Watermelon nutrition: glycemic index, calories weight loss and diets
Complete nutrition and health benefits analysis for Watermelon
Watermelon has become a symbol of summer in our culture. It is refreshing, bright and consists of more than ninety percent water, hence the name. In this article we will talk about the part of watermelon that isn’t water, how it affects our health and how it fits in different diets.
In its botanical classification watermelon is referred to as a pepo: a modified berry with a thick and hard outer rind. It is loosely considered to be a melon, however it is not in the Cucumis genus. It is in the same Cucurbitaceae family as melons, cucumbers and pumpkins.
The stripes of a watermelon indicate its variety. There are over 1200 types of watermelon varieties, however the most popular ones are the seeded, seedless, mini and yellow & orange ones.
The origin of watermelons is disputable. Scientists agree that watermelon’s progenitor was cultivated in the continent of Africa, the debate starts with the question of where exactly. 5000 year old remnants of watermelon seeds were found in Libya. In Egyptian tombs, there were not only 4000 year old seeds, but also paintings of watermelons. Centuries later, it spread and found popularity in Mediterranean countries (1).
In the Watermelon nutrition infographic below we tried to visualize some important values
Watermelon nutrition infographic
Every part of a watermelon can be eaten, thus it is considered to be a zero waste food. Watermelon seeds and rind, naturally, have different nutrition values compared to that on the inside. The seeds are often roasted and the rind can be used as a vegetable, stewed or fried, as well as pickled.
Some recommend incorporation of watermelon seeds in traditional recipes,especially in areas where chronic hunger is an issue, as it is usually locally available and thrown away, to improve the intake of protein, fat, calcium, carbohydrate, phosphorus (2).
Macronutrients and Calories
Around 92 percent of a watermelon’s weight is water. The predominant macronutrients in a watermelon are carbohydrates. The protein concentration is very low, with only 0.6g of it in a 100g of a watermelon. It also has an insignificant amount of fats, therefore it is low in saturated fats and has no trans fats or cholesterol. A 100g of a watermelon contains only 30 calories.
In protein quality breakdown, out of all the essential amino acids, tryptophan, threonine and lysine are contained in equal amounts and have the highest concentration. The rest of the essential amino acids are also equal in amounts but each make up only 1% of the protein.
Watermelon seeds have a lot more protein (around 8%) and fats (around 17%), as well as fiber (around 40%) and calories, however it is much more difficult to consume 100g of watermelon seeds (3). Another study about the nutritional value of watermelon seeds has found different numbers, with protein at around 34 percent, 32% fat, 27% carbohydrates and 0.1% of dietary fiber (4).
Watermelon rind is very rich in a non-essential amino acid called citrulline, which can also be found in the flesh. Red flesh watermelon has slightly less citrulline than yellow and orange flesh watermelons (5).
Watermelons are a great source of vitamin A and vitamin C. It also contains low to moderate amounts of B complex vitamins, in particular vitamins B1, B2, B3, B5 and B6. It is low in vitamin K and vitamin E. Watermelons are completely absent of vitamin D, vitamin B12 and vitamin B9.
Watermelon seeds are rich in vitamin E (4) and vitamin C. They are also much higher in vitamin B3 compared to the flesh (6).
The rind of a watermelon is richer in vitamin A and contains high amounts of vitamin C (6).
Watermelon pulp is rich in potassium, manganese, magnesium, calcium and phosphorus. It has moderate amounts of copper, iron, zinc, selenium and choline. It is very low in sodium.
Watermelon seeds also contain appreciable minerals; calcium, phosphorus, magnesium, sodium, potassium and zinc (3).
Based on the numbers from The International Tables of Glycemic Index, the glycemic index of a raw watermelon from Australia, containing 10g of carbohydrates, is 80±3. In parallel with that, a raw watermelon, containing 25g of carbohydrates has a GI of 72±13. The difference in carbohydrate concentration is based on season and the growing environment. Based on these numbers, the average GI of a watermelon is 76.
Despite the high GI, watermelon’s glycemic load of 4-6 is low, meaning one serving of a watermelon contains only 6g of carbohydrates.
According to Harvard Health Publishing a raw watermelon has a GI of 76±4.
Another study has shown different numbers for a GI of a watermelon. They found red-fleshed seedless watermelon to have a GI of 51±2. Red-fleshed seeded watermelon has a slightly lower GI of 48±1, with yellow-fleshed watermelon having an even lower GI of 47±2. This study has shown that there is no difference between the GI of a red fleshed seedless watermelon and the juice extracted from it. (3)
Other researches have shown watermelon from the Philippines to have a GI of 48±4 (4) and Malaysian watermelon to have a GI of 55±3 (5).
A watermelon’s glycemic index can be high or low, depending on the maturity stage, fibre and fat content, processing and treatment of the sample and other factors.
