What do olives, avocados, walnuts and fish all have in common? If you guessed that they're all delicious, I'd say you are spot-on. And if you guessed that they're all powerful disease-fighters, then you're even more on the ball. These foods - along with many others - make some of the world's healthiest oils. Oil, healthy, you ask? Yes, it's true. A 120-calorie spoonful of oil, depending on which source you choose, can provide fat and fat alone, or it can provide antioxidants, minerals and vitamins to keep your heart beating strong through the years. Read on to learn about the world's eight healthiest oils.

1) Olive oil

The health benefits have been well-documented for years as our understanding of the Mediterranean Diet has grown. In summary, this monounsaturated fat can reduce the risk of developing chronic diseases like heart disease and cancer, while increasing life expectancy and quality of life.

2) Grapeseed oil

A lesser popular oil, grapeseed oil is made from (surprise!) grapes, and it's thought to have the same powerful disease-fighting properties as wine, also from grapes. Grapeseed oil has been shown to reduce LDL cholesterol and blood pressure, reduce the risks of cancer, improve diabetes and vision problems, and act against the aging process. Take that, free radicals.

3) Avocado oil

Avocado, perhaps the world's fattiest fruit, is also one of the most healthful. Virgin avocado oil is green and delicious, and it's extremely high in vitamin E and chlorophyll. As a bonus for every home chef, it also has a much higher smoke point than other vegetable oils (at a whopping 500°F), so you may feel more comfortable using it as a sautéing, frying or grilling oil.

4) Walnut oil

Walnuts, along with many other nuts, have been shown to be very powerful against cardiovascular disease, in large part due to their high concentration of the omega-3 fatty acid alpha-linoleic acid. Walnut oil in particular is rich in antioxidants and contains strong amounts of heart-healthy, disease-fighting fatty acids.

5) Sesame oil

Sesame oil, while strong in flavor and intensity, is also rich in antioxidants, as well as minerals like magnesium, copper, iron and calcium. The darker the oil, the more disease-fighting antioxidants - as well as heart-protecting vitamin E - are present.

6) Flaxseed oil

Commonly used by vegetarians seeking an animal-free way to ingest omega-3 fatty acids, flaxseeds are a rich source of the disease fighting fat. The oil, while not as powerful as the full seeds, has been shown to treat heart disease, lower cholesterol and aid with certain autoimmune disorders.

7) Fish oil

Fish oil, taken for years by grandmothers around the globe, has been used in households to prevent disease. We now know that the high concentration of DHA and EPA, two omega-3 fatty acids, are what's responsible for making fish oil so powerful in fighting heart disease, strokes, mental decline and other aging disorders.

8) Peanut oil

Peanut oil, while not commonly used in today's kitchens, may be another healthy oil to consider. It's a monounsaturated fat that's been used to lower cholesterol, prevent heart disease and possibly even treat cancer.

Image: Jordan Sim