Oranges And Blood Pressure Control

Introduction

Blood pressure is essential to life and it is the pressure exerted by blood against the walls of the arterial vessels when the heart pumps blood in the blood system. It can be differentiated into systolic and diastolic blood pressure, which are respectively the highest and lowest values recorded during the measurements. Blood pressure is measured in millimeters of mercury and it is considered generally as standard and healthy around 120/80 mm/Hg with the systolic presented over the diastolic value. The lowest blood pressure still considered acceptable for a vital condition for the organs without causing consequences of hypotension is 90/60 mmHg.¹ 

It is important to control blood pressure as it is considered as the primary risk factor for cardiovascular disease (CVD), main cause of death and comorbidities world-wide. Being able to control and lower blood pressure has been demonstrated to be a paramount benefit in decreasing cases of stroke and heart attack, as well as coronary heart diseases. Changes in lifestyle, such as the reduction of salt intake in someone’s diet or increasing vegetables and fruit consumption would be a great starting point and benefit across the whole population to lower blood pressure and promote good health.2 Oranges (Citrus sinensis) can offer a great source of flavonoids as part of a healthy diet, reducing blood pressure and the related risk of cardiovascular events.³

Health implications of high and low blood pressure

High blood pressure, or hypertension, is recorded when blood in the vessels flows at a higher pressure than what is considered standard. Low blood pressure, or hypotension, is when blood flows at a lower pressure than normal. Studies have shown that high blood pressure can be considered one of the main risk factors linked to adverse cardiovascular events, such as heart failure, chronic kidney disease, atrial fibrillation, stroke, coronary heart disease, and dementia.⁴ On the other hand, hypotension can also affect the quality of life and lead to a shorter life expectancy, by also increasing the risk of cardiovascular conditions and traumatic falls. It is a common condition and it can increase with age.⁵

Blood pressure-friendly diet and citrus fruits

Diet and exercise have a significant impact on blood pressure control. The DASH eating plan is a good start to make changes in the daily nutritional habits. This diet is not restrictive, can provide guidelines to reach daily and weekly goals and can lower blood pressure in people with either high or normal blood pressure. The DASH plan has the goal to reduce LDL cholesterol other than blood pressure, also linked to adverse cardiovascular events when the levels are high. Generally, the DASH eating plan recommends to increase the consumption of vegetables, fruit, fish and other foods that are also considered part of the mediterranean diet, over the consumption of fatty meats, full-fat dairy, sweets, and sugary drinks. There are several foods that can be integrated in a healthy diet to specifically also improve blood pressure management, such as citrus fruits, which are rich in vitamin C and flavonoids.

Oranges: Nutritional profile and blood pressure management

Oranges have a rich nutritional profile that includes more than 30 essential nutrients such as potassium, vitamin C, folate, and flavonoids (hesperidin). Around 250mL of orange juice can contain 14% of potassium, 25% of folate, about 100% of vitamin C of the daily intake required. About 60% of the daily intake in flavonoids is contained in only a glass of orange juice. Moreover, orange juice contains fibers as macronutrients (soluble and insoluble), which contains about 5% of the daily necessary intake of fibers.⁶ 

Vitamin C has a protective function towards the endothelial cells of the blood vessels from oxidative stress. Folate can intervene and heal endothelial dysfunction in patients with cardiovascular conditions. Potassium also contributes to blood pressure management.³

Epidemiologic studies have demonstrated that the flavonoids taken from citrus fruits have a positive impact on reducing mortality caused by cardiovascular diseases, as they improve endothelial functions with antioxidant activity and reduce blood pressure.⁷

Data suggests that there is an association between flavanones contained in Citrus sinensis and lower cardiovascular risk factors. However, randomised controlled studies have shown limited proof of the mechanism by which these essential micronutrients can possibly reduce cardiovascular disease risk.⁷ Other studies demonstrated that commercial orange juice managed to decrease blood pressure significantly, although a higher concentration of flavonoids, fibers (pectin) and other essential nutrients contained in the commercial juice compared to the fresh orange juice could be the reason for these results.³

Flavonoids and blood pressure

Flavonoids are natural compounds highly contained in fruits, vegetables, and plants in general. These natural substances are indispensable for a healthy life and diet, as they are considered not only to have antioxidant, anti-inflammatory, and anti-cancerogenic activity, but also a reverse correlation with mortality caused by adverse cardiovascular events as well as protective properties against congenital heart diseases.

