A fish story - Fish oil for human bones
June 22, 2011
This is a fish story that is true. Fish oil is good for your bones. Evidence has been accumulating in the past decade that fish oil may prevent osteoporosis. How does fish oil affect bones? Fish oil contains a fat called omega-3 fatty acid. Omega-3 fatty acid is one of the two basic categories of essential fatty acids. The other is omega-6 fatty acid. Essential fatty acids are necessary for health and cannot be made by the body; they must be supplied by the diet. They are occasionally referred to as vitamin F because of their essentiality for human health. The ideal ratio of omega-6 to omega-3 fats is 1:1. Our ancestors evolved over millions of years on this ratio. Today, however, the ratio of omega-6 to omega-3 averages 20-:1 to 50:1 in the American diet. The primary sources of omega-6 are corn, soy, safflower, sunflower and canola oil. These oils are overabundant in the typical diet; and they are in all types of processed food, which explains our excess omega-6 levels. Omega-3 is typically found in flaxseed oil, walnut oil, green vegetables, ocean fish, and fish oils. The omega-3 in fish and fish oils is high in two fatty acids crucial to human health, DHA and EPA.
Animal studies with fish oil
Studies in animals suggest that fish oils and other foods rich in omega-3 fatty acids aid bone. Omega-3’s apparent stimulation of bone growth seems to arise from its effect on at least two hormone-like compounds: prostaglandin E (PGE2) and insulin-like growth factor. When omega-3 makes up only 10 percent of the fatty acids in the diet, production of PGE2 is high and insulin-like growth factor is low. High levels of PGE2 limit bone growth; whereas insulin-like growth factor fosters continued growth and rebuilding of bone. In experiments with rats and chicks, Bruce A. Watkins of Purdue University found that by increasing omega-3 to equal the amount of omega-6 in the diet, production of PGE2 was cut in half, bringing it to a level that is more conducive to bone growth; and insulin-like growth factor was increased by 50 percent. Production of insulin-like growth factor typically falls in old age, precipitating the bone loss underlying osteoporosis.
Human studies with fish oil
Human studies also indicate that essential fatty acids could help maintain bone mineral density in the elderly. In a 1998 study published in the journal Aging by M. C. Kruger and others, 65 elderly women, average age 79.5 years, with confirmed osteoporosis and osteopenia were randomly assigned to take 6 grams of a mixture containing evening primrose oil and fish oil or 6 grams of coconut oil as a placebo. Each group also received 600 milligrams per day of calcium for a total of 18 months. The fatty acid supplementation increased calcium absorption and bone density and prevented bone density loss; whereas the group that took calcium without any essential fats actually suffered bone density loss.
Another human study, done in 2001 and published in World Review of Nutrition and Diet by T. Terano, divided 40 elderly women with age-related osteoporosis into four groups. They received one of four treatments daily for 16 weeks; 4 grams evening primrose oil; 4 grams fish oil; 4 grams of fish oil and evening primrose oil mixture; or 4 grams of olive oil as a placebo. The women took no other medications, supplements, or special foods. In this study fish oil increased serum calcium and osteocalcin, a protein found in large amounts in the bone and involved in bone mineralization. It also increased collagen, the most abundant protein in the body, which reinforces bone to prevent breaking. The fish oil decreased alkaline phosphates. High levels of alkaline phosphates indicate that bone is being broken down. Evening primrose oil alone had no significant effect, but the positive results from the fish oil were also seen in the fish oil plus evening primrose group. According to the researchers, evening primrose oil may have enhanced the effects of fish oil. (Because it promotes the production of estrogen, women suffering from breast cancer should avoid evening primrose oil. Black currant seed oil is a good substitute.)
Where can you find omega-3 fatty acids?
The primary sources of omega-3 fatty acids are fish and seafood that accumulate fatty acids in their fat tissue. Cold-water fish, richer in fat, are the best sources of omega-3s. Ocean-fished salmon is an excellent source. Other good fish sources are mackerel, sardines, herring, tuna, haddock, and trout. Good vegetarian sources of omega-3s are flaxseed, flaxseed oil, and English walnut. All green leafy vegetables contain precursors of omega-3 fatty acids, though in lesser amounts. One of the best vegetable sources is purslane. Omega-3s can also be derived from spinach, seaweeds, and spirulina. Fish oil is available in capsule or oil form. Cod liver oil is a source of omega-3s as well as of vitamins A and D.
Although calcium is important in the prevention and reversal of osteoporosis, it is not the whole story. As these studies of omega-3 fatty acids demonstrate, there is also a fish story.
Mary Lou Williams, M. Ed., is a lecturer and writer in the field of nutrition. She welcomes inquiries. She can be reached at 267-6480.