Watermelon for blood pressure: a complete guide

watermelon juice jar and blood pressure monitor

Is watermelon good for blood pressure?

Watermelon has proven to have beneficial effects on blood pressure. This is because L-citrulline, which is a non-essential amino acid, is highly concentrated in watermelon. It is effectively converted into L-arginine. L-arginine increases nitric oxide’s bioavailability. Nitric oxide is the vasodilator that decreases blood pressure. Because of this watermelon will reduce your blood pressure, if you have high blood pressure. After eating watermelon it will take approximately 2 hours to maximize L-arginine concentration in our body.

Hypertension is a global health challenge because 1.13 billion people worldwide suffer from hypertension; in the USA, 45% of adults have hypertension. Hence it is very crucial to find new dietetic approaches to intervene in hypertension. This is because hypertension can progress into diseases such as cardiovascular diseases and chronic kidney diseases. If you can lower your blood pressure, if you have high blood pressure (hypertension) then you will reduce your chances of getting cardiovascular diseases in the future.

It is also said that when your endothelial in arteries cannot properly vasodilate, it will be the earliest marker of cardiovascular risk in the future. If you want to know, the endothelium is the innermost layer of blood vessels. It plays a major role in reducing blood pressure via L-arginine and nitric oxide pathways.

How much watermelon to lower blood pressure?

One kilogram of watermelon has 1.6 to 3.5 grams of L-citrulline. In previous chronic studies, after supplementing with watermelon extract that is equivalent to 1kg, blood pressure has reduced. So according to the evidence available up to now consuming about 1kg (minimum required) to 3 kg (maximum required) of watermelon per day will reduce your blood pressure. However, you should be careful with eating that much watermelon if you have diabetes because it will raise your blood glucose more. According to a review article[1]Allerton, T. D. et al. (2018a) ‘L-citrulline supplementation: Impact on cardiometabolic health’, Nutrients. MDPI AG. doi: 10.3390/nu10070921., the minimum dose of L-citrulline that you need to take to affect your blood pressure is 3g per day, the maximum effective dose is 10g per day.

Only consider taking a large quantity of watermelon if you ONLY have hypertension or prehypertension. Always refer to your healthcare provider before you make any changes to your current diet.

Mechanism-of-action-how-watermelon-reduce-blood-pressure

Mechanism of action of how watermelon lowers blood pressure

When we eat watermelon, L-citrulline in watermelon goes to the kidney and converts to L-arginine in the urea cycle. It enters the endothelial cells of the arterial wall. Then L-arginine is converted into nitric oxide by endothelial nitric oxide synthase. Nitric oxide then diffuses into vascular smooth muscle cells. Nitric oxide is a vasodilator; it will relax the smooth muscle cells in the arterial wall and reduce blood pressure. However, if we directly supplemented it with L-arginine, it will be catabolized in the intestine and liver. Therefore researchers have become more interested in L-citrulline, as well as watermelon.

Another very important aspect of L-citrulline is that it can inhibit the activity of arginase. Arginase inhibition will increase the bioavailability of dietary L-arginine and will increase nitric oxide bioavailability. This can act as a strategy to reduce the dysfunction of the endothelium.

Also since older adults have higher arginase activity watermelon will help to inhibit arginase and endothelium dysfunction will be reduced.

Watermelon nutrition composition

Following are the components in watermelon according to USDA food composition tables (2019) [2]https://fdc.nal.usda.gov/fdc-app.html#/food-details/167765/nutrients. Although L-citrulline is mainly responsible for blood pressure reduction,  there might be other compounds such as potassium, magnesium, lycopene, and beta-carotene that help to lower blood pressure. Following is a list of the main nutrients and non-nutrient in 1oog(30kcal) of raw red watermelon.

  • Water- 91.45 g
  • Protein- 0.61 g
  • Fat- 0.15 g
  • Carbohydrates- 7.55 g
  • Fiber- 0.4 g
  • Total sugars- 6.2 g
  • Sucrose- 1.21 g
  • Glucose- 1.58 g
  • Fructose- 3.36 g
  • Potassium- 112 mg
  • Vitamin A- 28 μg
  • Beta-carotenes- 303 μg
  • Lycopene- 4.5mg
  • Vitamin C- 8.1 mg
  • Magnesium- 10mg
  • sodium- 1mg

In watermelon, as you already saw, there are important antioxidants such as lycopene, beta-carotene, and vitamin C. These antioxidants will increase the plasma antioxidant capacity and it will reduce the oxidative stress in our body. In other words, watermelon enhances the ability of our body to fight against bad free radicals and reduce our body stress. As an example, betacarotene and lycopene will reduce superoxide free radicals that scavenge nitric oxide. This action will increase nitric oxide bioavailability.

The daily requirement of vitamin C for a healthy adult is 65- 90 mg. Lycopene in watermelon also has a cardioprotective and hypotensive effect.

Potassium is another important mineral that is present in abundance in fruits and vegetables. Watermelon also has potassium in decent amounts(112mg in 100g of watermelon). If you think about what is the daily requirement of potassium in an adult, it is around 3500mg.  Magnesium in watermelon also reduces blood pressure.

L-citrulline does not act alone to reduce blood pressure in watermelon. There are other compounds in watermelon that help to increase the effectiveness and bioavailability of L-citrulline as well as nitric oxide.

Why only watermelon?

