Fruit

Fruit is the basic energy-efficient food, evolved specifically to support animal life and disseminate seeds, making it fundamentally compatible with human physiology. 2 Peat argued that plants concentrate serious toxins in their bark, leaves, and roots, but create substances in the fruit that promote animal life, ensuring the animal lives long enough to spread the seeds. 3 This evolutionary design positions ripe fruit, particularly from the tropics, as an ideal calorie source that provides a clean flow of energy from the sun to the brain, minimizing the side effects and disease associated with other foods. 2

The fructose component of fruit is central to its metabolic advantages. Unlike pure glucose from starches, fructose does not require insulin for its metabolism and helps the liver produce more cholesterol, which, when thyroid function is adequate, serves as a precursor for protective hormones like pregnenolone and progesterone. 2 Peat noted that the combination of sugars in fruit results in a much lower glycemic index and glycemic load compared to starchy foods, which are 100% glucose and trigger a high insulin spike. 10 Furthermore, fruit comes with many minerals that work in place of insulin and have a slightly suppressive effect on it, aiding in blood sugar stabilization. 5 Dinkov has added that even among fruits, one should be mindful of preformed serotonin and tryptophan; he notes that very ripe pineapple and bananas are high in serotonin, and tryptophan is the only amino acid that is directly carcinogenic. 4

Tropical fruits are singled out as the ideal calorie source because they are likely to be reasonably low in iron, high in vitamins and minerals, and contain only small amounts of thyroid-inhibiting substances. 1 Peat emphasized that fruits are a major source of magnesium without overloading the body on iron, and that seeds, in contrast, contain the worst plant poisons, which are metabolic and enzyme inhibitors. 1 Well-strained, sweet orange juice is considered the safest fruit option, as indigestible fibers, including the chemically altered pulp in commercial juices, should be avoided. 8 Other beneficial tropical fruits include papayas, the custard apple family, and mangoes, though poorly ripened fruits of all sorts, as well as common allergens like bananas and jack-fruit, should be avoided. 2

A pure all-fruit diet over the long run presents a specific challenge because most fruits are very low in iron, though Peat suggested that a fairly low iron intake is tolerable if other metabolic factors are optimal. 7 He also cautioned that in the U.S., a fruit diet might default to large quantities of bananas and dates, which are high in serotonin and can create inflammatory problems. 7 The fruit's fiber and sugars stimulate the intestine, accelerating movement and keeping bacteria harmless, and Peat considered the flavonoids in fruit to be very beneficial, though not technically essential. 2 When fruit is unavailable, he recommended simply adding a little sugar to milk with coffee as a practical substitute. 9