The Doctor Had Us Show Our Work

TL;DR: Daily hydrolyzed collagen supplementation improved skin hydration, elasticity, and wrinkle appearance in women aged 40–60 within eight weeks.

What It Shows: RCT, 52 women aged 40–60. Daily hydrolyzed collagen over 56 days showed statistically significant improvements in skin moisturization, elasticity, and wrinkle depth vs. placebo (p < 0.01). Improvements in firmness and smoothness also observed.

TL;DR: In women aged 30–55, 2.5 g/day of hydrolyzed collagen improved skin hydration, elasticity, and texture within eight weeks.

What It Shows: RCT, 56 women aged 30–55. Daily 2.5g hydrolyzed collagen over 8 weeks produced significant improvements in facial skin hydration, elasticity, and roughness vs. placebo (p < 0.01).

TL;DR: In women aged 43–65, 5 g/day of hydrolyzed collagen peptides improved skin moisture, dermal density and elasticity, with some benefits seen in as little as 28 days.

What It Shows: RCT, 85 East Asian women aged 43–65. Daily 5g hydrolyzed collagen peptides over 84 days showed significant improvements in dermis density and skin moisture vs. placebo. Positive effects on elasticity, wrinkle visibility, nail color, and beauty perception observed within 28 days.

TL: DR: Calcium and vitamin D are essential nutrients for maintaining strong bones throughout adulthood.

What It Shows: The Institute of Medicine's landmark review established dietary reference intakes for calcium (1,000–1,200mg/day) and vitamin D (600–800 IU/day) in adults, identifying both nutrients as essential for bone mineralization, fracture risk reduction, and musculoskeletal function across the lifespan. 

TL;DR: Calcium is the primary mineral that gives bones their strength and structure, making adequate intake essential for maintaining healthy bones throughout life.

What It Shows: Authoritative review. Over 99% of body calcium is stored in the skeleton. Calcium is essential for bone mineralization and structural integrity. Inadequate intake disrupts bone remodeling balance.

TL:DR - Healthy collagen is an important part of bone strength and may help bones resist fractures as we age.

What It Shows: Cadaveric study, 30 human femurs aged 19–89. Age-related deterioration in collagen network integrity correlated significantly with decreased bone toughness, independent of bone density. Findings highlight collagen quality — not just mineral density — as a key determinant of bone fracture resistance. 

TL:DR: Creatine supplementation can improve power output and muscular endurance during high-intensity resistance training.

What It Shows: RCT, 14 resistance-trained men. One week of 25g/day creatine monohydrate significantly improved peak power output across all 5 sets of jump squats and total repetitions across all 5 sets of bench press vs. placebo. 

TL:DR: Taking 3–5g of creatine daily can help improve strength and exercise performance.

What It Shows: RCT, 36 male university students. Daily 3g or 5g creatine monohydrate without a loading phase over 35 days produced significantly greater increases in maximal strength vs. placebo (≈20% vs. 10%, p < 0.05). Upper limb endurance also improved significantly in the 5g group. 

TL:DR: Vegetarians may see greater gains in muscle mass and exercise performance from creatine supplementation than non-vegetarians.

What It Shows: RCT, 42 subjects (18 vegetarian, 24 non-vegetarian). Vegetarians had significantly lower baseline muscle creatine. Following 8 weeks of creatine supplementation and resistance training, vegetarians showed greater gains in total creatine, lean tissue mass, and work output than non-vegetarians (p < 0.05). 

TL;DR: Vitamin D helps muscles contract and function properly, and maintaining adequate vitamin D levels may support muscle strength and physical performance.

What It Shows: Authoritative review. Vitamin D acts on muscle via the VDR receptor, regulating calcium uptake essential for muscle contraction, relaxation, and cellular processes. Deficiency associated with muscle weakness and impaired physical performance.

TL:DR: Higher protein intake is linked to greater muscle mass and strength in middle-aged and older adults.

What It Shows: Cross-sectional study, 146,816 adults aged 40–69 (UK Biobank). Higher dietary protein intake was positively associated with greater fat-free mass (FFM) and grip strength across the full intake range. Per 0.5 g/kg/day increase in protein: FFM rose 5.1% in men and 7.7% in women; grip strength rose ~0.075 kg/kg in both sexes. Benefits persisted independently of physical activity, diet, and comorbidities, suggesting the current recommendation of 0.8 g/kg/day may be insufficient to optimise muscle mass and strength.

TL:DR: Higher protein intake may be needed to support muscle maintenance in adults over 50, particularly when eating just two meals a day.

What It Shows: RCT, 30 adults aged 50–70 in a 2-meal eating pattern (9-hour window). Only the highest protein intake (1.5 g/kg/day) achieved a significantly positive whole-body net protein balance compared to both 0.8 g/kg/day (current RDA) and 1.1 g/kg/day (typical US intake) (p < 0.01). No difference was found between the 0.8 and 1.1 g/kg/day groups, suggesting habitual protein intake may be insufficient to maintain protein balance when eating just two meals per day.

TL:DR: Getting enough protein in midlife may help maintain muscle mass and strength as you age.

What It Shows: Cross-sectional study, 2,417 adults aged 40–59 (NHANES 2011–2014). Higher protein intake was positively associated with lean mass and grip strength in both men and women. Compared to moderate intake (0.8–1.2 g/kg/day), low intake (<0.8 g/kg/day) was linked to lower lean mass and grip strength, while high intake (≥1.2 g/kg/day) was associated with greater grip strength. Men eating below the RDA had more than double the odds of low lean mass (OR 2.26). Findings suggest middle age may be a critical window for protein intake to reduce future sarcopenia risk.

TL:DR: Daily collagen supplementation may help reduce joint discomfort and support mobility in active adults.

What It Shows: RCT, 139 athletes with functional knee pain. Daily 5g hydrolyzed collagen peptides over 12 weeks produced statistically significant reductions in activity-related knee pain vs. placebo, confirmed by both participant and physician assessment (p < 0.05).

TL: DR: Daily collagen supplementation may help reduce exercise-related knee pain in active adults.

What It Shows: RCT, 180 physically active adults aged 18–30. Daily 5g hydrolyzed collagen peptides over 12 weeks produced a statistically significant reduction in exercise-induced knee pain vs. placebo, confirmed by both participant and physician assessment (p < 0.05).