10 Ways Refined Flour Can Damage Your Health | Chris Kresser
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10 Ways Refined Flour Can Damage Your Health

by Chris Kresser

Published on

refined flour
Processed baked goods made with refined flour could impact your health. iStock/hsanErolu

The Dietary Guidelines for Americans (issued by the U.S. Departments of Agriculture and Health & Human Services) recommend that the average American adult consume 225 to 325 grams of carbohydrates per day.

Unfortunately, for most Americans, a significant portion of this massive carbohydrate intake comes from refined flour in the form of cookies, cakes, cereal, bread, and pasta. (1) While once prized for its purported “purity,” we now understand that white flour is a nutritional travesty harmful to our health. Read on to learn how refined flour became so pervasive in the high-calorie, nutrient-poor Standard American Diet, the adverse health effects of refined flour, and which healthy, nutrient-dense carbohydrates you should eat instead.

Table of Contents:

A Brief History of Refined Flour

The earliest evidence of grain consumption by humans dates to 23,500 years ago in Israel, where archaeologists have discovered stone artifacts embedded with grains and oven-like hearths, which were presumably used to process grains and bake bread. (2) The storage of wild grain and grain domestication didn’t begin until approximately 12,000 years later, when an agricultural revolution occurred and some populations of hunter–gatherers exchanged their nomadic lifestyle for farming, forever changing the face of the human diet.

Refined flour may be connected to weight gain, metabolic problems, cardiovascular disease, and even cancer. Find out what’s wrong with refined flour, and learn more about what to eat instead. #lowcarb #paleo #wellness

From the beginning of this ancient agricultural revolution up until about 200 years ago, people ate grains in their whole, unrefined form. Whole grains have three components:

  • Germ: The reproductive part of a cereal grain that germinates to grow into a new plant
  • Bran: The hard outer layer of a cereal grain that provides protection against predators
  • Endosperm: The starchy inner portion of the grain

Over the centuries, people made attempts to refine whole-grain flour by sifting out the larger chunks of germ and bran. However, it wasn’t until the invention of the roller mill in around 1870, at the beginning of the Second Industrial Revolution, that they could finally mill flour into a highly refined, white powder. (3)

When it was first introduced to society, white flour was very expensive due to the significant effort required to process and bake it into bread. This made white bread primarily food for the upper classes. The majority of people, who couldn’t afford white flour, ate whole-grain bread that was dark, dense, and fibrous. However, the high cost of white flour was relatively short lived; as the milling techniques for white flour were further refined, the process became easier and white flour depreciated in price. (4) Soon, millers realized that refining grain by removing the bran and germ, leaving only the starchy endosperm, also extended the grains’ shelf life. (By removing the germ, they also removed the naturally occurring oil it contained; without the germ, the grain would no longer go rancid.) This discovery catapulted refined grain to a highly valued position in the food-processing industry. Over time, the price of refined grain plummeted further as more land was allocated for agriculture and huge flour mills were introduced. Eventually, what was once considered a “food for the rich” became a cheap “food for the masses” and a staple of the Western diet.

The pervasiveness of refined flour in the Western diet exploded again in the 1970s when the U.S. government released its low-fat dietary guidelines. These guidelines promoted an intense fear of fat and, in turn, an increased intake of carbohydrates to take the place of fat in the diet. Between 1980 and 1999, flour and cereal intake rose 36 percent in the United States. (5) Over 85 percent of the grains consumed in the current U.S. diet are highly processed refined grains such as refined flour. (6)

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What’s Wrong with Refined Flour?

Refined flour was once exalted for its purported “purity” and considered superior to whole-grain flour. However, over the past few decades, nutrition science has revealed that refined flour is anything but healthy.

