Folic Acid and Vitamin B12 Deficiency: Impact on Health and How to Overcome It

Two B vitamins quietly run some of the most important machinery inside the human body: folic acid (vitamin B9) and vitamin B12 (cobalamin). When either one falls short, the consequences are not subtle. Red blood cells balloon to abnormal sizes, fatigue becomes a daily companion, nerves start misfiring, and developing babies face the risk of serious birth defects. With a large vegetarian population, low awareness of supplementation, and one of the highest burdens of neural tube defects globally, this is a public health concern that deserves close attention.

Why folic acid and vitamin B12 matter so much 🔗

Folic acid and vitamin B12 are both water-soluble B-complex vitamins, and they share a central job: helping the body build DNA. Every time a cell divides, it must first copy its genetic material, and this process depends heavily on these two nutrients. Folic acid and its derivatives are extremely important in the synthesis of nucleic acids and act as coenzymes for the transfer of one-carbon units in the biosynthesis of purines, pyrimidines, and amino acids. Vitamin B12 works alongside folate, particularly in converting homocysteine to methionine, which keeps the folate cycle running.

Tissues that divide rapidly – bone marrow producing blood cells, the gastrointestinal lining, and the developing fetus – feel the impact of any shortage first. This is why the earliest and most visible signs of deficiency show up in the blood and, in the case of pregnancy, in the developing nervous system of the unborn child.

The role in nucleic acid synthesis 🔗

Inside the bone marrow, immature red blood cells need to divide repeatedly before they mature. When folate or B12 is missing, DNA synthesis slows down while the cell continues to grow in size. The result is a large, immature cell called a megaloblast. Megaloblasts occur when inhibition of DNA synthesis causes asynchronous maturation between the nucleus and the cytoplasm. These cells are fragile, short-lived, and inefficient at carrying oxygen – the biochemical basis of megaloblastic anaemia.

Megaloblastic anaemia: when blood cells grow too big 🔗

Megaloblastic anaemia is the most common consequence of folate or B12 deficiency. Unlike iron-deficiency anaemia, where red blood cells are smaller than normal, here the cells are abnormally large (macrocytic) and fewer in number. The body, despite having raw materials like iron, simply cannot produce enough functional red blood cells.

Typical symptoms include persistent fatigue, weakness, breathlessness on mild exertion, pale or slightly yellowish skin, a smooth and sore tongue (glossitis), poor appetite, and a rapid heartbeat. Many people dismiss these signs as overwork or stress, which delays diagnosis. In children, megaloblastic anaemia can also stunt growth and impair cognitive development, and in developing countries it most often results from deficiency of vitamin B12 or folic acid.

Pernicious anaemia: a special kind of B12 deficiency 🔗

One specific form of B12 deficiency deserves its own name: pernicious anaemia. Here, the problem is not what you eat but what your body can absorb. Vitamin B12 in food can only be absorbed if it binds to a stomach protein called intrinsic factor, produced by parietal cells in the stomach lining. In pernicious anaemia, the immune system attacks these parietal cells, intrinsic factor production crashes, and B12 absorption fails – even if the diet is rich in animal foods. The antibodies block this critical protein called intrinsic factor, preventing vitamin B12 from being transported to bone marrow where it is used to make new red blood cells.

The name “pernicious” comes from a time when this disease was fatal because doctors had no idea how to treat it. Today it is manageable, but it still requires lifelong attention – usually through intramuscular B12 injections rather than oral supplements, since the absorption defect is the core issue.

Neurological symptoms: the hidden danger of B12 deficiency 🔗

Folate and B12 cause many of the same blood-related symptoms, but B12 deficiency has a uniquely dangerous added dimension: neurological damage. Vitamin B12 is essential for maintaining the myelin sheath, the fatty layer that insulates nerve fibers. Without enough B12, this sheath degenerates, and nerve signals start to misfire.

Early neurological symptoms include tingling or numbness in the hands and feet (peripheral neuropathy), difficulty maintaining balance, muscle weakness, memory lapses, mood changes, and in severe cases, confusion or psychiatric symptoms. Vitamin B12 deficiency is associated with hematologic, neurologic, psychiatric, cutaneous, gastrointestinal, and cardiovascular disorders, with axonal sensorimotor neuropathy being a prevalent finding. If untreated for long, some of this damage can become permanent.

This is also why simply taking folic acid to “fix” anaemia without checking B12 status can be dangerous. Folic acid can correct the blood picture while the underlying B12 deficiency continues to silently damage the nervous system. If physicians only look for megaloblastic anemia, they can miss the diagnosis and thus allow neurological damage to progress unabated.

Folate, B12, and pregnancy: a critical connection 🔗

For women planning a pregnancy or in early pregnancy, folate is non-negotiable. The neural tube – which becomes the brain and spinal cord – closes within the first 28 days of pregnancy, often before a woman even knows she is pregnant. Inadequate folate at this stage can lead to neural tube defects (NTDs) such as spina bifida and anencephaly.

This is not a rare problem in India. India has one of the highest burdens of neural tube defects in the world, accounting for over one-third of all neural tube defects globally. The evidence for prevention is striking: in randomized trials, periconceptional folic acid supplementation reduced the risk of neural tube defects by approximately 70%.

Vitamin B12 status during pregnancy matters too, and not just for the mother. Low maternal B12 is now recognized as an independent risk factor for neural tube defects, separate from folate status. Inadequate B12 during pregnancy and breastfeeding can also affect infant growth and neurological development.

