Tomatoes are off-limits in Dr Gundry’s Plant Paradox protocol because of the lectins they contain. Removing the skins and the seeds, or, buying tinned tomatoes that have had the skins and seeds removed, is unlikely to make them lectin free as the lectins are in the juice.

In a 1980 study, published in the Biochemical Journal, it was found that “in the tomato (Lycopersicon esculentum) plant, the juice from ripe fruit was found to be the richest source of (lectin) specific agglutinating activity”.

Selected portions of ripe tomatoes were homogenised (blended) and centrifuged at room temperature (22 degrees C) to remove any seeds or contaminating debris. The clear juice obtained from each portion was chemically washed and purified and tested for agglutinating (lectin) activity towards untreated or trypsin-treated human erythrocytes. Agglutinating activity was generally about four times greater with trypsin-treated cells, which were subsequently used as a routine. As Table 1 shows, agglutinating activity was found in all the extracts tested, but by far the highest specific activity was found in the juice of ripe fruits. (1)

Table 1.

Tissue homogenate

Specific activity (units/mg of protein)

Dried seed


Seed from ripe fruits






Fruit skin


Fruit juice



This was corroborated in a more recent independent study by Merkle et. al. who noted that “all of the hemagglutinating activity (in the ripe fruit of the Tomato Lycopersicon esculentum Mill. was found in the fluid and placental tissues of the locules”. (2)

  1. “Purification and some properties of a lectin from the fruit juice of the tomato (Lycopersicon esculentum)”, D C Kilpatrick.
  2. “Tomato lectin is located predominantly in the locular fluid of ripe tomatoes”, Roberta K.Merkle et. al.