Watermelon nutrition, glycemic index, acidty and serving size

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.

Sources.

1. https://care.diabetesjournals.org/content/diacare/suppl/2008/09/18/dc08-1239.DC1/TableA1_1.pdf
2. https://www.health.harvard.edu/diseases-and-conditions/glycemic-index-and-glycemic-load-for-100-foods
3. http://www.ifrj.upm.edu.my/25%20(06)%202018/(41).pdf
4. https://www.academia.edu/17584643/
5. https://www.researchgate.net/publication/5488788
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4464475/
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073798/