NETs represent a group of rare cancers with heterogeneous clinical behaviour. 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 has increased, mainly due to better knowledge of these pathologies and improved diagnostic techniques. Although NETs can be found in all areas of the body (skin, thyroid, lungs, parathyroid and adrenals glands), the most frequent are located at the level of the gastroenteropancreatic area (70%). Here, we will refer only to the cancers of the gastroenteric area and in particular to those of the small intestine (jejunum, ileum). These cancers can cause a syndrome (a set of symptoms), which may require, in addition to an effective pharmacological therapy for their treatment, a specifically designed nutritional support. Let’s have a closer look at them.

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 – almost never chemotherapy).


Poorly differentiated forms which, 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 drugs, 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 the disease spreads, what stage it is at, and on the degree of cellular differentiation. Early-stage NETs have a very favourable 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, flushes accompanied by redness in the face and body 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 mass effect.


The above description is a simplified explanation of the clinical characteristics of neuroendocrine cancers. It gives an easily accessible description for users, and allows us to suggest useful foods for managing the side effects most expressed by the same cancers. Diarrhea is considered one of the most disabling side effects.

In addition to useful dietary advice, users will find in the table under the heading “Nutrition of secreting neuroendocrine tumors patients”, food to avoid before dosing the urinary 5-hydroxyindoleacetic acid which is 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 obtained 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. Tryptophan intake can 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. These foods have a high content of tryptophan or at least facilitate its absorption.

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

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

A carbohydrate-rich meal stimulates insulin secretion, making it easier for nutrients including amino acids, and tryptophan to get into the cells. As a result, tryptophan levels in the blood increase (because those of other amino acids decrease) favouring 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. The 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 give 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 finished 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 pay attention to one’s diet. 3 days before the urine test, the foods shown in the table should be avoided, as they could interfere with the results of the test. Contact your oncologist as certain medications can interfere with the results of the exam too.



ESSENTIAL AMINO ACIDS: these amino acids are substances that the body is not able to produce in sufficient amounts, so it is necessary to introduce them through food intake.

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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