Eating a Diet Rich in Fiber and Whole Grains Is Associated with Reduced Risk of Various Diseases
In a study published in the prestigious British journal, The Lancet, earlier this month, nearly 40 years of data from observational studies and clinical trials revealed the health benefits of eating a high fiber diet (at least 25g to 29g or more of dietary fiber daily). The study was commissioned by the World Health Organization to inform the development of new recommendations for optimal daily fiber intake and to determine which types of carbohydrates provide the best protection against non-communicable diseases and weight gain. The researchers included 185 observational studies containing data that relate to 135 million person years and 58 clinical trials involving 4,635 adult participants. They focused on premature deaths from and incidence of coronary heart disease, cardiovascular disease and stroke, as well as incidence of type 2 diabetes, colorectal cancer and cancers associated with obesity: breast, endometrial, esophageal, and prostate cancer. The authors only included studies with healthy participants, so the findings cannot be applied to people with existing chronic diseases.
The results suggest a 15-30% decrease in all-cause and cardiovascular related mortality when comparing people who eat the highest amount of fiber to those who eat the least. Eating fiber-rich foods also reduced incidence of coronary artery disease, stroke, type 2 diabetes, and colorectal cancer by 16-24%. Per 1,000 participants, the impact translates into 13 fewer deaths and six fewer cases of coronary artery disease.
In addition, a meta-analysis of clinical trials suggested that increasing fiber intakes was associated with lower bodyweight and cholesterol, compared with lower intakes.
Most people worldwide consume less than 20 g of dietary fiber per day. In 2015, the UK Scientific Advisory Committee on Nutrition recommended an increase in dietary fiber intake to 30 g per day, but only 9% of UK adults manage to reach this target. In the US, fiber intake among adults averages 15 g a day. Rich sources of dietary fiber include whole grains, vegetables and fruit.
These findings provide compelling evidence for public health guidelines to focus on increasing dietary fiber and on replacing refined grains with whole grains. This dietary change reduces incidence risk and mortality from a broad range of significant diseases.
“The health benefits of fiber are supported by over 100 years of research into its chemistry, physical properties, physiology and effects on metabolism. Fiber-rich whole foods that require chewing and retain much of their structure in the gut increase satiety and help weight control and can favorably influence lipid and glucose levels. The breakdown of fiber in the large bowel by the resident bacteria has additional wide-ranging effects including protection from colorectal cancer," said Professor Jim Mann, a coauthor of the paper.
Reynolds, A. et al: Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. Lancet, Jan 10, 2019. https://doi.org/10.1016/S0140-6736(18)31809-9