Watermelon consists of over ninety percent water, but another one of watermelon’s components is a carotenoid called lycopene. This is the compound that gives a watermelon its colour and it has gained attention from scientists due to its bioavailability and high absorption levels in a watermelon. It has been studied to have positive effects on cardiovasculature. It has a therapeutic role against life threatening metabolic diseases, such as cancer and diabetes(6).
Another compound found in high concentrations in a watermelon is an amino acid called L-citrulline. It has been proven to benefit cardiovascular health in direct and indirect pathways and can possibly be used as a non-pharmaceutical treatment for insulin resistance, high blood pressure and other cardiovascular diseases (7).
Despite all these positive effects people with diabetes are advised to moderate watermelon intake and combine high sugar fruits with healthy fats, fiber and proteins to slow the absorption of glucose into the bloodstream.
Watermelon allergies are quite rare but can still occur in both children and adults.
There are three major allergens that have been described in watermelons; malate dehydrogenase, triose phosphate isomerase and profilin. Among watermelon allergic patients, the frequencies of sensitization to these compounds are 96, 78 and 56 percent accordingly (7).
These allergens usually cause oral allergy syndrome as the main manifestation. It commonly presents with immediate swelling and an itching sensation in the mouth after consumption of the food allergen (8).
The protein profilin can also be found in other fruits, such as melons and oranges․
Watermelons have an average glycemic index of 76 (9), but that number can change depending on the maturity and carbohydrate composition of the watermelon.
Watermelons get their bright color from a carotenoid called lycopene. It has been proven to have a positive effect on the cardiovascular system, also playing a role in defending the organism from diseases such as diabetes and cancer (10).
Another important component of a watermelon is the non-essential amino acid called L-citrulline which has been studied as a potential non-pharmaceutical treatment for insulin resistance (11). L-citrulline is contained in especially high concentrations in the rind of a watermelon.
Consumption of watermelon is advised alongside with healthy fats, fiber and protein, such as nuts, for people with diabetic conditions, in order to slow the absorption of glucose.
As stated previously the carotenoid lycopene can also potentially have anti-carcinogenic qualities (10).
A group of compounds that the watermelon rind is also rich in are polysaccharides, such as arabinogalactan, galactose, arabinose, rhamnose and others. These polysaccharides are known for their antiproliferative and antioxidant properties. The antitumor activity of watermelon rind has a significant cytotoxic ability against laryngeal carcinomatose cells (12).
Watermelon rind is also rich in anthocyanin and flavonoids, which are known for their antioxidant, anti-inflammatory and anticancer qualities (13).
The amino acid L-citrulline can protect the organism not only from diabetes but it can also have a positive therapeutic effect on people with high blood pressure or other cardiovascular diseases (11).
A study has shown that it can prove to be effective in reducing the extent of cardiovascular disorders (10).
The antioxidant lycopene has also been proven to have the potential to reduce the development of pre-eclampsia and intrauterine growth retardation in first time pregnant women (14).
Watermelon can be advised to patients with hyperemesis gravidarum, a pregnancy complication characterized by severe nausea and vomiting, as the high water content can help to stay hydrated (15).
Watermelon pulp is known to have protective properties in chronic kidney failure and a potential ability to clear urine. It has been proven to possess significant anti-urolithiatic and diuretic activities (16) that can help people with bladder or urinary tract issues.
A watermelon diet, as the name suggests is a diet, during which you only eat watermelon. The high content of water in a watermelon makes this more of a cleanse, than a diet.
Daily consumption of watermelon can lead to reduction of body weight, body mass index, blood pressure, as well as improve some factors associated with obesity and being overweight. The mechanism for this action is watermelon’s ability to increase perceived satiety and moderate postprandial glucose and insulin response (17).
As a fruit, watermelon has a high density of water, with low caloric intake, which makes it a perfect snack for people trying to lose weight. We’ve already talked about the health benefits of watermelon consumption, however the watermelon diet is a radical form of dieting and due to lack of protein and fats cannot be recommended to children, pregnant women and to people with, such as diabetes or compromised immune functions (18).
Watermelon in Diets
The keto diet allows an average 10-20% of your daily caloric intake to be carbohydrates (19). A 100g of a watermelon contains only 8g of carbohydrates, therefore watermelons can be consumed during a keto diet, with careful management of the carbohydrate intake (20).
Watermelons are suitable for both DASH diets due to their low sodium and high potassium, magnesium and fiber concentrations. You can have 4-5 servings of fruits each day (21).
You can have watermelon if you’re on the Atkins 20 diet, phases 3 or 4, or on the Atkins 40 diet. However a cup of watermelons contains 11g of carbohydrates, so you have to eat it in moderation (22).
The Mediterraeian diet emphasizes using fruits and vegetables in your eating plan. Watermelon suits perfectly in this diet. The Mediterranean watermelon salad is a well known recipe.
