By PM Kris-Etherton, Denise Shaffer Taylor, et. al.
Nearly 90% of the polyunsaturated fat is the omega-6 fat linoleic acid (LA). The omega-3 fat linolenic acid (ALA) contributes the majority of the rest of polyunsaturated fat in the diets of the adult population. Americans consume 0.2 grams (200 mg) of EPA and DHA per day which is less than 2% of energy from polyunsaturated fat. Sources of Omega-3 Fats in the US Diet The predominant sources of omega-3 fats in the diet are vegetable oils and fish. Fish are the major source of EPA and DHA, whereas vegetable oils are the major source of ALA. Other sources include nuts and seeds, vegetables and some fruit, and egg yolk, poultry, and meat, all of which collectively contribute minor quantities of omega-3 fats to the diet. Of the commonly consumed oils in the United States, soybean and canola oil are the primary sources of ALA. The contents of ALA in soybean and canola oil are 7.8% and 9.2%, respectively. Flaxseed oil is a particularly rich source of omega-3 fats (ie, ALA) although it is not a commonly used food oil. Fats and oils contribute 87% of the ALA in the US diet (7), it is apparent that the contribution of other sources is currently minor. Purslane, a vegetable used in soups and salads along the Mediterranean basin and in the Middle East, is unique because it is the richest source of ALA of any green leafy vegetable examined (6, 8). Moreover, it is one of the few plants known to be a source of EPA. Although not typically consumed in the US diet, purslane is nonetheless found in all 50 states and certainly could be developed as an important source of dietary omega-3 fats. Dietary Omega-3 Fats Supplements A variety of omega-3 fat supplements are available to consumers. Many of these supplements are derived from marine oils and contain 180 mg EPA and 120 mg DHA per capsule. Another source of omega-3 fats is cod-liver oil in some capsules that contain 173 mg EPA and 120 mg DHA. Industry estimates indicate that 300 tons of fish oil are used yearly for fish-oil supplements in the United States. The average yearly contribution of EPA and DHA from fish-oil supplements to the US diet is 0.6-0.9 mg/person. Thus, fish-oil supplements currently are not an important source of omega-3 fat in the US diet. Manipulation of Omega-3 Fats in Animal Products On the basis of what is known about the effect of diet on the amount of omega-3 fats in animal products, researchers are manipulating animal feed in an attempt to increase the omega-3 content of eggs, milk, and meat. Animal feed enriched with algae, fishmeal, or fish oil correspondingly increases EPA and DHA concentrations in tissues (eg, muscle and egg yolk). Accordingly, feeding animals diets rich in flaxseed or flax oil, which are good sources of ALA, results in increased amounts of ALA in eggs, milk, pork, chicken, and beef. Major obstacles to this innovative technology include the tendency of these fats to oxidize, producing "off" flavors in food products, as well as the added expense of enriching animal feed with omega-3 sources. Increasing the vitamin E content of a hen's diet when feeding it omega-3 fats helps control oxidation and off flavors in eggs and meat (19), but increases the cost of feeding the animals. Of the animal products enriched with omega-3 fats, eggs are currently the only products available on the market. Eggs were probably targeted first because a large percentage of the omega-3 content of the hen's diet is transferred to the egg yolk. The Flax Council of Canada notes that one omega-3 fat-enriched egg has about the same amount of omega-3 fats as 85 g (3 oz) fish (20). Changes in the Ratio of Omega-6 to Omega-3 Fats over Time Over the course of evolution there appears, on the basis of estimates from studies of Paleolithic nutrition and modern-day diet assessment, to have been a remarkable change in the fat content and fat profile of the human diet (21, 22). The Paleolithic diet was likely much lower in total fat (21% of energy) and saturated fat (7-8% of energy) than our present-day diet (21, 22). Moreover, the diet of our hunter-gatherer ancestors contained approximately the same quantities of omega-6 and omega-3 fats (ie, the ratio is thought to have been 