The golden rule: test before you supplement
Supplementing without knowing your baseline is guesswork. Over-supplementing fat-soluble vitamins (A, D, E, K) can cause toxicity. Under-supplementing water-soluble ones means you spend money on expensive urine. Get these tested: Vitamin D, B12, Iron/Ferritin, Zinc, Magnesium (RBC test, not serum).
- Ask your doctor for: 25-OH Vitamin D, serum B12, serum ferritin, full blood count, fasting glucose
- Home testing kits are now widely available and accurate for most markers
- Retest after 12 weeks of supplementation to confirm levels have improved
- Never supplement based on symptoms alone — symptoms overlap between deficiencies
The supplements with strongest evidence
These are the supplements where the clinical evidence is robust and deficiency is common:
- Vitamin D3 (+ K2): 2000–4000 IU daily. Over 1 billion people deficient. Take with fat. K2 directs calcium to bones.
- Omega-3 (EPA+DHA): 2g daily. Brain, heart, inflammation. Fish oil or algae-based for vegans.
- Magnesium Glycinate: 300–400mg before bed. Sleep, anxiety, cramps, headaches.
- Vitamin B12: methylcobalamin form. Essential for vegans/vegetarians. 1000mcg daily.
- Zinc Picolinate: 15–25mg with food. Immunity, skin, hormones. Do not take with iron.
Natural vs synthetic — does it matter?
For most vitamins, the body cannot distinguish between natural and synthetic at the molecular level. However, form matters significantly:
- Vitamin D: D3 (cholecalciferol) is 87% more effective than D2 (ergocalciferol) — always choose D3
- Folate vs Folic Acid: methylfolate (active form) is superior, especially for those with MTHFR gene variants
- Magnesium: glycinate absorbs best; oxide is poorly absorbed (used in cheap products)
- B12: methylcobalamin absorbs and stays active longer than cyanocobalamin
- Iron: bisglycinate causes least gut upset; ferrous sulphate (cheap) often causes constipation
Supplements to avoid or approach with caution
These are either ineffective, overhyped, or potentially harmful at high doses:
- Megadose Vitamin A: fat-soluble and toxic at high doses — liver damage risk
- Pre-workouts with DMAA or stimulant blends: cardiovascular risk
- Weight loss supplements: no supplement has clinically meaningful weight loss evidence at safe doses
- Collagen supplements: the collagen is broken down to amino acids in digestion — eat protein instead
- Most antioxidant supplements at high dose: can interfere with exercise adaptation
Supplement timing guide
When you take supplements matters for absorption:
- With food (fat): Vitamin D, K2, omega-3, CoQ10, fat-soluble vitamins A and E
- On empty stomach: iron (with Vitamin C for absorption), some B vitamins for energy
- Before bed: magnesium glycinate (improves sleep quality)
- Separate by 2 hours: iron and zinc, iron and calcium, zinc and copper
- Morning: B vitamins (energising — may disrupt sleep if taken at night)