A new US study that analyzed data from a large national survey has found a significant link between diets low in fiber and increased cardiometabolic risk, a cluster of risk factors that increases a person's chances of having diabetes, heart disease or stroke.
The researchers report their findings online in the latest issue of The American Journal of Medicine.
The Institute of Medicine (IOM) recommends men aged 19-50 should consume 38 g of fiber per day, and women of that age should consume 25 g. The recommended levels for older people are 30 g a day for men over 50 and 21 g a day for women over 50.
Different foods have varying amounts of fiber, and in some cases the differences can be surprising. For instance, a 30 g serving of corn flakes has just 1 g of fiber, whereas a cup of lentil soup has 12 g.
For this latest study, the researchers not only looked at the link between fiber intake and various cardiometabolic risk factors - such as metabolic syndrome, cardiovascular inflammation and obesity - but they also examined how dietary fiber consumption varied by age, gender, racial/ethnic and socioeconomic status.
They used data taken from 23,168 men and non-pregnant women aged 20 and over who took part in the National Health and Nutrition Examination Survey (NHANES) 1999-2010.
Not eating enough fiber
They found that overall, the average daily fiber intake was only 16.2 g, considerably lower than the levels recommended by the IOM.
Senior investigator Dr. Cheryl R. Clark, of the Center for Community Health and Health Equity at Brigham and Women's Hospital and Harvard Medical School, says:
"Our findings indicate that, among a nationally representative sample of nonpregnant US adults in NHANES 1999-2010, the consumption of dietary fiber was consistently below the recommended total adequate intake levels across survey years."
She and her colleagues also found "persistent differences in dietary fiber intake among socioeconomic status and racial/ethnic subpopulations over time," she adds.
Their analysis shows that Mexican-Americans had more fiber in their diet than non-Hispanic whites, while non-Hispanic blacks had less.
When they looked at the links with cardiometabolic risks, they found men and women with the highest prevalence of metabolic syndrome, inflammation and obesity were in the bottom 20% ("lowest quintile") in terms of dietary fiber intake.
The analysis showed that the more dietary fiber there was in the diet, the lower the prevalence of metabolic syndrome, inflammation, and obesity, as Dr. Clark explains:
"Overall, the prevalence of the metabolic syndrome, inflammation and obesity each decreased with increasing quintiles of dietary fiber intake. Compared with participants in the lowest quintile of dietary fiber intake, participants in the highest quintile of dietary fiber intake had a statistically significant lower risk of having the metabolic syndrome, inflammation and obesity."
The bottom line of the study is that across all ethnic and racial groups, both men and women of all ages need to increase their daily fiber intake, say the researchers. They conclude there is a need to "develop new strategies and policies" to make this happen.
Further studies are needed to find out which approaches will work within in each these diverse groups, says Dr. Clark.
Tips for increasing dietary fiber
The Heart and Stroke Foundation in Canada has a useful page on its website showing their top 10 high-fiber foods and some tips on how to gradually incorporate them into your daily diet, such as:
- Add a high-fiber cereal to your regular cereal
- Eat more fruit, including the skin (i.e. apples and pears)
- Add one more vegetable to your daily intake
- Add a pulse food (beans, lentils) to your daily salad, sauces and soups
- Choose 100% whole-grain or whole-wheat breads and pastas
- Substitute some wholemeal flour for white flour in your baking.
Remember to increase your fiber intake slowly, a little each day, until you reach your goal, and drink plenty of water.
Eating the right amount of fiber may cut risk of death from cardiovascular, infectious and respiratory diseases, according to a study published in the Archives of Internal Medicine in 2011.
Written by Catharine Paddock PhD