Even though cavemen most probably didn’t eat watermelons, a moderate amount of it is acceptable during a paleo diet, it is one of the few sweet fruits that is (23).
Vegan/ Vegetarian/ Pescetarian
Since watermelons are plant species, you can naturally eat them on these diets.
You cannot eat watermelons, or fruits in general during the Attack and Cruise phases. You can add watermelon into your diet, during the Consolidation phase, but only one serving a day. You can have moderate amounts of watermelon throughout the Stabilization phase (24). Watermelon overall is considered to be a Dukan-friendly food, depending on the phase you’re in (25).
Traditionally you should abstain from watermelon during the fasting period and eat it during the eating periods. However some believe you can occasionally break the fast with seasonal fruit, like watermelon (26).
Low Fat & Low Calorie
Watermelon has almost no fat and since over 90 percent of it is water, it is one of the best fruits to eat during a low fat or a low calorie diet. A 100g serving of a watermelon has only 30 calories.
Watermelon is a great option to satisfy your sweet cravings during a low carb diet.
Watermelon is great for an anti-inflammatory diet due to its properties gained from lycopene, anthocyanin and flavonoids (10), (13).
If you are following the BRAT diet for a limited amount of time you can add watermelon as a bland food, since it is a great source of hydration. However you have to moderate your intake as large amounts of lycopene consumption can cause diarrhea (27).
Important nutritional characteristics for Watermelon
Watermelon Glycemic index (GI)
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NEW NUTRITION FACTS LABEL
Serving Size ______________
Mineral coverage chart
Mineral chart - relative view
Vitamin coverage chart
Vitamin chart - relative view
Protein quality breakdown
Fat type information
Carbohyrates breakdown for Watermelon
Fiber content / ratio for Watermelon
All nutrients for Watermelon per 100g
|Nutrient||DV%||In TOP % of foods||Value||Comparison|
|Protein||1%||89%||0.61g||4.6 times less than Broccoli|
|Fats||0%||90%||0.15g||222.1 times less than Cheese|
|Carbs||3%||54%||7.55g||3.7 times less than Rice|
|Calories||1%||94%||30kcal||1.6 times less than Orange|
|Fructose||4%||82%||3.36g||1.8 times less than Apple|
|Sugars||7%||46%||6.2g||1.4 times less than Coca-Cola|
|Fiber||1%||57%||0.4g||6 times less than Orange|
|Calcium||1%||85%||7mg||17.9 times less than Milk|
|Iron||1%||87%||0.24mg||10.8 times less than Beef|
|Magnesium||3%||84%||10mg||14 times less than Kidney bean|
|Phosphorus||2%||92%||11mg||16.5 times less than Chicken meat|
|Potassium||2%||80%||112mg||1.3 times less than Cucumber|
|Sodium||0%||98%||1mg||490 times less than White Bread|
|Zinc||1%||91%||0.1mg||63.1 times less than Beef|
|Copper||0%||84%||0.04mg||3.4 times less than Shiitake|
|Vitamin A||11%||23%||569IU||29.4 times less than Carrot|
|Vitamin E||0%||91%||0.05mg||29.2 times less than Kiwifruit|
|Vitamin C||9%||26%||8.1mg||6.5 times less than Lemon|
|Vitamin B1||2%||80%||0.03mg||8.1 times less than Pea|
|Vitamin B2||1%||90%||0.02mg||6.2 times less than Avocado|
|Vitamin B3||1%||88%||0.18mg||53.8 times less than Turkey meat|
|Vitamin B5||2%||79%||0.22mg||5.1 times less than Sunflower seed|
|Vitamin B6||2%||80%||0.05mg||2.6 times less than Oat|
|Folate, total||1%||87%||3µg||20.3 times less than Brussels sprout|
|Vitamin K||0%||88%||0.1µg||1016 times less than Broccoli|
|Folic acid (B9)||0%||100%||0µg||N/A|
|Tryptophan||0%||97%||0.01mg||43.6 times less than Chicken meat|
|Threonine||0%||96%||0.03mg||26.7 times less than Beef|
|Isoleucine||0%||97%||0.02mg||48.1 times less than Salmon|
|Leucine||0%||98%||0.02mg||135.1 times less than Tuna|
|Lysine||0%||94%||0.06mg||7.3 times less than Tofu|
|Methionine||0%||97%||0.01mg||16 times less than Quinoa, cooked|
|Phenylalanine||0%||98%||0.02mg||44.5 times less than Egg|
|Valine||0%||98%||0.02mg||126.8 times less than Soybean|
|Histidine||0%||98%||0.01mg||124.8 times less than Turkey meat|
|Saturated Fat||0%||92%||0.02g||368.4 times less than Beef|
|Monounsaturated Fat||0%||86%||0.04g||264.8 times less than Avocado|
|Polyunsaturated fat||0%||90%||0.05g||943.5 times less than Walnut|