Nutritional and physiological needs change significantly across decades — a protocol optimized for a 25-year-old is suboptimal for a 55-year-old.

20s-30s: Peak physiological capacity. Focus on: building foundational habits (exercise consistency, sleep discipline), establishing lean mass (muscle is easier to build now than any other decade), baseline testing (know YOUR numbers before they start changing), and bone density building (peaks around 30 — weight-bearing exercise and adequate calcium/D3/K2 NOW prevents osteoporosis later).

30s-40s: The inflection decade. Testosterone begins declining ~1% per year in men (from age 30). Women approach perimenopause (hormonal fluctuation begins in late 30s-early 40s for many). Metabolic rate starts declining (primarily from muscle loss, not inherent metabolic "slowing"). NAD+ decline accelerates. Recovery time from exercise and injury increases. Focus on: maintaining muscle mass (resistance training becomes non-negotiable), metabolic health monitoring (fasting insulin, TG/HDL), hormone awareness, and sleep optimization (sleep quality often deteriorates in the 40s).

50s-60s: Preservation and adaptation. Sarcopenia accelerates (muscle loss 1-2% per year without intervention). Bone density declining. Gut microbiome diversity typically decreasing. Immune function declining (immunosenescence). Cognitive reserve becoming increasingly important. Focus on: protein intake increases (1.2-1.6g/kg vs 0.8-1.0g/kg for younger adults), resistance training with progressive overload, balance work (fall prevention), cognitive stimulation, social connection (loneliness is a mortality risk factor), and more frequent lab monitoring.

70s+: Functional independence as the primary goal. Grip strength becomes a mortality predictor. Getting up from the floor without hands becomes a screening test. Focus on: maintaining functional movement, adequate protein, fall prevention, medication review (polypharmacy becomes dangerous), social engagement, and cognitive activity. The supplement priorities shift: D3 (skin synthesis declines dramatically), B12 (absorption impaired by age and PPIs), CoQ10 (if on statins), and creatine (emerging evidence for cognitive protection in elderly).

Most supplement and health protocols are designed for and tested on men. Women have specific physiological considerations that are routinely overlooked:

The Menstrual Cycle as a Training Variable: Women's physiology is not static across the month. During the follicular phase (day 1-14): higher estrogen improves insulin sensitivity, enhances recovery, and increases pain tolerance — ideal for higher-intensity training and heavier lifts. During the luteal phase (day 15-28): progesterone raises core body temperature, increases metabolic rate (~100-300 extra calories/day), reduces insulin sensitivity, and increases water retention. Training performance may naturally decrease. Adjusting training intensity to the cycle (harder in follicular, recovery-focused in late luteal) isn't weakness — it's physiological precision.

Iron Needs: Premenopausal women lose iron monthly through menstruation. The RDA for iron is 18mg/day for menstruating women vs 8mg/day for men. Iron deficiency is the most common nutritional deficiency in women of reproductive age globally. Symptoms (fatigue, brain fog, cold intolerance, poor exercise recovery) overlap with many other conditions and are often missed. Ferritin is the best screening test — optimal is 40-100 ng/mL.

Bone Health: Women lose bone density more rapidly after menopause (estrogen is bone-protective). Peak bone mass is built before age 30 — weight-bearing exercise and adequate calcium/D3/K2 in the teens and 20s is prevention that pays dividends for decades. Post-menopausal women need: resistance training (mechanical loading stimulates bone formation), adequate calcium (1200mg/day from food + supplement if needed), D3 (2000-5000 IU), K2 (100-200mcg), and potentially consideration of hormone therapy for bone protection.

Relative Energy Deficiency in Sport (RED-S): Formerly known as the "female athlete triad." When energy intake is insufficient for training demands, the body suppresses reproductive function first (amenorrhea), then bone density, then thyroid function, then immune function. This isn't exclusive to women (men can experience it too) but is more common in female athletes, especially in aesthetic or weight-class sports. Missing periods is NOT a normal consequence of training — it's a warning sign of insufficient energy availability.

