Should you Eat More Fiber for Longevity?

Highlights:

• High fiber intake is observed in Blue Zones, areas with a higher than usual number of people who live much longer than average
• Increasing fiber intake to at least 25 g per day correlates with a significant reduction in mortality and risk for chronic disease, including diabetes and cardiovascular disease

Introduction

Consuming dietary fiber, the indigestible carbohydrate, has a significant impact on our physiology. Soluble fiber dissolves in water, creating a gel that may improve digestion, reduce blood cholesterol and improve blood glucose control. Insoluble fiber attracts water into the stool, making it softer and easier to pass with less strain on the bowel. It can help promote bowel health and regularity and improve blood glucose control. Fiber is an important topic in healthy aging and longevity because the overall fiber consumption tends to be lower than recommended in the Western diet. Does this pose a risk to your clients, and would they benefit from increased fiber intake?

How much fiber do your clients need?

The Academy of Nutrition and Dietetics recommends a daily dietary fiber intake of 16 g of total fiber per 1,000 kcal, or, on average, 25 g for adult females and 38 g for adult males. After the age of 50, the requirements go down to 21 g for women and 30 g for men. During pregnancy or breastfeeding, women should aim for upwards of 28 g per day (1).

The core problem with fiber intake is that the Western diet is inherently low in fiber. This is because modern, ultra-processed foods are fiber-poor and take up an increasingly larger part of the Western diet. Research shows that the mean intake of dietary fiber for a person living in the US is only 17 g per day. And even more alarmingly, only 5% of the population meets the adequate intake recommendations (1). There are four main areas of human health where fiber plays a crucial role. It is a good idea to highlight these to your clients to understand how insufficient fiber intake connects to their health and longevity.

• Gut health

Intuitively,  a  place where fiber should play the most prominent role is the digestive tract. Research shows that fiber is, in fact, important for maintaining gut health. Sufficient fiber intake increases the bulk of stool, helps promote regular bowel movements, and reduces the time that waste spends inside the intestines (1). Fiber also positively alters the gut microbiota (2) and may even reduce the risk of colorectal cancer (3).

• Diabetes risk

The less obvious aspect of proper fiber intake is its impact on blood sugar. Fiber can help slow down the absorption of sugar, helping prevent blood sugar spikes after meals. Studies show that people who eat high fiber diets report a reduction in blood glucose levels and a lower risk of developing type 2 diabetes (4).

• Weight management

Fiber has been shown to improve satiety and help people feel full for longer, which has implications for weight management. Research shows that eating several servings of whole grains, a great source of fiber, every day causes less weight gain when compared to eating whole grains only rarely (5). Dietary fiber intake has also been found to promote weight loss and increase the ability to stick to a calorie-restricted diet in overweight or obese adults (6).

• Cardiovascular disease

Fiber consumption has an impact on cardiovascular health. Research shows that people eating high fiber diets have significantly reduced risk of cardiovascular disease and lower mortality from these conditions than those with a low fiber intake. These heart-protective effects are likely because fiber reduces total cholesterol and low-density lipoprotein (LDL) cholesterol, a major risk for cardiovascular disease (7).

The Blue Zones diet is known for high fiber intake

The connection between fiber and disease risk is well-supported by science. One more reason why fiber could be considered an important piece of the longevity puzzle. High fiber intake is common across all Blue Zones, areas with a higher than a usual number of people who live to be hundred years old. For example, the well-studied Okinawa diet is famous for being very high in fiber. This is because the traditional Okinawa diet is centered around whole grains, tubers, vegetables, and fruits (8).

Does adding more fiber make a difference?

Understanding that western pattern diets are typically low in fiber makes recommending an increase in fiber intake a straightforward choice. Research can help you quantify the effects of this intervention in terms of healthy aging and longevity. Even outside of Blue Zones, research shows that eating a lot of fiber reduces mortality. An analysis of 17 prospective studies showed that for every 10 grams of fiber consumed, the risk of mortality was reduced by 10% (9). A systematic review of 185 prospective studies and 58 clinical trials showed that for every additional 8 g of dietary fiber, the risk for the chronic disease could fall by 5 - 27%, and the most significant risk reduction was shown for a daily fiber intake of 25 - 29 g (10).

Practical tips for getting more fiber

Knowing how to add more fiber to today’s Western diet is essential. Here are several tips you can suggest to clients struggling with fiber intake.