1:1). Sources of omega-6 and omega-3 fats were wild plants, animals, and fish (23, 24). Plant seeds are good sources of omega-6 fats and the green leaves of wild plants are good sources of ALA. The wild animals and birds that ate these food sources were sources of these fats in the human food chain. Whereas EPA accounted for 4% of fats in the fat of wild animals (18), domestic animals raised for meat production had undetectable amounts of EPA in their tissues. At the onset of the industrial revolution, 140 years ago, there was a marked shift in the ratio of omega-6 to omega-3 fats in the diet. Omega-6 fat consumption increased at the expense of that of omega-3 fats (25). This change reflected the advent of the modern vegetable oil industry as well as the increased use of cereal grains for domestic livestock. In 1935 the omega-6 to omega-3 fat ratio was 8.4:1 (estimated by annual per capita food use 7). From 1935 to 1985, this ratio increased to 10.3 (23% increase). Meeting Dietary Recommendations for Omega-3 Fats To date, no official dietary recommendations have been made for omega-3 fats in the United States. Although the United States has not established official dietary recommendations for omega-3 fat intake, Canada (32) and the United Kingdom (33) have. Canada recommends a total omega-3 fat intake of 1.2-1.6 g/d, which is similar to the recommendation made by nutrition scientists in the United States but does not distinguish between individual omega-3 fats. The United Kingdom does distinguish between omega-3 fats and recommends that 1% of energy be from ALA and 0.5% be from EPA and DHA combined. Japan (39) has recently changed its recommendation from 4:1 to 2:1 (W Lands, personal communication, 1998). The recommended ratio of omega-6 to omega-3 fats is 2.3:1 and has been made to maximize the conversion of ALA to DHA (40). Because of competition between omega-6 and omega-3 fats for desaturase and elongase enzymes, the quantity of linoleic acid in the diet can affect the extent to which ALA is converted to EPA and DHA in vivo. The mean ratio of omega-6 to omega-3 fat intake in the United States is 9.8:1 which is much higher than that recommended (2.3:1). Sixty percent of the population consumes a ratio of 8-12:1 (Figure 2 ). However, it may be as high as 20-25:1 in some individuals (20). American Journal of Clinical Nutrition, Vol. 71, No. 1, 179-188, January 2000
Hard to believe that the average person in the US consumes less than 1 mg of a fish oil capsule per year. That is less than 1/300 of one capsule in one year.
Clearly, the average person in the US is totally clueless about the importance of omega-3 fats. If they had any idea of the benefits we would be using quite a bit more of fish oil capsules.
Fish oil capsules and cod liver oil are the most effective way to supplement omega-3 oils.
Omega three fats are essential to your health. You can certainly get them from cod liver oil or fish oil.
Please remember that nearly all fish are contaminated with mercury and should ideally be avoided. You will want to identify a clean source of fish oil.
If you already have significant sun exposure then you should not take cod liver oil as you will run the risk of overdosing on vitamin D.
You should then take fish oil capsules. The standard fish oil capsule is 180 mg of EPA and 120 mg of DHA. You should take approximately one capsule for every ten pounds of body weight, preferably in two divided doses.
So if you weigh 160 pounds you would take 8 capsules twice a day. If you have problems with belching them up, you will want to consider taking them on an empty stomach.
Cod liver oil has the benefit of providing you with vitamin D and A. A reasonable dose for cod liver oil is one teaspoon for every 30-40 pounds of body weight. If you use cod liver oil during your summer you will need to be careful of vitamin D toxicity and I suggest you review the information on vitamin D testing.
When you take fish oil supplements or cod liver oil in the doses I recommend please be sure and take an one vitamin E 400 unit supplement per day as this will help serve to protect the fat from oxidation. This is less of an issue with the cod liver oil as the vitamin D itself is a very potent anti-oxidant.
