High Fiber Intake Significantly Reduces Serious Disease Risk
A new meta-analysis of clinical trials published in The Lancet has found that people who eat high levels of dietary fiber and whole grains have lower rates of heart disease, diabetes, stroke and colorectal cancer.
The new analysis looked at observational studies and clinical trials conducted over nearly 40 years, and revealed the health benefits of eating at least 25-29 grams of dietary fiber daily.
The results of the meta-analysis 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 heart disease, stroke, type 2 diabetes and colorectal cancer by 16-24%.
This translates into a significant impact:
Out of 1,000 people, those eating a high fiber diet will have 13 fewer deaths and six fewer heart attacks than those on a low fiber diet.
In addition, a meta-analysis of clinical trials suggested that increasing fiber intakes was associated with lower bodyweight and cholesterol, compared with lower intakes.
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 carbohydrate provide the best protection against non-communicable diseases (NCDs) and weight gain.
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.
“Previous reviews and meta-analyses have usually examined a single indicator of carbohydrate quality and a limited number of diseases so it has not been possible to establish which foods to recommend for protecting against a range of conditions,” says corresponding author Professor Jim Mann, the University of Otago, New Zealand.
“Our findings provide convincing evidence for nutrition guidelines to focus on increasing dietary fiber and on replacing refined grains with whole grains. This reduces incidence risk and mortality from a broad range of important diseases.”
People who eat high levels of dietary fiber and whole grains have lower rates of heart disease, diabetes, stroke and colorectal cancer.
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 can’t be applied to people with existing chronic diseases.
“[a higher intake of dietary fiber] reduces incidence risk and mortality from a broad range of important diseases.”
-corresponding author Professor Jim Mann the University of Otago, New Zealand.
8g of Fiber Makes a Difference
For every 8g increase of dietary fiber eaten per day, total deaths and incidence of coronary heart disease, type 2 diabetes and colorectal cancer decreased by 5-27%.
Protection against stroke, and breast cancer also increased.
And consuming 25g to 29g each day was adequate but the data suggest that higher intakes of dietary fiber could provide even greater protection.
For every 8g of increased fiber, heart disease, diabetes and colorectal cancer decreased by 5-27%.
For every 15g increase of whole grains eaten per day, total deaths and incidence of coronary heart disease, type 2 diabetes and colorectal cancer decreased by 2-19%.
Higher intakes of whole grains were associated with a 13-33% reduction in NCD (non-communicable disease) risk — translating into 26 fewer deaths per 1,000 people from all-cause mortality and seven fewer cases of coronary heart disease per 1,000 people.
The meta-analysis of clinical trials involving whole grains showed a reduction in body weight.
Whole grains are high in dietary fiber, which appears to explain their beneficial effects.
Glycemic Index and Glycemic Load
The study also found that diets with a low glycemic index and low glycemic load provided limited support for protection against type 2 diabetes and stroke only.
It’s important to remember that foods with a low glycemic index or low glycemic load may also contain added sugars, saturated fats, and sodium, which likely accounts for the decreased benefits.
Over 100 Years of Fiber Research
“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.” says Professor Jim Mann.
No Associated Risks
While their study did not show any risks associated with dietary fiber, the authors note that high intakes might have some negative consequences in people with low iron or mineral levels, for whom high levels of whole grains can further reduce iron levels.
They also note that the study focused on naturally-occurring fiber rich foods rather than synthetic and extracted fiber, such as powders, that can be added to foods.
Multiple Benefits of High Fiber Intake
Commenting on the implications and limitations of the study, Professor Gary Frost, Imperial College London, UK, says:
“[The authors] report findings from both prospective cohort studies and randomized controlled trials in tandem.
This method enables us to understand how altering the quality of carbohydrate intake in randomized controlled trials affects non-communicable disease risk factors and how these changes in diet quality align with disease incidence in prospective cohort studies.”
This alignment is seen beautifully for dietary fiber intake, in which:
“Observational studies reveal a reduction in all-cause and cardiovascular mortality, which is associated with a reduction in body weight, total cholesterol, LDL cholesterol, and systolic blood pressure reported in randomized controlled trials…”
What is Dietary Fiber?
Dietary fiber, also known as roughage or bulk, includes the parts of plant foods your body can’t digest or absorb.
Unlike other food components, such as fats, proteins or carbohydrates — which your body breaks down and absorbs — fiber isn’t digested by your body. Instead, it passes relatively intact through your stomach, small intestine and colon and out of your body.
Types of Fiber
Fiber is commonly classified as soluble, which dissolves in water, or insoluble, which doesn’t dissolve.
This type of fiber dissolves in water to form a gel-like material. It can help lower blood cholesterol and glucose levels.
Soluble fiber is found in oats, peas, beans, apples, citrus fruits, carrots, barley and psyllium.
This type of fiber promotes the movement of material through your digestive system and increases stool bulk, so it can be of benefit to those who struggle with constipation or irregular stools.
Whole-wheat flour, wheat bran, nuts, beans and vegetables, such as cauliflower, green beans and potatoes, are good sources of insoluble fiber.
