Diet and blood pressure

Hypertension, or high blood pressure, is a common chronic condition that represents a risk for cardiovascular health. Besides other lifestyle factors, there is a clear link between diet and blood pressure which we’ll discuss in this article.

Blood pressure levels

In Australia, blood pressure is classified as follows (1):

Category	Systolic (mmHg)		Diastolic (mmHg)
Optimal	<120	and	<80
Normal	120-129	and/or	80-84
High-normal	130-139	and/or	85-89
Mild hypertension	140-159	and/or	90-99
Moderate hypertension	160-179	and/or	100-109
Severe hypertension	≥180	and/or	≥110
Isolated systolic hypertension	>140	and	<90

Target recommendations vary for individuals that have other health conditions.

Dietary factors

Sodium

In about half of people with hypertension and a quarter of non-hypertensive individuals, their blood pressure levels change in response to salt intake. This sensitivity depends on factors such as genetics and age. More than three quarters of the salt in our diets comes from processed foods, including processed meats. Chronic high intake of salt gradually increases blood pressure; this is why older people tend to have higher blood pressure (2).

A lower sodium intake has been shown to lower blood pressure in both healthy dietary patterns (such as the DASH – Dietary Approaches to Stop Hypertension) diet and a typical American diet (2, 3).

The Heart Foundation of Australia recommends consuming ≤6 grams of salt per day for primary prevention and ≤4 grams per day for secondary prevention (1).

Potassium

Potassium seems to undo the bad that excess sodium can cause. It seems that the ratio of sodium to potassium is more important in determining blood pressure than the level of either of them. Once again, processed foods tend to be high in sodium and low in potassium, while the opposite can be said about fresh produce (2).

Foods with a high potassium to sodium ratio include unsalted nuts, beans, fruits and vegetables.

Calcium

Low calcium levels are associated with higher blood pressure. This could be due to inadequate intake or alterations in calcium metabolism. For most of us, meeting dietary guidelines should be sufficient. Some populations such as women at risk of preeclampsia and hypertense individuals who are salt-sensitive might benefit from increased calcium intake (2).

The main food sources of calcium are dairy foods. There is some evidence that high fat in foods might reduce the bioavailability of calcium (2).

Magnesium

Magnesium deficiency could be implicated in the development of hypertension (2, 5). Magnesium has multiple roles in the body, including the modification of vascular tone, which subsequently affects blood pressure (5).

Food sources of magnesium include green vegetables, whole grains and nuts. Modern food production methods decrease the amount of magnesium in foods. High fat, salt, coffee and alcohol can interfere with magnesium absorption (2).

Fatty acids

There is some evidence that intake of 4 grams per day of fish oil may cause a modest reduction in blood pressure. The same applies to monounsaturated fatty acids, such as those present in olives and olive oil (2).

Fibre

Dietary fibre may reduce blood pressure, particularly in individuals with hypertension (2).

Fruits and vegetables

Dietary patterns that have been beneficial in lowering blood pressure include the DASH diet, rich in fruits, vegetables, low-fat dairy foods, whole grains, poultry, fish and nuts, and Mediterranean diets supplemented with either olive oil or nuts (4).

Caffeine

Moderate caffeine consumption (up to 4 cups per day) doesn’t seem to have detrimental effects in blood pressure for most people (2).

Alcohol

Heavy drinkers who reduce alcohol intake significantly reduce their blood pressure. It seems that the elevation of blood pressure after alcohol consumption is transitory and might be unnoticed (2).

Intermittent fasting

Some interventions have demonstrated that fasting or fasting-mimicking (e.g. energy restricted) diets can lower blood pressure. This can be explained by a variety of mechanisms, which include an increase in parasympathetic activity and in the secretion of norepinephrine (a.k.a. noradrenaline) (6).

Other lifestyle factors

Smoking

Cigarette smoking has been shown to cause hypertension. Passive smoking may increase systolic blood pressure in some individuals as well (2).

Obesity

Obesity is directly related with high blood pressure, potentially due to an overactive renin-angiotensin-aldosterone system, as well as in the sympathetic nervous system. Cytokines secreted by the adipose tissue may also induce an elevation in blood pressure (2).

Physical inactivity

Physical inactivity is responsible for 5% to 13% of hypertension (2). While physical activity can cause a transient elevation of blood pressure during exercise, the net effects seem to be a decrease in blood pressure. Low-to-moderate intensity exercise seems to be more effective in lowering blood pressure than high intensity exercise, although a combination of both modalities can also be effective. Physical activity must be kept up in order to maintain its benefits on blood pressure. Several organisations worldwide recommend aerobic exercise supplemented by resistance exercise for managing blood pressure (2).

Stress

Chronic stress causes an elevation of adrenaline and over-activity of the sympathetic system, elevating blood pressure. Relaxation techniques, such as breath work can help lower blood pressure, among other benefits to the cardiovascular system (2).

Summary and recommendations

Hypertension is a common health condition that often goes unnoticed. To prevent and treat high blood pressure:

1. Eat a diet based on fresh unprocessed foods, including plenty of vegetables, fruit, nuts and seeds. Avoid processed foods.
2. If you have hypertension and are salt-sensitive, you should pay attention to recommended limits for salt intake
3. Avoid smoking and consuming alcohol in excess
4. Maintain a healthy weight
5. Exercise regularly
6. Manage your stress

References

1. National Heart Foundation of Australia. Guideline for the diagnosis and management of hypertension of adults – 2016. Melbourne: National Heart Foundation of Autralia, 2016.
2. Samadian F, Dalili N, Jamalian A. Lifestyle Modifications to Prevent and Control Hypertension. Iranian journal of kidney diseases. 2016;10(5):237-63.
3. Juraschek SP, Miller ER, 3rd, Weaver CM, Appel LJ. Effects of Sodium Reduction and the DASH Diet in Relation to Baseline Blood Pressure. J Am Coll Cardiol. 2017;70(23):2841-8.
4. Ros E, Martínez-González MA, Estruch R, Salas-Salvadó J, Fitó M, Martínez JA, et al. Mediterranean diet and cardiovascular health: Teachings of the PREDIMED study. Adv Nutr. 2014;5(3):330s-6s.
5. Gröber U, Schmidt J, Kisters K. Magnesium in Prevention and Therapy. Nutrients. 2015;7(9):8199-226.
6. Malinowski B, Zalewska K, Węsierska A, Sokołowska MM, Socha M, Liczner G, et al. Intermittent Fasting in Cardiovascular Disorders-An Overview. Nutrients. 2019;11(3).

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