trial found theanine (200mg) to antagonise the hypertensive effect of caffeine when the two agents were taken together.
L-theanine is found in green tea leaves but only at very low levels. Supplementation may provide a more therapeutic dose, especially if taken on an empty stomach, away from other amino acids.
Clinical trials indicate that soy isoflavones (60–110mg/day) are associated with significant reductions in blood pressure in hypertensive subjects.
Probiotics have been reported to moderately improve blood pressure. The greatest effects have been in hypertensive patients, with the use of multiple species, and when taken for 8 weeks or more, at a dose of ≥1011 colony‐forming units.
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The content of this article was written by Lorraine Nicolle Nutrition and was first published by Lamberts Healthcare Ltd.
© 2019 Lorraine Nicolle