| 1> | | | | offer more significant benefits and show a closer |
| | | | relationship between dietary fat and breast cancer |
| In 2006, results from the world's largest low fat diet | | | | risk. |
| project were published and led to much speculation | | | | 5) Baseline body mass index. In this study, 74% |
| as to the relationship between a low fat diet and | | | | of the women were classified as overweight by |
| breast cancer. Co-author is Dr. James Watson. | | | | body mass index at the beginning of the study. So |
| In 2006, results from the world’s largest low | | | | we don't really know if a low-fat diet would offer |
| fat diet project were published (see reference at | | | | benefits to women who are at a normal weight to |
| end). This was a US government-funded study of | | | | begin with. |
| 48,835 postmenopausal women in a multicenter | | | | 6) All the women were postmenopausal. It may |
| prospective, randomized clinical trial known as the | | | | be that dietary fat plays a more important role in the |
| Women's Health Initiative Randomized Controlled | | | | diets of younger, premenopausal women. It makes |
| Dietary Modification Trial. The study was conducted | | | | sense that your diet in the first 50 years of your life |
| from 1993 to 2005 at 40 centers around the country. | | | | might affect your cancer risk in the second half of |
| The volunteers were randomly assigned to either a | | | | your life. This study doesn't address that question. |
| low-fat diet group (19,541 women) or a regular diet | | | | 7) The type of fat wasn't specified. There are |
| group (29,294 women). After about eight years of | | | | three basic types of fats: saturated, |
| follow-up, this large and costly study did not find any | | | | mono-unsaturated, and poly-unsaturated. In this |
| significant differences in breast cancer incidence | | | | study, women were asked only to reduce fat. They |
| between postmenopausal women who were asked | | | | weren't asked to consider the various types of fat |
| to eat a low-fat diet and those who continued to eat | | | | or told that reducing saturated fats may offer more |
| their regular diet. On the other hand, the results did | | | | health benefits than reducing unsaturated fats. |
| suggest that changing to a low-fat diet may reduce | | | | Saturated fats are only found in foods that come |
| the risk of breast cancer for women who had diets | | | | from animals and are the types of fats that raise |
| very high in fat to begin with. | | | | your blood cholesterol level. Trans fats (also called |
| According to most experts, the following may be | | | | trans-saturated fats) are man-made fats. |
| reasons why this study showed no significant benefit: | | | | (Vegetable oils are modified to form margarine and |
| 1) Not many women met the 20% fat intake goal. | | | | vegetable shortening, both of which are trans fats.) |
| This "low-fat diet" regimen may not have truly been | | | | Trans fats also are added to prepackaged foods. |
| low in fat. Since most women did not meet the | | | | Saturated fats raise your blood's "bad" cholesterol |
| fat-reduction goal, this study may have proven only | | | | (low-density lipoprotein or LDL) level and lower your |
| that the approach to the intervention did not work. | | | | "good" cholesterol (high-density lipoprotein or HDL) |
| It did not prove that a truly low-fat diet doesn't | | | | level. Mono-unsaturated and poly-unsaturated fats |
| help protect you from breast cancer. Getting only | | | | are found in plant foods like vegetables, nuts, and |
| 20% of your calories from fat is very difficult to | | | | grains, as well as oils made from these nuts and |
| do. This means that, if you eat 2,000 calories per | | | | grains (canola, corn, soybean). Omega-3 and omega-6 |
| day, only 400 calories could come from fat. So it's | | | | fatty acids are poly-unsaturated. Besides |
| not surprising that less than a third of the women | | | | vegetables, nuts, and grains, omega-3 and omega-6 |
| met this goal after the first year, and only 14% | | | | fatty acids are also found in coldwater fish such as |
| continued to meet the goal after six years. Because | | | | tuna, salmon, and mackerel. Some studies have |
| so few women met the requirements of the study, | | | | shown that eating foods that have mono- or |
| it means that we don't really know how a diet low in | | | | poly-unsaturated fats can help reduce your levels of |
| fat affects breast cancer risk. | | | | "bad cholesterol." Mono- and polyunsaturated fats |
| 2) Diets were self-reported and infrequent, which | | | | may also keep your triglyceride levels low. |
| may make them unreliable. This study relied on the | | | | Triglycerides are a form of fat in your bloodstream. |
| women's written reports of what they ate, which | | | | 8) None of the women in either group were asked |
| may not be an accurate reflection of true intake. | | | | to change their health-related behaviors, such as |
| These reports were done occasionally. No daily | | | | exercise, drinking or smoking. These known risk |
| food log or journal was done and checked. Most of | | | | factors for breast cancer were left uncontrolled and |
| us aren't proud to admit in an interview or | | | | may obscure any benefit from eating less fat. |
| questionnaire that we've broken the rules and haven't | | | | 9) This study is about a low fat diet; it is not about |
| stuck to the "prescribed diet." So there may be a | | | | going from an overweight/obese state to a normal |
| tendency to under-report the amount of fat actually | | | | weight. Eating less fat while staying persistently fat |
| eaten. | | | | may not help anyone! Since this study cost nearly |
| 3) Other changes besides the low-fat diet. The | | | | half a billion dollars, it is unlikely that another lifestyle |
| study did not separate out the effects of reducing | | | | intervention clinical trial at this large scale would be |
| the amount of fat eaten vs. the effects of increasing | | | | done again anytime soon, particularly in the current |
| fruit and vegetable servings. Women in the low-fat | | | | US economy. |
| diet group ate almost two more servings per day of | | | | Reference: Prentice RL, et al. Low-fat dietary pattern |
| fruits and vegetables than women in the regular diet | | | | and risk of invasive breast cancer: the Women's |
| group and about one more serving of grains. | | | | Health Initiative Randomized Controlled Dietary |
| 4) Length of follow-up time. While 48,835 women | | | | Modification Trial. Journal of the American Medical |
| is a lot of people, eight years isn't a lot of follow-up | | | | Association, volume 295, pages 629-42, 2006. |
| time. Eating a low-fat diet for 15 or 20 years may | | | | |