Specifically, there are three main problems with refined flour:

  1. The consumption of refined flour raises blood sugar and insulin, causing metabolic dysfunction.
  2. Refined flour is depleted in nutrients and contains harmful additives.
  3. Refined flour displaces healthier foods from the diet.
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Blood Sugar, Insulin, and Metabolic Dysfunction

While whole grains contain three components—bran, germ, and endosperm—refined flour is made from grain that has been processed to remove the bran and germ, as mentioned above, leaving behind the starchy endosperm, which is pulverized into flour. The high starch content of refined grain and lack of fiber due to the removal of the bran and germ produces a rapid increase in blood sugar when consumed. The hyperglycemic and hyperinsulinemic effects of refined flour can cause severe blood sugar swings, which over time can significantly increase the risk of chronic diseases such as type 2 diabetes and cardiovascular disease. (7)

Refined Flour Is Nutrient Depleted and Full of Additives

To make matters worse, the refining process results in a substantial loss of dietary fiber, B vitamins, iron, magnesium, and vitamin E. (8)  Don’t be fooled by the term “enriched wheat flour”; so many nutrients are stripped away during processing that manufacturers attempt to replace them through “enriching” the flour with vitamins and minerals. But the flour is still a refined carbohydrate that will have a negative impact on blood sugar, canceling out any “enriched” benefits. Furthermore, the refining process makes use of several man-made chemical compounds to turn whole-grain flour into homogenous white flour:

  • Potassium bromate strengthens gluten development; “bromate” is derived from bromine, a chemical that displaces iodine from tissues throughout the body and may have especially harmful effects on the thyroid.
  • Chlorine gas is also used as a bleaching agent and weakens gluten development, making a thicker batter and stiffer dough. Chlorine gas undergoes oxidation reactions with proteins in flour, creating alloxan, a toxic byproduct that induces diabetes in animal models.
  • Benzoyl peroxide is a bleaching agent used to impart a “pure” white hue to refined flour. This is the same industrial chemical used in some acne medications.

Refined Flour Displaces Healthy Foods

Refined flour, unfortunately, makes up a significant portion of the average American’s diet. The consumption of bread, cakes, cookies, cereal, crackers, snack foods, and pasta made with refined grains frequently displaces healthier foods in the diet, such as high-quality protein, vegetables, and fruits.

If refined flour is so terrible, then whole-grain flour must be better, right? Not exactly. Most of the whole-grain flour used to make whole-grain bread and bread products, cereal, and pasta has been milled to a fine particle size, with just some germ and bran added back. This flour may be labeled “whole grain,” but it is still relatively depleted in nutrients and has a higher glycemic index and glycemic load than intact whole-grain kernels such as oats and quinoa. (9) A food’s glycemic index and glycemic load deal with its potential to impact your blood sugar levels. For more, check out my podcast “RHR: Is the Glycemic Index Useful?

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10 Harmful Health Effects of Refined Flour Intake

Clearly, refined flour doesn’t do our health any favors. Increasingly, research indicates that it significantly increases the risk for many health conditions, including weight gain and obesity, metabolic syndrome, diabetes, hypertension, heart disease, cognitive decline, food addiction, depression, cancer, and acne.

1. Weight Gain and Obesity

The United States is suffering from an obesity epidemic, with two-thirds of American adults currently classified as overweight or obese. (10) Refined flour is a key contributor to this epidemic, as its consumption promotes fat in the body and impairs fat oxidation, the process by which the body “burns” fat for fuel. (11) Refined flour may also promote an inflammatory gut microbiota, or inflammation caused by bacteria in the gut, a condition that fosters metabolic dysfunction and weight gain. (12)

2. Metabolic Syndrome and Type 2 Diabetes

Currently, metabolic syndrome afflicts 35 percent of the U.S. population, and 100 million Americans have either prediabetes or full-blown type 2 diabetes. (13, 14) Refined carbohydrate intake is an established risk factor for insulin resistance, the most powerful predictor of metabolic syndrome and diabetes. (15, 16) In fact, the odds of having metabolic syndrome are 41 percent higher among people who eat the most refined carbohydrates, compared to those who eat the least. (17)