Flavonoids include several subgroups depending on their chemical structure, such as flavones, flavonols, anthocyanins and others. Flavones are one of the main subgroups of this family of polyphenols, and are widely contained in leaves, flowers and fruits. The peels of citrus fruits, for instance, represent a source rich in flavones.⁸

Studies and Research on flavonoids and blood pressure

• A single-blind study, which means that the subjects were not aware of which group they were part of, involved 22 healthy people and randomly assigned them to either the group that had commercial orange juice for 4 weeks to then switch to natural orange juice for 4 more weeks, or to the one that followed the reversed process, therefore natural orange juice first and the commercial version afterwards. After the consumption of commercial orange juice the data showed a significant reduction of both systolic and diastolic blood pressure, whilst subjects who had natural orange juice did not have the same benefits.³
• A double-blind study, which means that both participants and researchers did not know of which groups the participants were part of, was conducted on 159 subjects that consumed 500 mL/day of either orange juice with natural levels of hesperidin (flavones) or hesperidin-enriched orange juice, for 12 weeks. Those who had the orange juice enriched in flavonoids, had their systolic blood pressure and pulse pressure significantly reduced after a sustained treatment. Moreover, after 12 weeks of hesperidin-enriched juice consumption, four genes linked to hypertension have also been found expressing differently.⁹ 
• A 12 weeks randomized, double-blind study was conducted to observe the effects that orange juice had with either normal concentration (NPJ) or high concentration (HPJ) of polyphenols (flavanone) on non-smoking participants with either overweight or obesity. The findings showed that blood pressure was positively influenced differently depending on the levels of flavanone contained, also attributed to a vasodilation mechanism mediated by a nitric oxide-activity.¹⁰

Vitamin C and blood pressure

Vitamin C, or ascorbic acid, is considered as one of the main essential vitamins for life, it is highly contained in oranges and has an antioxidant activity, neutralizing rapidly the damage caused by several reactive oxygen species (ROS). Thanks to its characteristic, vitamin C could protect the walls of the blood vessels from oxidation whilst promoting relaxation of the blood vessels by increasing availability of nitric oxide (NO). Short-term trials have found a reverse connection between vitamin C consumption (about 500 mg/day for eight weeks) and blood pressure in both people with either normal or high blood pressure, just like a higher vitamin C concentration in plasma has been also associated with a lower blood pressure in the population analysed. 

The daily recommended dose is 400 mg and out of the citrus fruits analyzed during a study, orange was the one with the highest dose of vitamin C with 58.30 mg/100.¹¹

FAQ’s

How long does it take for oranges to lower blood pressure?

Studies have already demonstrated improvements in lowering blood pressure in studies conducted over a period of 4 and 12 weeks.

What kind of orange juice is good for high blood pressure?

Commercial orange juice can significantly influence blood pressure, probably due to the higher concentration in flavonoids and fibers that natural orange juice does not have.

What food can bring blood pressure down?

Not only citrus fruits can help, but also following the DASH eating plan is good to consider for blood pressure management, as it is rich in potassium, fibers, and other nutritional essentials, but low in sodium.

Summary

Blood pressure management is paramount, as values outside the standards are considered as one of the main risk factors for cardiovascular events. Appropriate nutrition and physical exercise can have a significant impact on this factor, and following a diet that also includes fruit, fish, and vegetables, that is therefore rich in potassium, polyphenols, fibers and vitamins has been associated with a better control of blood pressure and consequent cardiovascular benefits. In particular, the consumption of Citrus sinensis (oranges) has been associated with a correct intake of flavonoids and vitamin C, other than other essentials such as potassium and fibers (pectin). Studies have shown that a consistent intake of flavonoids with a daily dose of orange juice, can improve blood pressure even in subjects that were either obese or overweight. What the findings also demonstrated is that the commercial and therefore concentrated orange juice is what had primarily a positive impact, possibly related to the fact that it has a higher concentration of polyphenols, vitamin C and fibers, compared to the normal orange juice. Vitamin C also has a beneficial impact on the cardiovascular system, thanks to its antioxidant activity that protects the blood vessels and enhances their endothelial function. In essence, it is crucial to embrace a healthy lifestyle not only for our blood pressure and cardiovascular system as discussed in this article, but because it is also beneficial for our metabolism and various systems that eventually contribute to overall health.