Long-Term Randomized Controlled Trials of Diet Intervention Reports and Their Impact on Cancer: A Systematic Review

Area of Science:

• Oncology
• Nutritional Science
• Clinical Trials

Background:

• Most dietary randomized controlled trials (RCTs) are short-term (<1 year) and focus on breast cancer survivors.
• Long-term adherence to lifestyle changes like diet modification is challenging.
• This review focuses on RCTs of ≥1 year, examining dietary interventions for cancer risk reduction in overweight/obese individuals.

Purpose of the Study:

• To systematically review longer-term (≥1 year) randomized controlled trials (RCTs) of dietary interventions for cancer-related outcomes.
• To assess the effectiveness of different dietary strategies, including caloric restriction and macronutrient modifications.

Main Methods:

• Systematic review of RCTs lasting at least 1 year.
• Inclusion criteria: dietary interventions with primary or secondary cancer endpoints or cancer-related biomarkers.
• Data extraction focused on diet type (low-calorie, isocaloric, low-fat, Mediterranean) and reported outcomes.

Main Results:

• Fifty-one reports met the criteria; 20 had cancer/biomarker as primary endpoints.
• Low-calorie diets (LCDs) showed higher benefit rates (71% primary, 85% secondary) compared to isocaloric diets (38% primary, 73% secondary).
• Mediterranean diets (MedD) showed benefit in all three reports; low-fat diets (LFDs) were evaluated in most isocaloric studies. Most studies enrolled women.

Conclusions:

• Longer-term RCTs are crucial for understanding diet's impact on cancer risk and prognosis.
• Further research is needed, particularly for cancers beyond breast cancer.
• Low-calorie and Mediterranean diets show potential for cancer prevention in longer-term studies.