CD38 (Cluster of Differentiation 38)

In One Sentence

CD38 is an enzyme found mainly on immune cells that breaks down NAD+, the coenzyme your cells need for energy and repair, and mouse research suggests that rising CD38, driven by inflammation, is a major reason tissue NAD+ falls with age.

At a Glance

• What it is: A protein on immune cells and many other cells that works as both an enzyme and a receptor. Its gene sits on chromosome 4.1

• Main jobs: Breaking down NAD+ and making the calcium messengers cyclic ADP-ribose (cADPR) and NAADP.2, 3

• NAD+ cost: CD38 uses up almost 100 molecules of NAD+ for every molecule of cADPR it makes.4

• Ageing link: CD38 levels and activity rise with age in mice, and mice without CD38 keep their tissue NAD+ into old age.5

• Main trigger: Inflammation, including signals released by ageing “senescent” cells.6, 7

• Human evidence: A 2026 study of seven groups of people found that NAD+ in whole blood stays steady with age.8

• Food compounds: Apigenin and quercetin, two plant flavonoids, block CD38 in laboratory and mouse studies. This has not been shown in people.9

• In medicine: The antibody medicines daratumumab and isatuximab target CD38 to treat multiple myeloma. Around 6,500 people in the UK are diagnosed with myeloma each year.10, 11, 12

• Blood transfusions: Anti-CD38 medicines can affect blood-matching tests for up to six months after the last dose.13

What is CD38?

CD38 (cluster of differentiation 38) is a protein on the surface of immune cells and many other cell types, where it works as an enzyme. Its best-known job is breaking down NAD+ (nicotinamide adenine dinucleotide), the coenzyme your cells use to make energy and repair themselves.1, 4

Scientists first identified CD38 in the late 1970s at the Dana-Farber Cancer Institute in Boston. At the time, it was called “T10”, a marker on developing T cells.1

The “CD” stands for cluster of differentiation, the naming system for molecules on white blood cells. CD38 is still used as a marker in hospital laboratories, and its closest relative, CD157, sits beside it on chromosome 4.1

NAD+ helps turn the food you eat into ATP, your cells' energy currency. It also powers enzymes such as sirtuins and PARPs that take part in DNA repair.14 Because CD38 is one of the main enzymes that use up NAD+, it is a central topic in NAD+ and longevity research.4, 14

Interest in this area is growing quickly. Our NAD+ From Lab to Lifestyle study found that NAD+ research papers indexed on PubMed rose from 1,006 in 2000 to a record 2,530 in 2025.

Key Takeaways

• What does CD38 do? It breaks down NAD+, makes calcium messengers and helps immune cells communicate.

• Why is CD38 linked to ageing? In mice, CD38 rises with age as inflammation builds. It appears to drive much of the fall in tissue NAD+.

• Does NAD+ fall with age in people? It depends on the tissue. A 2026 study found whole-blood NAD+ stays steady with age.8

• Can food block CD38? Apigenin and quercetin block CD38 in laboratory and mouse studies. This has not been shown in people eating normal amounts.

• Why do doctors target CD38? Myeloma cells carry a lot of CD38. Antibody medicines such as daratumumab use it to help the immune system destroy them.

• What can you do day to day? Exercise regularly, sleep well and eat a varied, plant-rich diet. Exercise also boosts the enzyme that recycles NAD+ in muscle.

What Does CD38 Do in the Body?

CD38 has three main jobs. It breaks down NAD+ and related molecules, makes messengers that release calcium inside cells, and acts as a receptor that helps immune cells signal. Most of this happens on the outer surface of cells, so scientists call CD38 an “ecto-enzyme”.2, 3

How Does CD38 Break Down NAD+?

