Supplements · lesson 9 of 11
Who actually needs what
Life stages, diets, athletes, and tested deficiencies — 'food first, then supplement the gap.'
7 min read · reviewed October 2026
There is no universal supplement everyone should take. The right stack is personal — it depends on your diet, life stage, health, and any tested deficiencies. The most powerful question isn't "what's the best supplement?" but "what gap do I actually have?"
The guiding principle for this whole track: food first, then supplement the gap. Whole food delivers nutrients in forms and combinations supplements can't fully copy. Supplements are for the gaps food genuinely can't close for you.
Food first, supplement the gap
Reach for a supplement only when there's a real, identified shortfall — a diet that excludes a nutrient (e.g. no animal foods → no B12), a life stage with higher needs (pregnancy → folate), low sun exposure (vitamin D), or a blood test showing a deficiency. A supplement filling no gap does nothing but cost money and risk over-supplementing.
Common gaps by situation
Vitamin B12 is the non-negotiable one — it's essentially absent from plant foods, so supplementation is genuinely necessary on a vegan diet. Often also worth attention: omega-3 (algae-based EPA/DHA), iron, zinc, iodine, and vitamin D. Calcium and protein need planning but are usually achievable from food.
Folate (folic acid) before and during early pregnancy reduces the risk of neural-tube defects and is a standard recommendation. Iron, iodine, choline, and omega-3 (DHA) often matter too, and a prenatal is commonly advised. This is the clearest case to follow clinical guidance, not self-experiment.
B12 absorption declines with age (and with some medications), vitamin D is commonly low, and protein needs are higher to fight muscle loss. Calcium and vitamin D support bone health. Appetite and absorption both tend to fall, widening the gaps food can leave.
Higher protein needs, plus the strongest case for creatine. Electrolytes and iron (especially in endurance athletes and menstruating women) can matter. Most 'sports' supplements beyond these are marketing — the core basics do the heavy lifting.
A blood test showing low vitamin D, iron/ferritin, B12, etc. is the gold-standard reason to supplement — you're correcting a measured shortfall, ideally with dosing and follow-up testing guided by a clinician.
On a strict vegan diet, how many nutrients are essentially impossible to get from food, so that they genuinely require supplementation?
Somewhere between 0 and 8 nutrients.
Reveal the answer →
1 non-negotiable: vitamin B12
Vitamin B12 is the one nutrient that is essentially absent from plant foods, so a vegan diet truly requires a B12 supplement (or fortified foods) — a deficiency can cause serious, sometimes irreversible nerve damage. Others (omega-3, iron, zinc, iodine, vitamin D) are worth attention and may need help, but B12 is the non-negotiable.
Why personalization beats a one-size stack
Your needs are set by what you eat, your age and life stage, your sun exposure, your health conditions, and your blood work. Two people can need completely opposite stacks. Testing where practical, and targeting real gaps, beats copying someone else's routine.
How it works →
Nutrient requirements shift with physiology. Pregnancy raises demand for folate, iron, and choline to build a new body. Aging reduces stomach acid and intrinsic factor, cutting B12 absorption, and reduces skin's vitamin D synthesis. A vegan diet removes the only reliable dietary B12 source (animal products) and the most bioavailable iron and zinc forms. Intense training increases protein turnover and depletes creatine and electrolytes. Medications can deplete specific nutrients. Because these drivers differ per person, the same supplement can be essential for one individual and pointless for another.
What the studies show →
The strongest, least controversial supplement recommendations are exactly the gap-filling ones: B12 for vegans, folate in early pregnancy (backed by robust evidence for reducing neural-tube defects), vitamin D for the deficient, and protein/creatine for athletes and aging muscle. By contrast, broad multivitamin use in well-nourished people has repeatedly shown little benefit in large trials — reinforcing that supplements pay off when they correct a real deficit, not as blanket insurance. Where a blood test can identify a shortfall, correcting it is the most evidence-based supplementation of all.
Someone eating a varied omnivorous diet with regular sun exposure and good blood work asks which supplements they 'should' take. Best answer?
- A daily multivitamin, fish oil, and a greens powder for insurance
- Possibly none beyond filling any specific gap — food first, supplement only real shortfalls
- Whatever is trending right now
- The full core six from Lesson 7, regardless of need
Show the answer →
B.Possibly none beyond filling any specific gap — food first, supplement only real shortfalls
If the diet is varied, sun exposure is adequate, and labs look fine, there may be no gap to fill — and a supplement that corrects nothing adds nothing. The right move is to identify specific shortfalls (diet, life stage, or test) and target only those. 'Food first, supplement the gap.'
Set your goals and diet, and Formulate highlights the nutrient gaps worth closing — so your stack targets what you actually need.