The Food Combining Diet

We previously had an article by the title: Table of Compatible Foods. We found that the information regarding this diet was lacking in scientific evidence. Please find below more information on this diet and why it is not effective.

What is the Food Combining Diet?

The Food Combining diet stems from the 20th century from a doctor by the name of Dr. William Howard Hay, therefore this diet is sometimes known as the Hay Diet. The idea behind the Food Combining Diet is that certain foods, as well as combinations of foods cause an unfavourable acid-alkaline balance within the body which increases the risk for disease and weight gain. The rules behind it are as follows:

  1. Carbohydrates cannot be eaten at the same time as proteins or acid-based fruits.
  2. Salad, fruits, and vegetables should be the main component of the diet.
  3. Proteins, starches, and fats should be eaten in a smaller quantity.
  4. Avoid refined or processed foods.
  5. There should be four to four-and-half hours between meals which are made out of different types of foods. (1)

Dr. Hay created a chart to simplify what could and could not be eaten together (2).

Balanced Diet Chart

Advocates for this diet claim it is essential that these foods are combined in this manner because acid forming (meat, starches, and dairy) and alkaline forming (majority of fruits and vegetables) foods “don’t utilize the same digestive juices in the same fashion during digestion. Acidic and alkaline compounds have the ability to essentially neutralize each other. When this happens, digestion can be significantly delayed, which can be detrimental to your health” (3). 

Does it Work?

Although there are claims that it is an effective tool and even Dr. Hay based this diet on what he used to lose weight and recover from kidney problems, there seems to be a lack of scientific evidence in general on the topic. The studies done appear to be inconclusive on its effectiveness. For example, one study done looked at weight loss when individuals were on a food combining diet versus a balanced diet. Both groups were given a diet of 1100 kcal/day. The group on the food combining diet were given 25% protein, 47% carbohydrates and 25% fats and the people on the balanced diet were given 25% protein, 42% carbohydrates and 31% fats. The results showed that there was no difference in weight loss between the two groups (4).

Just because this diet does not have a lot of scientific research articles backing it up, doesn’t mean that it doesn’t work. However, from a physiological perspective, the information that this diet is based on is false. The body is incredibly proficient and is able to digest and extract nutrients from different groups of foods (macronutrients) at the same time. What happens when food is eaten is as follows. Let’s say that you eat a peanut butter sandwhich. The sandwich is mechanically broken down in the mouth through chewing. Carbohydrates begin to get digested by your salivary glands. As the food is swallowed, it travels down the esophagus and enters the stomach. In the stomach, gastric juices are released which halts the digestion of carbohydrates. The gastric juices activate enzymes to break down protein. Fat from the peanut butter for a separate layer on top the watery mixture. Something to consider is that all foods contain some varying combination of carbohydrates, proteins, and fats, so it does not matter if you eat different food groups together. Peanut butter, for example, contains carbohydrates, fats, and protein. As the peanut butter sandwich slowly enters the small intestine, the pancreas releases its own digestive enzymes along with bicarbonate which neutralizes the acid. The pancreas actually requires that the pH drop in the stomach to be able to release those enzymes. The majority of digestion and absorption of nutrients then occurs in the small intestine (5).

The reality of the matter is that it can actually be beneficial to combine macronutrients together in a meal. Combining protein with starch in a meal slows down digestion and helps you feel satisfied for longer – something that can help, not hinder, weight loss efforts. Doing so also slows down the release of sugar (glucose) into the bloodstream, stabilizing blood glucose levels for longer lasting energy. This is important for someone with diabetes who needs to maintain blood glucose levels (6).

Another issue to consider with the Food Combining Diet is that certain nutrients are absorbed better when they are combined with fats. There are a group of vitamins (Vitamin A, D, E, and K) which  by nature mix with fat and are absorbed that way. So by not combining foods together, you are not absorbing as much of those nutrients (6).

So why might someone claim that they lose weight and feel better when on this diet? One explanation could be that if you only eat one food group at a time, it won’t taste as good, and you therefore eat less of it. Imagine only being able to eat a baked potato – no butter, no sour cream – just a potato. In all likelihood, you would eat less of it which would help you lose weight.


This diet has many good components to it, such as increasing fruit and vegetables and decreasing processed and refined foods. Increased fruit and vegetable consumption benefits bone health, reduces muscle wasting, reduces risk for many chronic diseases, aids in vision, memory, and cognition. (7). Decreasing processed meats lowers the risk for heart disease and diabetes (8) and decreasing milled and refined grains decreases risk of weight gain, diabetes, and heart disease (9).

However, it is not necessary to avoid combining foods. One can get countless number of health benefits if one just increases fruit and vegetable intake, eats more whole grains, decreases portion size, and eats whole foods in general.


  1. Acid Alkaline Diet (2010). The Hay Diet: Food Combining For Health.

  1. Hay, W. H. (1967). How to always be well. Groton Press.
  2. Acid Alkaline Diet (2010). Food Combination Benefits.
  3. Golay, A., Allaz, A. F., Ybarra, J. Bianchi, P., Saraiva, S., Mensi, N… de Tonnac, N. (2000). Similar weight loss with low-energy food combining or balanced diets. Internaltional Journal of Obesity, 24:4, 492-496.
  4. Whitney, Rolfes, Hammond, Piche (2013). Understanding Nutrition: First Canadian Edition. Toronto, ON: Nelson.
  5. Marksteiner, K., Schoenfeld, L. (Speaker) (2013, November 4). Ask the RD.: All About Food Combining [Audio podcast].
  6. Schwalfenberg, G. K. (2012). The Alkaline Diet: Is There Evidence That an Alkaline pH Diet Benefits Health? Journal of Environmental Public Health. doi:  10.1155/2012/727630
  7. Bernstein AM, Sun Q, Hu FB, Stampfer MJ, Manson JE, Willett WC. Major dietary protein sources and risk of coronary heart disease in women. Circulation, 2010:122, 876-83.
  8. Abete I, Astrup A, Martinez JA, Thorsdottir I, Zulet MA. Obesity and the metabolic syndrome: role of different dietary macronutrient distribution patterns and specific nutritional components on weight loss and maintenance. Nutrition Reviews, 2010:68, 214-31.