What changes in your 40s — and why it matters nutritionally

Turning 40 does not come with a sudden nutritional cliff edge. But it does mark the beginning of a decade where several biological shifts converge, each with measurable consequences for nutrient requirements.

The decline in oestrogen — gradual at first during perimenopause, then accelerating through menopause — affects calcium absorption, bone turnover, and cardiovascular markers. Independently of hormonal changes, the body's ability to absorb vitamin B12 from food decreases with age as gastric acid production declines. Endogenous production of CoQ10 begins to fall. Vitamin D synthesis in the skin becomes less efficient.

None of this is a crisis. But it does mean that a supplement strategy designed for a 25-year-old is unlikely to serve a 45-year-old well. The nutrients that matter most shift, and the doses need to shift with them.

This guide covers what UK women over 40 should actually prioritise — based on authorised health claims under EU Regulation 432/2012 (retained in UK law), NHS guidance, and verified clinical evidence.

Why is vitamin D so important after 40?

Vitamin D is the single most universally recommended supplement for UK adults, and its importance increases with age. The Scientific Advisory Committee on Nutrition (SACN) recommends that all UK adults consider supplementing with 10 mcg (400 IU) daily, particularly from October to March.

For women over 40, the case is stronger. Cutaneous vitamin D synthesis declines with age — a study by MacLaughlin and Holick (1985) demonstrated that the capacity of skin to produce vitamin D3 decreases significantly from age 20 onwards. By age 70, the skin produces roughly 25% of what it did at age 20.

The authorised EU health claims for vitamin D include:

This combination of claims is directly relevant to the skeletal, muscular, and immune changes that begin in the 40s. PARTICULAR uses vitamin D3 (cholecalciferol) from a vegan lichen source — the same form the body produces naturally, and the form shown by Tripkovic et al. (2012) to be significantly more effective than D2 at raising serum 25(OH)D levels.

For a detailed comparison of D3 and D2, see our guide to vitamin D supplements.

Do women over 40 need more calcium?

Calcium contributes to the maintenance of normal bones — an authorised EU health claim. It also contributes to normal muscle function and normal blood clotting.

Oestrogen facilitates intestinal calcium absorption. As oestrogen levels decline during perimenopause and menopause, the body becomes less efficient at extracting calcium from food. The National Diet and Nutrition Survey shows that 11% of UK women aged 19–64 already have calcium intakes below the Lower Reference Nutrient Intake — a figure that is likely to understate the functional gap in women with declining oestrogen.

A systematic review by Liu et al. (2020) found that combined calcium and vitamin D supplementation in postmenopausal women significantly increased total bone mineral density and reduced the incidence of hip fracture. The evidence supports these two nutrients working together rather than in isolation.

What role does vitamin K2 play in bone health?

Vitamin K2 (MK-7) contributes to the maintenance of normal bones and contributes to normal blood clotting — both authorised EU health claims.

Vitamin K2 activates osteocalcin, a protein that binds calcium to the bone matrix, and matrix GLA protein, which helps direct calcium away from arterial walls and towards bone tissue. This makes K2 a natural partner for vitamin D3 and calcium.

Knapen et al. (2013) conducted a three-year, double-blind, randomised, placebo-controlled trial in 244 healthy postmenopausal women. Those receiving 180 mcg of MK-7 daily showed significantly decreased bone loss at the lumbar spine and femoral neck, alongside improvements in bone strength indices.

PARTICULAR uses the MK-7 form of vitamin K2 — the most bioavailable form, with a longer half-life than MK-4 that maintains consistent blood levels from a single daily dose.

Why does magnesium matter more in your 40s?

Magnesium is one of the most broadly relevant nutrients for women over 40 because of the range of authorised EU health claims it carries:

These claims span the exact areas — bone health, energy, mood, muscle function — where women in their 40s and 50s most commonly report changes.

Aydin et al. (2010) found that oral magnesium citrate supplementation in postmenopausal women with osteoporosis significantly suppressed bone turnover markers over 30 days, decreasing bone resorption and increasing bone formation. The National Diet and Nutrition Survey consistently shows that a substantial proportion of UK adults do not meet the recommended magnesium intake through diet alone.

PARTICULAR uses magnesium citrate — a form with significantly better bioavailability than magnesium oxide, which is common in cheaper supplements.

For more on magnesium's role in nervous system function and sleep, see our guide to magnesium for sleep.

Does B12 absorption really decline with age?

Yes. Vitamin B12 absorption is dependent on gastric acid and intrinsic factor, both of which decline with age. Allen (2009) reviewed the evidence and noted that food-bound B12 malabsorption — distinct from pernicious anaemia — becomes increasingly common from middle age onwards, even in people with adequate dietary intake.

The authorised EU health claims for vitamin B12 include:

Women following a plant-based diet face a compounding risk: dietary intake is already low, and age-related absorption decline further reduces what reaches the bloodstream. A systematic review by Niklewicz et al. (2024) confirmed that unsupplemented vegans have significantly lower serum B12 and elevated homocysteine compared to omnivores.

PARTICULAR uses methylcobalamin — the bioactive form that requires no conversion by the body — rather than the synthetic cyanocobalamin found in most off-the-shelf supplements.

Read more: Vitamin B12: Methylcobalamin vs Cyanocobalamin

What about folate and cell division?

Folate (5-MTHF) has a role in the process of cell division — an authorised EU health claim. It also contributes to normal psychological function and the reduction of tiredness and fatigue.

