When thinking about starting the carnivore diet, one of the first questions people ask is, “Where will I get my fiber?” This is based on our conception that fiber is good for us and that our bodies need to process fiber in order to function properly. We’ve all heard of a “high fiber, heart-healthy diet” or been told that “an apple a day keeps the doctor away.”
However, similar to other popular nutritional advice, science does not support the claim that fiber is healthy, necessary or even beneficial. Keep reading to learn where the fiber myth originated, why conventional advice about fiber is inaccurate, and how much fiber – if any – you should be eating per day.
What is fiber?
Fiber is a carbohydrate composed of indigestible plant matter that is further categorized as soluble and insoluble. Soluble fiber can be partially dissolved by water while soluble fiber cannot. Despite this distinction, by definition, the body cannot fully digest fiber, which leads many people to believe that it moves through the colon “sweeping” other waste matter along to its inevitable exit out of our bodies.
How much fiber do we need?
Believe it or not, the answer is none. According to the 2015-2020 Dietary Guidelines for Americans, an essential nutrient is defined as “a vitamin, mineral, fatty acid, or amino acid required for normal body functioning that either cannot be synthesized by the body at all, or cannot be synthesized in amounts adequate for good health, and thus must be obtained from a dietary source. Other food components, such as dietary fiber, while not essential, also are considered to be nutrients.”
Not convinced? Well, if you’ve been following a low-carbohydrate diet, then you may be familiar with the following statement from the Panel on Macronutrients: “The lower limit on dietary carbohydrate compatible with life apparently is zero, provided that adequate amounts of protein and fats are consumed.” If fiber is a subset of carbohydrates, then we don’t have a need for fiber, right?
Unfortunately, convincing most people why fiber is unnecessary is not as simple as this logic. Our medical and lay community is filled with high-fiber recommendations and conflict with the Panel’s. Let’s take a closer look.
Where did high-fiber recommendations come from?
High-fiber recommendations originated in the 1970s based on observations of Ugandan populations by Dr. Denis Burkitt. He compared their disease patterns to Western diseases and concluded in the British Medical Journal that many Western diseases – such as coronary heart disease, diabetes type II, colorectal cancer, obesity, and hypertension – were the result of Western diet and lifestyle. His book about fiber became an international bestseller and led to the now widespread conventional advice that low-fiber diets cause disease.
Why Burkitt’s simplistic approach was readily and widely accepted is unclear. But it has led many to believe that necessary for digestion and is protective again colon cancer, heart disease, and digestive issues. According to human physiology and research studies, does increasing fiber increase our overall health?
Don’t we need fiber to break down undigested carbohydrates?
A lot of people will argue that we should eat copious amounts of fiber to break down carbs. But let’s take a look at what fiber does once consumed – it is broken down into short-chain fatty acids, namely propionic acid (propionate), acetic acid (acetate), and butyric acid (butyrate), which is the fuel source preferred by the large intestines endothelial cells.
But you don’t need to eat fiber to get butyrate. In fact, butter is the best dietary source of butyrate and it doesn’t require carbohydrate consumption. There is no need to consume glucose, fructose, and/or processed foods to realize the benefits of butyrate for digestion.
Does fiber reduce the risk of colon cancer?
In 2005, a study was published that aimed to get to the bottom of inconsistent observational findings related to fiber and colon cancer. Researchers followed 725,628 men and women involved in 13 other cohort studies for 6 to 20 years to determine which individuals had higher incidents of colorectal cancer. While dietary fiber intake was inversely associated with the risk of colorectal cancer in age-adjusted analyses, after accounting for other dietary risk factors, high dietary fiber intake was not associated with a reduced risk of colorectal cancer. Similar to other nutrition-based research, other factors were at play.
Fast-forward to 2017 and researchers still do not have strong evidence. This study systematically reviewed five studies of over 4000 subjects. Researchers concluded there was no evidence to suggest that increased dietary fiber intake would reduce the incidence or recurrence of adenomatous polyps within a two to four-year period.
Does fiber reduce the risk of heart disease?
But what about heart disease? Fiber is widely recommended as part of the “heart-healthy diet.” While fiber intake has been shown to improve glycemic control, a factor related to diabetes – a risk factor for heart disease – that fiber administration using psyllium has no effect and does not lower serum cholesterol.
What about fiber and digestive issues like constipation and IBS?
If fiber acts like a broom in the colon, then shouldn’t it help with digestive issues like constipation and IBS? Should it accelerate transit to push matter to its inevitable exit? One systematic research review of 17 randomized controlled trials found that the treatment of IBS (irritable bowel syndrome) patients with fiber is controversial.
The conclusion: “The benefits of fibre in the treatment of irritable bowel syndrome are marginal for global irritable bowel syndrome symptom improvement and irritable bowel syndrome-related constipation. Soluble and insoluble fibres have different effects on global irritable bowel syndrome symptoms.” Clinically, bran was no better than placebo in the relief of the overall symptoms of IBS and is possibly worse than a normal diet for some symptoms.
Is fiber beneficial? In some instances, like lowering blood sugar, yes, it can help. Is fiber necessary? No. Unfortunately, recommendations for high-fiber diets started with mere observations that confused association with causation and we can support our digestion with animal fats, butter being an excellent source of butyrate. Hopefully, these facts provide you with the information you need to move forward with an animal-based way of eating.