Americans have long been told that vitamin D is crucial for our health. Depression, arthritis, and cancer are just a few problems that vitamin D supplements can “cure”. 

But a new study suggests that vitamin D supplements may not provide many (or any) of these benefits. The 5-year, 26,000-subject study found vitamin D was no more effective than a placebo at protecting against:

  • Heart disease
  • Cancer
  • Broken bones
  • Or memory loss

So, does that mean this nutrient can’t protect health or further longevity in supplement form? And what about its essential-yet-unheard-of counterpart, vitamin K2?


Shining Light on Vitamin D

Vitamin D is an essential, fat-soluble nutrient used to build and maintain healthy bones. Without vitamin D, your body can’t properly absorb and manage calcium or phosphorous, two crucial building blocks for bones. 

Aside from this crucial function, vitamin D regulates and supports other systems through its anti-inflammatory and antioxidant properties, including:


Sources of Vitamin D

The best source of vitamin D is a daily dose of sunlight. UV rays from the sun convert your skin’s cholesterol into vitamin D3, which is stored in your fat cells until needed. 

You can also consume vitamin D via foods, but because it’s fat-soluble, very few sources contain adequate amounts. A few exceptions include:

  • Cheese
  • Egg yolks
  • Beef liver
  • Mushrooms
  • Fatty fish and fish liver oils like cod, swordfish, salmon, and tuna
  • Fortified foods with added vitamin D like milk, cereal, and orange juice

For most people, 15-30 minutes of sunlight daily provides all the vitamin D you need. But if you’re older, have darker skin, or live in low-sunlight areas, you may need to make up the difference in your diet. 

When you don’t consume sufficient levels of vitamin D, you run into several problems. To start, you can’t absorb or use calcium or phosphorous, leading to low nutrient levels in your blood. 

If the issue isn’t quickly corrected, your body may leach calcium from your bones, putting you at higher risk of:

  • Rickets: a condition in infants and children that causes soft bones and skeletal deformities
  • Osteomalacia: essentially, the adult form of rickets that leads to weak or soft bones

But how much dietary vitamin D is enough?


Recommended Amounts

For most individuals aged 1-69, the recommended dietary intake for vitamin D is 600 international units (IUs), or 15 micrograms. Adults over 70 should take at least 800 IU (20mcg). 

That said, it’s possible to take more (though there’s no evidence to suggest that more vitamin D promotes better outcomes). Experts generally believe that up to 4,000 IU (100mcg) per day is a safe upper limit, while some studies suggest 10,000 IU (250mcg) is acceptable. 

But there is such a thing as too much of a good thing. Though you can’t overdose on vitamin D from sunlight, taking too much vitamin D long-term can lead to hypercalcemia, or high blood calcium levels. And in people with hardened arteries, certain fungal infections, and kidney disease, vitamin D can exacerbate existing problems


Vitamin D and Longevity

Though the benefits of vitamin D supplements remain in question, adequate vitamin D levels are essential for your health. Inversely, chronically low levels of vitamin D can contribute to aging and age-related diseases.  

For instance, vitamin D could lower your risk of developing heart disease. Because it manages and regulates blood calcium levels, vitamin D can prevent calcium from depositing in your blood vessels (atherosclerosis). Relatedly, this nutrient may relax your arteries, contributing to lower blood pressure

There’s also some evidence that vitamin D activates so-called “longevity genes” that increase lifespan. These genes may also prevent the accumulation of toxic proteins linked to age-related diseases like Alzheimer’s. Vitamin D’s activities in stress response pathway genes could cause similar impacts

There’s also a lot of “negative” science about vitamin D. That is, while taking more may not actively fight diseases, not having enough can produce negative outcomes. 

For example, low blood vitamin D levels have been linked to several age-related diseases, including an increased risk of:


Vitamin D and the Science

Despite all this evidence, the science of vitamin D remains mixed. 

For instance, while some studies say vitamin D prevents fractures, others suggest the mineral does no such thing

Similarly, while low vitamin D is correlated to higher cancer risk, there’s little evidence that more vitamin D reduces risk. (Though vitamin D may promote better survival odds after developing cancer.) 

Some experts propose that the absence of positive impacts could be because low vitamin D levels are just a marker of disease. In other words, low vitamin D levels may result from other issues that underpin age-related health diseases, such as inflammation or poor nutrition. 

Additionally, while doctors have long suggested that Americans chronically suffer vitamin D deficiency, the evidence for pill supplements isn’t there. Instead, a daily dose of sunlight and eating more natural sources of vitamin D, such as fatty fish, may encourage better outcomes. 


