|The Skinny on Fat|
Over the years, fats have been both maligned and hyped for their health effects. We know that dietary fat can have a pronounced influence on heart health (see sidebar), but the link between the fats we eat and our cancer risk is not as clear. AICR’s expert report found a weak link between diets high in fat and cancer risk. Yet a steady stream of laboratory studies indicates that certain unsaturated fats may actually play a role in fighting cancer.
We All Need Fat
Everyone needs fat – it’s one of the essential nutrients our bodies require to function. Fat provides our body with energy, performs key regulatory functions and absorbs fat-soluble vitamins. It also contains relatively more energy – calories – than the other two nutrients.
- Fat: 9 calories per gram
- Protein: 4 calories per gram
- Carbohydrate: 4 calories per gram
But this higher calorie density means that eating too much fat can add up quickly, causing the body to store excess fat. And extra body fat is strongly linked to a higher risk for chronic diseases, including several cancers. Cancers most strongly associated with excess body fat include colon, kidney and post-menopausal breast.
The 2005 Dietary Guidelines for Americans and the Institute of Medicine recommends that adults consume no more than 20% to 35% of total calories from fat. Saturated fats should provide no more than 10% of total calories, or even less for people with high blood cholesterol.
If you were eating about 2,000 calories a day…
- 20% to 35% of 2000 = 400 to 700 total fat calories
- 10% of 2000 = 200 (or less) saturated fat calories
The Big Fats
Dietary fats come in both solid and liquid forms. The main types are:
|The Fat||What It Is||Where It's Found|
||beef, pork, poultry fat, butter, whole milk, coconut oils|
liquid at room temperature
||olive and canola oils, avocados, peanut butter, almonds|
||Foods fried in partially hydrogenated fats, processed foods, commercial baked goods, stick margarines|
Studies suggest that one type of polyunsaturated fat, omega-3s, may be especially protective in cancer development. But there is another type of polyunsaturated fat, omega-6, which is found in many processed foods. Omega-6s are not unhealthy in and of themselves, but American diets tend to be far higher in omega-6 than omega-3. Some evidence suggests that bringing these two kinds of fat into closer balance a healthy ratio of omega-3s to omega-6s – may help protect against cancer.
Recent studies include:
- A study presented at a major cancer research conference in April found that when mice ate a daily dose of walnuts – rich in omega-3s -- they showed significantly fewer and smaller tumors than the comparison group. Funded by AICR, the study fed one group of mice a diet infused with the estimated human equivalent of two ounces of walnuts daily. The researchers found that the increased amount of omega-3s, as well as other compounds in walnuts, contributed to the reduced tumor incidence.
- A study published in March linked eating high amounts of omega-3 fatty acids to lower incidence of advanced prostate cancer. The degree to which omega 3s may offer protection appears to vary depending upon if men carry a certain inflammatory gene, the authors found. The strongest effect of a protective effect was seen from eating dark fish such as salmon, a common and rich source of omega 3s, one or more times per week, noted an author.
- Preliminary research looking at ovarian cancer and flaxseed-fed chickens – which produce omega-3 enriched eggs – found that after one year, the flaxseed-fed hens had an overall lower mortality rate than the hens fed a conventional diet. The scientists are investigating if the ratio of omega-6 to omega-3 may play a role.
The Health Halo Effect
Part of the protection of a healthy fat diet against cancer could relate to weight and protective plant compounds. Foods like vegetables, fruits, whole grains and beans contain numerous cancer-fighting phytochemicals – and have little fat. Filling your plate with vegetables and fruits can also lead to weight loss.
To learn more about which fats to watch out for, read:
- AICR’s The Facts about Fats
- Does “Zero Trans Fat” Mean It’s Healthy?
- Questions and Answers about Trans Fat Nutrition Labeling
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