The Impact of B12 Deficiency

Midlife represents a period of transformation, encompassing physical, emotional, and hormonal changes. Many women encounter challenges such as fluctuating energy levels, mood shifts, sleep disruptions, and a general decline in their body's resilience. Among these changes, an often-overlooked factor that may contribute to fatigue and brain fog is vitamin B12 deficiency.

What Is Vitamin B12?

Vitamin B12 (also known as cobalamin) is an essential water-soluble nutrient that plays a critical role in energy production, red blood cell formation, neurological function, and DNA synthesis NIH Office of Dietary Supplements, 2024. It’s a foundational vitamin which your body needs to thrive, but can't be produced on its own. It must come from food or supplements.

Low B12 can lead to a wide range of symptoms: fatigue, weakness, memory issues, tingling in the hands and feet, mood changes, and even anemia. Yet, it is shockingly easy to overlook or misdiagnose, and is often mistaken for depression, burnout, or just “getting older.”

Why Women in Midlife Are Especially Vulnerable

During perimenopause and menopause, hormonal fluctuations can impact how well your body absorbs and utilizes nutrients. Estrogen and progesterone levels shift, digestion can slow, and stress hormones often spike, all of which can affect B12 absorption.

To further complicate issues, many midlife women begin to experience subtle gastrointestinal changes (like lower stomach acid or more frequent bloating), which can interfere with B12 uptake from food.

The Symptoms You Shouldn’t Ignore

B12 deficiency often develops gradually, which makes it easy to dismiss as "just aging." But if you're experiencing any of the following, it's worth asking your doctor for a simple blood test:

• Fatigue that doesn’t improve with rest

• Brain fog or memory slips

• Tingling or numbness in hands or feet

• Low mood or irritability

• Light-headedness or pale skin

  
  

Who is at Risk?

While anyone can develop low B12, certain diets and ethnicities are more prone to deficiency:

• Plant-Based Eaters: B12 is found almost exclusively in animal-based foods like meat, eggs, dairy, and fish. Vegans and vegetarians often need fortified foods or supplements to maintain adequate levels.

• People of South Asian Descent: In developed countries, studies show higher rates of B12 deficiency in these populations due to both dietary patterns and genetic factors affecting absorption Jeruska-Bielak, Isman et al., 2017

• Women Over 40: Age-related changes in stomach acid, combined with hormonal shifts, can decrease B12 absorption even with a well-rounded diet Allen, 2009.

Supporting Your B Vitamin Levels

If you're low in B12, the good news is it is easily treatable. Injections or high-dose supplements can quickly replenish depleted stores, and many people begin to feel a dramatic improvement in energy, focus, and mood within just a few days or weeks.

Long-term vitality—especially during midlife—means supporting all eight B vitamins, not just B12. These nutrients work together to help your body convert food into energy, maintain healthy skin and brain function, and regulate mood and stress. A nutrient-dense, varied diet that includes both animal and plant-based foods, and thoughtful supplementation if you’re on a plant-based diet.

• If you’re dealing with chronic fatigue, stress, or multiple deficiencies, monitor your levels through regular blood work, especially if you're over 40

• Discuss supplementation with a high-quality B-complex with your health practitioner.

• Always check the dosages—especially for B6—and go with methylated forms (like methylfolate and methylcobalamin) if you have trouble with absorption

B12 Rich Foods:

Vitamin B12 is primarily found in animal products. To support healthy levels, aim to include:

• Fatty fish - salmon, sardines, and tuna

• Eggs - especially the yolks

• Dairy - milk, yogurt, and cheese

• Beef liver - (the most concentrated natural source)

• Shellfish - clams, oysters, and crab

If you're vegan or vegetarian:

• Choose fortified plant milks, nutritional yeast, and fortified cereals

• Consider a reliable B12 supplement, ideally in the methylcobalamin form

Practical Tips:

• Cook with whole foods more often: swap refined grains for quinoa, brown rice, or oats

• Keep snackable sources of B vitamins on hand—like roasted chickpeas, hard-boiled eggs, or nut mixes

• Rotate in leafy greens, legumes, and seeds regularly

• If you're feeling fatigued, foggy, or moody, ask your provider for a complete B vitamin panel, not just B12

Disclaimer: This article is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider before making changes to your diet, supplements, or health routine—especially if you have underlying health conditions or are taking medications.