By Dr. Mercola
Most people equate a high-fiber diet with digestive health. While it’s certainly useful for that purpose, this by no means gives the full picture of fiber’s health benefits.
One eye-opening report found, for instance, that if U.S. adults over the age of 55 with heart disease took psyllium dietary fiber daily, it could save nearly $4.4 billion a year in health care costs and more than $35 billion in cumulative health care costs between 2013 and 2020.1
Another study revealed that every 10-gram increase of fiber intake was associated with a 15 percent lower risk of mortality, and those who ate the most fiber had a 25 percent reduced risk of dying from any cause within the next nine years, compared to those whose fiber intake was lacking.2
Mounting research suggests that a high-fiber diet can help reduce your risk of premature death from any cause, likely because it helps to reduce your risk of a number of chronic diseases.
This includes type 2 diabetes, heart disease, stroke, and cancer. New research suggests the benefits even extend to your lung function.
Eating More Fiber May Improve Your Lung Function
A study involving nearly 2,000 adults revealed low fiber intake was associated with reduced measures of lung function while a diet rich in fiber-containing foods may play a role in improving lung health.3 Specifically:4
- 68 percent of those with the highest fiber consumption had normal lung function compared to 50 percent with the lowest fiber intake
- 15 percent of those who ate the most fiber had airway restriction compared to 30 percent of those who ate the least
- People who ate a lot of fiber scored better on two breathing tests, indicating larger lung capacity and the ability to exhale more air in one second
In this study, the high-fiber group was consuming 18 grams of fiber a day or more, which is still on the low end of what you should, ideally, be eating. The U.S. Department of Agriculture (USDA) recommends getting 14 grams of fiber per 1,000 calories consumed.
A more general recommendation is to make sure you get 20 to 30 grams of fiber per day. I believe about 50 grams per 1,000 calories consumed is ideal.
Still, if the findings can be confirmed with future studies, public health campaigns may one day include eating a high-fiber diet as a way to prevent lung disease.
However, you needn’t wait for the confirmation to come in; there’s no risk to eating more fiber and a laundry list of benefits if you do.
A High-Fiber Diet May Lower Your Risk of Breast Cancer, Colon Cancer
Teenagers aren’t exactly known for their attention to healthy eating, but eating right during young adulthood may affect your risk of cancer in the future, especially if you eat a high-fiber diet.
Women who ate a high-fiber diet during high school had a 24 percent lower risk of breast cancer during the 20-year study than those who ate a low-fiber diet. In this case, high levels of fiber were defined as 28 grams per day compared to 14 grams per day for the low-level group.5
For women eating a high-fiber diet, the lifetime breast cancer risk was slashed by 16 percent. Further, for every extra 10 grams of daily fiber, breast cancer risk went down by 13 percent, and the effect was particularly noted for women who ate a lot of vegetables and fruits.
Fiber helps reduce circulating levels of estrogen in your body, which may be why it helps lower breast cancer risk.6 High fiber intake is also linked to a lower risk of other types of cancer, including incident colorectal adenoma, a known precursor to colorectal cancer, and distal colon cancer.7
High fiber content is one likely reason why dried plums (prunes) also appear to have anti-cancer properties. Rats on a dried-plum diet had reduced numbers of aberrant crypts, which are signs of precancerous lesions that may be an indicator for future colon cancer development.8
A new review of data from 133 meta-analyses also concluded that dietary fiber was associated with a decreased risk of cancer.9
What Your Low-Fiber Diet Does to Your Health
If you eat a lot of processed foods, you’re missing out on important dietary fiber, which acts as food for the microbes in your gut. If you don’t eat enough fiber, your gut microbes won’t have enough to feed on, leading to both short- and long-term consequences.
Researchers from Stanford University School of Medicine conducted a study on germ-free mice (sterile mice raised in isolation) to find out what happens when you’re starved of dietary fiber. When the mice were fed a high-fiber diet, they enjoyed diverse bacterial colonies in their gut.10
However, when mice were fed no fiber for a few months, they experienced a drastic reduction in bacterial diversity. Adding fiber back to their diets helped restore the diversity to their guts, but there was a serious caveat. As reported by TIME:11
“ … [A]fter the mice were bred for several generations, a low-fiber diet was too great an assault for some bacteria types to bounce back from.
Even when the researchers switched the newest generation of mice a diet that was very high fiber, it didn’t help. The bacterial species didn’t rebound to levels seen in the control mice.”
