It's a good idea to understand the differences between hemp seed oil and flaxseed oil before you decide which is best for your dietary needs.
Alpha-Linolenic Acid (ALA)
Flaxseed oil has a high percentage (as much as 58 percent) of alpha-linolenic acid (ALA or Omega-3), whereas hemp seed oil averages around 20 percent. These essential fatty acids have been shown to prevent heart disease, cancer and lower overall and LDL ("bad") cholesterol.
Gamma Linolenic Acid
In his article, "Therapeutic Hemp Oil", Dr. Andrew Weil reports that hemp seed oil contains 1.7 percent gamma-linolenic acid. This polyunsaturated fatty acid stimulates hair and nail growth, improves your skin and actually reduces inflammation, whereas Omega-3s--such as linolenic acid--increase it.
Flax seed oil has a 4:1 ratio of Omega-3 to Omega-6, and may cause Omega-6 deficiencies if used for a long period of time; however, hemp seed oil contains a balance of Omega-6 to Omega-3 (3 to 1 ratio), which matches the natural balance of the body, making it easiest to digest. While hemp seed oil is safe to use on its own, it's best to combine flax seed oil with other oils to ensure a better balance in your diet.
Hemp seed oil is safe for cooking up to 300 degrees Fahrenheit. When cooked at high temperatures, flaxseed oil can produce hydrogenated or refined trans-fatty acids, which are known to negatively affect cholesterol levels.
Hemp seed oil is best within 8 to 12 weeks after it is opened, while flaxseed oil lasts only 2 to 4 weeks. However, Dr. James O. Hill, in an article on www.revolutionhealth.com, says adding 1,000 international units of vitamin E per pint of flaxseed oil may extend its shelf life to 2 to 3 months.