L-citrulline which is the game changer amino acid is sadly poorly represented in food. However, it is highly concentrated in the Cucurbitaceae family which includes watermelon, squash, pumpkin, and cucumber. In the Cucurbitaceae family also, watermelon has the highest concentration of L-citrulline.

Can’t I only use blood pressure drugs to reduce blood pressure?

Well, when you only use drugs to lower blood pressure, it will only reduce up to 6.8-9.3 mmHg.

Watermelon blood pressure studies

Different researchers have supplemented watermelon or L-citrulline in different concentrations.

Chronic L-citrulline supplementation

  • The research conducted with hypotensive individuals, they have given a supplement of 6g of L-citrulline per day. This has resulted in reduced brachial systolic blood pressure (SBP) and brachial diastolic blood pressure (DBP)[3] Figueroa, A. et al. (2010) ‘Oral L-citrulline supplementation attenuates blood pressure response to cold pressor test in young men’, American Journal of Hypertension. Am J Hypertens, 23(1), pp. … Continue reading, [4] Wong, A., Chernykh, O. and Figueroa, A. (2016) ‘Chronic L-citrulline supplementation improves cardiac sympathovagal balance in obese postmenopausal women: A preliminary report’, Autonomic … Continue reading
  • Supplementing with 3g of L- citrulline has shown positive effects in reducing blood pressure[5] Alsop, P. and Hauton, D. (2016) ‘Oral nitrate and citrulline decrease blood pressure and increase vascular conductance in young adults: a potential therapy for heart failure’, European Journal … Continue reading.

Chronic watermelon extract supplementation (4g)

  • When supplemented with watermelon, which contains L-citrulline/L‑arginine, 2.7 g/1.3 g per day has resulted in reduced brachial blood pressure, aortic SBP, and aortic PP.[6] Figueroa, A. et al. (2011a) ‘Effects of watermelon supplementation on aortic blood pressure and wave reflection in individuals with prehypertension: A pilot study’, American Journal of … Continue reading

Chronic watermelon extract supplementation (6g)

  • Watermelon supplementation was given which contains 6g of l-citrulline/l-arginine (this amount equals 2.3 pounds or 1.0 kg of red watermelon raw). The result was a reduction in SBP and DBP.[7] Figueroa, A. et al. (2012a) ‘Watermelon extract supplementation reduces ankle blood pressure and carotid augmentation index in obese adults with prehypertension or hypertension’, American … Continue reading, [8]Figueroa, A. et al. (2013) ‘Effects of watermelon supplementation on arterial stiffness and wave reflection amplitude in postmenopausal women’, Menopause, 20(5), pp. 573–577. doi: … Continue reading

Can watermelon juice lower blood pressure?

  • Watermelon juice was also tested by scientists in research. However supplementing with 300mL of watermelon juice concentrate, which provides about 3.4g of L-citrulline, has increased resting blood pressure. However, this study has used healthy normotensive individuals. Hence experimenting with healthy adults may cause conflicting results regarding BP reduction [9]Bailey, S. J. et al. (2016) ‘Two weeks of watermelon juice supplementation improves nitric oxide bioavailability but not endurance exercise performance in humans’, Nitric Oxide – Biology … Continue reading.

What watermelon variety should you eat to lower blood pressure?

The variety of watermelon that is suitable to eat depends on its availability and the L-citrulline concentration in it. The more L-citrulline in it, it will be better. L-citrulline in watermelon varies with cultivar, genotype, flesh color, and many more factors.

Red, seedless, ripen watermelon has the highest concentration of L-citrulline however the yellow and orange watermelon and seeded watermelons have lower L-citrulline concentration. According to research, crimson sweet watermelon and Dixielee watermelon types have the highest concentration of L-citrulline. crimson sweet watermelon has an L-citrulline concentration of  2.85g and 1.47g of L-arginine. in 1 kg. Dixielee watermelon has L-citrulline and L-arginine of 3.7g in 1kg of watermelon. So if your region has these watermelon types, go for them to lower your blood pressure.

Another research also showed that the ‘Tom Watson’ and ‘Jubillee’ cultigens have the highest L-citrulline which is 3.5- 4.5 g per 1 kg of watermelon.

Q & A

  1. Can you drink watermelon juice if you are taking high blood pressure pills?

Actually, you can consume watermelon even if you are taking antihypertensive drugs to lower blood pressure. In one study[10]Massa, N. M. L. et al. (2016) ‘Watermelon extract reduces blood pressure but does not change the sympathovagal balance in prehypertensive and hypertensive subjects’, Blood Pressure, 25(4), pp. … Continue reading, where researchers have studied the antihypertensive effect of watermelon, they have recruited stage 1 hypertensive people who take antihypertensive drugs. This study was success full in reducing blood pressure in those individuals. So you can also take watermelon while you take antihypertensive medication and that will benefit you.

2. When is the right time to eat watermelon for high blood pressure?

Actually, you can eat watermelon whenever you like. However, you have to be aware of other health conditions you have if you have any. Always be sure to ask your health care provider about what suits you. As an example, if you have diabetes, you might have to eat less watermelon. The same goes for if you have any chronic kidney disease, your kidneys might have a hard time excreating all the potassium you eat, maybe those you taken by watermelon.

References[+]

Dilini Tharaka

Dilini Tharaka

BSc. (sp.) in Food Science and Nutrition, Specializing in Applied Nutrition (Founder, Editor, and an Author)
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