A normal blood pressure is somewhere between 90/60mmHg and 120/80mmHg. A raised blood pressure just outside this range at 135/85mmHg has been shown to double your risk of a heart attack. For every 10mmHg you can lower your blood pressure by, you reduce your risk of dying by 13%1. What is the relationship between high blood pressure and diet, and are there foods that help lower high blood pressure?
High blood pressure is the number one risk factor for death
The Global Burden of Disease 2010 study identified high blood pressure as the number one risk factor worldwide for death and disability2. In 2013 the World Health Organisation deemed hypertension as a global crisis since it is the leading risk factor attributed to global mortality, affecting 40% of the population.
What changes to my diet can I make to reduce my blood pressure?
Several studies have shown a dose response relationship with fruit and vegetable intake and blood pressure. This means that the more fruit and vegetables you eat, the lower your risk of high blood pressure3. However, there is evidence that the quality of your diet is also important, so just eating a plant-based diet full of vegan processed food is not helpful. Increasing the range of your fruit and vegetable intake, and including pulses4, has also been shown to reduce blood pressure.
The results on studies which have looked to see if consumption of meat affects blood pressure is mixed. Some have found that the more meat you eat, the higher your risk of high blood pressure5,6. Whereas a meta-analysis (combined aggregate analysis) of 24 randomised controlled trials found that consumption of meat did not influence blood pressure7. Another study found that the type of meat mattered more that quantity, with those unprocessed meat not influencing risk for hypertension, whereas consumption of processed meat (5 or more times per week) increased risk of high blood pressure by 17%8. The Approaches to Reduce Hypertension (DASH) diet has also found to be effective in reducing blood pressure, and this advocates a plant-focused diet with limited diary and meat, similar to the Mediterranean diet.
Omega 3 fatty acids have been shown to reduce blood pressure9and can be incorporated into your diet by eating oily fish or seeds such as chia seeds, flaxseeds and nuts.
Flaxseeds contain a polyphenol compound called Secoisolariciresionol diglucoside (SDG), which reduces blood pressure in animal models10. The data suggests that the SDG compound inhibits Angiotensin Converting Enzyme (ACE), thereby lowering blood pressure. There are already medications, which block this enzyme, called ACE inhibitors which are used in the treatment of hypertension (high blood pressure). In one study flaxseed powder decreased blood pressure in pre-diabetic people (who had slightly raised sugar levels in the precursor stage to diabetes)11. The true value of flaxseed will hopefully be determined by a randomised double blinded trial currently recruiting people with hypertension who have yet to start medication12.
Reduce your salt intake. Try to cut out ready meals which are commonly high in salt, and reduce the amount of added salt on food. Use low sodium soya sauce.
Cutting back on alcohol can lower your blood pressure.
Quit smoking and aim to exercise regularly. Stress levels can also contribute to hypertension, so taking some time out for meditation, yoga or a walk can help.
Summary
In summary, to reduce your blood pressure, or reduce your risk of high blood pressure, eating whole foods, with a varied plant focused diet including pulses, nuts, chia seeds and flaxseeds, with limited dairy and meat consumption has the greatest supporting evidence. If you do choose to eat meat, choose unprocessed avoiding foods such as sausages and eat extra vegetables. Give up smoking, reduce your alcohol intake, take regular exercise and stress relieving activities.
References
1. Ettehad, D. et al. Blood pressure lowering for prevention of cardiovascular disease and death: a systematic review and meta-analysis. Lancet387, 957–967 (2016).
2. Lim, S. S. et al. A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet380, 2224–2260 (2012).
3. Steffen, L. M. et al.Associations of plant food, dairy product, and meat intakes with 15-y incidence of elevated blood pressure in young black and white adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Am. J. Clin. Nutr.82, 1169–77– quiz 1363–4 (2005).
4. Jayalath, V. H. et al.Effect of dietary pulses on blood pressure: a systematic review and meta-analysis of controlled feeding trials. Am. J. Hypertens.27, 56–64 (2014).
5. Steffen, L. M. et al.Associations of plant food, dairy product, and meat intakes with 15-y incidence of elevated blood pressure in young black and white adults: the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Am. J. Clin. Nutr.82, 1169–77– quiz 1363–4 (2005).
6. Borgi, L. et al.Long-term intake of animal flesh and risk of developing hypertension in three prospective cohort studies. J. Hypertens.33, 2231–2238 (2015).
7. O’Connor, L. E., Kim, J. E. & Campbell, W. W. Total red meat intake of ≥0.5 servings/d does not negatively influence cardiovascular disease risk factors: a systemically searched meta-analysis of randomized controlled trials. Am. J. Clin. Nutr.105, 57–69 (2017).
8. Lajous, M. et al.Processed and unprocessed red meat consumption and hypertension in women. Am. J. Clin. Nutr.100, 948–952 (2014).
9. Miller, P. E., Van Elswyk, M. & Alexander, D. D. Long-chain omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid and blood pressure: a meta-analysis of randomized controlled trials. Am. J. Hypertens.27, 885–896 (2014).
10. Prasad, K. Secoisolariciresinol Diglucoside (SDG) Isolated from Flaxseed, an Alternative to ACE Inhibitors in the Treatment of Hypertension. Int. J. Angiol.22, 235–238 (2013).
11. Javidi, A., Mozaffari-Khosravi, H., Nadjarzadeh, A., Dehghani, A. & Eftekhari, M. H. The effect of flaxseed powder on insulin resistance indices and blood pressure in prediabetic individuals: A randomized controlled clinical trial. J Res Med Sci21, 70 (2016).
12. Caligiuri, S. P. B., Penner, B. & Pierce, G. N. The HYPERFlax trial for determining the anti-HYPERtensive effects of dietary flaxseed in newly diagnosed stage 1 hypertensive patients: study protocol for a randomized, double-blinded, controlled clinical trial. Trials15, 232 (2014).