You will also need extra amounts of the "fourth and unforgotten" oil soluble vitamin, vitamin K. If you are juicing plenty of green vegetables and taking the cod liver oil or fish oil with the juice you should absorb the vitamin K in the vegetable juice. However, if you have osteoporosis or osteopenia, you will want to consider adding an extra 1000 mcg ( 1 mg ) of vitamin K per day.
Generally our diet contains far to much omega 6 fats. Experts looking at the dietary ratio of omega-6 to omega-3 fatty acids suggest that in early human history the ratio was about 1:1. Currently most Americans eat a dietary ratio that falls between 20:1 and 50:1. The optimal ratio is most likely closer to the original ratio of 1:1. For most of us this means greatly reducing the omega-6 fatty acids we consume and increasing the amount of omega-3 fatty acids.
Please recognize that we get ALL the omega-6 and omega-9 fat we need from food. We do NOT need to take any supplements for these fats. Many of the omega fat supplements you see in health food stores will only serve to worsen your health, not improve it as they contain omega 6 fats which will worsen your omega-6 to omega-3 ratio.
I strongly recommend avoiding sunflower, corn, soy, safflower, canola, or products that contain these oils. That is no hydrogenated or partially hydrogenated fats, no margarine, no vegetable oil, no shortening. These oils are chock full of omega-6 fats and will only worsen your omega 6:omega 3 ratio.
Acceptable oils will be a high quality extra virgin olive oil, coconut oil, avocados, and organic butter, or better yet grass-fed organic butter.
Another way to improve your omega 6:3 ratio is to change the type of meat you are eating. You could consume more game meat like venison, or other game animals that are raised exclusively on grass type foods. However, these are hard to find and generally more expensive than beef.
Since nearly all cattle are grain fed before slaughter, if you eat most traditionally raised beef, it will typically worsen you omega 6:omega 3 ratio.
Normally a good ratio for omega 6:3 in fish is 2 or 3 to 1. The lower the better. Grassfed beef from Grassfed Organics is much higher in Omega 3 than fish, with a 6:3 ratio of 0.16 to 1. This information is from a study done at Iowa State University in August 2001.
To get the necessary Omega-3 fatty acids, you should consider eating meat that is allowed to "free-range", or in the case of cattle, to be grass-fed. Unfortunately, you cannot buy this grass-fed beef at your local grocery store.
You must also be careful as many stores will advertise grass-fed beef but it really isn't. They do this as ALL cattle are grass fed, but the key is what they are fed the months prior to being processed.
Most all cattle are shipped to giant feed lots and fed corn to fatten them up. You will need to call the person who actually grew the beef, NOT the store manager, to find out the truth.
The least expensive way to obtain authentic grass fed beef would be to find a farmer who is growing the beef who you can trust and buy a half a side of beef from him. This way you save the shipping and also receive a reduced rate on the meat.
An inexpensive, yet effective way to determine if the meat is really from a grass fed animal is to purchase the ground beef. Slowly cook the beef till done and drain and collect all the fat. Grassfed beef is very high in omega-3 fats and will be relatively thin compared to traditionally prepared ground beef.
It will also be a liquid at room temperature as it has very few saturated fats which are mostly solid at room temperature.
However, most of us live in large urban areas and do not have the time for this process. Just as it would be ideal to have an organic garden and grow your own vegetables, most of us elect not to do that for time or space reasons.
I used to have an organic garden, but my schedule just would not allow me to have that luxury anymore. So, if you are convinced, like I am, that grass-fed beef is better for you and you would like the convenience of being able to order it over the Net, you can buy grass-fed beef online, shipped overnight to your door, at Grassfed Organics.
References 1. Jonnalagadda SS, Egan SK, Heimbach JT, Harris SS, Kris-Etherton PM. Fat consumption patterns of Americans: 1987-1988 USDA Nationwide Food Consumption Survey. Nutr Res 1995;15:1767-81.