CD38 splits NAD+ into nicotinamide and ADP-ribose, mostly on the outside of cells. A 2019 review in Frontiers in Immunology on the many roles of CD38 reports that more than 90% of CD38 works this way.2

CD38 is also very inefficient at making messengers. For every molecule of cyclic ADP-ribose it produces, it breaks down almost 100 molecules of NAD+.4

It also breaks down NMN (nicotinamide mononucleotide) outside cells. NMN is one of the building blocks cells use to make NAD+, so this reduces the supply.5, 7

A smaller pool of CD38 faces into the cell. This helps explain how an enzyme that mostly works outside cells can still affect NAD+ inside them.3

What Is Cyclic ADP-Ribose and Why Does It Matter?

Cyclic ADP-ribose (cADPR) is a messenger molecule that tells a cell to release calcium from its internal stores. CD38 is the main known enzyme that makes it. CD38 also makes a second calcium messenger, NAADP, from a related molecule called NADP.3

These calcium signals help cells respond to many different triggers. One example comes from a 2007 study in Nature on CD38 and oxytocin.

Mice without CD38 released much less oxytocin, the hormone linked to bonding. They also showed poorer maternal care and social memory until oxytocin was replaced.15

Where in the Body Is CD38 Found?

CD38 is found throughout the immune system, including on T cells, natural killer cells and macrophages. It is especially high on myeloma cells, which are cancerous plasma cells.1, 7, 16 It also appears on the endothelial cells lining blood vessels, and at low levels on red blood cells.16, 17

CD38 rises when immune cells are switched on. That is why laboratories have long used it as an “activation marker” when they analyse blood and bone marrow samples.1

The table below summarises CD38's main roles and why each one matters.

Why Does CD38 Matter for NAD+ and Ageing?

CD38 matters because, in mouse studies, it appears to be the main reason NAD+ falls in tissues with age. A 2016 Mayo Clinic study in Cell Metabolism found that CD38 levels and activity rise as mice get older. Mice without CD38 kept their NAD+ levels and mitochondrial function into old age.5

Mice bred without CD38 have 10 to 20 times more NAD+ in their tissues than normal mice. They are also protected against obesity and metabolic syndrome.4, 9

What Switches CD38 On?

Inflammation is the main trigger identified so far. In a 2020 Mayo Clinic study in Nature Metabolism on CD38 in immune cells, inflammation raised CD38 and lowered NAD+. The rise in CD38 in ageing fat and liver came from a build-up of CD38-carrying immune cells.7

As we age, senescent cells build up. These are old or damaged cells that have stopped dividing, and they release inflammatory signals known as the SASP (senescence-associated secretory phenotype).

Research on senescent cells and CD38-positive macrophages, published in the same issue of Nature Metabolism, showed what happens next. These signals prompt macrophages, immune cells that clear debris, to multiply and make CD38 in visceral fat and the liver.6

The senescent cells themselves carry little CD38. Instead, their signals switch CD38 on in nearby immune cells and blood vessel cells.17

When researchers cleared senescent cells from older mice, CD38 fell and NAD+ partly recovered.7 Scientists call this slow, age-related build-up of chronic inflammation “inflammaging”.

“Studies suggest that NAD⁺ levels may decrease during ageing, although this depends on the tissue and individual. One possible cause is an increase in CD38 levels. Animal studies show that inflammation can increase CD38 activity, leading to NAD⁺ depletion. As we age, inflammation tends to increase in the body, a process often called inflammaging. Strategies to manage inflammation, such as following a healthy diet, exercising regularly, and getting enough sleep, may help support healthy ageing and NAD+ levels.”

Yusra Serdaroglu Aydin, MSc RD, Head of Nutrition at Vivere

Does NAD+ Really Fall With Age in People?

It depends on where you measure it. Much of the CD38 evidence comes from mouse fat, liver and muscle. In people, a 2026 study in Nature Metabolism on whole-blood NAD+ measured seven separate groups.

NAD+ in whole blood stayed steady with age and after lifestyle changes such as exercise. It did rise when people took nicotinamide riboside, as expected.8

So a blood NAD+ result says little about what CD38 is doing inside your organs. Headline claims that NAD+ “halves” by middle age should be read with care. You can read more about how NAD+ levels change in the body in our dedicated guide.

