Hello, Jorge (or your bot).
That these vitamins increase the risk of cancer complications is not a reason to avoid supplementation, but to be more cautious with them.
One suggestion was to offer B-vitamins in separate products, something like:
Mitochondrial function and toxicity: role of the B vitamin family on mitochondrial energy metabolism
Mitochondrial function and toxicity: role of B vitamins on the one-carbon transfer pathways
But it's challenging to have a clear separation of vitamins because of interrelationships. Pyridoxin was excluded from their 'energy metabolism' group, but it's directly involved in glycogen use and the transaminases to prepare amino acids for oxidation. Biotin was included, but associated with anabolic functions, and one of the catabolic pathways would be dependent on the vilified (adenosyl)cobalamin. If all came down to an energy problem, the nucleotides of the energy-releasing coenzymes involve folate in their syntheses.
Cancer Cells Tune the Signaling Pathways to Empower de Novo Synthesis of Nucleotides
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Growth-promoting substances don't just fuel cancer, they're also needed for cell and tissue regeneration.
Supplementation is discouraged for folate, cobalamin, and choline (or betaine). We know that the message is reaching a community that doesn't consume a lot of leaves (foliage→folate), nor legumes. The availability of folate in oranges is arguably lower than expected.
Properties of Food Folates Determined by Stability and Susceptibility to Intestinal Pteroylpolyglutamate Hydrolase Action
Tipping the reliance in favor of folate-cobalamin over choline might yield extra glycine, that can be formed for every folate cycled. The simultaneous restriction of these vitamins, along with a predisposition to their insufficiency, malabsorption syndromes, and the adoption of a diet low in methionine doesn't seem promising.
Do we have indications that the population is adequate in the anabolic vitamins and can afford a restriction? Because the typical consumption and positive reactions to supplementation suggest otherwise.
Not only a deficiency of any vitamin tends to predispose to cancer, but cancer is not the only disease to worry about. Cardiovascular problems and infections are major threats.
Digestion weakens in advanced age and disease, making it helpful to have available these vitamins in purified form. The issue here is that you're leaving for other vendors to do the dirty job of guaranteeing adequacy in a considerable number of people that would benefit from the carcinogenic nutrients.