Nutritional Insurance

Nutritional insurance is the rationale most people give for taking a multivitamin: not treating a condition, but covering the possibility of a shortfall. Whether that is sensible depends entirely on the probability of a gap. For people eating a varied diet, that probability is low and the trial evidence reflects it. The Physicians' Health Study II found no reduction in cardiovascular events over more than a decade, and the US Preventive Services Task Force has repeatedly concluded that the evidence is insufficient to recommend multivitamins for preventing cardiovascular disease or cancer in generally healthy adults. The COSMOS cognitive substudies are the one recent finding pointing the other way, reporting modest memory benefits in older adults — promising but not yet settled. For people with a real likelihood of shortfall, the calculus changes completely. Vegans need B12, without exception. Pregnancy needs folic acid started before conception. Older adults absorb B12 poorly and often have low vitamin D. Bariatric surgery, coeliac disease and Crohn's disease all cause malabsorption. Metformin depletes B12; proton pump inhibitors reduce B12, magnesium and iron absorption. The more precise approach is to test where you suspect a gap and treat the specific shortfall, since a broad multivitamin often provides too little of what you actually need and unnecessary amounts of everything else.

Begin with food: a varied diet built on vegetables, fruit, legumes, whole grains, adequate protein and oily fish covers most requirements, and no supplement reproduces the fibre, polyphenols and food matrix that carry much of the benefit. Then identify your actual risk of shortfall. If you follow a vegan diet, B12 is non-negotiable and vitamin D, iodine, iron, zinc and algal omega-3 all deserve attention. If pregnant or planning pregnancy, take a prenatal formula with 400-800 mcg folic acid starting at least a month before conception. If over 65, prioritise B12 and vitamin D. If you have had bariatric surgery or have coeliac or Crohn's disease, follow a specialist protocol with monitoring. If you take metformin, check B12 periodically. Where a specific deficiency is confirmed, treat it with a targeted supplement at a corrective dose rather than relying on a multivitamin, which usually contains too little to fix a real deficit. If you do choose a multivitamin, pick one near 100% RDA, iron-free unless iron is needed, third-party tested, and avoid high-dose beta-carotene if you smoke or used to. Retest at three months.

• •Build the diet first — variety covers most requirements
• •Include oily fish twice weekly, or algal omega-3 if you avoid fish
• •Get sensible sun exposure and supplement vitamin D in winter months
• •Take B12 without exception on a vegan diet
• •Start folic acid before conception, not after
• •Check B12 periodically on long-term metformin
• •Add up totals across products to avoid exceeding upper intake levels
• •Take fat-soluble vitamins with a meal containing fat