Dietary Supplements

Briefing: Dietary Supplements Purpose: Understanding which dietary supplements are most evidence-based for healthy aging based on clinical trial data, with a focus on brain function and cardiovascular health for adults 40–70.

Key Insights

• Vitamin D at 2,000 IU/day is the single most trial-validated supplement for healthy aging across both cardiovascular and broad systemic outcomes. The VITAL trial — a large-scale randomized controlled trial of 25,000+ healthy US adults aged 50+ — found that 2,000 IU/day of vitamin D reduced telomere shortening from four years of biological aging down to approximately one year over a four-year period, delivered a 22% reduction in autoimmune disease risk, and showed a 17% reduction in advanced (metastatic or fatal) cancers. Critically, vitamin D drove these benefits; omega-3s tested alongside it showed only a non-significant trend toward telomere protection, meaning you should not assume omega-3s are interchangeable for these specific outcomes. For a healthy adult in the 40–70 range at normal body weight, the trial's lead researcher states personally that the benefits of 2,000 IU/day likely outweigh the risks — though official Endocrine Society guidelines stop short of a universal healthy-adult recommendation.

• Harvard: The 4-Year Study That Froze Aging For 3 Years

• A critical and widely overlooked modifier: BMI determines whether vitamin D supplementation works at all. The VITAL trial found that participants with a BMI above 30 experienced substantially blunted benefits from vitamin D supplementation across multiple health outcomes — effects that were robust in healthy-weight participants simply did not materialize in those with higher adiposity. The mechanism is not fully understood, but the implication for regimen-building is concrete: if you are in or near the obese BMI range, 2,000 IU/day may be insufficient, and monitoring your 25-hydroxy vitamin D blood level becomes essential to confirm you're actually achieving the target level of approximately 40 ng/mL. No other supplement in this content set has an analogous, trial-documented personalization factor this actionable.

• Harvard: The 4-Year Study That Froze Aging For 3 Years

• MCT oil is the most rigorously tested supplement specifically for brain energy metabolism, but its applicability to healthy agers requires honest qualification. The BENEFIC trial — a placebo-controlled study using 30g/day of MCT oil split across two meals — found that it reduced the brain energy gap in participants with mild cognitive impairment (MCI) by 30–40% at peak ketone levels, with cognitive improvements in memory, executive function, and language directly correlated to the degree of metabolic correction. The catch: participants already had measurable cognitive impairment; the trial does not tell us whether MCT oil provides meaningful benefit before a deficit is present. Treat this as strong directional evidence for a mechanism worth understanding — the aging brain's progressive shift away from glucose as its primary fuel is real and begins decades before MCI — rather than a proven healthy-ager intervention.

• A 40% Energy Rescue for the Aging Brain in Clinical Trial | Dr Stephen Cunnane

• Creatine has 25 years of safety data and ISSN endorsement for physical performance, but its cognitive evidence for healthy aging is explicitly mixed and lacks a dedicated aging-focused RCT. For adults 40–70 already doing or planning resistance training, creatine is a reasonable addition for muscle preservation, where the evidence is strong and the risk profile well-established. On the brain side, the Stanford Lifestyle Medicine source acknowledges promising signals but is direct: creatine "is not a proven treatment for cognitive disorders, and findings across studies are still mixed." If your primary goal is brain function support in a healthy aging context, creatine is a third-tier consideration behind vitamin D and MCT oil — valuable if resistance training is already part of your lifestyle, but not warranted as a standalone cognitive supplement on current evidence.

• The Creatine Craze!

Emerging Patterns

1. Cardiovascular biomarkers are converging as practical tools for evaluating whether any supplement you try is actually working. The VITAL trial used telomere length as a surrogate for biological aging, while the Novos Core trial tracked flow-mediated dilation (FMD), pulse wave velocity (PWV), and systolic blood pressure as validated arterial health metrics. These markers are not just interesting research endpoints — FMD and PWV in particular are clinically accessible measurements that a cardiologist or sports medicine physician can order, giving you a way to track progress independent of how any supplement company frames its own results. The implication: build a baseline measurement of at least one of these before starting a new cardiovascular-focused supplement, so you have objective data rather than subjective impression after 6 months.
2. Harvard: The 4-Year Study That Froze Aging For 3 Years

3. This Formulation Outperforms HIIT For Vascular Health

4. Every source frames supplements as optimizers that amplify lifestyle — not substitutes for it — and this framing directly shapes which supplements earn inclusion in a minimalist regimen. The Stanford creatine piece is explicit that lifestyle medicine prioritizes movement, nutrition, sleep, stress management, and social connection above supplements, and that creatine's greatest benefits are seen specifically in people already engaged in resistance training. The Novos Core video echoes this: "lifestyle comes first... supplements are optimizers." The practical implication for the reader building a regimen "without unnecessary supplements" is that each supplement should have a clear lifestyle foundation it amplifies — vitamin D amplifies immune and cellular resilience, MCT oil amplifies fuel availability for an energy-stressed brain, creatine amplifies resistance training — and supplements without that foundational pairing are harder to justify.

