An acid process (gastric digestion) and an alkaline process (salivary digestion) can not be carried on at the same time in an ideal way in the stomach. Before long, they cannot proceed at all , as the rising acidity of the stomach soon completely stops carbohydrate digestion. The highest efficiency in digestion demands that we eat in such a way as to offer the least hindrance to the work of digestion.
2. Do not eat a concentrated protein and a concentrated carbohydrate at the same meal. This means do not eat nuts, meat, eggs, cheese, or other protein foods at the same meal with bread, cereals, potatoes, sweet fruits. Cakes, etc. Candy and sugar greatly inhibit the secretion of gastric juice and markedly delay digestion and if consumed in large quantities can depress the stomach activity.
3. Do not eat two concentrated proteins at the same meal. Avoid nuts and meat, or eggs and meat, cheese and nuts, cheese and eggs, meat and milk, or eggs and milk or nuts at milk at the same meal. Milk, if taken at all, is best taken alone. The reason for avoiding eating these combinations is because each protein requires a specific character and strength of digestive juice to be secreted. Eggs require different timing in stomach secretions than do either meat or milk.
4. Do not eat fats with proteins. This means do not use cream, butter, oil, etc with meat, eggs, cheese, nuts, etc. Fat depresses the action of the gastric glands by delaying the development of appetite juices and inhibiting the pouring out of the proper gastric juices for meats, nuts, eggs or other protein. Fats may lower the entire gastric tone more than fifty per cent.
5. Do not eat acid fruits with proteins. This is to say, oranges, tomatoes, lemons, pineapples, etc., should not be eaten with meat, eggs, cheese or nuts. Acid fruits seriously hamper protein digestion and results in putrefaction. Milk and orange juice, while by no means an indigestible combination, is far from a good combination. Orange juice and eggs form an even worse combination.
6. Do not consume starch and sugars together. Jellies, jams, fruit, butter, sugar, honey, syrups, molasses, etc., on bread, cake, or at the same meal with cereals, potatoes, etc., or sugar with cereal, will produce fermentation. The practice of eating starches that have been disguised by sweets is also a bad way to eat carbohydrates. If sugar is taken into the mouth it quickly fills with saliva but no ptyalin is present which we know is essential for starch digestion.
7. Eat but one concentrated starch food at a meal. This rule is more important as a means of overeating than as a means of avoiding a bad combination. While overeating of starches may lead to fermentation, there is no certainty that the combination of two starches will do so.
8. Do not consume melons with any other foods. Watermelon, muskmelon, honeydew melon, cantaloupe and other melons should always be eaten alone. This is possibly due to the ease and speed in which melons decompose.
9. Milk is best taken alone or let alone. Milk is the natural food of the mammalian young, each species producing milk peculiarly and precisely adapted to the needs of its young. It is the rule that the young take the milk alone, not in combination with other foods. Milk does not digest in the stomach, but in the duodenum, hence in the presence of milk the stomach does not respond with its secretion. The use of acid fruits with milk does not cause any trouble and apparently does not conflict with its digestion.