Flax is something of a mystery food to most Americans; it's probably best known as an ingredient in breakfast cereal. Yet it's a powerhouse of omega-3 that's definitely worthy of inclusion in our top 10.
Flax can be purchased in seed form and in oil form. In each, about 70 percent of all its fats are polyunsaturated, and close to 60 percent of its fats are omega-3. The seeds provide fiber, protein and high levels of lignans. Lignans are plant estrogens -- like the isoflavones found in edamame -- that actually seem to help prevent the growth of cancerous tumors. Whole seeds are a healthful snack. They add crunch and a nutty flavor to salads, smoothies and baked goods.
Flax seed oil is the best plant source of ALA, and it's the only culinary oil to win out over canola in omega-6 to omega-3 ratio. Flax oil is actually lopsided with omega-3, with a ratio of 1:3.5. However, it has a low smoke point, about 225 degrees Fahrenheit (107 degrees Celsius). Thus, it's best used in fresh recipes such as salad dressings or pesto.
Another overlooked seed source of omega-3 worth mentioning here is chia. Yes, the same seed that sprouts on novelty gifts also has heart-protective properties.