5. The Creatine Craze!
6. This Formulation Outperforms HIIT For Vascular Health

Dissenting Views

• There is a genuine methodological tension between testing single ingredients versus multi-ingredient stacks — and the answer shapes how you should read any supplement trial. The VITAL trial's strength comes precisely from isolating vitamin D and omega-3s independently, which is how it could determine that vitamin D drove telomere protection while omega-3s did not. The Novos Core video takes the opposite position: its speaker argues that aging is multifactorial and that a multi-ingredient strategy addressing several hallmarks simultaneously is "more scientifically sensible" than isolated ingredients — and the trial data shows Novos Core's FMD improvements were 2–3x greater than benchmarks for single ingredients like CoQ10, resveratrol, or omega-3s. This is a difference in methodology, not a direct contradiction: VITAL answers "which single ingredient works?" while Novos Core answers "does a stack beat single ingredients?" Both can be true simultaneously, but the reader should be cautious about using the Novos Core finding to justify any particular multi-ingredient product, given that study's preprint status, small sample size (n=61), and company-linked design. The appropriate takeaway is that synergy between ingredients is a plausible mechanism worth watching — not a proven reason to abandon well-studied single ingredients.
• Harvard: The 4-Year Study That Froze Aging For 3 Years
• This Formulation Outperforms HIIT For Vascular Health

Read & Act

What to read

• Harvard: The 4-Year Study That Froze Aging For 3 Years — This is the most important single piece of content for your purpose: it covers the only large-scale, peer-reviewed RCT in this set that was conducted specifically in healthy midlife and older adults, tests two supplements you're likely considering, and includes the BMI-modifier finding and dosing rationale that cannot be responsibly compressed into a summary. Watch it before making any decision about vitamin D or omega-3s.

• A 40% Energy Rescue for the Aging Brain in Clinical Trial | Dr Stephen Cunnane — Dr. Cunnane's own framing of the BENEFIC trial's limitations — specifically his candor about the temporal nature of the brain energy correction and the MCI-specific population — is exactly what you need to assess whether MCT oil belongs in your regimen now or is worth watching for future evidence. The C8/C10 composition details and split-dose rationale are also practically necessary if you decide to trial MCT oil.

• This Formulation Outperforms HIIT For Vascular Health — Despite its limitations as a study, this video is worth watching for two reasons independent of its findings: it introduces FMD and PWV as accessible cardiovascular biomarkers you can use to evaluate any supplement you try, and the speaker's balanced self-critique of conflicts of interest models exactly the critical lens to apply across this entire category of research.

What to do

1. Start vitamin D at 2,000 IU/day and get a baseline 25-hydroxy vitamin D blood test within 3 months. The VITAL trial's target was ~40 ng/mL — request this specific test from your physician and use it to confirm you're hitting that level, not just assuming the dose is working. If your BMI is above 25 and especially above 30, discuss with your doctor whether your dose needs to be higher to achieve the same blood level, since the VITAL trial found benefits were blunted in higher-adiposity participants even at 2,000 IU.

2. Run a 12-week personal trial of MCT oil at 30g/day (split: 15g with breakfast, 15g with dinner) and track your subjective cognitive performance on a consistent task. The BENEFIC trial's dosing protocol is the best available guide for a healthy ager to calibrate from. Start low (e.g., 5–10g/day) and ramp up over two weeks to reduce the gastrointestinal side effects documented in the trial. If you notice no difference in sustained focus or mental clarity at 12 weeks, the current evidence does not strongly justify continuing in a healthy adult without cognitive impairment.

3. Before adding any cardiovascular supplement beyond vitamin D, get a baseline FMD or PWV measurement from a cardiologist or sports medicine physician. This gives you an objective benchmark to evaluate any subsequent cardiovascular supplement against, turning a subjective regimen decision into a measurable experiment. Without this baseline, you have no way to distinguish supplement effect from normal variation — and you risk accumulating supplements that feel justified but have no personal evidence behind them.