How common is the deficiency in India? 🔗

The scale of B12 deficiency in particular is striking. A 2025 meta-analysis covering 18,750 participants found the pooled frequency of inadequate cobalamin levels in Indian populations at 51%, rising to 65% among vegetarians and 67% among pregnant women. Studies from individual regions report figures ranging from 16% to 77%, with the burden particularly heavy in vegetarian populations.

Why so high? Several factors converge:

• Vegetarian diets: Vitamin B12 is found almost exclusively in animal foods – meat, fish, eggs, and dairy. Plant foods do not naturally contain bioavailable B12.
• Limited dairy and egg consumption: Even among non-vegetarians, intake of animal products is often modest.
• Long-term use of acid-suppressing medications: Drugs like PPIs and H2 blockers reduce stomach acid, which is needed to release B12 from food.
• Poor awareness: Many people are simply unaware that B12 is a nutrient of concern.

The National Institute of Nutrition has officially included Vitamin B12 as a nutrient of concern for vegetarians in its Dietary Guidelines for Indians, a meaningful policy acknowledgment of how widespread the problem has become.

Food sources: what to put on your plate 🔗

For folic acid (vitamin B9) 🔗

Folate is widely distributed in plant foods, which makes pure folate deficiency less common than B12 deficiency. Good dietary sources include dark green leafy vegetables, beans, oranges, and fortified flours, breads, pastas, rice, and breakfast cereals. In an Indian kitchen, this translates to:

• Leafy greens like palak (spinach), methi (fenugreek), and sarson (mustard greens)
• Pulses and legumes – chana, rajma, masoor dal, moong dal
• Beetroot, broccoli, asparagus, and bhindi (okra)
• Citrus fruits like oranges and mosambi
• Peanuts and other nuts
• Eggs (also a good B12 source)

One important note: folate is sensitive to heat. Folic acid, the synthetic form, is more stable through cooking than natural food folate. Heavy boiling and discarding vegetable water can destroy a significant share of folate, so quick cooking methods and using the cooking liquid in dals or gravies help preserve it.

For vitamin B12 🔗

B12 is the harder nutrient to get from a vegetarian diet. The reliable sources are:

• Dairy products: milk, dahi (curd), paneer, and cheese
• Eggs: particularly the yolk
• Fish, chicken, mutton, and other meats for non-vegetarians
• Fortified foods: some breakfast cereals and plant milks have added B12

Strict vegans face the highest risk and almost always require supplementation, since there is no reliable natural plant source. Lacto-vegetarians can meet a fair share of their needs through generous, daily consumption of milk and dahi, but many still fall short.

Supplements, fortification, and treatment 🔗

For women planning pregnancy, supplementation is the gold standard. Getting 400 micrograms of folic acid daily can help prevent neural tube defects, and this is especially important during early pregnancy because the neural tube develops in the first few weeks, often before pregnancy is recognised. In India, the government’s Anaemia Mukt Bharat programme provides iron and folic acid (IFA) tablets free of cost through public health channels to pregnant women, lactating mothers, adolescents, and women of reproductive age.

For diagnosed deficiencies, treatment depends on the cause. In cases of B12 deficiency due to absorption issues, intramuscular B12 injections may be required for several weeks initially, and sometimes lifelong; folate deficiency is typically treated with oral folic acid tablets.

A critical clinical rule: before giving high-dose folic acid for suspected megaloblastic anaemia, B12 status should be checked. Otherwise, the folate may correct the blood picture while neurological damage from undiagnosed B12 deficiency continues to progress.

Prevention: small habits, big difference 🔗

The good news is that prevention is straightforward and affordable for most people. A few practical habits go a long way:

• Eat a varied diet: include a green leafy vegetable and a pulse every day, and rotate fruits and vegetables across the week.
• Don’t skip dairy: for vegetarians, daily milk, dahi, or paneer is a key B12 source. Aim for at least 2-3 servings.
• Cook smart: use minimal water for boiling greens, cover the pot, and avoid prolonged reheating.
• Get tested if symptoms persist: unexplained fatigue, tingling in hands or feet, memory issues, or pale skin warrant a blood test that includes B12 and folate levels.
• Plan supplementation around pregnancy: ideally start folic acid at least one month before conception and continue through the first trimester, under medical guidance.
• Be cautious with long-term acid-suppressing medications: if you are on PPIs or metformin (which can also lower B12), periodic monitoring is wise.

For vegetarians and vegans, regular screening every couple of years is a sensible precaution, even in the absence of symptoms. Sub-clinical deficiency is common and can progress quietly for years before producing obvious problems.

What do you think? If most people in your circle are vegetarian and rarely get tested for B12, how would you start a conversation about screening without making it sound alarming? And do you think India should move toward mandatory fortification of staple foods like rice or atta with folic acid and B12, as several countries have done – what might be the trade-offs?

References

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11081602/
2. https://www.sciencedirect.com/science/article/pii/S0185106315000426
3. https://link.springer.com/article/10.1007/s12098-010-0121-2
4. https://my.clevelandclinic.org/health/diseases/22377-pernicious-anemia
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC9480660/
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC11288374/
7. https://clinicaltrials.gov/study/NCT03853304
8. https://healthcare-bulletin.co.uk/article/india-s-unseen-nutritional-emergency-a-meta-analysis-of-vitamin-b12-deficiency-3355/
9. https://telanganatoday.com/widespread-vitamin-b12-deficiency-in-india-linked-to-vegetarian-and-vegan-diets
10. https://www.cdc.gov/folic-acid/about/intake-and-sources.html
11. https://www.cdc.gov/folic-acid/about/index.html
12. https://my.clevelandclinic.org/health/diseases/23160-megaloblastic-anemia