What About Vitamin K2?

Vitamin K comes in two forms: K1, found in dark, leafy greens, and K2, found in fermented foods. Vitamin K1 gets all the credit as an essential nutrient to promote blood clotting. However, modern science suggests that many of vitamin K’s benefits can be attributed to vitamin K2. 

If you haven’t heard of vitamin K2, you’re not alone. However, it’s still a crucial vitamin that impacts many aspects of your health. In fact, preliminary studies point to vitamin K2 as a “missing link” between diet and several chronic diseases.  


What is Vitamin K2?

Like its counterpart, vitamin K2 encourages your body’s natural clotting processes. This fat-soluble nutrient is essential to prevent excessive bleeding and bruising, regulate calcium metabolism, and promote heart health. 

Specifically, vitamin K2 activates proteins involved in clotting and two proteins needed for building healthy bones. In doing so, it helps your body place calcium where it needs to go (your bones) and prevents it from going where it shouldn’t (your heart, blood vessels, and kidneys). 

Inversely, low vitamin K2 levels are linked to increased calcium buildup, decreased cognition, and early death. 


Sources of Vitamin K2

Most modern diets contain about 90% more vitamin K1 than K2. Fortunately, your body can partly convert K1 to K2 when needed, though the conversion process appears inefficient. 

Generally, K2 is produced via fermentation processes. For instance, bacteria in your large intestine produce vitamin K2. You can also consume it from a handful of foods like:

  • Egg yolks
  • Organ meats like liver
  • Grass-fed beef and chicken
  • Fermented foods like sauerkraut, miso, and natto (fermented soybeans)
  • Harder cheeses, like muenster and aged gouda, as well as fermented cheeses like bleu 

Unfortunately, the exact amount you need is unknown. Current vitamin K recommendations only pertain to K1, at 90-120 micrograms per day. While evidence suggests that benefits associated with K2 kick in at 10-45 micrograms daily, more research is needed. 


Vitamin K2 and Longevity

Like vitamin D, science indicates that vitamin K2 can extend your lifespan by preventing various age-related diseases and early death. 

For example, vitamin K2 appears to prevent arterial calcium buildup, potentially reducing your risk of heart disease.

In one study, people who took vitamin K2 supplements were 52% less likely to develop calcified arteries and 57% less likely to die from heart disease. A second study of 16,000 women found that for every 10 micrograms of K2 consumed daily, heart disease risk dropped 9%. 

Evidence also shows that low vitamin K2 levels can lead to greater arterial calcium buildup, which is directly linked to increased mortality rates. 

Vitamin K2 may also boost bone health and lower your risk of developing osteoporosis, or porous bones, particularly among older women. And substantial research shows that vitamin K2 can decrease age-related bone demineralization and lower the risk of spine and hip fractures. 

Meanwhile, three separate studies found that lower vitamin K2 levels led to a 20% increase in mortality rates in people aged 54-76. Another showed that K2 could inhibit ferroptosis, a type of cell death promoted by iron accumulation that’s linked to cancer, kidney injuries, and neurological diseases like Alzheimer’s. 

That said, most of these studies were observational; very little clinical data exists on the subject. As such, official evidence of vitamin K2’s benefits remains limited and controversial until more research is done. 

Still, with no adverse effects or toxicities reported, it doesn’t hurt to boost your intake! 



The Interplay Between Vitamin D and Vitamin K2

It’s thought that vitamins D and K2 share a synergistic link – that is, they enhance each other’s impacts. Combining the two vitamins could more effectively promote healthy bones and decrease certain age-related impacts like bone loss or demineralization

This interplay is due to their unique impacts. While vitamin D regulates proper blood mineral levels, vitamin K2 ensures it gets where it needs to go. Additionally, vitamin D promotes the production of proteins that require vitamin K2 to activate, further cementing the link. 


Vitamins D and K2: Essential for Bone Health and More

Vitamins D and K2 are both required for your body to function smoothly and build strong bones. And both vitamins – preferably taken together – can reduce instances of age-related disease and lead to longer, healthier lives. 

But in both cases, science indicates that supplements don’t produce the same benefits as natural sources. So, if you’re in need of a robust dose of vitamins D and K2, consider crunching a delicious grilled aged gouda cheese sandwich in the sunlight. 



If you’re ready to start your journey to longevity, Afiya Health is here to help. Our personalized, data-driven plans use trusted biomarkers to help you live longer and healthier. We’ll empower you to feel your best, while providing the support you need to make lasting changes.


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