What Happens When CD38 Is Blocked?

In mice, blocking CD38 raises tissue NAD+ and improves several signs of ageing. A 2018 study in Cell Metabolism on the CD38 inhibitor 78c tested this experimental compound in older mice. It reversed age-related NAD+ decline and improved glucose tolerance, muscle function, exercise capacity and heart function.18

In a follow-up lifespan study in Aging Cell, 78c increased median survival by about 10% in naturally aged male mice. It also improved their endurance and metabolic health.19

So far, 78c has been studied in cells and animals, and it is not a licensed medicine. CD38 itself also does useful work, supporting immune signalling and, in mice, the release of oxytocin.2, 15

Can Foods or Supplements Lower CD38?

Some plant compounds called flavonoids, especially apigenin and quercetin, block CD38 in laboratory studies. No human study has yet shown that eating them, or taking them as supplements, lowers CD38 or raises NAD+. The key evidence comes from a 2013 study in the journal Diabetes on apigenin and CD38.9

In that study, apigenin and quercetin blocked CD38 and raised NAD+ in cells grown in the laboratory. Apigenin also raised liver NAD+ in obese mice. However, it was injected into the abdomen at a high dose (100mg per kg of body weight) rather than eaten.9

How much apigenin the body absorbs from food depends on the form it comes in, and this is still being studied.20

Which Foods Contain Apigenin and Quercetin?

Parsley and celery are the richest everyday sources of apigenin. Onions, apples, berries, tea and capers are good sources of quercetin.20, 21 The table below shows where these flavonoids are found and what the CD38 research shows so far.

Most people in the UK have room to eat more of these foods. In the National Diet and Nutrition Survey 2019 to 2023, only 17% of adults met the 5 A Day recommendation for fruit and vegetables.22 Our guides to an anti-inflammatory diet and eating for long-term health have practical ideas.

“Flavonoids are an important group of plant compounds with potential anti-inflammatory effects. Apigenin and quercetin have been shown to inhibit CD38 in laboratory studies, while apigenin also increased NAD⁺ levels in mice. However, the mouse study used injections rather than dietary intake, so more research is needed to understand whether eating these compounds has similar effects in humans. A varied diet rich in plant foods can help us get a range of flavonoids. Foods such as parsley, celery, apples and onions can contribute to flavonoid intake and may help support the body's regulation of inflammation.”

Yusra Serdaroglu Aydin, MSc RD, Head of Nutrition at Vivere

Does CD38 Affect NAD+ Supplements?

It may. In mice, CD38 is the main enzyme that breaks down NMN, a popular NAD+ building block. The study's authors concluded that CD38 has a key role in how well NAD+-replacement approaches work.5

Blocking CD38's outer-surface activity also raised NAD+ in mice through an NMN-dependent route.7 In Great Britain, NMN is not currently authorised for sale as a food, because its novel food application is still being assessed by the Food Standards Agency.23 Our guide to how NAD+ supplements are regulated in the UK explains the rules.

If you are interested in NAD+ itself, our guide to how NAD+, NMN and NR compare sets out the main forms. Vivere's liposomal NAD+ capsules are a food supplement option for daily use alongside a healthy lifestyle.

“NAD+ levels may vary depending on the body's ability to produce NAD⁺ from its precursors and factors that contribute to its depletion, including CD38 activity. Supplementation with NAD⁺ precursors may help increase NAD⁺ levels. If you have an existing health condition or take medication, consult your GP before taking any supplements.”

Yusra Serdaroglu Aydin, MSc RD, Head of Nutrition at Vivere

How Is CD38 Used in Medicine?

