Summary

Many women over 45 eat well and still find they are short of certain nutrients. The reason is often not what they eat, but how much of it their body absorbs. Stomach acid, falling oestrogen and changes to your periods all affect that.

This post explains what changes after 45 and why it happens. It covers the seven nutrients most often low after 45, the foods that provide them, and where herbs come in.

Key takeaways

• Most women over 45 still make enough stomach acid. About one in ten older adults make too little, and medicines that reduce stomach acid cause the same problem.
• Without enough acid, B12, iron, calcium and probably magnesium are absorbed less well, whatever you eat.
• Iron stores often fall during perimenopause and rise after menopause.
• A quarter of UK women aged 20 to 59 eat less iron than the lowest reference amount. One in ten eat less magnesium than the lowest reference amount.
• Only about half of plant milks sold in the UK contain any iodine.
• Bitter herbs have been used for poor digestion for centuries. Whether they suit you is decided in consultation.

Being short of a nutrient is common in women over 45, even with a good diet. Vitamin D, iron, B12 and magnesium are the usual ones.

Some of these nutrients are hard to measure accurately in a blood test. Your body keeps blood levels steady by drawing on bone and other stores. A blood test can look normal while those stores are low.

Even so, research shows that being short of them is common.

Have you ever been told your diet looks fine, and wondered why you still feel tired? The difference between what you eat and what you absorb is what this post is about.

Why absorption changes after 45

Your stomach acid does more than digest a meal. It frees B12 from the proteins it’s bound to. And it converts iron and calcium into forms your gut can take up.

A review of the stomach’s role found that acid is needed to absorb B12, iron and calcium. Magnesium probably depends on it as well.

Many websites say stomach acid falls with age in everyone. The research does not support that. When researchers tested 248 people over 65, nearly 90 per cent still made acid normally. About one in ten consistently didn’t.

Most of those who didn’t had atrophic gastritis, a thinning of the stomach lining. It often follows a long-standing Helicobacter pylori infection, and it produces few signs of its own.

In a study of 3,299 adults over 60, 15 per cent had atrophic gastritis. Of those, 38 per cent were short of B12.

Low stomach acid is not inevitable. For the women who have it, less of every meal is absorbed.

More women are affected by medicines that reduce stomach acid than by atrophic gastritis. Proton pump inhibitors such as omeprazole are widely prescribed. In that same study, more than a third of people over 60 had taken one for six months or longer.

Long-term use reduces the absorption of B12, iron, calcium and magnesium. Hormones play a part too. Researchers described how oestrogen helps your tissues to take up and hold magnesium. As oestrogen falls through perimenopause, magnesium can fall with it.

My post on stomach acid and digestion covers the signs of low acid, and how it differs from too much.

How much you’re actually eating

Absorption is not the only reason levels fall. Many women eat less of these nutrients than they think.

Researchers looked at what UK adults actually eat. A quarter of women aged 20 to 59 ate less iron than the lowest reference amount. Half ate less selenium than that amount, and more than one in ten ate less magnesium.

The lowest reference amount is enough for only the few people with the smallest needs. Eating less than that is a real shortfall.

Calcium and the other bone nutrients are covered in my post on vitamins and minerals for women over 40. This post looks at the ones that fall most often after 45, and why.

Vitamin D

Your skin makes vitamin D from summer sunlight. At UK latitudes it makes too little between October and early March. Your skin also becomes less efficient at making it as you get older.

Researchers found that skin from people aged 77 and 82 made less than half the vitamin D of young skin.

The result is that more than a fifth of the UK population has a blood level below 25 nmol/L. That is the level the UK counts as poor. Women aged 15 to 49 and adults over 65 are the groups most at risk.

Vitamin D lets you absorb calcium from your gut, and it needs magnesium to become active. Every enzyme that activates vitamin D appears to need magnesium. If magnesium is short, a vitamin D supplement may not give you its full benefit.

Oily fish, egg yolks and mushrooms left in the sun add small amounts. Food alone rarely provides enough.

The NHS advises 10 micrograms a day, and a supplement through autumn and winter. That is the amount needed to avoid deficiency. How much you need beyond it depends on your own level, and that varies from one woman to the next.

My post on vitamin D in winter explains more.

Magnesium

Magnesium is needed for hundreds of reactions in your body. Muscle relaxation, sleep, blood sugar control and nerve signalling all depend on it. As oestrogen falls, your tissues hold less of it.