While the U.S. dietary guidelines recommend switching out refined grain products for whole grains to reduce the risk of metabolic syndrome and type 2 diabetes, research indicates that this change leads only to minute improvements in blood sugar. (18) A far more effective strategy for managing blood sugar is to remove grains from the diet altogether (i.e., consuming a Paleo diet), thereby inhibiting the development of an inflammatory gut microbiota and the insulin resistance and metabolic dysfunction with which it is associated. (19)

3. Hypertension

One of the most significant contributors to high blood pressure (hypertension) is insulin resistance. The consumption of refined carbohydrates—which behave like sugar in the body—can disrupt the relationship between glucose and insulin and ultimately could lead to the development of high blood pressure or worsen existing hypertension. Cutting out refined carbohydrates such as refined flour should be the first step in hypertension treatment. Indeed, diets low in refined carbohydrates lead to significant reductions in blood pressure. (20, 21)

4. Cardiovascular Disease

For decades, dietary fat was wrongly blamed for causing cardiovascular disease, a mistake that led to the development of the United States’ infamous low-fat, high-carb dietary guidelines. Unfortunately, we now understand that these guidelines, which led Americans to consume more refined carbohydrates, may have exacerbated the cardiovascular disease epidemic.

A 2017 article published in The Lancet, one of the world’s most prestigious medical journals, demonstrates that high carbohydrate intake is associated with higher total mortality from cardiovascular disease, whereas total fat and types of fat are not associated with cardiovascular disease, myocardial infarction, or cardiovascular death. (22) This finding is supported by many more studies indicating a strong association between refined grain intake and cardiovascular disease risk. (23, 24)

How exactly do carbohydrates such as refined flour contribute to heart disease? The serious blood sugar imbalances caused by refined carbohydrates promote systemic inflammation, damage the vascular system, and negatively impact blood lipids (increasing “bad” LDL cholesterol while lowering “good” HDL levels), thereby compromising the cardiovascular system. A low intake of refined carbohydrates, on the other hand, significantly reduces cardiovascular disease risk factors. (25)

5. Cancer

The connection between dietary carbohydrates and cancer was dismissed by the medical community until 2017, when an article in PLOS Biology published internal documents indicating that evidence of a link between sugar and cancer was purposely covered up by the sugar industry decades ago. (26)

There is also research that supports evidence of a link between processed carbohydrates, such as refined flour, and cancer risk. A high intake of refined carbohydrates is associated with a moderate, but statistically significant, increased risk of breast, colon, and endometrial cancers. (27, 28, 29) This effect is likely mediated by the increased release of insulin-like growth factor 1 (IGF-1), which triggers cell division induced by refined carbohydrate intake. The impact of refined carbohydrates on cancer risk may be even more pronounced when combined with the other unhealthy components of the Standard American Diet, such as industrial seed oils and food additives.

6. Cognitive Impairment

It is increasingly clear from research that insulin resistance and chronic elevated blood sugar are major risk factors for cognitive impairment, Alzheimer’s disease, and Parkinson’s disease. (30, 31) Insulin resistance promotes brain dysfunction by impairing glucose transport to the brain, inducing neuroinflammation, altering synaptic plasticity (which harms the brain’s ability to learn and memorize), and stimulating the production of harmful compounds called advanced-glycation end products in the brain. A diet high in refined carbohydrates is associated with an increased concentration of beta-amyloid protein in the brain, a characteristic feature of Alzheimer’s disease, while also raising the risk of mild cognitive impairment and dementia. (32, 33)

7. Food Addiction

Refined carbohydrates are known to trigger food addiction, a condition in which certain foods—including refined flour products loaded with excess salt or sugar and bad fats (think doughnuts or pretzels)—are consumed in amounts that exceed the body’s energy needs. Food addiction also features binge eating behavior, cravings, and lack of control around foods. (34)

8. Depression

A diet high in refined carbohydrates is associated with an increased risk of depression. (35) While the relationship between these two variables is bidirectional—depressed individuals tend to “self-medicate” their depression with high-carbohydrate foods—refined flour may also contribute to depression by promoting systemic inflammation and inducing mood-altering blood sugar swings.