CD38 is the target of antibody medicines used to treat multiple myeloma, a blood cancer that starts in plasma cells in the bone marrow. Myeloma cells carry large amounts of CD38. Antibodies that attach to it help the immune system find and destroy these cells.16, 24

Around 6,500 people are diagnosed with myeloma in the UK each year, according to Cancer Research UK's myeloma statistics.12 Myeloma is more common as people get older. It cannot usually be cured, but it can be managed with treatment.24

Daratumumab (Darzalex) was the first anti-CD38 antibody medicine to be approved.16 NICE recommends it in specific situations. These include first treatment for people who can have a stem cell transplant (NICE TA763), and use on its own when myeloma returns after three earlier treatments (NICE TA783).10, 25

A second anti-CD38 antibody, isatuximab (Sarclisa), has also been assessed by NICE for relapsed myeloma.11 Daratumumab is also used to treat AL amyloidosis.13 If you or someone you care for is having myeloma treatment, the haematology team is the best source of advice about these medicines.

Why Do Anti-CD38 Medicines Affect Blood Transfusions?

Red blood cells carry small amounts of CD38, so anti-CD38 medicines also stick to the red cells used in hospital blood-matching tests. This can make the antibody screen (the indirect antiglobulin, or Coombs, test) look positive for up to six months after the last dose. ABO and RhD blood group results are not affected.13, 16

People having daratumumab are given a patient ID card to show healthcare staff before any blood transfusion. They should carry it for six months after treatment ends.13

Hospital laboratories can remove the interference by treating test red cells with a chemical called DTT (dithiothreitol).16 Telling the team early helps them plan the right tests.

Is CD38 Linked to Gut Health?

Early research in mice suggests it may be. A 2015 study in PLOS ONE on CD38 in the intestine found high levels of CD38 on immune cells lining the mouse colon. Levels rose further during inflammation, and CD38 helped drive gut inflammation in a model of colitis.26

Gut bacteria also feed into NAD+ itself. A 2020 study in Cell Metabolism on bacteria and NAD+ found that gut microbes help mammals make NAD+ through an alternative route. In mice, they accounted for a substantial part of the NAD+ boost from oral nicotinamide and nicotinamide riboside.27

To explore this further, read how NAD+ and your gut microbiome interact. Vivere's gut microbiome test kit maps the bacteria living in your gut. It does not measure CD38 or NAD+, but it can be a useful starting point for improving your diet and gut health.

“The gut is where food, microbes and the immune system meet, so it makes sense that researchers are now looking at CD38 there. The practical advice stays the same. Feed your gut bacteria with plenty of fibre and a wide variety of plant foods, because fibre is what they live on.”

Yusra Serdaroglu Aydin, MSc RD, Head of Nutrition at Vivere

Can You Test Your CD38 Levels?

Not as a routine health check. CD38 is usually measured in specialist hospital laboratories using flow cytometry, a technique that labels and counts individual cells. Its main use is to identify and monitor immune and blood cancer cells.1, 28

Home NAD+ tests measure NAD+ in blood rather than CD38 activity in your organs. The 2026 whole-blood research suggests blood NAD+ is not a reliable marker of ageing.8

How Can You Support Healthy NAD+ Levels Day to Day?

Everyday healthy-ageing habits are the place to start: regular aerobic and strength exercise, good sleep and a varied, plant-rich diet. NAD+ levels reflect a balance between how much your body makes and how much enzymes such as CD38 use up. Exercise has been shown to support the making side in human muscle.14, 29

A 12-week exercise study in Physiological Reports measured NAMPT, the main enzyme that recycles NAD+ in muscle. Aerobic training raised it by 12% in adults aged 35 or under and by 28% in adults aged 55 and over. Resistance training raised it by 25% and 30%.29

The UK Chief Medical Officers' physical activity guidelines recommend at least 150 minutes of moderate activity, or 75 minutes of vigorous activity, each week. They also recommend strength exercises on at least two days.30

Healthy ageing is about the years you spend in good health. In England, men can expect around 61.5 years in good health and women around 61.9 years, according to the Office for National Statistics.31

• Move most days: mix brisk walking, cycling or running with strength work. Our exercise hub has ideas to get started.