Many women notice cramps, restless sleep or a lower mood around perimenopause. Falling magnesium can be part of the reason, alongside the change in hormones.

Stomach acid probably matters here too. The same review found that magnesium absorption is likely to depend on acid. Long-term use of medicines that reduce stomach acid is known to lower magnesium.

Pumpkin seeds are one of the richest everyday sources. Dark leafy greens, almonds, cashews, black beans, dark chocolate and whole grains all contribute. Cooking doesn’t destroy magnesium, so cooked spinach counts just as much as raw.

Nettle has a long history of use here. Herbalists have used the leaf for centuries as a nourishing spring tonic, and it is one I use in clinic. Young nettle tops cook like spinach, or dry well for tea.

My post on spring tonic herbs explains how to use it. There is more on which forms absorb best in my post on magnesium forms and absorption.

Iron: too little before menopause, too much after

Iron stores tend to be low before menopause and high after it. Most articles describe only one of these.

Before menopause, iron stores often fall

Periods often become heavier and longer in the years before they stop.

In a study of 1,320 women followed through the years around menopause, a third had repeated spells of heavy bleeding. More than three quarters had at least three periods lasting ten days or longer.

That blood loss lowers iron stores slowly, over months and years. Tiredness, brain fog, breathlessness on the stairs and hair thinning can all appear before anaemia shows on a routine test.

Researchers tested 7,241 Danes from infancy to old age. Among women aged 30 to 50, 18 per cent had exhausted iron stores.

After menopause, iron stores often rise

Once periods stop, iron stores rise. In that same Danish study, ferritin rose steadily after menopause and approached the levels seen in men. Among women aged 60 to 70, only 2.3 per cent had depleted stores and none had iron deficiency anaemia.

Too much iron isn’t harmless. It’s why iron isn’t something to take on a guess. When I suspect low iron, I look at the signs and any recent results before anything else.

Why a routine test can miss it

Haemoglobin measures the iron in your red blood cells. Ferritin measures the iron in your reserves, and it falls first. The WHO uses ferritin as the marker of iron stores for that reason.

You can have normal haemoglobin and empty reserves at the same time. Ferritin isn’t always part of a routine panel, and “normal” covers a wide range.

When recent results exist, I read them alongside everything else I learn about you at a first appointment.

Where to find it

Red meat, liver, lentils, chickpeas, dark leafy greens, tofu and pumpkin seeds all provide iron. Vitamin C in the same meal helps you to absorb iron from plant foods.

Researchers who studied 299 people found that around 50 mg of vitamin C with each main meal worked best. A red pepper, a handful of berries or a squeeze of lemon does that.

Stomach acid matters here more than for any other mineral. If your acid is low, or you take a proton pump inhibitor, iron from plant foods is absorbed poorly.

Vitamin B12

B12 is needed for nerve function, red blood cells and energy. Low levels show up as tiredness, brain fog, low mood and tingling in the hands and feet.

It’s the nutrient most affected by stomach acid. B12 in food is bound to protein, and acid releases it before it can be absorbed.

In large UK and US surveys, about 6 per cent of people over 60 were deficient. Closer to 20 per cent had marginal levels.

Most people assume low B12 means pernicious anaemia, the autoimmune condition. It accounts for only 15 to 20 per cent of cases in older adults.

More than 60 per cent come from food-bound malabsorption. The B12 is in the food, but the stomach can’t release it.

Meat, fish, eggs and dairy provide B12. Plant foods don’t, unless they’re fortified. If you eat little animal produce, B12 has to come from fortified foods or a supplement.

When absorption is the problem, the form of B12 makes a difference. Crystalline B12, the form in supplements and fortified foods, doesn’t need stomach acid.

A trial of 500 micrograms a day compared tablets dissolved under the tongue with swallowed tablets. Both raised levels equally well over four weeks.

Zinc

Zinc supports your immune system, wound healing, taste and smell, and mood. Low zinc is easy to miss because its signs overlap with so much else. Slow healing, more colds than usual, a dulled sense of taste and thinning hair are the common ones.

Intake often falls as appetite drops or the diet narrows. In a large US survey, 35 to 45 per cent of adults over 60 ate less zinc than they needed. Medicines that reduce stomach acid reduce zinc absorption as well.