Plant-based diets offer well-documented benefits (lower cardiovascular risk, reduced cancer risk, lower environmental impact) but have specific nutritional vulnerabilities that require awareness and supplementation:

Vitamin B12: Not available from any plant source (despite marketing claims about spirulina and fermented foods). B12 deficiency causes: megaloblastic anemia, peripheral neuropathy (tingling, numbness), cognitive decline, depression, and irreversible nerve damage if prolonged. EVERY vegan must supplement B12 — methylcobalamin 1000-2000mcg daily or 2500mcg twice weekly. No exceptions.

Omega-3 (EPA+DHA): Plants provide ALA (alpha-linolenic acid), but conversion to EPA is only 5-10% and to DHA is <5%. This means vegans typically have very low EPA and DHA levels. Solution: algae-derived EPA+DHA supplements (the omega-3 in fish originally comes from algae — you're cutting out the middleman). 250-500mg combined EPA+DHA daily.

Iron: Plant iron (non-heme) absorbs at 2-20% vs animal iron (heme) at 15-35%. Combine with vitamin C to enhance absorption. Avoid coffee/tea/calcium with iron-rich meals (all inhibit absorption). Vegans need roughly 1.8x the iron RDA to compensate for lower absorption.

Zinc: Similar absorption challenge — phytates in legumes and grains bind zinc, reducing bioavailability. Soaking, sprouting, and fermenting grains/legumes reduces phytate content. Consider supplementing 15-30mg zinc (as zinc picolinate or bisglycinate).

Iodine: Vegans who don't eat seaweed or use iodized salt may be deficient. Iodine is critical for thyroid function. 150mcg/day from supplement or iodized salt.

Creatine: Found almost exclusively in animal products. Vegans have lower baseline creatine stores, which may affect high-intensity exercise performance and cognitive function. Creatine supplementation (3-5g/day) shows larger performance benefits in vegans than omnivores — because they're starting from a lower baseline.

As discussed in earlier tiers, many common medications deplete specific nutrients. A medication-aware approach means supplementing what your prescriptions are taking:

Statins (atorvastatin, rosuvastatin, simvastatin): Deplete CoQ10 by blocking the mevalonate pathway that produces both cholesterol AND CoQ10. Supplement: CoQ10 100-300mg (ubiquinol form for better absorption). Also consider: vitamin D (some statins impair D synthesis), and omega-3 (complementary cardiovascular support).

Metformin: Depletes B12 over time (impairs absorption in the ileum). 10-30% of metformin users develop B12 deficiency. Supplement: methylcobalamin 1000-2000mcg daily. Monitor B12 levels annually.

PPIs (omeprazole, pantoprazole): Reduce stomach acid, impairing absorption of: magnesium, calcium, iron, B12, and zinc. Long-term users should supplement: magnesium glycinate 200-400mg, B12 1000mcg, and monitor iron and calcium status.

Oral Contraceptives: Deplete B6, B12, folate, magnesium, zinc, and selenium. Supplement: a quality B-complex with methylated forms, magnesium glycinate 200mg, and zinc 15mg.

SSRIs (sertraline, fluoxetine, escitalopram): May deplete folate and B12 (which are required for serotonin synthesis — the very neurotransmitter SSRIs target). Supplementing methylfolate alongside SSRIs has shown enhanced antidepressant response in multiple studies. Also: magnesium (deficiency worsens depression and anxiety) and omega-3 (complementary mood support).

Thyroid Medication (levothyroxine): Absorption impaired by calcium, iron, coffee, and soy within 4 hours. Take thyroid medication on empty stomach, 30-60 minutes before anything else. Separate from calcium and iron supplements by 4 hours.

The principle: every long-term medication comes with nutrient implications. Ask "what does this drug deplete?" for every prescription you take.