• Eat a wide range of plants: herbs, onions, apples, berries and other plant foods add flavonoids and fibre.

• Get enough niacin (vitamin B3): your body uses it to make NAD+. Good sources include meat, fish, eggs and wheat flour. Men need about 16.5mg a day and women about 13.2mg.14, 32

• Protect your sleep: keep a regular routine, and see our guide to NAD+, sleep and your body clock.

• Check before using high-dose extracts: most people can get the nutrients they need from a varied, balanced diet.33 Speak to your GP or pharmacist before adding concentrated supplements, especially if you take regular medicines.

Our guide to ways to support healthy biological ageing covers these habits in more depth.

Frequently Asked Questions

Is CD38 a protein or an enzyme?

CD38 is both: a glycoprotein (a protein with sugar chains attached) that sits in the cell membrane. It works as an enzyme that breaks down NAD+ and makes calcium messengers, and as a receptor that helps immune cells signal.1, 2

Is CD38 good or bad for you?

CD38 is neither simply good nor bad. It supports immune signalling and calcium signals inside cells. In mice, though, higher CD38 activity driven by long-term inflammation is linked to falling tissue NAD+ and age-related metabolic problems.2, 5, 7

What does CD38-positive mean on a blood test report?

It means the cells tested carry CD38 on their surface, which helps laboratories identify cell types such as myeloma cells or activated immune cells. In chronic lymphocytic leukaemia, having 30% or more CD38-positive leukaemia cells has been linked to poorer outcomes.1, 28 Your haematology team can explain what your own result means.

What is a CD38 inhibitor?

A CD38 inhibitor is a substance that blocks CD38's enzyme activity. Examples include the experimental compound 78c and plant flavonoids such as apigenin and quercetin, all studied so far in cells or mice.9, 18 Anti-CD38 antibody medicines such as daratumumab work differently, attaching to CD38 on myeloma cells so the immune system can target them.16

Should I take apigenin or quercetin supplements to boost NAD+?

There is no human evidence yet that apigenin or quercetin supplements lower CD38 or raise NAD+. The CD38 effects come from laboratory and mouse studies, some using injected doses.9 If you are considering a high-dose plant extract, speak to your GP or pharmacist first, especially if you take regular medicines.

Does exercise lower CD38?

Exercise has not been clearly shown to lower CD38 in people, but it does support the other side of the NAD+ balance. In one study, 12 weeks of aerobic or resistance training raised NAMPT, the main NAD+-recycling enzyme in muscle, by 12% to 30%. The biggest rises were in adults aged 55 and over.29

Final Thoughts From Our Experts

“CD38 is one part of the NAD+ story. It helps break NAD+ down, and studies in cells and mice suggest that ageing and inflammation may increase its activity. In humans, the evidence is still evolving. Rather than chasing a quick fix, focus on what supports healthy ageing: move regularly, include strength training, prioritise sleep and eat a varied, plant-rich diet. If you're considering supplements, check with your GP or pharmacist first, especially if you take medication. And if you or someone close to you is receiving treatment for myeloma, always speak to the haematology team before taking supplements.”

Yusra Serdaroglu Aydin, MSc RD, Head of Nutrition at Vivere

References

Quarona V, Zaccarello G, Chillemi A, et al. CD38 and CD157: a long journey from activation markers to multifunctional molecules. Cytometry Part B: Clinical Cytometry. 2013;84(4):207-217. Traces CD38 from its identification in the late 1970s as the T10 marker on thymocytes and T cells, describes its presence throughout the immune system and the location of the CD38 and CD157 genes on chromosome 4 (4p15), and notes its continued use as an activation marker in routine flow cytometry.

Hogan KA, Chini CCS, Chini EN. The multi-faceted ecto-enzyme CD38: roles in immunomodulation, cancer, aging, and metabolic diseases. Frontiers in Immunology. 2019;10:1187. Reviews CD38 as a multifunctional enzyme that regulates NAD+, extracellular nucleotides and intracellular calcium; reports that over 90% of CD38 acts as an NAD+-degrading enzyme on the cell surface and that its NMN-degrading activity shapes NAD+ levels during ageing.

