Nutrition at 55: Metformin, B12 and Grip Strength

Fifty-five is the age at which most people are taking at least one long-term medicine, and several of the common ones affect nutrition directly. Metformin, the most prescribed diabetes drug in India, impairs vitamin B12 absorption, and long-term users show a substantially higher rate of deficiency — a problem whose symptoms are easily mistaken for diabetic neuropathy.

The metformin and B12 problem

Metformin is the first-line treatment for type 2 diabetes and among the most widely prescribed medicines in India. It interferes with calcium-dependent B12 absorption in the terminal ileum, and studies of long-term users report deficiency at substantially higher rates than in non-users, with risk increasing with dose and duration.

The clinical trap is specific and worth understanding. B12 deficiency causes peripheral neuropathy — tingling, numbness and burning in the hands and feet. So does diabetes. A patient on metformin for eight years who develops tingling feet is very likely to have it attributed to diabetic neuropathy, and if the cause is actually B12 deficiency, that is a treatable condition being left untreated.

Indian vegetarians carry additional baseline risk, since B12 occurs almost exclusively in animal foods. A lifelong vegetarian on long-term metformin has two independent reasons to be deficient.

The resolution is an annual B12 test for anyone on long-term metformin. It is inexpensive, and correction is straightforward.

Other medicines worth knowing about

The levothyroxine interaction is the one that causes most avoidable trouble day to day. Taking a thyroid tablet with morning tea and a calcium supplement, or with milk, measurably reduces absorption. It should be taken on an empty stomach with water, well separated from calcium and iron.

Proton pump inhibitors deserve a mention of their own because they are so frequently taken for years without review. They work by suppressing stomach acid, and stomach acid is required to liberate B12 from food and to absorb iron efficiently. Long-term use without periodic review is common and worth questioning.

None of this is an argument for stopping any medicine. It is an argument for knowing what to test.

Stomach acid declines anyway

Independent of medication, gastric acid secretion tends to decline with age, and atrophic gastritis becomes more common. Both reduce the absorption of B12 and non-haem iron from food.

This creates a situation that confuses people: dietary intake has not changed, the diet looks adequate on paper, and blood levels fall anyway. The intake was fine; the absorption was not.

It also explains why supplemental B12 often works when dietary advice does not. Supplemental B12 is not bound to food protein and therefore does not require stomach acid to liberate it, so it is absorbed by people who cannot efficiently extract it from food.

Grip strength, the measure worth tracking

Of all the things measurable at 55, grip strength is among the most informative and the least used. It correlates with overall muscle strength, and low grip strength is a diagnostic criterion for sarcopenia in the European consensus definition. It also predicts future disability, fracture risk and mortality in large cohort studies.

A hand dynamometer costs very little, and the chair-stand test requires only a chair and a clock. These numbers change in response to training, which makes them motivating in a way that weight is not, and declining in a way that is worth catching early.

If standing from a chair without using your hands has become noticeably harder, that is a signal to act on rather than a normal part of being 55.

What to put in place

• Annual B12 if you take metformin or a PPI — and before accepting 'diabetic neuropathy' as the explanation for tingling.
• Know your medicine interactions — particularly levothyroxine with calcium, iron and milk.
• Protein at 1.0–1.2 g/kg, around 30 g per meal — the threshold discussed in nutrition at 50 still applies.
• Measure grip strength and chair-stand time — twice a year, and act if they decline.
• Resistance training twice a week — the thing that moves every measure on that list.

Nutrition at 58 deals with the mechanical obstacles — appetite and chewing — that start to limit protein intake regardless of knowledge.

Where KABO fits in

If you take metformin or a long-term PPI, the action item on this page is a B12 test, not a purchase. Supplemental B12 at a corrective dose is a pharmacy item and your doctor's call.

The protein and grip-strength side is where food does the work, and the target is still roughly 30 g a meal. A KABO serving carries 25 g of complete plant protein with 26 vitamins and minerals, which is a straightforward way to reach that at the meal where it is hardest. If you are on levothyroxine, keep any calcium-containing food or drink well away from your tablet.

Frequently asked questions

Does metformin cause B12 deficiency?

Long-term metformin use is associated with impaired B12 absorption and a substantially higher rate of deficiency, with risk rising with dose and duration. An annual B12 test is reasonable for anyone taking it long term, particularly vegetarians, who already have lower baseline intake.

Can B12 deficiency be mistaken for diabetic neuropathy?

Yes, and this is the main clinical risk. Both cause tingling, numbness and burning in the hands and feet. In someone on long-term metformin, these symptoms are easily attributed to diabetes when the cause may be a treatable B12 deficiency, so testing before concluding is important.

Which medicines affect nutrient absorption?

Metformin reduces B12 absorption; proton pump inhibitors reduce B12, iron, magnesium and calcium absorption; diuretics can lower potassium and magnesium; and levothyroxine absorption is blocked by calcium and iron, so it needs separating by about four hours.

What is a good grip strength at 55?

Rather than a single target, what matters is your own trend and whether you fall below the thresholds used to identify sarcopenia in clinical criteria. Measuring every six to twelve months with an inexpensive dynamometer, alongside a timed chair-stand test, is more useful than a one-off number.

Why do nutrient levels fall even when diet has not changed?

Because absorption declines. Gastric acid secretion falls with age and atrophic gastritis becomes more common, both of which reduce absorption of B12 and non-haem iron from food. Supplemental B12 is not bound to food protein, which is why it often works when dietary change does not.

Sources

• ICMR-NIN, Nutrient Requirements for Indians (RDA 2020) and Dietary Guidelines for Indians, 2024. nin.res.in
• Cruz-Jentoft AJ et al., "Sarcopenia: revised European consensus on definition and diagnosis", Age and Ageing, 2019;48(1):16-31.
• de Jager J et al., "Long term treatment with metformin in patients with type 2 diabetes and risk of vitamin B-12 deficiency: randomised placebo controlled trial", BMJ, 2010;340:c2181.