There actually is a low-fat diet that has been extensively tested for reduction of cardiovascular disease, and multiple studies have documented its efficacy for other conditions as well. This is the DASH diet – Dietary Approaches to Stop Hypertension. DASH has been the highest-rated diet in US News and World Report for four years in a row, and has been shown to lower cholesterol and heart disease, as well as to reduce fasting insulin. It emphasizes vegetables, fruits, whole grains, low-fat dairy, poultry, fish and nuts. The diet is low-sodium and aims for approximately a 27% fat content – not what I’d personally consider “low fat” but closer than the American Heart Association’s recommendations, and certainly closer to optimal than either of the diets in the PREDIMED study. As is the case with the Mediterranean diet, the DASH diet isn’t specifically what I recommend for our patients, but it does have a very strong background of clinical trials showing its beneficial results. To cite just a few examples of studies:
- A review of 20 randomized controlled trials examined the effect of DASH on factors that affect the risk for developing Type 2 diabetes. The review found that DASH significantly reduced fasting insulin levels. This is definitely a higher level of evidence than a single trial of two high-fat diets that was stopped prematurely, as was the case with the PREDIMED trial!
- When the DASH diet was compared to a control diet high in fruits and vegetables, it was significantly better at controlling hypertension, both in subjects with metabolic syndrome and those without.
- Some studies have assessed how well people in the population at large stick to a DASH-style diet, and correlated this with health outcomes. These so-called cohort studies are considered as reliable as randomized trials in answering health questions. An analysis of 6 such cohort studies that assessed adherence to the DASH diet found that it reduced cardiovascular disease by 20%, coronary heart disease by 21%, risk of stroke by 19%, and heart failure risk by 29%.
- And, importantly for cancer patients, in a study of 491,841 initially health Americans, those whose diets were the most similar to the DASH diet had approximately a 20% reduction in colorectal cancer incidence, depending on exactly how their adherence to the DASH diet was calculated.
And DASH is not the only low-fat diet that has interesting data relevant to cancer patients. The Ornish diet has a radically low level of fat – less than 10% — accomplished by using a vegetarian eating pattern supplemented with fish oil. Although the Ornish diet was originally designed for reversing already-existing heart disease, when it was tested in a randomized trial with early prostate cancer patients who were in a “watchful waiting” stage of disease, only 5% of Ornish diet patients progressed to conventional prostate cancer treatment, whereas 27% of usual diet patients had to get conventional treatment.
As a cancer patient, your diet needs to be tailored to your own unique needs. However, for most cancer patients, I recommend a diet low in saturated fats and high in fiber, plant-based sources of protein, cold water fish rich in omega-3 fatty acids, complex carbohydrates, fruits and berries rich in antioxidants, and nuts, seeds and cruciferous vegetables, with careful use of healthful fats and oils, including monounsaturated fats. Our diet generally aims for an overall fat level of approximately 15-20%. For patients who are dealing with cachexia or rapid cancer-induced weight loss, a diet with a significantly higher fat content and caloric density is necessary, although the fats need to be carefully chosen to avoid stoking inflammation.
In conclusion
As if there isn’t already enough conflicting and confusing information out there about what constitutes a healthful diet, the PREDIMED trial has provided one more opportunity to further muddy the waters. Based on the erroneous assumption that this trial actually tested a low-fat diet and found it wanting, many are touting the now-popular high-fat/low carbohydrate diets as the most healthful. There are certainly unhealthful ways to implement a low-fat diet, such as indulging in low-fat cookies that are loaded with sugar as a replacement for fat, one of the really bad ideas that came out of the early commercialization of low-fat diets. But there are also extremely healthy low-fat diets that have a proven scientific record of improving health.
If you have concerns or questions about your own diet – and particularly if you’re battling serious disease – consider consulting with an experienced dietitian who will work with you to develop a nutrition program that best fits your specific needs.