The amount of soluble and insoluble fiber varies in different plant foods. To receive the greatest health benefit, eat a wide variety of high-fiber foods.
Benefits of a High-Fiber Diet
A high-fiber diet:
Normalizes Bowel Movements
Dietary fiber increases the weight and size of your stool and softens it. A bulky stool is easier to pass, decreasing your chance of constipation.
If you have loose, watery stools, fiber may help to solidify the stool because it absorbs water and adds bulk to stool.
Helps Maintain Bowel Health
A high-fiber diet may lower your risk of developing hemorrhoids and small pouches in your colon (diverticular disease).
Studies have also found that a high-fiber diet likely lowers the risk of colorectal cancer.
Some fiber is fermented in the colon. Researchers are looking at how this may play a role in preventing diseases of the colon.
Lowers Cholesterol Levels
Soluble fiber found in beans, oats, flaxseed and oat bran may help lower total blood cholesterol levels by lowering low-density lipoprotein, or “bad,” cholesterol levels.
Studies also have shown that high-fiber foods may have other heart-health benefits, such as reducing blood pressure and inflammation.
Helps Control Blood Sugar Levels
n people with diabetes, fiber — particularly soluble fiber — can slow the absorption of sugar and help improve blood sugar levels.
A healthy diet that includes insoluble fiber may also reduce the risk of developing type 2 diabetes.
Aids Weight Loss
High-fiber foods tend to be more filling than low-fiber foods, so you’re likely to eat less and stay satisfied longer.
And high-fiber foods tend to take longer to eat and to be less “energy dense,” which means they have fewer calories for the same volume of food.
May Extend Your Life
Studies suggest that increasing your dietary fiber intake — especially cereal fiber — is associated with a reduced risk of dying from cardiovascular disease and all cancers.
How Much Fiber?
The optimal amount of daily fiber intake varies depending on a person’s age and sex.
The current Dietary Guidelines for Americans recommend the following approximate daily intake:
- adult men require about 34 grams (g) depending on their age
- adult women require about 28 g depending on their age
Intakes of fiber are modified for certain groups as energy requirements vary at different life stages.
For example, it’s recommended that children consume less than adults, with the following lower and upper bounds representing females and males respectively:
- teens aged 14 to 18 require 25.2–30.8 g
- adolescents aged 9 to 13 require 22.4–25.2 g
- children aged 4 to 8 require 16.8–19.6 g
- children aged 1 to 3 require 14 g
Tips For Adding More Fiber to Your Diet
If you’re new to eating high-fiber foods, it’s best to start by gradually adding fiber to your diet and increasing your water intake.
Fiber absorbs water so the more fiber you add to your diet, the more fluids you should drink.
Suddenly adding a large amount of fiber to your diet can sometimes cause side effects such as abdominal cramps, intestinal gas, bloating, or diarrhea. These should go away once your digestive system becomes used to the increase in fiber, but adding fiber gradually and drinking plenty of fluids can help avoid discomfort.
Fiber From Whole Grains
Refined or processed foods are lower in fiber content, so try to make whole grains an integral part of your diet. There are many simple ways to add whole grains to your meals.
Start your day with fiber.
Look for whole grain cereals to boost your fiber intake at breakfast.
Simply switching your breakfast cereal from Corn Flakes to Bran Flakes can add an extra 6 grams of fiber to your diet; switching to All-Bran or Fiber-One will boost it even more.
Recommended: For the amount of fiber per serving and good flavor, I think it’s hard to beat General Mills Fiber One Original.
Use brown rice and whole grain products.
Experiment with wild rice, barley, whole-wheat pasta, and bulgur.
These alternatives are higher in fiber than their more mainstream counterparts—and you may find you love their tastes.
Choose whole grain bread for toast and sandwiches.
Bulk up your baking.
When baking at home, substitute whole-grain flour for half or all of the white flour, since whole-grain flour is heavier than white flour.
In yeast breads, use a bit more yeast or let the dough rise longer.
Try adding crushed bran cereal or unprocessed wheat bran to muffins, cakes, and cookies. Or add psyllium husk to gluten-free baked goods, such as breads, pizza dough, and pasta.
Flaxseeds are small brown seeds that are high in fiber and omega-3 fatty acids, which can lower your total blood cholesterol.
You can grind the seeds in a coffee grinder or food processor and add to yogurt, applesauce, or breakfast cereals.
Tip: Whether you purchase ground flaxseeds or grind them at home, it is important to keep them in a tightly sealed container in the refrigerator or freezer to prevent them from becoming rancid.
Ground flaxseeds stored in the refrigerator in this manner will keep fresh for six months; and in the freezer, for one year.
Recommended: Spectrum Organic Whole Premium Flaxseed has excellent reviews.
Fiber From Fruit and Vegetables
Most fruits and vegetables are high in fiber, another good reason to include more in your daily diet. Here are some simple strategies that can help:
Add fruit to your breakfast.
