Neuroendocrine Tumours (NETs) – A Spotlight on Vitamin B9 (Folate)

Before you read this
This information is designed to help you understand how vitamins work in the body and how certain NET-related factors might affect them. It is not a substitute for personalised medical advice. Every NET patient is different — tumour type, treatments, surgery, symptoms, and nutritional needs can vary widely. If you have concerns about vitamin levels, supplements, or symptoms, please speak with your NET clinical team. They can assess your individual situation and guide you safely.

🟧 SPOTLIGHT: FOLATE (Vitamin B9) – A general‑population overview with NET‑specific considerations where relevant.

Disclaimer: This Spotlight provides general educational information about Folate (Vitamin B9). It is not a substitute for medical advice. Individual needs vary, particularly for those with conditions affecting digestion or absorption. Always consult your medical team before making changes to supplements or nutrition.

What is Folate?

Folate (Vitamin B9) is a water‑soluble B‑vitamin involved in DNA synthesis, red blood cell formation, and methylation reactions. Naturally occurring folate is found in foods, while folic acid is the synthetic form used in supplements and fortified foods.

Interest point. When you research vitamins, you’ll not that B9 is more commonly referred to as ‘Folate’. This is because “folate” is one of the few vitamins whose name comes directly from its natural food source, not its chemical structure or discovery order. And historically, the name stuck earlier and more strongly than for other vitamins.

What does Folate do?

Supports DNA and RNA synthesis
Enables red blood cell production
Participates in methylation (with B12)
Supports cell division and tissue growth

Deficiency

Folate deficiency can develop quickly because body stores are limited. It is more likely with malabsorption, chronic diarrhoea, poor diet, alcohol excess, or certain medications (e.g., methotrexate, anticonvulsants).

Megaloblastic anaemia (large red cells)
Fatigue and weakness
Sore tongue or mouth ulcers
Shortness of breath

Testing

In the UK, folate is usually tested alongside Vitamin B12 because deficiencies can overlap and correcting folate alone may mask B12 deficiency. Serum folate reflects recent intake; red cell folate reflects longer‑term status.

Sources

Natural folate — leafy greens, legumes, citrus fruits, whole grains
Folic acid — supplements and fortified foods

Absorption occurs mainly in the proximal small intestine, making it sensitive to diarrhoea and mucosal disease.

Supplements

Folic acid — widely used, effective, stable
Methyl‑folate (5‑MTHF) — active form; useful in rare metabolic conditions

Supplementation is standard in pregnancy and when deficiency is confirmed.

Toxicity

Folate has a wide safety margin. High folic acid intake does not cause toxicity but may mask B12 deficiency by correcting the anaemia while neurological damage continues.

NET‑Specific Considerations

Folate deficiency is more likely in NET patients with:

Chronic diarrhoea affecting proximal small bowel absorption
Small bowel NETs or resection
Bacterial overgrowth (can disrupt folate/B12 balance)
Poor dietary intake due to symptoms or food avoidance

Folate deficiency may coexist with B12 deficiency but arises from different mechanisms. Both cause megaloblastic anaemia, but only B12 deficiency causes neurological symptoms. The ESMO 2025 NET nutrition paper (see resource 3 below) does not specifically mention Folate (B9), but the physiological mechanisms that cause B9 deficiency in NETs are well‑established and consistent with the paper’s broader micronutrient framework. Deficiency is much less common than B12 because the source of absorption is mainly proximally (jejunum) and is less “NET specific”.

References Used

Thanks for reading

See also Vitamin B12 – click here

See the fat soluble vitamin series below

Vitamin A – click here

Vitamin D – click here

Vitamin E – click here

Vitamin K – click here

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.