While folate is most commonly associated with pregnancy, its role in cell division and homocysteine metabolism remains relevant well beyond reproductive years. Homocysteine levels tend to rise after menopause as oestrogen's role in clearance diminishes, and folate is one of the key nutrients involved in normal homocysteine metabolism.

PARTICULAR uses 5-MTHF — the body-ready form of folate — rather than synthetic folic acid, which requires enzymatic conversion that a significant proportion of the population performs inefficiently due to MTHFR gene variants. Scaglione and Panzavolta (2014) described the practical advantages of 5-MTHF over folic acid, including consistent bioavailability regardless of MTHFR genotype.

Should women over 40 take iron?

It depends entirely on menstrual status. Women who are still menstruating lose iron monthly and often do not replace it through diet alone — the National Diet and Nutrition Survey reports that 25% of UK women aged 19–64 have iron intakes below the LRNI.

Iron contributes to normal cognitive function, the reduction of tiredness and fatigue, and normal energy-yielding metabolism — all authorised EU health claims.

But after menopause, when menstrual losses cease, iron requirements drop significantly. Unnecessary iron supplementation in postmenopausal women may be inappropriate without confirmed deficiency.

This is precisely where personalisation matters. PARTICULAR's questionnaire captures menstrual status and adjusts iron inclusion and dosage accordingly. The formula uses ferrous gluconate — a form associated with fewer gastrointestinal side effects than the commonly prescribed ferrous sulfate, as documented in a systematic review by Tolkien et al. (2015).

Read more: Iron Supplements: Forms, Absorption and How to Choose

Does CoQ10 production really decline with age?

CoQ10 does not have authorised EU health claims. This must be stated clearly. However, the clinical evidence for its role in cellular energy production is well established.

CoQ10 (ubiquinone) is a coenzyme involved in mitochondrial electron transport — the process by which cells generate ATP. Endogenous production peaks around age 20 and declines progressively thereafter. Hernández-Camacho et al. (2018) reviewed the evidence and concluded that declining CoQ10 levels are associated with the ageing process and may contribute to age-related decreases in cellular energy capacity.

Research indicates that supplemental CoQ10 may support mitochondrial function, particularly in tissues with high energy demands such as the heart and skeletal muscle. PARTICULAR includes CoQ10 as ubiquinone when your questionnaire responses indicate it is relevant.

Which other nutrients deserve attention?

Zinc

Zinc contributes to the maintenance of normal skin, maintenance of normal hair, normal function of the immune system, and normal fertility and reproduction — all authorised EU health claims. It also has a role in the process of cell division.

For women over 40, the immune function, skin maintenance, and fertility claims are particularly relevant. PARTICULAR uses zinc bisglycinate — a chelated form with higher bioavailability than zinc oxide or zinc sulfate.

Selenium

Selenium contributes to normal thyroid function and the protection of cells from oxidative stress — both authorised EU health claims. It also contributes to the maintenance of normal hair and normal fertility and reproduction.

Thyroid function becomes an increasing concern for women in their 40s and 50s, and adequate selenium status supports the selenoenzymes involved in thyroid hormone metabolism.

Vitamin C

Vitamin C contributes to normal collagen formation for the normal function of skin, cartilage, bones, gums, teeth, and blood vessels — an authorised EU health claim unique to vitamin C. It also contributes to the protection of cells from oxidative stress and the reduction of tiredness and fatigue.

The collagen formation claim is especially relevant for women over 40, as collagen synthesis declines with age. Vitamin C is also the only nutrient with an authorised claim for contributing to normal iron absorption — important for women who are still menstruating and supplementing with iron.

Why one-size-fits-all supplements fail women over 40

A 42-year-old with heavy periods, high stress, and a plant-based diet has fundamentally different nutritional gaps from a 52-year-old who is post-menopausal, eats a varied diet, and is primarily concerned with bone health. A standard "women's 40+" multivitamin cannot account for these differences.

PARTICULAR's questionnaire captures age, menstrual status, dietary pattern, activity level, health goals, medication use, and other factors that determine which of 31 ingredients belong in your formula — and at what dose. Your formula arrives as loose vegan microgranules in a pouch, one daily scoop, with each granule individually coated so nutrients are released and absorbed independently in the gut.

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Key takeaways

  1. Vitamin D3 is the top priority — SACN recommends supplementation for all UK adults, and skin synthesis declines with age. D3 contributes to the maintenance of normal bones, muscle function, and immune function.
  2. Calcium and vitamin K2 (MK-7) work together with D3 for bone health. A three-year RCT showed MK-7 significantly decreased bone loss in postmenopausal women.
  3. Magnesium spans bone, muscle, mood, and energy — with authorised claims across all four areas and widespread dietary insufficiency in the UK.
  4. Vitamin B12 absorption declines with age — methylcobalamin is the bioactive form that requires no conversion.
  5. Iron needs depend on menstrual status — still essential for menstruating women, but potentially unnecessary after menopause. Personalisation is critical.
  6. CoQ10 has no authorised health claims but clinical evidence supports its role in cellular energy production, which declines with age.
  7. Folate (5-MTHF), zinc, selenium, and vitamin C each carry authorised claims relevant to cell division, immune function, thyroid health, and collagen formation.
  8. A personalised formula beats a generic "40+" tablet — take the questionnaire to find out which nutrients and doses match your specific needs.

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