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Can Vitamin D Slow Aging? Here’s What Science Says
Why does Vitamin D matter?
It is extremely common for people who want to live longer to take Vitamin D supplements. If there is credible research that Vitamin D could slow down aging then people may decide to use higher doses of Vitamin D, get their blood tested for Vitamin D, and assume that taking Vitamin D will give them a longer life.
The question is not "Does Vitamin D change your laboratory test?" Rather, the question is, "Are the changes caused by Vitamin D enough to reduce your risk of dying from an aging-related disease?"
What the Study Looked At
The researchers used data from a portion of the participants of the VITAL trial, which is a very large randomized controlled trial (RCT) involving over 25,000 adults. Participants were randomly placed into one of four different groups. Each group received:
- Vitamin D at 2,000 IU/day
- Omega-3 fatty acid at 1 gram/day
- Both Vitamin D and Omega-3
- Placebo
White blood cell telomere length was measured before the start of the trial (at baseline), two years into the trial, and four years into the trial. Telomeres are the protective caps on the end of every chromosome. Every time you divide a cell, you lose a little bit of your telomere. Eventually when the telomere gets too short the cell becomes senescent.
What the Study Found
There was no change in telomere length due to the use of Omega-3 supplements. There was a slowing of telomere length loss in participants who took 2,000 IU of Vitamin D per day. Specifically, the rate of loss was decreased by approximately 140 base pairs over four years. Based upon this, the authors concluded that daily use of Vitamin D supplements may protect against telomere loss and cellular senescence.
Why Telomeres Are Related to Aging
When cells divide, the telomeres on the ends of the chromosomes get shorter. When the telomere gets so short that the cell can no longer replicate, the cell goes into a state called cellular senescence. Senescent cells continue to function but release inflammatory signals. These signals can contribute to:
- Inflammation of tissues
- Disruption of functioning of nearby cells
- Age-related disease processes
Therefore, many scientists believe that telomere shortening is a useful marker of biological aging.
Is 140 Base Pairs Meaningful?
On the surface, 140 base pairs appears like a lot. Typically, white blood cell telomeres shorten by around 20-40 base pairs per year. Therefore, over four years, this represents several years' worth of telomere loss. However, this is based on the assumption that the measurement is accurate. Measurement error is significant in this area of research.
Limitations of Measuring Telomeres
Quantitative polymerase chain reaction (PCR) is the method that was employed to measure telomere length. While this method is commonly used, it has been shown to be less reliable than other methods. Studies have shown that even when using the exact same DNA sample, the estimated length of telomeres varies by more than 20% across different labs. Additionally, when measuring the same sample multiple times in the same lab, the repeated measurements vary by approximately 1 to 10%. Therefore, a difference of 140 base pairs falls within the range of expected measurement variability. It is therefore difficult to discern whether the observed effect is due to a true biological change or measurement variability.
Would Even If Accurate Change Health Outcomes?
Even if the change in telomere length is a true reflection of the effects of Vitamin D, the next question is, would this change have any impact on the health outcomes? Large-scale population studies have shown that there is a correlation between shorter telomeres and increased risk of death. In fact, studies of hundreds of thousands of participants have shown that there is approximately an 8% increase in mortality risk per standard deviation decrease in telomere length. However, these studies provide no information about how many base pairs equate to a given amount of risk. As mentioned earlier, individual variation in telomere length is quite large. Therefore, even if a moderate-sized difference is detected, it is unlikely to translate to a measurable change in disease risk. Importantly, these studies are observational. Therefore, they cannot establish causality between shorter telomeres and increased disease risk.
What Did the VITAL Trial Show About Real Outcomes?
- No reduction in myocardial infarction or stroke in the vitamin D treated group
- No reduction in all-cause mortality
- No statistically significant reduction in cancer mortality
Given that Vitamin D has the potential to slow down aging through preserving telomeres, there should have been some indication of a benefit in one of these outcomes. There was not.
Why Do Traditional Risk Factors Remain More Important Than Telomeres?
The authors of related analyses emphasize that the predictive value of telomere length is relatively poor compared to established risk factors. Established risk factors that have consistently demonstrated a relationship to long-term health include:
- Blood pressure
- LDL cholesterol and apoB
- Body mass and body composition
- Cardiorespiratory fitness
These risk factors have been shown to be much more reliable predictors of disease and mortality than the small changes in telomere length. For example, there is stronger evidence regarding blood pressure and dementia risk than there is regarding telomere testing.
Vitamin D Supplementation in Context
Vitamin D became a hot topic in the early 2000s based on the results of observational studies that indicated low levels of Vitamin D were associated with many chronic diseases. This generated interest in Vitamin D supplementation. High dose Vitamin D supplementation and Vitamin D blood testing followed. However, subsequent RCT's have generally failed to demonstrate a major benefit of Vitamin D supplementation for reducing the risk of cancer or cardiovascular disease. Furthermore, RCT's have also shown that high doses of Vitamin D can result in adverse outcomes. One long-term RCT compared three dosages of Vitamin D (400 IU, 4,000 IU, and 10,000 IU per day). The results were:
- There was no improvement in bone density in the high-dose groups.
- Bone density actually decreased in the high-dose groups compared to the lower-dose group.
As with most things in life, too much of anything can be bad for you. Just because something may be beneficial at a certain level does not mean that it will always be beneficial.
Current Guidelines Regarding Vitamin D
There is still a great deal of controversy about what constitutes an appropriate serum level of Vitamin D. Current guidelines are somewhat ambiguous regarding routine Vitamin D blood testing. There are some subgroups of people where Vitamin D supplementation is strongly supported. Some of these groups include:
- Children and Adolescents
- Pregnant women
- Individuals with Prediabetes
- Adults aged >75
Most adults have been told that they need to consume about the following amounts of Vitamin D:
- Younger Adults: 600 IU (International Units) of Vitamin D per day
- Older Adults: 800 IU of Vitamin D per day
Practical Takeaways
While the results of this study suggest that Vitamin D may slow down the shortening of Telomeres, the amount of uncertainty in the measurements was too large to be able to conclude anything definitively. Even if there was an actual effect of Vitamin D on Telomeres, it has not yet been established that slowing down Telomere shortening would lead to improved health outcomes. As stated earlier, high doses of Vitamin D were not effective in reducing Heart Disease, Stroke or Total Mortality in the VITAL Trial. High doses of Vitamin D carry risks and should never be taken lightly. There are many Health Markers that are much more important than Telomeres.
Summary
There has been some hype surrounding the idea that Vitamin D can help to "slow down" the aging process. The current body of scientific evidence does not support the idea that Vitamin D can slow down the aging process. While the evidence does show that Vitamin D does appear to slightly alter a laboratory marker of aging, it is unclear whether this slight alteration will actually result in significant improvements in health.
In summary, Vitamin D is still a very important nutrient for maintaining good Bone Health and for certain groups of people, but it is not a proven method to slow down the aging process. In order to maximize one's overall health, it is generally best to focus on well-known Risk Factors for Poor Health, including Fitness, Blood Pressure, Metabolic Health, etc. This is consistent with why more Health Testing is not always better and with the larger picture of Evidence-based Eating made Simple.