Food combining, or scientifically called, Trophology, is the science of correct food-combining, that is, the art of knowing which foods go best with which others. ‘Food combining’ may also mean to the combination of foods that are compatible with each other in terms of digestive chemistry. Food combining is a basic component of optimal nutrition because it allows the body to digest and utilize the nutrients in our foods to their full extent.

Most would agree that “Food combining is based on the theory that different food groups require different digestion times. Digestion is helped the most by using foods that have roughly the same digestion time.”  Thus, correct food combinations are important for proper digestion, utilization, and assimilation of the nutrients in our diet. The principles of food combining are dictated by digestive chemistry. Different foods require different digestive enzymes to aid in the digestive process – some acid, some alkaline.

Below is a list of foods and their digestion time.


  • Water when the stomach is empty leaves immediately and goes into intestines,
  • Juices
    • Fruit vegetables, vegetable broth – 15 to 20 minutes.
  • Semi-liquid
    • (blended salad, vegetables or fruits) – 20 to 30 min.
  • Fruits
    • Watermelon – 20 min. digestion time.
      Other melons – Cantaloupes, Cranshaw, Honeydew etc. – 30 min.
      Oranges, grapefruit, grapes – 30 min.
      Apples, pears, peaches, cherries etc. – digest in 40 min.
  • Vegetables
    • Raw tossed salad vegetables – tomato, lettuces, cucumber, celery, red or green pepper, and other succulent vegetables – 30 to 40 min. digestion. –
  • Steamed or cooked vegetables
    • Leafy vegetables – escarole, spinach, kale, collards etc. – 40 min. – Zucchini, broccoli, cauliflower, string beans, yellow squash, and corn on cob – all 45-min. digestion time
      Root vegetables – carrots, beets, parsnips, and turnips etc. – 50 min.
  • Semi-Concentrated Carbohydrates – Starches
    • Jerusalem artichokes & leafy, acorn & butternut squashes, corn, potatoes, sweet potatoes, yam, chestnuts – all 60-min. digestion.
  • Concentrated Carbohydrates – Grains
    • Brown rice, millet, buckwheat, cornmeal, oats (first 3 vegetables best) – 90 min.
  • Legumes & Beans – (Concentrated Carbohydrate & Protein)
    • Lentils, limas, chick peas, peas, pigeon peas, kidney beans, etc. – 90 min. digestion time
      soy beans -120 min. digestion time
  • Seeds & Nuts
    • Seeds – Sunflower, pumpkin, pepita, sesame – Digestive time approx. 2 hours.
      Nuts – Almonds, filberts, peanuts (raw), cashews, brazil, walnuts, pecans etc. – 2 1/2 to 3 hours to digest.
  • Dairy
    • Skim milk, cottage or low-fat pot cheese or ricotta – approx. 90 min. digestion time
      whole milk cottage cheese – 120 min. digestion
      whole milk hard cheese – 4 to 5 hours digestion time
  • Animal proteins
    • Egg yolk – 30 min. digestion time
      Whole egg – 45 min.
      Fish – cod, scrod, flounder, sole seafood – 30 min. digestion time
      Fish – salmon, salmon trout, herring, (more fatty fish) – 45 min. to 60 digestion time
      Chicken – 1½ to 2 hours digestion time (without skin)
      Turkey – 2 to 2 ¼ hours digestion time (without skin)
      Beef, lamb – 3 to 4 hours digestion time
      Pork – 4½ to 5 hours digestion time


Dr. Hay and Food Combining

“Any carbohydrate foods require alkaline conditions for their complete digestion, so must not be combined with acids of any kind, as sour fruits, because the acid will neutralize. Neither should these be combined with a protein of concentrated sort as these protein foods will excite too much hydrochloric acid during their stomach digestion.” – Dr. Hay, How to Always Be Well

According to common story, when William Howard Hay (1866–1940) graduated from New York University Medical College in 1891, he practiced medicine and specialized in surgery. That changed 16 years later when his own medical troubles led him to research the connection between diet and health. Hay then weighed 225 pounds (102 kilograms) and had high blood pressure and Bright’s disease, a kidney condition. Hay discovered that his heart was dilated while running to catch a train.

The dilated heart caused by weakened heart muscles meant that his blood could not pump efficiently. Hay knew from treating patients that his future did not “look overlong or very bright,” according to his 1929 book Health via Food. The title described Hay’s health theories, his condition, and treatment.

Hay diagnosed the causes of his conditions as the “very familiar trinity of troubles” that then ranked as the primary cause of death: the combination of high blood pressure, kidney disease, and dilated heart. But he could not accept the fact that his legs, which have swollen that time might be chopped off. So, he looked for other reasons and so Hay looked at his eating habits.

Thus, he went into research and it was said that, Hay’s research led to a diet based on the theory that health was affected by the chemical process of digestion. The body uses an alkaline digestive process for carbohydrates, the group that Hay classified as consisting of starchy foods and sweet things. The digestion of proteins involved acid. If carbohydrates and proteins were consumed at the same time, the alkaline process was interrupted by the acid process. Combining incompatible foods caused acidosis, the accumulation of excess acid in body fluids. Hay linked the combination of foods to medical conditions like Bright’s disease and diabetes. The wrong combinations “drained vitality” and caused people to gain weight.

Hay maintained that the solution was to eat proteins at one meal and carbohydrates at another. He classified fruits with acids. Hay labelled vegetables in the neutral category that could be consumed with either group. He also advocated the daily administration of an enema to cleanse the colon.

This was the starting point for the interest in the field by other doctors who would later have a classification of the food system.

Dr. Herbert Shelton in his book” Combining Food Made Easy”, gave some easy and simple combinations so as not to confuse a beginner or someone interested in the diet.

The  Basic Rules of Proper Food Combining:

  • Eat acids and starchy foods at separate meals. Acids neutralize the alkaline medium required for starch digestion and the result is fermentation and indigestion. 
  • Eat food containing protein and carbohydrate at separate meals. Protein foods require an acid medium for digestion.
  • Eat only one kind of protein food at a meal.
  • Proteins and acid foods must be eaten at separate meals. The acids of acid foods inhibit the secretion of the digestive acids required for protein digestion. Undigested protein putrefies in bacterial decomposition and produces some potent poisons.
  • Fatty foods and proteins should be eaten at separate meals. Some foods, especially nuts, are over 50% fat and require hours for digestion.
  • Fruits contain natural sugar and proteins should be eaten at separate meals.
  • Eat sugars (fruits) and starchy foods at separate meals. Fruits undergo no digestion in the stomach and are held up if eaten with foods that require digestion in the stomach. 
  • Eat melons alone. They do not combine with any other type of food.
  • Desserts should be eaten separately without combining them with any other type of food. Eaten on top of meals they lie heavy on the stomach, requiring no digestion there, and ferment. Bacteria turn them into alcohols, vinegar, and acetic acids.


Check Out Secrets of Food Combinations # 2 -click here



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