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QUICKLINKS AND VIEW OPITONS
Facts about dietary fat
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Friday, May 21, 2004 7:28 am Email this article
Here is a summary of research findings about the effects of omega-3 and -6 fatty acids on breast cancer, colon cancer, prostate cancer, diabetes, cholesterol.
BREAST CANCER AND PROSTATE CANCER
- High-fat diets rich in linoleic acid (found in corn, soy, safflower, and sunflower oils) promote chemically-induced, and virally-induced breast cancer in rats and mice, and increase the growth and metastasis of non-estrogen-dependent human breast cancer cells in mice.
- Saturated fat appears to have no effect on breast cancer.
- Omega-6 polyunsaturated fatty acids (like found in corn, soy, safflower, and sunflower oils) may increase the growth of prostate cancer.
REFERENCE
Rose DP. Effects of dietary fatty acids on breast and prostate cancers: evidence from in vitro experiments and animal studies. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1513S-1522S.
- There is little evidence that trans fatty acids (found in partially hydrogenated vegetable oils like margarine and vegetable shortening) adversely affect cancer.
- The data suggesting oleic acid (found in olive, almond, avocado, and peanut oils) protects against cancer is not convincing. Its suggested protective effect may simply be due to a reduced intake of linoleic acid.
However, at least one study has found that monounsaturated fat (like found in olive oil and canola oil) reduces the risk of breast cancer, whereas polyunsaturated fat (like found in corn oil) increases the risk (Wolk et al, 1998).
They found that a 10 gram increase in daily monounsaturated fat intake, the equivalent of about 1 tablespoon, was associated with a 55 percent decreased risk of breast cancer.
For every 5 gram increase in polyunsaturated fat there was a 69 percent increase in breast cancer risk.
Saturated fat was not associated with the risk of breast cancer.
The study followed 61,471 Swedish women ages 40 to 76 years for an average of 4 years.
OMEGA-3 FATTY ACIDS AND CLA PROTECT AGAINST CANCER
- Omega-3 fatty acids (found in fish and flax oil) appear to protect against cancer in most cases, however, some of this protection may be due to a reduced intake of linoleic acid.
- Conjugated linoleic acid (CLA), found in beef fat, protects against cancer independent of the other fatty acids at an intake of 1 percent or maybe less.
REFERENCES
Ip C. Review of the effects of trans fatty acids, oleic acid, n-3 polyunsaturated fatty acids, and conjugated linoleic acid on mammary carcinogenesis in animals. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1523S-1529S.
Wolk A, Bergstrom R, Hunter D, Willett W, Ljung H, Holmberg L, Bergkvist L, Bruce A, Adami HO. A prospective study of association of monounsaturated fat and other types of fat with risk of breast cancer. Archives of Internal Medicine, 1998 Jan 12, 158(1):41-5.
COLON CANCER
- Total dietary fat, rather than any specific fat, is thought to increase the risk of colon cancer.
- Omega-3 fatty acids from fish inhibit colon cancer.
Klurfeld DM, Bull AW. Fatty acids and colon cancer in experimental models. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1530S-1538S.
OMEGA-3’S PROTECT AGAINST BREAST CANCER
- Omega-3 fatty acids (found in fish and flax oil) appear to protect against breast cancer.
- Omega-6 polyunsaturated fatty acids (like found in corn, soy, safflower, and sunflower oils) appear to increase the risk of breast cancer.
- Increasing the ratio of omega-3 to omega-6 fatty acids (such as consuming more fish oil and less corn oil) appears to help protect against breast cancer.
- High intakes of monounsaturated fatty acid like those found in olive oil have been associated with a reduced incidence of breast cancer.
- Trans fatty acids (found in partially hydrogenated vegetable oils like margarine and vegetable shortening) may increase the risk of breast cancer.
REFERENCE
Kohlmeier L. Biomarkers of fatty acid exposure and breast cancer risk. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1548S-1556S.
BREAST CANCER AND PROSTATE CANCER
- Monounsaturated fat, especially in the form of olive oil, may reduce the risk of breast cancer.
- Animal fat seems to increase the risk of prostate cancer, but vegetable fat does not.
- Neither linoleic acid (found in corn, soy, safflower, and sunflower oils) or omega-3 fatty acids (found in fish and flax oil) appear to affect the risk of prostate cancer.
REFERENCE
Willett WC. Specific fatty acids and risks of breast and prostate cancer: dietary intake. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1557S-1563S.
HIGH CALORIE DIET AND RED MEAT INCREASE COLON CANCER
- A higher calorie intake seems to increase the risk of colon cancer rather than total fat composition, however, physical activity appears to reduce the risk, whereas obesity increases the risk.
- Red meat and beef appear to increase the risk of colon cancer. However, the increased risk does not seem to be related to the total fat content of the meat, but possibly to chemicals formed during cooking.
