Watermelon

Watermelon is mostly water and the amino acid citrulline, which the body converts to arginine and then to nitric oxide. That is why the 50 Man Foods keeps it on the list: it supports blood flow without the sugar load of tropical fruit.

It is the lightest fruit on the list — 30 calories per 100 g — and the one that hydrates you fastest.

  • As a snack or with a meal
  • Fruit
  • Updated Sep 2026

What it supplies

Nutrient · per 100 g, raw Amount % DV Relative amount
Vitamin C 8 mg 9%
Vitamin A 28 mcg 3%
Carbohydrate 7.6 g 3%
Calories 30 kcal 2%

Source: USDA FoodData Central.Percent Daily Values are based on adult reference intakes. The bars stop at 100%; the numbers do not.

Why it works

Citrulline is the amino acid the body uses to make arginine, which is the precursor to nitric oxide. Nitric oxide dilates blood vessels and supports blood flow.

Hydration matters more than most men think. Even mild dehydration raises cortisol and lowers testosterone; watermelon is the fastest way to fix it.

How much, how often

  • 200–300 g

    As a snack or with a meal

    Citrulline and hydration without the sugar load of tropical fruit.

  • Summer

    When it is in season

    Winter watermelon is often bland; summer is the point.

How to buy and prepare it

A ripe watermelon sounds hollow when tapped, has a yellow ground spot and feels heavy for its size.

Seedless varieties are convenient; the seeded ones are often sweeter.

Slice and eat plain, or cube and toss with feta and mint as a salad.

Grilled watermelon with salt and lime is a side that goes with pork or chicken.

Whole watermelon keeps a week at room temperature. Cut watermelon keeps 3 days in the fridge.

Frozen watermelon is fine for smoothies but the texture is soft when thawed.

In these guides

Questions

Does watermelon really help blood flow?
Citrulline is a real precursor to nitric oxide, and studies show it improves blood flow. It is not a drug, but it is a meaningful food source.
Is watermelon keto?
Not strictly — 7 g net carbs per 100 g. A small serving fits; it is not a free food.
How much watermelon is too much?
200–300 g a day is a reasonable amount. More is fine if you are not watching carbs closely.