A blog by Ronny Allan

Neuroendocrine Tumours – A Spotlight on Vitamin A (Retinol)

Neuroendocrine Tumours – A Spotlight on Vitamin A (Retinol)
Disclaimer: This Spotlight provides general educational information about Vitamin A. It is not a substitute for medical advice. Individual needs vary, particularly for those with conditions affecting digestion, absorption, or liver function. Always consult your medical team before making changes to supplements or nutrition.

🟧A general‑population overview with NET‑specific considerations where relevant.

What is Vitamin A?

Vitamin A refers to a group of fat‑soluble retinoids (retinol, retinal, retinoic acid). These are the active forms used by the body. Plant pigments such as beta‑carotene are pro‑vitamin A carotenoids that must be converted into retinol before use.

What does Vitamin A do?

  • Supports vision, especially low‑light vision
  • Maintains epithelial and mucosal surfaces
  • Supports immune function
  • Regulates gene expression and cell differentiation
  • Assists with iron mobilisation

Deficiency

Vitamin A deficiency is uncommon in high‑income countries but can occur with malabsorption, pancreatic insufficiency, bile acid loss, liver disease, or very low intake.

  • Night blindness
  • Dry eyes and dry skin
  • Increased susceptibility to infections
  • Conjunctival or corneal changes in severe deficiency

Testing

The standard test is serum retinol. It is reliable for moderate–severe deficiency but less sensitive for early depletion. Levels may be influenced by inflammation and liver function.

Sources

  • Preformed Vitamin A (retinol) — liver, dairy, eggs, oily fish, fortified foods
  • Pro‑vitamin A carotenoids — carrots, sweet potatoes, leafy greens, peppers, mango, papaya, apricots

Carotenoid conversion varies widely and is reduced in malabsorption, pancreatic insufficiency, and low‑fat diets.

Carotenoids

Carotenoids are plant pigments that can be converted into retinol. They are safe and contribute to overall Vitamin A intake, but:

  • They are not active Vitamin A
  • Conversion is variable and often reduced in malabsorption
  • They cannot reliably correct deficiency
  • They do not cause toxicity

Supplements

  • Retinol/retinyl esters — effective for correcting deficiency; risk of toxicity at high doses
  • Carotenoids — safer but less reliable in malabsorption

Toxicity

Only retinol causes toxicity. Carotenoids do not.

  • Acute toxicity: neurological symptoms
  • Chronic toxicity: liver injury, bone effects, skin changes, teratogenicity

NET‑Specific Considerations

Vitamin A deficiency is more likely in NET patients with:

  • Pancreatic NETs with exocrine insufficiency
  • Ileal NETs or ileal resection → bile acid loss
  • Chronic diarrhoea or steatorrhoea
  • Somatostatin analogue therapy
  • Liver metastases affecting storage

Deficiency often co‑exists with low Vitamins D, E, and K.

NET‑Specific Evidence: The NET‑related mechanisms described in this Spotlight (pancreatic insufficiency, bile acid loss, somatostatin analogue effects, steatorrhoea, and liver involvement) are supported by the 2025 ESMO review on nutritional and micronutrient considerations in neuroendocrine neoplasms.  ESMO’s observations show that patients with NETs frequently have fat-soluble vitamins (ADEK) deficiencies and deficiencies of vitamin B3 and B12 that can be successfully supplemented. As long-term deficiencies in fat-soluble vitamins and vitamins B12 and B3 can cause severe symptoms, repetitive evaluation of the status of vitamins A, D, E, K, B3, and B12 and supplementation of deficiencies is recommended in patients with NETs.  Citation  at Reference 3 below.

 

Personal note

Always speak to your specialist before taking vitamin and mineral supplements — you may not need them if your levels are normal.  Many NET patients assume Vitamin and Mineral deficiencies are inevitable, but with proper monitoring and management (including PERT where appropriate), levels can remain stable. A warning on taking vitamins and minerals generally.  I very often see patients discussing this on my public pages and in my private group.  I just wanted to say that you must always take advice from a professional, just because one patient takes a vitamin ‘x’ or mineral ‘y’, that does not mean you should take it too. 


References Used

  1. NHS Vitamin A Guidance
  2. NIH Office of Dietary Supplements – Vitamin A Fact Sheet
  3. ESMO – Reducing deficiencies of fat-soluble vitamins, vitamin B12, and vitamin B3 in patients with neuroendocrine tumors treated with somatostatin analogues – L.D. de Hosson, S. Bunskoek, J. Stelwagen, B. Sijtema, S. Huitema, M. van Faassen, G.H. de Bock, D.J.A. de Groot, M.J.E. Campmans-Kuijpers, I.P. Kema, E.G.E. de Vries, A.M.E. Walenkamp, Volume 4, 2025, 100032, ISSN 3050-4619, https://doi.org/10.1016/j.esmorc.2025.100032. (https://www.sciencedirect.com/science/article/pii/S3050461925000310)


See other fat soluble vitamins here:

Vitamin D – click here
Vitamin E – click  here
Vitamin K – click here

 

Thanks for reading.


Ronny



Disclaimer

I am not a doctor or any form of medical professional, practitioner or counsellor. None of the information on my website, or linked to my website(s), or conveyed by me on any social media or presentation, should be interpreted as medical advice given or advised by me. Neither should any post or comment made by a follower or member of my private group be assumed to be medical advice, even if that person is a healthcare professional. Please also note that mention of a clinical service, trial/study or therapy does not constitute an endorsement of that service, trial/study or therapy by Ronny Allan, the information is provided for education and awareness purposes and/or related to Ronny Allan’s own patient experience. This element of the disclaimer includes any complementary medicine, non-prescription over the counter drugs and supplements such as vitamins and minerals.

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CategoriesA Spotlight on Vitamins & Minerals Diet and Nutrition Patient Advocacy
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By Ronny Allan

Ronny Allan is a 3 x award-winning accredited patient leader advocating internationally for Neuroendocrine Cancer and all other cancer patients generally. Check out his Social Media accounts including Facebook, BlueSky, WhatsApp, Instagram and and X.

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