- Dietary fat from dairy, poultry, and vegetable oils, does not appear to increase the risk of colon cancer.
REFERENCE
Giovannucci E, Goldin B. The role of fat, fatty acids, and total energy intake in the etiology of human colon cancer. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1564S-1571S.
- Currently there is insufficient evidence to conclusively say that any specific fatty acids are associated with human cancers.
REFERENCE
Dwyer JT. Human studies on the effects of fatty acids on cancer: summary, gaps, and future research. American Journal of Clinical Nutrition, 1997 Dec, 66(6 Suppl):1581S-1586S.
RECOMMENDED FAT INTAKE: POLYUNSATURATED 7%, OLEIC ACID 15%, TOTAL FAT 30%
- Intake of polyunsaturated fatty acids should not exceed the current intake of approximately 7 percent of calories.
- Total fat should be limited to 30 percent of calories.
- Oleic acid should account for half of fat calories, or 15-16 percent of total calories.
REFERENCE
Grundy SM. What is the desirable ratio of saturated, polyunsaturated, and monounsaturated fatty acids in the diet? American Journal of Clinical Nutrition, 1997 Oct, 66(4 Suppl):988S-990S.
OMEGA-3’S MAY REDUCE RISK OF DIABETES
- The prevalence of diabetes may be correlated with the ratio of omega-6 to omega-3 fatty acids.
- Omega-3 fatty acids (found in fish and flax oil) may reduce insulin resistance, lowering blood pressure and lowering triglycerides.
- Animal studies suggest that omega-3 fats (like found in fish and flax oil) may cause less weight gain than other fats, but may also increase LDL cholesterol, increase sugar output from the liver, and decrease insulin secretion in type II non-insulin-dependent diabetes, adversely affecting blood sugar control in relatively few type II diabetics.
- Omega-6 fatty acids (like found in corn, soy, safflower, and sunflower oils) may lower cholesterol levels, but may increase oxidation of LDL cholesterol.
- Omega-3 fatty acids (found in fish oil) may help blood vessels relax in response to nitric oxide, which can be damaged in diabetics.
- High-carbohydrate, low-fat diets are no longer recommended for diabetics because they increase already elevated triglyceride levels.
- The recommended diet for diabetics is one high in monounsaturated fats, like olive oil, provided saturated fat intake is kept to a minimum.
- Diets rich in monounsaturated fatty acids, found in olive oil and canola oil, improve lipid profiles and may have antioxidant properties.
- High-fat diets, whatever their composition, promote obesity.
REFERENCE
Berry EM. Dietary fatty acids in the management of diabetes mellitus. American Journal of Clinical Nutrition, 1997 Oct, 66(4 Suppl):991S-997S.
HIGH FAT DIETS INCREASE PROSTATE CANCER MORE THAN BREAST CANCER
- The evidence is stronger that high-fat diets are associated with aggressive prostate cancer, than with breast cancer.
- A relatively high intake of omega-3 fatty acids (found in fish oil and flax oil) and monounsaturated fatty acids (found in olive oil) appear to reduce the risk of breast cancer by reducing the risks associated with omega-6 polyunsaturated fatty acids (like found in corn, soy, safflower, and sunflower oils).
- A high intake of omega-6 fatty acids (like found in corn, soy, safflower, and sunflower oils) may increase breast cancer invasion and metastasis. Omega-3 fatty acids (found in fish oil and flax oil) may be protective.
- Omega-3 fatty acids (found in fish oil and flax oil) may slow the progression of prostate cancer.
REFERENCE
Rose DP. Dietary fatty acids and cancer. American Journal of Clinical Nutrition, 1997 Oct, 66(4 Suppl):998S-1003S.
TRANS FATS INHIBIT METABOLISM OF OTHER FATS
- Trans Fatty acids (found in partial hydrogenated vegetable oils like margarine and vegetable shortening) inhibit the metabolism of other fats, specifically linoleic acid and alpha-linolenic acid.
- Trans fatty acids increase LDL cholesterol, decrease HDL cholesterol and increase the ratio of total-to-HDL cholesterol nearly twofold compared with saturated fats.
- It is estimated the trans fatty acids cause 30,000 premature deaths each year in the United States.
- Trans fatty acids have no known nutritional benefits, and therefore their intake should be reduced to a minimum.
Ascherio A, Willett WC. Health effects of trans fatty acids. American Journal of Clinical Nutrition, 1997 Oct, 66(4 Suppl):1006S-1010S.
PREMATURE TO SAY TRANS FATS CAUSE 30,000 DEATHS PER YEAR
- It is premature to say that trans fatty acids cause 30,000 deaths per year, because the studies may have been biased.
REFERENCE
Shapiro S. Do trans fatty acids increase the risk of coronary artery disease? A critique of the epidemiologic evidence. American Journal of Clinical Nutrition, 1997 Oct, 66(4 Suppl):1011S-1017S.
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