What is a vitamin deficiency, and how can you recognize it?
A vitamin deficiency occurs when the body does not have enough of one or more vitamins to perform its essential functions. Vitamins are not produced by the body (except for vitamin D3 from sunlight and vitamin K2 from gut bacteria)—they must come from the diet or targeted supplementation. Explore our full range of nutritional supplements and immune-boosting products to help prevent the most common deficiencies.
- Common signs of all vitamin deficiencies: persistent fatigue with no obvious cause—weakened immune system (frequent infections)—mood swings or difficulty concentrating—dull skin, brittle hair, and weak nails—diffuse muscle pain
- The 5 most common deficiencies in France: vitamin D3 (80% of French people in winter) — vitamin B12 (vegans, older adults) — vitamin B9 (women of childbearing age) — vitamin C (smokers, diets low in fruit) — vitamin A (in developed countries, deficiencies are most common among the elderly)
- How deficiencies develop: diets that are too limited in variety or too highly processed — restrictive diets without adequate compensation (veganism, strict gluten-free diets) — malabsorption (irritable bowel syndrome, Crohn’s disease, bariatric surgery) — medications that deplete certain vitamins (PPIs → B12, metformin → B12, antiepileptics → B9)
- Common combined deficiencies: deficiencies rarely occur in isolation—vitamin D3 deficiency + magnesium deficiency (vitamin D3 is inactive without magnesium)—vitamin B12 deficiency + vitamin B9 deficiency (interdependent methylation cycle)—iron deficiency + vitamin C deficiency (vitamin C enhances iron absorption)
- Diagnosis: Only a blood test can confirm a deficiency—symptoms often overlap with those of other conditions—never self-diagnose or take supplements blindly without a blood test
Groups at highest risk for vitamin deficiency
- Vegans and strict vegetarians: lack of dietary vitamin B12 (found only in animal products) — non-heme iron is absorbed less efficiently — reduced zinc and calcium intake — B12 supplementation is mandatory, along with regular monitoring of other micronutrients
- Older adults (>65 years): reduced absorption of B12 (decreased intrinsic factor) + vitamin D (less efficient skin absorption) + calcium + zinc—often nutrient-deficient diets—polypharmacy that interferes with several vitamins—annual screening recommended
- Pregnant and breastfeeding women: needs doubled or tripled for folate (fetal neural tube closure), B12, vitamin D3, iron, and iodine — routine supplementation recommended before and during pregnancy
- Smokers: Tobacco depletes vitamin C (increased requirements of 35 mg/day) + accelerates the breakdown of vitamin E + reduces calcium absorption — increased cardiovascular and bone risk
- People on long-term medications: PPIs and metformin → B12 — antiepileptics → B9 — corticosteroids → D3, calcium, zinc — diuretics → B9, magnesium, potassium — monitor blood tests regularly
Prevent deficiencies through diet and supplementation
- Ideal anti-deficiency meal: green vegetables at every meal (B9, C, K) + animal protein or legumes (B12, iron, zinc) + whole grains (B1, B3, magnesium) + high-quality fats (A, D, E, fat-soluble K) + fresh fruit (C, B9) — variety is the best protection against deficiencies
- Cooking and storage: Heat destroys 30–80% of water-soluble vitamins (B9, C, B1) — opt for gentle steaming and short cooking times — eat some of your daily fruits and vegetables raw — store vegetables in a cool place away from light
- Targeted and appropriate supplementation: prioritize biological testing to guide choices — do not take multiple supplements at the same time without consulting a healthcare professional (possible interactions and overdoses) — bioavailable forms (methylcobalamin for B12, 5-MTHF for B9, D3 rather than D2) — take fat-soluble vitamins (A, D, E, K) with meals
- Digestive health: A healthy gut is essential for vitamin absorption — dysbiosis, prolonged use of PPIs, and intestinal disorders reduce absorption — support the microbiome with mineral cofactors and probiotics
- Sports and Increased Needs: Intense physical activity increases the need for B vitamins (energy), vitamin C (antioxidant), D3 (muscles), and electrolyte minerals—endurance athletes: an annual assessment is recommended to detect subclinical deficiencies before they affect performance
