The 5 Most Common Deficiencies I See (and How to Fill the Gaps)
Many women walk into their 30s, 40s, and 50s thinking they’re “just tired,” “just stressed,” or “just getting older.”
But the more I work with women across these life stages, the more obvious it becomes:
A large part of the way women feel — the fatigue, anxiety, mood shifts, cravings, slower recovery, or stubborn weight changes — often comes down to a handful of nutrient gaps.
Not dramatic deficiencies.
Not emergency-level lows.
Just suboptimal nutrition that directly affects energy, hormone balance, metabolism, and nervous system regulation.
And the tricky part?
These deficiencies often don’t show up on standard labs, because many nutrients are tightly regulated in the bloodstream. Your body will keep those numbers in range even when your deeper stores are running on fumes.
Below are the five nutrient gaps I see most often in women over 30 — especially when stress is high, hormones are shifting, digestion is off, or life is simply full — plus simple ways to start filling those gaps.
1. Magnesium
Many women are surprised when I tell them this, but magnesium is one of the most common deficiencies I see — and one of the most important.
Magnesium is involved in hundreds of enzymatic reactions, supporting:
energy metabolism
stress resilience
nervous system regulation
blood sugar balance
muscle recovery and relaxation
sleep quality
bone health
Women are particularly vulnerable during perimenopause and menopause, when estrogen fluctuations affect magnesium absorption and retention. Chronic stress compounds this — stress increases magnesium loss through the urine, raising your needs even when intake hasn’t changed.
Food-first support:
Pumpkin seeds
Almonds
Cashews
Spinach
Black beans
Dark chocolate (70%+ cacao)
2. Vitamin D
Over 97% of women have intake levels below recommended thresholds, and more than one quarter show inadequate levels on biomarker testing.
Vitamin D plays a major role in:
immune function
bone density
mood regulation
inflammation balance
hormone support
muscle function
Even women who live in sunny states can struggle — skin synthesis decreases with age, stress alters vitamin D metabolism, and many women don’t get consistent outdoor exposure.
Food-first support:
Fatty fish (salmon, sardines, mackerel)
Egg yolks
Mushrooms exposed to sunlight
Fortified plant milks
3. Iron (and Ferritin)
Iron deficiency is the most common deficiency in women in the U.S., affecting roughly 1 in 5 women.
Even if your hemoglobin looks normal, ferritin (your iron storage) may be low — and ferritin often drops long before anemia shows up. Heavy bleeding, poor absorption, high stress, gut issues, and inadequate intake all play a role.
Low iron can look like:
fatigue
breathlessness during workouts
hair shedding
brain fog
cold intolerance
restless legs
rapid heart rate
Food-first support:
Grass-fed red meat
Lentils
Pumpkin seeds
Chickpeas
Spinach + vitamin C foods (bell peppers, citrus)
4. B Vitamins (especially B6 and B12)
B vitamins are essential for energy production, nervous system function, neurotransmitter synthesis, and metabolic health.
Up to 23% of women show B6 deficiency on biomarker testing, and many have marginal B12 levels even when serum values appear “normal.”
These deficiencies are more common during stress, perimenopause, menopause, or when digestion is impaired.
Food-first support:
Eggs
Salmon
Nutritional yeast
Beef
Chickpeas
Dark leafy greens
5. Omega-3 Fatty Acids
Most women don’t consume enough EPA and DHA, the anti-inflammatory fatty acids that support:
brain health
heart health
hormone balance
inflammation regulation
mood stability
skin health
Women in their 30s through 50s particularly benefit from adequate omega-3s because they help counteract inflammation and support metabolic and cardiovascular health as hormones shift.
Food-first support:
Salmon
Mackerel
Sardines
Walnuts
Chia seeds
Ground flaxseed
Why These Deficiencies Slip Through the Cracks
Most women are told, “Your labs are normal,” even when they’re dealing with real symptoms.
Here’s why these deficiencies often go undetected:
Blood levels don’t reflect tissue stores (like magnesium, B12, or zinc)
Some markers remain normal until stores are severely depleted
Inflammation can mask deficiency markers
Serum levels don’t tell you about absorption
Functional needs increase during stress or hormonal transitions
This is why a holistic, functional approach — one that looks at symptoms, intake patterns, stress load, hormone changes, and gut health — paints a far more accurate picture than labs alone.
How to Start Closing Your Nutrient Gaps
You don’t need a complicated overhaul. Most women benefit from beginning with:
✔ Food-first upgrades
Add magnesium-rich foods, omega-3s, iron sources, and B-vitamin–rich meals into your weekly rhythm.
✔ Gentle gut support
Digestion and absorption improve when gut motility, stomach acid, and stress load are supported.
✔ Stress reduction
Stress depletes magnesium, zinc, B vitamins, and iron faster than most people realize.
✔ Strategic supplementation (when appropriate)
Especially when symptoms are present or absorption is compromised.
I use Fullscript to ensure quality, potency, and third-party testing for my clients.
✔ Tracking your own patterns
Many women notice improvements in energy, mood, digestion, sleep, and cravings within weeks of filling their gaps.
The Bottom Line
Women over 30 face unique physiological demands — shifting hormones, higher stress loads, disrupted sleep, and changes in digestion.
These make nutrient gaps incredibly common, and they show up long before labs flag a problem.
Supporting these nutrients isn’t about perfection.
It’s about giving your body what it needs to keep up with the season you’re in.
Small shifts → big changes.
References
Devarshi PP, Legette LL, Grant RW, Mitmesser SH. Total Estimated Usual Nutrient Intake and Nutrient Status Biomarkers in Women of Childbearing Age and Women of Menopausal Age. American Journal of Clinical Nutrition. 2021.
Allen LH. Micronutrients—Assessment, Requirements, Deficiencies, and Interventions. New England Journal of Medicine. 2025.
Mazza E, et al. Magnesium: Exploring Gender Differences in Its Health Impact and Dietary Intake. Nutrients. 2025.
Lopresti AL. The Effects of Psychological and Environmental Stress on Micronutrient Concentrations in the Body. Advances in Nutrition. 2020.
Tardy AL, et al. Vitamins and Minerals for Energy, Fatigue and Cognition. Nutrients. 2020.
Matek Sarić M, et al. Magnesium: Health Effects, Deficiency Burden, and Future Public Health Directions. Nutrients. 2025.
Harak SS, et al. Navigating Nutrition Through the Decades. Nutrition. 2025. Erdélyi A, et al. The Importance of Nutrition in Menopause and Perimenopause. Nutrients. 2023.
Disclaimer
This post is for educational purposes only and is not intended as a substitute for professional medical or mental health advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or mental health concerns.
Author: Dianne Bly, Functional Health & Nutrition Specialist, RN, BSN, PN1 Nutrition, CFMP
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