A Food Combination Diet
The basic idea of a food combination diet is that certain foods do not digest optimally if eaten together, while others mix well. It’s true, some foods require a more acidic environment and take longer to digest, while others need less acid and digest quicker. The thought is that mixing the two creates an inefficient breakdown process, leading to stress for the digestive system, poor metabolism or undigested food fermenting in the stomach. By combining certain foods it may lead to better metabolism, weight loss and overall health. Let’s take a closer look at this theory.
The common food combination diet guidelines suggest eating fruit only on an empty stomach, avoiding combinations of proteins and starch, acidic foods and starch, and different types of proteins. Some plans also recommend eating dairy products only on an empty stomach, especially milk. Sugar is eliminated and processed foods limited. This means no steak and potatoes, no chicken and rice, no spaghetti and meatballs, and certainly no fruit with entrees.
Fruits are the most quickly digested foods, taking about 30 minutes to break down. Combining fruit with much slower digesting foods may delay the digestion of fruit creating a condition where the fruit is left undigested and allowed to ferment, creating rotten food in the stomach.
Proteins, such as meat, seafood, eggs, cheese and dairy require lots of stomach acid and more time to facilitate their breakdown. Starches, such as grains, potatoes, squash and bread require less acid, or a more alkaline environment, and take less time for digestion. So the idea is eating the two groups together is counter-productive for the digestive system. Whereas, mixing protein with non-starchy vegetables, such as leafy greens, cruciferous vegetables, carrots, celery, green beans, and ocean vegetables such as kelp is ok.
Macronutrients and the Digestion Process
The three macronutrients in our food are carbohydrates, proteins and fats. In order to absorb food through the gut wall, the macronutrients must be broken down by enzymes to their most basic building blocks – monosaccharides, amino acids and fatty acids.
Carbohydrates, or carbs, exist as single sugar molecules (monosaccharides), double sugar molecules (disaccharides), small chains of sugar molecules (oligosaccharides) and large chains of sugar molecules (polysaccharides). Only the monosaccharides are able to cross the gut wall for absorption and all the other carbs must be broken down by an enzyme called amylase, which is secreted in the mouth and small intestine. There are also enzymes in the gut wall that complete carb digestion. Carb breakdown by enzymes doesn’t really happen much in the stomach.
Proteins are long chains of amino acids. Protein-digesting enzymes, also known as proteolytic enzymes or proteases, break down proteins into smaller peptides and ultimately into single amino acids. These enzymes are produced in various parts of the digestive system, each functioning optimally in specific environments. Pepsin is the main enzyme for proteins and is activated by stomach acid, thriving in the acidic environment. From there, multiple enzymes for proteins are released in the more alkaline environment of the small intestine. There are even a few enzymes for proteins within the lining of the gut wall. Only the final single amino acids are absorbed.
Fats begin digestion begins in the mouth to a small degree with lingual lipase enzyme, continues to a small degree in the stomach with gastric lipase, and really finalizes in the small intestine with intestinal lipase. The gallbladder releases bile which, sort of like dishwashing soap, emulsifies or breaks fat down into smaller particles to aid digestion of fatty acids in the small intestine.
Evan just thinking of eating our mouth begins making more saliva and the stomach secretes more acid. We start breaking down food by chewing and the stomach mixes and churns the food to further the physical breakdown until finally the macronutrients are broken down in the intestine to their smallest building blocks for absorption. All along the way saliva, stomach acid, bile and various enzymes support digestion.
The digestive tract is elegantly designed to do all this at the same time for all foods. The mouth starts digestion for everything. The stomach is the main acidic environment and is especially needed for protein breakdown. Bile is especially needed for fat breakdown. On into the small intestine region the body neutralizes the acid to create an alkaline setting where all macronutrients finalize their breakdown.
Concerns of Food Combinations
As for avoiding the mixing of food groups, all food has varying degrees of the macronutrients and the digestive system is quite able to multitask allowing it to address all components of food at once. A simple summary is that all food digestion starts in the mouth, proteins and really hit a secondary stage in the stomach, and the final stage for all foods wraps up in the small intestine. The leftovers make it to the large intestine for fermentation.