2. Allison DB, Egan SK, Barraj LM, Caughman C, Infante M, Heimbach JT. Estimated intakes of trans fatty and other fats in the US population. J Am Diet Assoc 1999;99:166-74.[Medline]
3. Hepburn FN, Exler J, Weilharach JL. Provisional tables on the content of omega-3 fats and other fat components of selected foods. J Am Diet Assoc 1986;86:788-93.[Medline]
4. Ackman RG. Concerns for utilization of marine lipids and oils. Food Technol 1988;42:151-5.
5. US Department of Agriculture, Agricultural Research Service, Nutrient Data Laboratory. USDA nutrient database for standard reference, release 12. Nutrient Data Laboratory home page. Version current 1998. World Wide Web: http://www.nal.usda.gov/fnic/foodcomp/ (accessed 3 November 1999).
6. Simopoulos AP. Terrestrial sources of omega-3 fats: purslane. In: Quebedeaux B, Bliss F, eds. Horticulture and human health: contributions of fruits and vegetables. Englewood Cliffs, NJ: Prentice-Hall, 1988:93-107.
7. Raper NR, Cronin FJ, Exler J. omega-3 Fat content of the US food supply. J Am Coll Nutr 1992;11:304-8.[Medline]
8. Simopoulos AP, Norman HA, Gillaspy JE, Duke JA. Common purslane: a source of omega-3 fats and antioxidants. J Am Coll Nutr 1992;11:374-82.[Medline]
9. Basiotis PP, Welsh SO, Cronin FJ, Kelsay JL, Mertz W. Number of days of food intake records required to estimate individual and group nutrient intakes with defined confidence. J Nutr 1987;117:1638-41.[Medline]
10. Dolecek TA, Grandits G. Dietary polyunsaturated fats and mortality in the Multiple Risk Factor Intervention Trial (MRFIT). World Rev Nutr Diet 1991;66:205-16.[Medline]
11. Aggelousis G, Lazos ES. Fat composition of the lipids from eight freshwater fish species from Greece. J Food Compos Anal 1991;4:68-76.
12. Pigott GM, Tucker BW. Science opens new horizons for marine lipids in human nutrition. Food Rev Int 1987;3:105-38.
13. Perkins FG. Composition of soybeans and soybean products. In: Erikson DR, ed. Practical handbook of soybean processing and utilization. Champaign, IL: AOSC Press and United Soybean Board, 1995:22-3.
14. Grain Research Laboratory, Canadian Grain Commission. Harvest survey of western Canadian canola crop. Crop bulletins. Winnipeg, Canada: Canadian Grain Commission, 1982-1996.
15. Grain Research Laboratory, Canadian Grain Commission. Harvest survey of Western Canadian canola crop. Crop Bulletin no. 230. Winnipeg, Canada: Canadian Grain Commission, 1996.
16. Grain Research Laboratory, Canadian Grain Commission. Quality of western Canadian flaxseed 1996. Crop Bulletin no. 231. Winnipeg, Canada: Canadian Grain Commission, 1996.
17. Crawford MA, Gale MM, Woodford MH. Muscle and adipose tissue lipids of the warthog. Phacochoerus aethiopicus. Int J Biochem 1970;1:654-8.
18. Simopoulos AP, Salem N Jr. omega-3 Fats in eggs from range-fed Greek chickens. N Engl J Med 1989;321:1412-5.[Medline]
19. Cherian G, Wolfe FW, Sim JS. Dietary oils with added tocopherols: effects on egg or tissue tocopherols, fats, and oxidative stability. Poult Sci 1996;75:423-31.[Medline]
20. Sims JS, Qi GH. Designing poultry products using flaxseed. In: Cunnane SC, Thompson LU, eds. Flaxseed in human nutrition. Champaign, IL: AOCS Press, 1995;315-33.