Oysters contain more zinc than any other food. Beef, lamb, pumpkin seeds, cashews, chickpeas, lentils and dark chocolate all contribute. Zinc from animal foods is absorbed more easily than zinc from plants. A vegetarian diet needs more of the plant sources.

Go carefully with high-dose zinc supplements. Over time they interfere with copper absorption. Food is the safer route. There is more in my post on zinc for gut health.

Omega-3 fats

The omega-3 fats EPA and DHA form part of your cell membranes, reduce inflammation and support your brain and heart. Your body makes very little of either, so they have to come from food.

DHA makes up a large part of the membranes of your brain cells. Researchers who pooled 48 studies of more than 100,000 people found a clear pattern. Higher omega-3 intake was linked with around 20 per cent lower risk of cognitive decline.

Each extra 100 mg a day of DHA or EPA was linked with 8 to 10 per cent lower risk.

Oily fish is the richest source. Salmon, mackerel, sardines, anchovies and herring all provide EPA and DHA directly, and tinned counts. The NHS advice is two portions of fish a week, one of them oily.

Walnuts, flaxseed and chia provide the plant form, ALA. Your body converts very little of it into EPA and DHA. If you don’t eat fish, an algal oil supplement provides both from the same source the fish get them from.

My post on the omega-3 to omega-6 ratio explains why the balance between the two matters.

Iodine

Your thyroid hormones are built from iodine, and your thyroid sets your metabolism, energy, body temperature and mood. Mild iodine shortage doesn’t cause obvious signs. It can contribute to a sluggish thyroid, tiredness, weight gain and poor concentration, all of which overlap with perimenopause.

The UK has no salt iodisation programme. A 2026 review found that mild to moderate iodine deficiency has returned in the UK, particularly in women. Dairy and white fish intake has fallen, and plant milks have taken their place.

Swapping cow’s milk for a plant milk is a common reason for low iodine. About half of plant milks have no iodine added, so the iodine dairy provided can be lost.

A survey of UK supermarkets in 2024 found that only 48 per cent of non-organic plant milks contained any iodine. Almost no plant yoghurts or cheeses did.

If you’ve swapped dairy for oat or almond milk, check the label. When iodine has been added, the label has to say so. Cow’s milk has iodine without any being added. It gets there through the cattle feed and the milking process.

Seaweed is often suggested instead, and it’s an unreliable source. Researchers who tested 12 seaweeds found a huge range. Nori had 16 micrograms per gram, and one kelp product had over 8,000. Kelp supplements can contain far too much.

Cow’s milk, yoghurt, cheese, white fish such as cod and haddock, prawns and eggs are the reliable sources.

Where bitter herbs fit

When absorption is the problem, eating more of a nutrient does not solve it. The question is why the stomach isn’t making enough acid, and the answer differs from one woman to the next.

Where low stomach acid is part of the problem, bitters have a long history of use.

Bitter herbs such as gentian, dandelion root and wormwood have been given before meals for centuries. The European herbal monograph for gentian records its traditional use for poor appetite and digestive complaints.

Researchers reviewing how bitters work found that tasting gentian and wormwood triggers a reflex that prepares the gut to digest. Swallowed in a capsule, they produced no such response. The taste itself is what works.

Which bitter, at what strength and for how long, depends on the person. That is what a consultation settles. My post on bitter herbs for digestion explains more about how they work.

Nettle can be used alongside bitters, as a food herb rich in minerals rather than a supplement. If you take a proton pump inhibitor, it stays as prescribed. Herbs and supplements are chosen carefully around it.

What you can do this week

Eat a wide range of foods. Pumpkin seeds, dark leafy greens, oily fish, eggs, lentils and nuts each provide several of these nutrients.

Combine foods that help each other. Iron from lentils, beans and leafy greens is absorbed better with vitamin C in the same meal. Zinc from beans, nuts and seeds is absorbed better when eaten with some meat, fish or eggs.

Vitamin D needs magnesium to work, so eat foods rich in magnesium as well.

Check the label on your plant milk for iodine. If it has none, eat dairy or white fish regularly instead.

A blood test shows some of these nutrients well and others poorly. It doesn’t show why a level is low, and the reason decides what will help. Low acid, heavy periods, falling oestrogen and a narrowed diet each need a different answer.

Deciding whether a test is needed, and reading any results against the whole picture, is how I help.

A medical herbalist can help to identify which of these fits what you’re experiencing. Once that is clear, the right foods and herbs can be chosen.