Regarding the idea of “fermenting” or “rotting” food in the stomach, this seems unlikely. First of all, fermentation is a biological process in which microorganisms, such as bacteria, yeasts, or fungi, convert organic compounds – primarily carbohydrates like sugars and starches – into simpler compounds. The normal stomach environment is highly acidic and few bacteria or fungi can even survive under this condition. Fermentation does take place in the gut, but mainly in the large intestine, where beneficial bacteria convert residual food particles, namely soluble fibers and undigested proteins, into beneficial short chain fatty acids and branched chain amino acids, as well as gases such as hydrogen and methane.
Altering stomach acidity doesn’t happen by eating more or less acidic foods. The stomach tightly controls the acidity via various neurologic and hormonal controls. In the same fashion, various foods don’t alter blood acidity as the lungs and kidneys tightly regulate blood acidity. Food does influence the acidity of urine as the kidneys excrete excess acid or base. This is often mistaken for changes in overall body pH.
The only study I could find that addresses food combinations, “Similar weight loss with low-energy food combining or balanced diets“, did not find any difference when it came to weight loss.
Clinical Implications
All of the above is describing a normal functioning digestive system. There are special conditions that deserve mention and ultimately do influence the digestive process, but not necessarily in relation to food combinations.
Low stomach acid is quite common, caused by aging, low thyroid, autoimmune gastritis, medications that lower stomach acid, etc. This can cause a major hiccup in digestion leading to poor breakdown of all macronutrients, but especially proteins. It also hinders absorption of certain nutrients that require acid, such as iron, b12, folate, fat soluble vitamins and minerals such as calcium, magnesium and zinc. Patients with low stomach acid may indeed do better eating small amounts of protein without the starch that tends to buffer and lower the stomach acid further. Eating smaller portions also helps.
Missing a gallbladder can impair the timing of bile release thus impairing fat breakdown. This may impact the absorption of fat soluble vitamins and fatty acids. Pancreatic disease leading to lower enzyme secretion will disrupt the final breakdown of all macronutrients. Again, eating proteins alone would probably help someone without a gallbladder or low on pancreatic enzymes. And, so would eating smaller portions.
Any disruption of the normal digestive process, such as those noted above, that limits the breakdown of macronutrients, can result in larger food particles making their way downstream in the gut where they don’t belong. This can “feed” the wrong bacteria causing dysbiosis, or a disruption in the microbiome. It can cause a bacterial overgrowth in the small intestine called small intestinal bacterial overgrowth (SIBO). It can lead to an overgrowth of fungi, especially candida, leading to all sorts of problems. It can also stimulate an immune reaction as larger food particles make better antigen stimulates for the immune system. Symptoms of irritable bowel syndrome (IBS) are often caused by these situations.
See my article on digestive health protocols for information on how to treat some of these conditions. Consider delayed food allergy testing as an easy starting point if you have gut issues. Seek help from a functional medicine practitioner to help get to the root cause of digestive symptoms or illness. Testing for autoimmune gastritis, celiac, dysbiosis, leaky gut, or SIBO is simple. An advanced stool study can give great insight into the gut microbiome and enzyme activity.
Some Proven Food Combinations
Vitamin C helps with iron absorption, so combining foods rich in vitamin C such as citrus fruits or bell peppers with sources of iron such as meat, spinach, or beans may be helpful in raising iron levels.
Fat-soluble vitamins and heart healthy carotenoids need fat in order to be absorbed by the body. Combining foods that are bright in red, orange, and dark green colors, including carrots, tomatoes, red bell peppers, spinach, and broccoli, with fats like nuts, seeds, salad dressing, olive oil, or avocados increases the absorption of carotenoids.
Food Combination Diets, Magic or Myth?
I’d say more myth. That said, there may be a role for food combination for some people. If you do have digestive issues, you may find a food combination diet is helpful. Although, to me, this would imply that there was some underlying disturbance in the normal digestive process that was really the root cause. On one downside, the diet may cause excess food worry, be unsafe for some people such as diabetics, can be confusing and is unsustainable for most people. I was not able to find any scientific studies to support food combining. On the upside, it does encourage more whole foods, little to no sugar, and less processed foods, which is a good thing for all of us.
Author
Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine. He specializes in bioidentical hormone replacement for men and women, thyroid and adrenal disorders, fibromyalgia and other complex medical conditions. He is founder and medical director of the Integrative Medicine Center of Western Colorado (www.imcwc.com) and Bellezza Laser Aesthetics (www.bellezzalaser.com). Call (970) 245-6911 for an appointment or more information.
