Nutrients That Become Harder to Absorb as You Age

Why Absorption Changes With Age

Eating a nutritious diet is only half the equation. Your body must also be able to extract and use what you consume — and that process becomes less efficient as you get older. Several biological shifts drive this: reduced stomach acid production, slower gut motility, changes in digestive enzyme output, and a less diverse gut microbiome. Together, these factors can meaningfully reduce the amount of specific nutrients your body absorbs from food, even when dietary intake appears adequate.

Understanding which nutrients are most affected — and why — helps you make smarter choices about food sources and when to discuss supplementation with a healthcare provider. For a deeper look at the mechanics behind these digestive changes, see our article on how digestion shifts with age.

Key Nutrients Most Affected by Age-Related Absorption Decline

Vitamin B12

B12 is perhaps the most well-documented absorption challenge in older adults. The vitamin requires a protein called intrinsic factor and adequate stomach acid to be released from food and absorbed in the small intestine. As gastric acid secretion declines — a condition known as atrophic gastritis, which affects an estimated 10–30% of adults over 60 — B12 from animal foods becomes much harder to extract. Crystalline B12, found in fortified foods and supplements, does not require the same acid-dependent process and is generally better absorbed by older adults.

Calcium

Calcium absorption decreases progressively with age, driven partly by lower vitamin D levels and reduced active transport in the intestinal lining. Older adults absorb roughly 25% less calcium from food than younger adults do. This matters considerably for bone density. Spreading calcium intake across meals, rather than consuming it all at once, supports more efficient uptake.

Vitamin D

The skin's ability to synthesize vitamin D from sunlight diminishes with age — older skin produces significantly less vitamin D per unit of sun exposure than younger skin. Simultaneously, the kidneys become less efficient at converting vitamin D into its active hormonal form. Vitamin D is critical not just for calcium absorption but for muscle function and immune regulation, making deficiency a meaningful concern. This is one reason nutrient needs shift notably across the decades.

Iron

Stomach acid plays a key role in converting dietary iron — particularly the non-heme form found in plant foods — into a form the body can absorb. Lower acid production in older adults can reduce this conversion. Pairing iron-rich plant foods with vitamin C sources helps improve non-heme iron absorption. Older adults following plant-based diets may want to pay particular attention; see our guide to nutritional gaps in plant-based eating after 65.

Magnesium

Intestinal absorption of magnesium declines with age, and many older adults already consume less than recommended through diet. Magnesium supports over 300 enzymatic reactions in the body, including protein synthesis, blood pressure regulation, and nerve function. Low magnesium is also associated with reduced bone density and increased cardiovascular risk, areas already under pressure in older adults.

Zinc

Zinc absorption efficiency decreases with age, and older adults are more likely to consume diets lower in zinc-rich animal proteins. Zinc plays a central role in immune function, wound healing, and taste perception — the latter of which can itself reduce appetite and food variety, creating a compounding effect on overall nutritional adequacy. These gaps are covered more broadly in our look at where older adults' diets tend to fall short.

This article is for general informational purposes only and is not a substitute for professional medical advice. If you have concerns about your nutritional status or digestion, consult a qualified healthcare provider before making changes to your diet or supplement routine.