9. Acne

While dermatologists have long disputed the role of diet in acne, it is now well established that refined carbohydrates contribute to the development and progression of this frustrating skin condition. Interestingly, acne is nonexistent among hunter–gatherer societies consuming diets devoid of refined carbs, but it is exceedingly common in industrialized societies subsisting on a Western diet.

The consumption of refined carbohydrates triggers excessive insulin secretion; elevated insulin increases sebum production in skin follicles, leading to obstruction of the follicles and the development of inflamed skin lesions, i.e., pimples. Some researchers have gone so far as to call acne a “metabolic syndrome” of the hair follicle due to the pivotal role insulin plays in the condition’s pathogenesis. (36) Conversely, a diet low in refined carbohydrates can significantly improve acne by increasing insulin sensitivity and decreasing inflammation. (37)

10. Gluten: Yet Another Problem with Refined Flour

Aside from its high carbohydrate density, refined flour is also a source of another potentially problematic ingredient—gluten. The term “gluten” refers to a family of proteins found in wheat, rye, barley, and triticale that are responsible for the elastic texture of dough. Gluten is perhaps most well known for its harmful effects in people with celiac disease, a condition in which the body launches an immune response to gluten, resulting in significant damage to the small intestine.

However, celiac disease is a response to just one member of the gluten protein family—alpha-gliadin—and to one gluten-digesting enzyme in the gastrointestinal tract, tissue transglutaminase-2 (tTG-2). It’s entirely possible to be sensitive to other components of wheat and gluten in the absence of celiac disease. This condition, called non-celiac gluten sensitivity (NCGS), is a distinct clinical condition supported by a substantial body of scientific literature. (38, 39)

It’s important to note that gluten isn’t a problem for everyone. While it’s true that gluten intolerance is far more common than was previously believed, statistics suggest that, at most, one in 10 people are affected. (40) That said, most of the foods that contain gluten—bread, crackers, cookies, cakes, and other processed and refined foods—are high in calories and low in nutrients and should thus be minimized in the diet even if you do tolerate gluten.

Celiac Disease and NCGS—How Gluten Could Harm the Body

While people typically associate celiac disease with gastrointestinal symptoms, research indicates that most occurrences of celiac disease are atypical cases without GI symptoms. (41) NCGS also frequently manifests as symptoms outside the digestive tract, for example:

  • Anemia and fatigue (42, 43)
  • Anxiety and depression (44, 45)
  • Brain fog (46)
  • Eczema/psoriasis and other skin problems (47)

If left undiagnosed and untreated, celiac disease and gluten sensitivity can have serious ongoing consequences. Some of the long-term health problems associated with celiac disease and gluten sensitivity include:

  • ADHD (48)
  • Amyotrophic lateral sclerosis (ALS) (49)
  • Autism spectrum disorder (50)
  • Epilepsy (51)
  • Hashimoto’s disease (52)
  • Multiple sclerosis (53)
  • Osteoporosis (54)
  • Peripheral neuropathy (55)
  • Schizophrenia (56)
  • Type 1 diabetes (57)
If you suffer from any of the symptoms or conditions mentioned above and have been unable to find relief, I recommend trying a gluten-free diet for 30 to 60 days to see if you feel better off gluten. At the end of this trial elimination period, add gluten back into your diet and see if your symptoms return. If they do, this is an indicator that you are sensitive to gluten and should continue to avoid it in your diet.

In addition to doing a trial elimination of gluten, you may also want to consider gluten sensitivity testing. Cyrex Labs offers comprehensive gluten sensitivity testing that we use in our practice. Cyrex Array 3 measures wheat and gluten proteome reactivity (gluten sensitivity), and Array 4 covers gluten cross-reactive proteins.

