Growing up, one of the many things about adults I just didn’t get was why so many turned their cars into unsightly mobile billboards with bumper stickers. Aesthetics aside, I couldn’t figure out for the life of me why it was so important for others to know “This car climbed Mt. Washington” or “Virginia is for lovers.”

But there was one bumper sticker back then that struck me as being important, very important, so important that I now implore each and every one of my students to make it part of each and every day.

“Question Authority.”

You should do the same in your pursuit of health and fitness. Don’t read and do.

Read and doubt.

Only “do” if the evidence read, augmented by common sense, eliminates that doubt. Since I do think you should eat more fiber, I’ll offer the obvious evidence to all those dutiful doubting Thomases first: Most Americans don’t eat nearly enough of it.

According to the Dietary Guidelines for Americans, men should get 33.6 grams and women should get 28 grams of fiber every day. Yet only 5 percent of adult Americans reach those numbers — numbers that even should be higher if optimal health is your goal.

Now for the less-than-obvious evidence that could — dare I say should? — rid you of any doubt: The cells in your body need to eat, too.

The main meal for the ones that comprise your colon comes from the soluble fiber you eat that gets fermented there by the good-for-you bacteria in your gut.

The fermentation produces short-chain fatty acids (SCFAs).

Now the fiber that you eat comes in two forms, soluble and insoluble. While insoluble fiber passes through your body without being absorbed into your bloodstream, soluble fiber does get absorbed — even though it too cannot be digested.

When soluble fiber makes its way to your colon, the good-for-you bacteria there breaks down soluble fiber into the aforementioned SCFAs, and your body benefits. First, SCFAs increase the muscular contractions behind bowel movements, creating the regularity foods high in soluble fiber, especially prunes, are so famous for.

The benefit of consuming soluble fiber and creating SCFAs, however, does not end there.

Solid evidence suggests that SCFAs make it less likely you gain weight and more likely that you avoid diabetes, heart disease, certain cancers and other life-shortening diseases.

Consider the findings from research published last March in the journal Science. In it, the composition of the bacteria in the colons of diabetics changed after following a high-fiber diet for 12 weeks. By the end, the total number of the 15 known strains of bacteria that convert soluble fiber into the specific SCFAs that lower high blood sugar and cholesterol levels had increased significantly.

Moreover, the diabetics placed on the high-fiber diet had lower blood sugar levels after fasting and eating — and experienced enough weight loss naturally that the researchers deemed it “significant.”

Other studies have uncovered other benefits.

Butyrate, one type of SCFA, has not only exhibited anti-inflammatory effects but also seems to keep the anti-inflammatory agents in your body from malfunctioning — and you definitely want to do what you can to keep them from malfunctioning. Sometimes, for some reason, the anti-inflammatory agents in your body get confused and do a terrible thing.

They stop battling invading organisms and turn on you, attacking healthy parts of your body, and causing what we call an auto-immune disease.

Diseases like these include lupus, rheumatoid arthritis, scleroderma, multiple sclerosis, rheumatic fever, Addison’s disease, hypothyroidism, pernicious anemia, and ulcerative colitis.

Finally, while it’s already been established that being placed under too much stress can adversely affect gut bacteria, new evidence suggests good gut bacteria might actually help reduce stress.

Recently published in The Journal of Physiology, research done at APC Microbiome Ireland at University College Cork and the Teagasc Food Research Centre in Ireland found that when added to the guts of mice, SCFAs significantly reduced the number of anxiety-based behaviors created by stress-induced situations when compared to mice experiencing the same stress-induced situation that had not received additional SFCAs.

To recap, the consumption of soluble fiber creates SCFAs. Higher amounts of SCFAs in your body have been shown to reduce the incidence of type 2 diabetes, colon cancer, and heart disease — while making it less likely that you gain weight.

If you want to increase your ingestion foods high in soluble fiber, eat more fruits, vegetables, and legumes. The types of each that have significant amounts of soluble fiber and are easy to fit into a diverse family’s diet follow: avocados, pears, apples, oranges, and bananas; artichokes, potatoes, sweet potatoes, broccoli, and squash; navy beans, pinto beans, black beans, lima beans, soybeans, chick peas, and green beans.

You also find a fair amount of soluble fiber in whole grains and nut seeds, too.