NETs represent a group of rare cancers with heterogeneous clinical behavior. In Italy they account for less than 0.5% of all malignant tumors with about 3-4 new cases per 100,000 people in a year. In recent decades, their incidence increased, mainly due to better knowledge of these pathologies and improved diagnostic techniques. Although NETs can be found in all areas of the body (cute, thyroid, lungs, parathyroid and adrenals glands), the most frequent are located at the level of the gastroenteropancreatic area (70%). In this issue, we will refer only to the cancers of the gastroenteric area and in particular to those of the small intestine (jejunum, ileum), because they can cause a syndrome, that is, a set of symptoms, which may require in addition to an effective pharmacological therapy for their treatment an especially designed nutritional support. Let’s get to know them better:

The gastroenteropancreatic neuroendocrine neoplasms fall into two main types:

Well differentiated forms have a slow growth and although non-operable can be cured and made chronic with new and effective therapies (usually molecular targeted therapies and almost never chemotherapy).

Poorly differentiated forms that, as the terminology itself indicates, have a faster growth and an earlier tendency to spread to remote locations. This group of cancers can be cured by new therapeutic regimens, which are mainly chemotherapeutic. However, we must emphasize that the aggressive forms of the jejunum-ileal segment are indeed a rarity.

The prognosis of these pathologies will therefore depend on how spread the disease is (its stage) and on the degree of cellular differentiation. Early-stage NETs have a very favorable prognosis with high recovery rates.

With regard to clinical characteristics, NETs are divided into:

Functional, which cause a syndrome (set of symptoms) known as carcinoid syndrome, characterized mainly by two symptoms: diarrhea, sometimes watery, and flushing accompanied by redness in the face and trunk, and lacrimation. These and other peculiar symptoms can be attributed to the increased production and secretion of biologically active substances: serotonin (also responsible for diarrhea), histamine (also responsible for the episodes of flushing) and insulin (responsible for a symptomatology characteristic of certain pancreatic cancers, called insulinomas).

Non-functional (about 70% of the total), which do not produce active substances and whose symptoms are attributable only to the mass effect.

The description made above is just a simplified explanation of the clinical characteristics of neuroendocrine cancers, but it represents an easily accessible description for users, and allows us to suggest useful foods for managing the one side effect most expressed by the same cancers and considered, in extreme cases, also disabling diarrhea.

In addition to useful dietary advice, users will find in the table described under the heading “Nutrition of secreting neuroendocrine tumors patients”, foods to avoid before dosing the urinary 5-hydroxyindoleacetic acid, useful and often required by oncologists in order to confirm the diagnosis of carcinoid syndrome.


Serotonin (5-HT) is a neurotransmitter that is synthesized in the brain and central nervous system in the presence of tryptophan (essential amino acid), a substance that cannot be produced by the body, but must be taken in through food. Serotonin, also known as the “happiness hormone,” deals primarily with mood regulation.

The recommended dose of tryptophan for an adult is between 250-425 mg per day, corresponding to about 3.5-6 mg per kg of body weight. These values are easily attainable by having a varied and balanced diet. Through nutrition and consequently, tryptophan intake it is possible to increase or decrease serotonin levels in the brain.

Some foods stimulate the production of serotonin: foods rich in vitamin B, protein foods (eggs, fresh cheeses, white meats, legumes, soy, dried fruit), some vegetables (especially green leafy vegetables, potatoes, mushrooms, bananas, pineapples, spirulina seaweed), whole grains and dark chocolate. Said foods have a high content of tryptophan or at least facilitate its absorption.

After a protein-rich and consequently, tryptophan-rich meal, the blood concentration of this amino acid increases without affecting considerably brain levels of serotonin. This happens because also the blood concentration of other amino acids increases, and that hinders and slows down the passage of tryptophan to the brain.

Most tryptophan-containing foods are of protein origin, but protein foods are not the only ones to increase tryptophan levels.

A carbohydrate-rich meal stimulates insulin secretion, making it easier for nutrients including amino acids, but tryptophan to get into the cells. As a result, tryptophan levels in the blood increase (because those of other amino acids decrease) favoring their passage into the central nervous system and thus increasing the production of serotonin.

As already described in the article about neuroendocrine tumors, some tumors with a low degree of malignancy of the gastrointestinal area give rise to a carcinoid syndrome. Said syndrome is characterized mainly by diarrhea and flushing and is caused by the hypersecretion of serotonin and histamine.

In patients with carcinoid syndrome it is important to adequately calibrate the level of protein and carbohydrates not only during the day, but also within a meal. Therefore, we suggest you some tips in order not to increase the levels of serotonin:

  • Avoid taking high amounts of simple sugars along with a protein-rich meal containing high amounts of tryptophan;
  • Consume protein sources, excluding those richer in tryptophan, together with small amounts of complex carbohydrates.


The biochemical examination that is carried out to confirm the presence of carcinoid syndrome is the dosage of 5-hydroxyindolacetic acid (5-HIAA) in the urines produced over 24 hours. 5-HIAA is a metabolite of serotonin, a hormone produced primarily by the central nervous system but also, in small amounts, by the lungs and intestine. After having exhausted its function, serotonin is transformed into 5-HIAA which is expelled through urine. 5-HIAA levels in urines are higher in patients with carcinoid syndrome than in healthy individuals. Before the dosage of 5-HIAA it is therefore important to cure the diet, avoiding taking (starting 3 days before urine collection) the foods shown in the table, which could interfere with the result of the examination. Contact your oncologist because even taking certain medications can interfere with the results of the exam.



ESSENTIAL AMINO ACIDS: these amino acids are substances that the body is not able to produce in sufficient amount, so it is necessary to introduce them with nutrition.

INSULIN: hormone produced by the pancreas; its main function is to regulate blood glucose levels by reducing it.

METABOLITE: a substance that is part of a chemical process called metabolism.

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