21. Simopolous AP, Leaf A, Salem N Jr. Essentiality of and recommended dietary intakes for omega-6 and omega-3 fats. Ann Nutr Metab 1999;43:127-130.[Medline]
22. Eaton SB, Konner M. Paleolithic nutrition: a consideration of its nature and current implications. N Engl J Med 1985;312:283-9.[Medline]
23. Simopoulos AP. omega-3 Fats in growth and development and in health and disease. Part 1: the role of omega-3 fats in growth and development. Nutr Today 1988;23:10-9.
24. Simopoulos AP. omega-3 Fats in growth and development and in health and disease. Part 2: the role of omega-3 fats in health and disease: dietary implications. Nutr Today 1988;23:12-8.
25. Leaf A, Weber PC. Cardiovascular effects of omega-3 fats. N Engl J Med 1988;318:549-57.[Medline]
26. Putnam JJ, Allshouse JE. Food consumption, prices, and expenditures, 1970-97. Washington, DC: Food and Rural Economics Division, Economic Research Service, US Department of Agriculture, 1999 (Statistical Bulletin no. 965.)
27. Ernst ND. Fat composition of present day diets. In: Nelson GJ, ed. Health effects of dietary fats. Champaign, IL: AOCS Press, 1991:1-11.
28. Huth PJ. Nutritional aspects of soybean oil and protein. In: Erickson DR, ed. Practical handbook of soybean processing. Champaign, IL: AOCS Press and the United Soybean Board, 1995:460-82.
29. Holman RT. Biological activities of and requirements for polyunsaturated acids. In: Progress in the chemistry of fats and other lipids. New York: Pergamon Press, 1970;607-82.
30. National Research Council. Diet and health. Implications for reducing chronic disease risk. Washington, DC: National Academy Press, 1989.
31. National Cholesterol Education Program. Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Adult Treatment Panel II. Second report of the Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Bethesda, MD: The National Heart, Lung, and Blood Institute of the National Institutes of Health, 1993:3093-5.
32. Scientific Review Committee. Nutrition recommendations. Ottawa: Minister of National Health and Welfare Canada, 1990:H49-42/1990E.
33. British Nutrition Foundation. Unsaturated fats nutritional and physiological significance: the report of the British Nutrition Foundation's task force. New York: Chapman & Hall, 1992.
34. COMA Cardiovascular Review Group. Report on health and social subjects. nutritional aspects of cardiovascular disease. London: Department of Health, 1994:46.
35. NHMRC Working Party Report. The role of polyunsaturated fats in the Australian diet. Melbourne: Kay Gibbons, 1992.
36. Kris-Etherton PM, Taylor DS, Yu S, et al. Present estimates of omega-3 fat intakes in the U.S. World Rev Nutr Diet. 1998;83:228 (abstr).
37. World Health Organization. Fats and oils in human nutrition: report of a joint expert consultation. Food and Agriculture Organization of the United Nations and the World Health Organization. FAO Food Nutr Pap 1995:57:1-147.
38. Nordic Working Group on Diet and Nutrition within Nordic Committee of Senior Officials for Food Issues, the Nordic Council of Ministers. Nordic nutrition recommendations 1996. Scand J Nutr 1996;40:161-5.
39. President Summary 1997. J Lipid Nutr 1997;6:5-87.
40. Masters C. omega-3 Fats and the peroxisome. Mol Cell Biochem 1996;165:83-93.[Medline]
41. Emken EA, Adlof RO, Gulley RM. Dietary linoleic acid influences desaturation and acylation of deuterium-labeled linoleic and ALAs in young adult males. Biochim Biophys Acta 1994;1213:277-88.[Medline]
42. Hunter JE. omega-3 Fats from vegetable oils. Am J Clin Nutr 1990;51:809-14.[Abstract]
43. Newton I. Food enrichment with long-chain omega-3 PUFA. Food Technol 1996;7:169-77.
44. Hills MJ, Murphy DJ. Biotechnology of oilseeds. Biotechnol Genet Eng Rev 1991;9:41-6.
45. Somerville CR. Future prospects for genetic modification of the composition of edible oils from higher plants. Am J Clin Nutr 1993;58(suppl):270S-5S.