Lee HC, Deng QW, Zhao YJ. The calcium signaling enzyme CD38: a paradigm for membrane topology defining distinct protein functions. Cell Calcium. 2022;101:102514. Explains that CD38 makes two calcium messengers, cyclic ADP-ribose from NAD and NAADP from NADP, and that it sits in the cell membrane in two opposite orientations, with an inward-facing form producing cyclic ADP-ribose inside cells.

Chini EN. CD38 as a regulator of cellular NAD: a novel potential pharmacological target for metabolic conditions. Current Pharmaceutical Design. 2009;15(1):57-63. Describes CD38 as the main NAD+-degrading enzyme in mammalian tissues, present in nearly every tissue; notes it breaks down almost 100 molecules of NAD+ for each molecule of cyclic ADP-ribose it makes, and that tissue NAD+ in CD38-deficient mice is 10 to 20 times higher than in normal mice.

Camacho-Pereira J, Tarragó MG, Chini CCS, et al. CD38 dictates age-related NAD decline and mitochondrial dysfunction through an SIRT3-dependent mechanism. Cell Metabolism. 2016;23(6):1127-1139. Showed that CD38 levels and activity rise with age in mice, that CD38 is required for age-related NAD+ decline and mitochondrial dysfunction (acting partly through the sirtuin SIRT3), and that CD38 is the main enzyme breaking down the NAD+ precursor NMN in the body.

Covarrubias AJ, Kale A, Perrone R, et al. Senescent cells promote tissue NAD+ decline during ageing via the activation of CD38+ macrophages. Nature Metabolism. 2020;2(11):1265-1283. Found that pro-inflammatory macrophages carrying high levels of CD38 build up in visceral fat and liver with age, and that inflammatory signals released by senescent cells (the SASP) cause macrophages to multiply and express CD38, lowering tissue NAD+.

Chini CCS, Peclat TR, Warner GM, et al. CD38 ecto-enzyme in immune cells is induced during aging and regulates NAD+ and NMN levels. Nature Metabolism. 2020;2(11):1284-1304. Showed that CD38-carrying immune cells accumulate in fat and liver with age, that inflammation raises CD38 and lowers NAD+, that removing senescent cells reduced CD38 and partly reversed NAD+ decline, and that blocking CD38's outer-surface activity raised NAD+ through an NMN-dependent process.

Trętowicz MM, Scantlebery AML, Houtkooper RH, et al. Human whole-blood NAD+ levels do not vary with age or lifestyle interventions. Nature Metabolism. 2026;8:1282-1290. Across seven independent human cohorts, whole-blood NAD+ stayed stable with age and across lifestyle interventions, including exercise and protein-rich diets, but rose with nicotinamide riboside supplementation.

Escande C, Nin V, Price NL, et al. Flavonoid apigenin is an inhibitor of the NAD+ase CD38: implications for cellular NAD+ metabolism, protein acetylation, and treatment of metabolic syndrome. Diabetes. 2013;62(4):1084-1093. Identified quercetin and apigenin as CD38 inhibitors that raised NAD+ in cultured cells; apigenin injected into obese mice (100mg/kg) lowered liver CD38 activity and raised liver NAD+. Also notes that CD38-deficient mice have higher NAD+ and are protected against obesity and metabolic syndrome.

National Institute for Health and Care Excellence. Daratumumab in combination for untreated multiple myeloma when a stem cell transplant is suitable (TA763). NICE technology appraisal guidance; 2022. Recommends daratumumab with bortezomib, thalidomide and dexamethasone as induction and consolidation treatment for untreated multiple myeloma in adults when an autologous stem cell transplant is suitable.