Interestingly, a fecal transplant from mice fed a high-fiber diet was able to restore the lost microbes in the low-fiber mice. Study author Justin Sonnenburg, Ph.D., associate professor in the Department of Microbiology and Immunology at Stanford University School of Medicine, told TIME:12
“Fairly immediately, within three days, virtually all of the diversity came back in the fecal transplant group … It’s a magic combination of microbes by diet that enables the ecosystem to reconstitute.”
As processed diets are now the norm, the researchers suggested that “microbiota reprogramming” to incorporate lost varieties of microbes may be necessary to optimize Americans’ gut microbes.
9 More Health Benefits of Fiber
Why else should you be sure you’re getting plenty of dietary fiber each and every day?
- Blood sugar control: Soluble fiber may help to slow your body’s absorption of sugar, helping with blood sugar control. Research also shows that women with the highest soluble fiber intake had 42 percent less insulin resistance.13
In another study, people who had the highest intake of fiber (more than 26 grams a day) also had an 18 percent lower risk of developing type 2 diabetes than those with the lowest intake (less than 19 grams a day).14
The fiber may benefit diabetes by altering hormonal signals, slowing down nutrient absorption or altering fermentation in the large intestine, along with promoting feelings of satiety.15
- Heart health: An inverse association has been found between fiber intake and heart attack, and research shows that those eating a high-fiber diet have a 40 percent lower risk of heart disease.16
- Stroke: Researchers have found that for every 7 grams more fiber you consume on a daily basis, your stroke risk is decreased by 7 percent.17
- Weight loss and management: Fiber supplements have been shown to enhance weight loss among obese people,18 likely because fiber increases feelings of fullness.
However, there's more to it than that. When microbes in your gut digest fiber, a short-chain fatty acid called acetate is released. The acetate then travels from your gut to the hypothalamus in your brain, where it helps signal you to stop eating.
- Skin health: Fiber, particularly psyllium husk, may help move yeast and fungus out of your body, preventing them from being excreted through your skin where they could trigger acne or rashes.19
- Diverticulitis: Dietary fiber (especially insoluble) may reduce your risk of diverticulitis — an inflammation of your intestine — by 40 percent.20
- Hemorrhoids: A high-fiber diet may lower your risk of hemorrhoids.
- Irritable bowel syndrome (IBS): Fiber may provide some relief from IBS.
- Gallstones and kidney stones: A high-fiber diet may reduce the risk of gallstones and kidney stones, likely because of its ability to help regulate blood sugar.
Forget the Grains — Increase Your Fiber by Eating More Veggies
Grains are not the best source of dietary fiber. A high-grain diet tends to promote insulin and leptin resistance, which is counterproductive as this actually promotes many of the chronic diseases that healthy fiber can help reduce, most notably type 2 diabetes, heart disease and cancer.
Not to mention, most grains are grown using agricultural chemicals such as glyphosate, which has now been identified as a "probable human carcinogen" and a promoter of antibiotic resistance. Glyphosate contamination has also been linked to celiac disease and other gut dysfunction, which is the opposite of what you're trying to achieve by adding fiber to your diet.
Your best source of dietary fiber comes from vegetables, and most people simply aren't eating enough veggies. There are basically two types of fiber:
- Soluble fiber, found in cucumbers, blueberries, beans, and nuts, which dissolves into a gel-like texture, helping to slow down your digestion. This helps you to feel full longer, which can help with weight control
- Insoluble fiber, found in foods like dark green leafy vegetables, green beans, celery, and carrots, which does not dissolve at all, and helps add bulk to your stool. This helps food to move through your digestive tract more quickly for healthy elimination
Many whole foods, especially fruits and vegetables, naturally contain both soluble and insoluble fiber, both of which serve as excellent fodder for the microorganisms living in your gut. Organic whole-husk psyllium is another great fiber source, as are sunflower sprouts and fermented vegetables, the latter of which are essentially fiber preloaded with beneficial bacteria. The following whole foods also contain high levels of soluble and insoluble fiber.
Flax, hemp, and chia seeds
||Vegetables such as broccoli and Brussels sprouts
|Root vegetables and tubers, including onions, sweet potatoes, and jicama
If you're not sure how much fiber you're eating, take a minute to find out. Use a dietary fitness app or even WebMD's Fiber-o-Meter.21 If you come up short, consider adding in a serving or two of organic psyllium husk, sunflower sprouts and fermented vegetables, and definitely start eating more high-fiber vegetables such as broccoli, Brussels sprouts and cauliflower.
To learn even more about how you can optimize your health through diet, including boosting your fiber intake, please refer to my free online nutrition plan.