You might be accustomed to spitting them out as you eat — seed spitting contest, anyone? Some people just opt for seedless. But the nutritional value of watermelon seeds may convince you otherwise.
Watermelon seeds are low in calories and are nutrient dense. When roasted, they’re crispy and can easily take the place of other unhealthy snack options.
 seeds

How to Roast Them

Roasting watermelon seeds is easy. Set your oven at 325°F and place the seeds on a baking sheet. It should only take about 15 minutes for them to roast, but you may want to stir them halfway through to ensure an even crispiness.
Cut the Calories
Trade in chips for seeds! Because eating watermelon seeds take longer, a handful should last you as long as a bag of chips. That’s just 22 calories compared to the 160 calories you’d get from chips!
You can make the seeds taste even better by adding a little olive oil and salt, or sprinkling them with cinnamon and a light dusting of sugar. If you prefer more flavor, you can add lime juice and chili powder, or even cayenne pepper.

Nutritional Benefits

How much nutrition you reap from watermelon seeds depends largely on how many you eat. Because they’re small, you need to eat quite a few to get their considerable benefits. However, when you compare their nutritional value to that of other snacks out there, watermelon seeds come out far ahead.

1. Low Calorie

One ounce of watermelon seeds contains approximately 158 calories. That’s not much lower than an ounce of Lay’s Potato Chips (160 calories), but let’s take a look at what constitutes an ounce. There are approximately 400 watermelon seeds in a single ounce, far too many to eat in one sitting. By contrast, there are only 15 potato chips in an ounce, far less than most people would normally munch in one sitting.
A large handful of watermelon seeds weighs about 4 grams, which contains about 56 seeds and just 22 calories. Far less than a bag of potato chips!

2. Magnesium

One of several minerals found in watermelon seeds is magnesium. In a 4 gram serving, you’ll get 21 mg of magnesium. The FDA recommends adults get 400 mg of this mineral daily. Magnesium is essential for many of the body’s metabolic functions. It’s also required to maintain nerve and muscle function, as well as immune, heart, and bone health.

3. Iron

A handful of watermelon seeds contains about 0.29 mg of iron. It might not seem like much, but the FDA only recommends adults get 18 mg in their day. Iron is an important component of hemoglobin — carrying oxygen through the body. It also helps your body convert calories into energy.

4. Folate

There are 2 μ of folate in a single serving of watermelon seeds. The FDA recommends adults get 400 μ each day. Folate, also known as folic acid or vitamin B-9, is important for proper brain function and also works to control homocysteine levels. Women of childbearing years need even more, since folate deficiency has been associated with certain neural tubal birth defects.

5. ‘Good’ Fats

Watermelon seeds also provide a good source of both monounsaturated and polyunsaturated fatty acids — 0.3 and 1.1 grams, respectively. According to the American Heart Association, these fats are useful in protecting against heart attack and stroke, and lowering levels of “bad” cholesterol in the blood.

The Takeaway

Watermelon seeds have many health benefits. Although the amounts of some minerals and vitamins within them may seem low, they are still far preferable to potato chips and other unhealthy snacks.

source: http://www.healthline.com/health/food-nutrition/best-watermelon-seed-benefits