National Institute for Health and Care Excellence. Isatuximab with pomalidomide and dexamethasone for treating relapsed and refractory multiple myeloma (TA658). NICE technology appraisal guidance; 2020. Appraises isatuximab (Sarclisa), a monoclonal antibody against CD38, used with pomalidomide and dexamethasone for relapsed and refractory multiple myeloma in adults.

Cancer Research UK. Myeloma statistics. Accessed October 2026. Around 6,532 new myeloma cases are diagnosed in the UK each year (2019, 2021 to 2022), with around 3,200 deaths a year (2022 to 2024).

Janssen-Cilag Ltd. Patient ID card for daratumumab. Electronic medicines compendium (emc) risk minimisation material; January 2025. States that daratumumab can make the indirect antiglobulin (Coombs) test positive for up to 6 months after the last dose, that ABO and RhD blood typing are not affected, and that patients should show the card before any blood transfusion and carry it for 6 months after treatment ends. Lists use in multiple myeloma and AL amyloidosis.

Covarrubias AJ, Perrone R, Grozio A, Verdin E. NAD+ metabolism and its roles in cellular processes during ageing. Nature Reviews Molecular Cell Biology. 2021;22(2):119-141. Reviews how NAD+ supports energy metabolism, the sirtuins and PARP-driven DNA repair, how NAD+ levels reflect the balance between its synthesis from vitamin B3 forms and its consumption by enzymes including CD38, and how this balance shifts with age.

Jin D, Liu HX, Hirai H, et al. CD38 is critical for social behaviour by regulating oxytocin secretion. Nature. 2007;446(7131):41-45. Mice without CD38 had much lower blood oxytocin and showed defects in maternal care and social memory, which were restored by oxytocin replacement or by delivering human CD38 to the hypothalamus.

Lancman G, Arinsburg S, Jhang J, et al. Blood transfusion management for patients treated with anti-CD38 monoclonal antibodies. Frontiers in Immunology. 2018;9:2616. Notes that daratumumab was the first anti-CD38 antibody approved (2015) and that isatuximab is a further anti-CD38 antibody; explains that these medicines bind CD38 on red blood cells, causing pan-reactivity in the indirect antiglobulin test that can mask other antibodies, while ABO and RhD typing are unaffected; describes treating test red cells with DTT to remove the interference.

Chini C, Hogan KA, Warner GM, et al. The NADase CD38 is induced by factors secreted from senescent cells providing a potential link between senescence and age-related cellular NAD+ decline. Biochemical and Biophysical Research Communications. 2019;513(2):486-493. Senescent cells themselves had little CD38, but the factors they secrete (the SASP) switched on CD38 and increased its NAD+-breaking activity in endothelial cells and macrophages, cell types in which CD38 is highly expressed.

Tarragó MG, Chini CCS, Kanamori KS, et al. A potent and specific CD38 inhibitor ameliorates age-related metabolic dysfunction by reversing tissue NAD+ decline. Cell Metabolism. 2018;27(5):1081-1095. The CD38 inhibitor 78c reversed age-related NAD+ decline and improved glucose tolerance, muscle function, exercise capacity and cardiac function in naturally aged and accelerated-ageing mice; its effects depended on tissue NAD+ levels.

Peclat TR, Thompson KL, Warner GM, et al. CD38 inhibitor 78c increases mice lifespan and healthspan in a model of chronological aging. Aging Cell. 2022;21(4):e13589. In naturally aged male mice, 78c increased median survival by about 10% and improved exercise performance, endurance and metabolic function.

Hostetler GL, Ralston RA, Schwartz SJ. Flavones: food sources, bioavailability, metabolism, and bioactivity. Advances in Nutrition. 2017;8(3):423-435. Identifies parsley and celery as the main food sources of the flavone apigenin, with fresh parsley among the richest, and reviews how absorption depends on the form (sugar-bound or free) in which flavones occur in food.