Berries are high in fiber, so try adding fresh blueberries, raspberries, strawberries, or blackberries to your morning cereal or yogurt
Keep fruit and vegetables at your fingertips.
Wash and cut fruit and veggies and put them in your refrigerator for quick and healthy snacks. Choose recipes that feature these high-fiber ingredients, like veggie stir-fries or fruit salad.
Replace dessert with fruit.
Eat a piece of fruit, such as a banana, apple, or pear, at the end of a meal instead of dessert. Top with cream or frozen yogurt for a delicious treat.
Eat whole fruits instead of drinking fruit juice.
You’ll get more fiber and consume fewer calories. An 8oz. glass of orange juice, for example, contains almost no fiber and about 110 calories, while one medium fresh orange contains about 3g of fiber and only 60 calories.
Eat the peel.
Peeling can reduce the amount of fiber in fruits and vegetables, so eat the peel of fruits such as apples and pears.
Incorporate veggies into your cooking.
Add pre-cut fresh or frozen vegetables to soups and sauces. For example, mix chopped frozen broccoli into prepared spaghetti sauce or toss fresh baby carrots into stews.
Bulk up soups and salads.
Liven up a dull salad by adding nuts, seeds, kidney beans, peas, or black beans.
Artichokes are also very high in fiber and can be added to salads or eaten as a snack.
Beans, peas, lentils, and rice make tasty high-fiber additions to soups and stews.
Don’t leave out the legumes.
Make snacks count.
Fresh and dried fruit, raw vegetables, and high fiber, whole-grain crackers are all good ways to add fiber at snack time. A handful of nuts can also make a healthy, high-fiber snack.
Recommended: I love prunes – they’re great as a quick snack, or tossed into cereal.
It’s trendy to call them “dried plums” nowadays, but no matter what you call them, always have a bag on hand to up your fiber intake!
Sunsweet Pitted Prunes are my fave (never tough, and don’t have incidental pit “chips” in them).
Best Sources of Dietary Fiber
High Fiber Foods
Rich sources of dietary fiber include whole grains, pulses, vegetables and fruit.
|Food||Serving size||Fiber grams|
|Fiber One||1/2 cup||14|
|Bran Flakes||1 cup||7|
|Shredded Wheat||1 cup||6|
|Oatmeal (cooked)||1 cup||4|
|Spinach (cooked)||1 cup||4|
|Brussels sprouts||1/2 cup||2|
|Green beans||1/2 cup||2|
|Whole-wheat bread||1 slice||3|
|Rye bread||1 slice||2|
|Kidney beans||1/2 cup||6|
|Lima beans||1/2 cup||6|
|Baked beans (canned)**||1/2 cup||5|
|Green peas||1/2 cup||4|
|Wheat bran/wheat berries, dry||1/4 cup||6|
|Spaghetti, whole wheat||1 cup||4|
|Brown rice||1 cup||4|
|Pear (with skin)||1 medium||6|
|Apple (with skin)||1 medium||4|
|Strawberries (fresh)||1 cup||4|
|Nuts and seeds|
|Peanuts, dry roasted*||1/4 cup||3|
|* Choose no-salt or low-salt version of these foods,* *Choose low-sugar version of these foods|
While the best way to get fiber in your diet is from foods naturally rich in fiber—fruit, vegetables, whole grains, beans, nuts—when that proves difficult, taking a fiber supplement can help make up the shortfall.
Supplements can also be useful to top up your daily fiber intake while you transition to a high-fiber diet.
Fiber supplements come in a variety of forms, including powders you dissolve in water or add to food, chewable tablets, and wafers. However, there are some drawbacks to getting your fiber from supplements instead of fiber-rich foods:
- Fiber supplements won’t provide the same vitamins, minerals, and other nutrients offered by high-fiber foods.
- Supplements won’t fill you up or help you manage your weight.
- Fiber supplements can interact with some medications, including certain antidepressants, cholesterol-lowering medications, and the anticoagulation drug warfarin. Check with your doctor or pharmacist about potential drug interactions before taking a fiber supplement.
- If you have diabetes, fiber supplements may also reduce your blood sugar levels so, again, check with your healthcare provider before adding supplements to your diet.
If you decide to take a fiber supplement, start with small amounts and gradually build up to avoid any abdominal bloating and gas, and drink plenty of fluids.
Best Fiber Supplements
Metamucil Multi-Health Psyllium Fiber Supplement Sugar-Free Powder
(Orange Flavored, 180 Servings).
Metamucil is the #1 doctor recommended fiber brand and has been trusted by doctors for more than 80 years.
Reviewers rave about this old stand-by, plus, it’s sugar-free. This is an excellent choice for boosting your daily fiber intake.
Garden of Life Beyond Organic Fiber
If you’re someone who doesn’t do well with psyllium fiber (like me), Garden of Life is an excellent choice.
This vegan, psyllum-free fiber contains 9 grams of fiber per serving, plus 7 grams of protein, probiotics, and omega 3 fatty acids.
Its raw, organic fiber comes from 15 superfoods, including sprouted seeds, grains and legumes. This is truly a high quality supplement.
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