• Replace regular bread and pasta with their whole-grain variants; those contain a lot more fiber.
• Beans and lentils are an excellent source of fiber; add them to salads, soups, or as side dishes.
• Snack on raw fruits and vegetables and eat them with the skins on them; they contain lots of fiber.
• Always aim to eat five servings of vegetables each day. Get in the habit of including a piece of fruit or vegetable with every meal.
• Add nuts and seeds to your salads, yogurt, oatmeal, or stir-fry to boost the fiber content.
• Consider a fiber supplement if you struggle to get at least 25 g of fiber into your diet regularly.

It is worth reminding your clients that too much fiber or increasing fiber intake too rapidly can sometimes result in negative symptoms. Some people experience gas, bloating, abdominal cramping, constipation, or nausea. If your clients encounter any of these symptoms, they should reduce fiber intake until the issues subside. Drinking lots of water and light exercise or walking can help relieve the symptoms as well.

Conclusion

Fiber intake appears to have a notable impact on several aspects of human health. Following a typical Western diet is likely to lead to a lower than recommended fiber intake. Those interested in longevity should aim to get at least 25 g of fiber per day to lower their risk of chronic diseases such as diabetes or cardiovascular disease. Increasing fiber intake has very little downside yet promises better health and possibly even improved longevity. It should be at the top of the list of dietary interventions for your clients.

References

1) Wendy J. Dahl, Maria L. Stewart. Position of the Academy of Nutrition and Dietetics: Health Implications of Dietary Fiber. J Acad Nutr Diet. 2015 Nov;115(11):1861-70. doi: 10.1016/j.jand.2015.09.003.

2) Peter Cronin, Susan A. Joyce, Paul W. O’Toole, Eibhlís M. O’Connor. Dietary Fibre Modulates the Gut Microbiota. Nutrients. 2021 May; 13(5): 1655. Published online 2021 May 13. doi: 10.3390/nu13051655

3) Soeren Ocvirk, Annette S Wilson, Corynn N Appolonia, Timothy K Thomas, Stephen J D O'Keefe. Fiber, Fat, and Colorectal Cancer: New Insight into Modifiable Dietary Risk Factors. Curr Gastroenterol Rep. 2019 Dec 2;21(11):62. doi: 10.1007/s11894-019-0725-2.

4) Marc P. McRae. Dietary Fiber Intake and Type 2 Diabetes Mellitus: An Umbrella Review of Meta-analyses. J Chiropr Med. 2018 Mar; 17(1): 44–53. Published online 2018 Mar 1. doi: 10.1016/j.jcm.2017.11.002

5) Caleigh M Sawicki et al. Whole- and Refined-Grain Consumption and Longitudinal Changes in Cardiometabolic Risk Factors in the Framingham Offspring Cohort. The Journal of Nutrition, Volume 151, Issue 9, September 2021, Pages 2790–2799, doi.org/10.1093/jn/nxab177

6) Derek C Miketinas, George A Bray, Robbie A Beyl, Donna H Ryan, Frank M Sacks, Catherine M Champagne. Fiber Intake Predicts Weight Loss and Dietary Adherence in Adults Consuming Calorie-Restricted Diets: The POUNDS Lost (Preventing Overweight Using Novel Dietary Strategies) Study. The Journal of Nutrition, Volume 149, Issue 10, October 2019, Pages 1742–1748, doi.org/10.1093/jn/nxz117

7) Marc P. McRae. Dietary Fiber Is Beneficial for the Prevention of Cardiovascular Disease: An Umbrella Review of Meta-analyses. J Chiropr Med. 2017 Dec; 16(4): 289–299. Published online 2017 Oct 25. doi: 10.1016/j.jcm.2017.05.005

8) Donald Craig Willcox, Giovanni Scapagnini, Bradley J. Willcox. Healthy aging diets other than the Mediterranean: A Focus on the Okinawan Diet. Mech Ageing Dev. 2014 Mar-Apr; 136-137: 148–162. Published online 2014 Jan 21. doi: 10.1016/j.mad.2014.01.002

9) Yang Yang, Long-Gang Zhao, Qi-Jun Wu, Xiao Ma, Yong-Bing Xiang. Association Between Dietary Fiber and Lower Risk of All-Cause Mortality: A Meta-Analysis of Cohort Studies. American Journal of Epidemiology, Volume 181, Issue 2, 15 January 2015, Pages 83–91, doi.org/10.1093/aje/kwu257

10) Andrew Reynolds, Prof Jim Mann, Prof John Cummings, Nicola Winter, Evelyn Mete, Lisa Te Morenga. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses. The Lancet, VOLUME 393, ISSUE 10170, P434-445, FEBRUARY 02, 2019, doi.org/10.1016/S0140-6736(18)31809-9

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