Li Y, et al. Quercetin, inflammation and immunity. Nutrients. 2016;8(3):167. Lists apples, berries, Brassica vegetables, capers, grapes, onions, shallots, tea and tomatoes among dietary sources of quercetin, with onions, tea and apples among the richest.

Office for Health Improvement and Disparities. National Diet and Nutrition Survey 2019 to 2023: report. GOV.UK; 2025. Less than 1 in 5 adults (17%) met the 5 A Day recommendation, and children aged 11 to 18 ate an average of 2.8 portions of fruit and vegetables a day.

Food Standards Agency. Regulated product application RP-2116: beta-nicotinamide mononucleotide (NMN). FSA register of regulated product applications. Records NMN as a novel food application still under assessment, so it is not currently authorised for sale as a food in Great Britain.

NHS. What is myeloma? Page last reviewed 13 May 2025. Myeloma is a cancer affecting the blood and bone marrow that happens when the bone marrow makes plasma cells that do not work properly; it is more common with age and cannot usually be cured, but can be managed with treatment.

National Institute for Health and Care Excellence. Daratumumab monotherapy for treating relapsed and refractory multiple myeloma (TA783). NICE technology appraisal guidance; 2022. Recommends daratumumab on its own as an option for relapsed and refractory multiple myeloma in adults who have had three previous treatments, including a proteasome inhibitor and an immunomodulator, and whose disease progressed on the last treatment.

Schneider M, Schumacher V, Lischke T, et al. CD38 is expressed on inflammatory cells of the intestine and promotes intestinal inflammation. PLOS ONE. 2015;10(5):e0126007. CD38 was highly expressed on immune cells of the mouse colon lining, rose on immune cells recruited during inflammation, and promoted inflammation in a chemically induced (DSS) colitis model.

Shats I, Williams JG, Liu J, et al. Bacteria boost mammalian host NAD metabolism by engaging the deamidated biosynthesis pathway. Cell Metabolism. 2020;31(3):564-579. Gut bacteria use an enzyme (nicotinamidase, PncA) to help mammalian cells make NAD+ through an alternative route; in mice, this bacterial step contributed substantially to the NAD+-raising effect of oral nicotinamide and nicotinamide riboside.

Damle RN, Wasil T, Fais F, et al. Ig V gene mutation status and CD38 expression as novel prognostic indicators in chronic lymphocytic leukemia. Blood. 1999;94(6):1840-1847. In chronic lymphocytic leukaemia, cases with 30% or more CD38-positive leukaemia cells responded poorly to chemotherapy and had shorter survival; the authors noted CD38 can be measured conveniently in most clinical laboratories.

de Guia RM, Agerholm M, Nielsen TS, et al. Aerobic and resistance exercise training reverses age-dependent decline in NAD+ salvage capacity in human skeletal muscle. Physiological Reports. 2019;7(12):e14139. Muscle levels of NAMPT, the rate-limiting NAD+ salvage enzyme, fell with age; 12 weeks of aerobic training raised NAMPT by 12% in young (35 or under) and 28% in older (55 and over) adults, and resistance training raised it by 25% and 30%.

Department of Health and Social Care. Physical activity guidelines: UK Chief Medical Officers' report. GOV.UK; first published 2019, updated July 2026. Adults should aim for at least 150 minutes of moderate intensity activity or 75 minutes of vigorous intensity activity each week, plus muscle-strengthening activities on at least two days a week.

Office for National Statistics. Healthy life expectancy in England and Wales: between 2011 to 2013 and 2021 to 2023. ONS statistical bulletin. In 2021 to 2023, males in England could expect to spend 61.5 years of their lives in good health and females 61.9 years.

NHS. B vitamins and folic acid. Niacin (vitamin B3) helps the body release energy from food; good sources include meat, fish, wheat flour and eggs; men need about 16.5mg a day and women about 13.2mg a day, which a varied and balanced diet should provide.

NHS. Vitamins and minerals. Most people should get all the nutrients they need by having a varied and balanced diet, although some people may need to take extra supplements.