Unlike what it sounds, the term "food combining" isn't referring to taking a mixed bite of steak and mashed potatoes. Rather, it's an ancient Ayurvedic idea that different foods digest at different rates and should be eaten in a certain order or combination for optimal digestion and nutrient extraction. Sounds promising, but is it actually based in science?
What Is Food Combining All About?
In recent years, food combining has become a popular fad diet, with supporters claiming to eat certain foods together to improve digestion and rid the body of toxic substances, or toxins. But unfortunately, scientific evidence just doesn't support the idea, says New York-based dietitian Megan Stoutz, RD.
Proponents of the diet offer a number of rationales for food combining. For example, Stoutz says, it's believed that if fast-digesting foods are eaten with slow-digesting foods, the fast traveling foods will become stuck in the GI tract and begin to "rot," which is thought to cause poor digestion and health problems.
Food combiners also advocate separating foods with different acidity levels, supposedly because nutrient-specific enzymes only work at certain acidity levels.
Like most fad diets and restrictive eating plans, food combining has a litany of rules:
- Eat fruit — especially melons, which are acidic — on an empty stomach.
- Don't combine starches and proteins. (There goes your meat-and-potato dinner!)
- Don't mix starches with acidic foods.
- Don't eat different types of protein — say, plant-based or animal-based — together.
- And don't eat dairy products — especially milk — on an empty stomach.
Why You Shouldn't Try It
Despite its centuries-old history, there is no scientific evidence supporting the rules of food combining, says Kelly Hogan, RD. These rules also add more stress around eating, which can be harmful in the long run, she adds.
In fact, there's almost no research on food combining. One lone study, published 20 years ago, examined food combining's potential for weight loss, which isn't the focus of food combining proponents.
The small April 2000 study, published in the International Journal of Obesity and Related Metabolic Disorders, encompassed just 54 people. The participants were divided into two groups: One ate a normal, balanced diet, and the other followed food combining rules. Both groups consumed the same number of calories, and both groups lost weight. The researchers concluded that the food combining diet didn't aid in additional weight loss or body fat reductions.
Read more: 6 Reasons the Keto Diet Is NOT for You
As far as ridding the body of toxins, scientists and dieticians agree that your body does that naturally, through the liver, lungs, colon and kidneys. The liver and kidneys filter your blood of toxins while the lungs push out contaminants that are inhaled, per Rush University Medical Center.
The one pro of food combining? It encourages people to eat more non-starchy vegetables — broccoli, kale, beets and spinach, to name a few — which are full of fiber, vitamins and minerals. "The foods recommended on this diet are generally unprocessed whole foods, which are generally healthier than processed or packaged foods," Stoutz says. However, you don't have to subscribe to food combining to incorporate these foods into your diet.
What's the Problem With Avoiding Mixed Meals?
Mixed meals are meals that combine fat, carbohydrates and protein — in other words, a balanced meal. Food combining rules say to avoid mixed meals, but there's no evidence that it's beneficial to do that either, Stoutz says.
"It's really hard to separate foods into categories as this diet attempts to," she says. "For example, brown rice is considered a starch, but whole grains [like brown rice] also contain protein, which sort of negates the whole theory [of mixed meals]."
Digestion happens in two ways, Stoutz explains. The first is mechanical, which includes chewing, mixing and churning in the stomach, which breaks food down into smaller pieces of fat, protein and carbohydrates. Once the food is broken down, the body can't tell whether a protein molecule comes from meat, dairy or whole grains. That debunks the food combining idea that you can't combine different proteins.
Receptors in the digestive tract, especially the small intestine, release hormones based on the content of the food being digested, which tells the body what enzymes it needs for chemical digestion, the second type of digestion, Stoutz explains. At this point, the body secretes the enzymes lipase, amylase and protease — which digest fats, carbohydrates and proteins, respectively — into the small intestine. The small intestine also contains enzymes that can detect and digest specific molecules. For example, the enzyme lactase digests lactose, the sugar in dairy, when it's in the small intestine.
"It's through this complex system of specific receptors and enzymes that mixed meals are effectively digested," Stoutz says. This eating plan unnecessarily restricts the diet and there are many benefits to eating mixed meals. For example, combining protein and carbohydrates — a direct violation of food combining — can help keep blood sugar levels more stable, keeping you fuller for longer. Mixed meals are also more satiating, which can help prevent overeating.
A Healthy Diet That Promotes Digestion
If you're still thinking about food combining because you've got digestive problems that you haven't been able to solve, speak with your doctor or registered dietitian, Hogan and Stoutz recommend.
"There is no one-size-fits-all approach," Hogan says. A popular diet for people with digestive concerns that is backed by some science is the low-FODMAP diet. FODMAP stands for fermentable oligo-, di-, mono-saccharides and polyols, which are short-chain carbohydrates, that for some, may cause digestive symptoms.
Read more: What Vegetables Can I Eat With IBS?
"Keep a log to determine if certain foods cause digestive symptoms," Stoutz says. "Many people are sensitive to certain FODMAPs and can benefit from trying an elimination diet."
But, she points out, digestive issues can also be attributed to an imbalance in the gut microbiome, the diverse and vital microbial colonies that inhabit your digestive system. For example, too much bad bacteria and not enough good bacteria can cause gas and bloating, she says. Stoutz recommends increasing your intake of prebiotics — fiber-rich foods like vegetables, which fuel the good bacteria — and probiotics — fermented foods like kimchi and yogurts with live and active bacterial cultures, which can help repopulate the good bacteria and ease digestion.