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When It Comes to Carbs, Quality Matters Most

Modern nutrition science and epidemiological evidence indicate that the quality of the carbohydrates we consume matters far more than the quantity. Studies of hunter–gatherer groups demonstrate that humans can consume high amounts of carbohydrates as part of a healthy diet without experiencing adverse health effects. For example, the Kitavan islanders of Papua New Guinea obtain approximately 60 to 70 percent of their total energy intake from carbohydrates yet do not suffer from type 2 diabetes, obesity, or any of the other chronic diseases associated with Western civilization. (58) The caveat is that the carbohydrates these people eat are of a much higher quality than those consumed by the average American. Hunter–gatherer societies obtain carbohydrates primarily from tubers and fruits, which contain carbohydrate bound up in the fibrous cell walls of plants. These fiber-walled cells largely remain intact during cooking, giving the foods a low carbohydrate density. Low-carbohydrate-density foods support our commensal (or friendly) gut microbiota and healthy metabolic function.

Conversely, refined flour is composed of acellular carbohydrates, or carbohydrates that have been released from plant cells. The breakdown of acellular carbohydrates in the gut rapidly releases sugars, promoting the development of an inflammatory gut microbiota and metabolic dysfunction. (59)

While carbohydrate quality matters more than quantity for many people, you may need to be stricter about the amount of carbohydrate included in your diet if you have metabolic syndrome, type 2 diabetes, or are overweight or obese. However, even in these instances, merely improving the quality of carbohydrates consumed can often lead to vast improvements in health.

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What to Eat Instead of Refined Flour

Clearly, refined flour offers no real benefits to our health—and in fact can make us quite sick. But what sources of carbohydrates should we eat instead?

I believe we should take a cue from hunter–gatherers and consume most of our carbs from plant foods, such as whole fruit and starchy tubers.

Whole Fruit

Whole fruits are high in fiber, vitamins, minerals, and phytonutrients; frequent consumption of whole fruit, but not fruit juice, is associated with a reduced risk of all sorts of chronic diseases. I recommend referring to the Environmental Working Group’s Dirty Dozen and Clean 15 lists to determine which fruits are lowest in pesticide residues (and therefore safe to buy conventional) and which should be purchased organic.

Starchy Tubers

Hunter–gatherer groups with traditionally high carbohydrate intakes frequently consume much of their carbs in the form of starchy tubers such as sweet potatoes and cassava. Other nutrient-dense starches to include are winter squash, beets, rutabaga, plantains, and white potatoes.

Gray-Area Carbs: Whole Grains and Legumes

If refined grains aren’t optimal for our health, then what about whole grains? After all, health authorities have been telling us for years to “eat more whole grains” to support our health. Research indicates that if your goal is to lose weight, improve blood sugar control, or reduce your risk of chronic disease, then replacing refined grains with whole grains yields only modest improvements in health. (60) Removing grains altogether and instead consuming carbohydrates from fruit and tubers (aka a Paleo diet) consistently produces more dramatic improvements in metabolic health.

If you are an insulin-sensitive and/or very active individual, you can consider adding legumes and whole grains as sources of carbohydrates. If gluten is a concern, stick to gluten-free grains such as amaranth, millet, buckwheat, teff, quinoa, and sorghum. To maximize the nutrient bioavailability of legumes and whole grains, soak, sprout, or ferment them before cooking. Interestingly, sourdough bread may represent a viable health-promoting alternative to bread made from refined flour; research indicates that eating sourdough bread produced a much lower postprandial blood sugar response compared to conventional bread. (61) The fermentation process used to create sourdough bread also enhances the bioavailability of B vitamins and minerals in the grain, meaning you get more nutritional bang for your buck.

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Now I want to hear from you. Have you removed refined flour from your diet? Has removing refined flour led to improvements in your health? Let me know in the comments below.

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