Only 5% Have Enough—How to Join Them
The Hidden Epidemic Affecting 95% of People
Up to 95% of the United States population has a vitamin D deficiency (Linus Pauling Institute, 2018), with levels even higher in many European countries (Biesalski & Jana, 2018).
Although this deficit is linked to most chronic diseases, this does not necessarily mean it is the cause.
The only thing we know to date is this:
Low vitamin D levels are associated with disease
The Sunshine Vitamin
Vitamin D, often referred to as “the sunshine vitamin,” is not technically a vitamin, as the body can synthesize it when exposed to UVB rays from sunlight.
To maintain optimal levels, it’s recommended to spend time in the sun without sunscreen several times a week: about 10 minutes in summer and 20 minutes in winter, preferably early in the morning or late in the afternoon, adjusting the duration based on factors such as skin type, latitude, and season.
Health Benefits You’re Missing
This “vitamin” plays a fundamental role in the body. While it is known for keeping our bones strong, its functions go far beyond that.
It is essential for the proper functioning of the immune system against diseases such as rheumatoid arthritis, lupus, multiple sclerosis, type 1 diabetes, and certain types of cancer (Holick et al., 2011).
Additionally, it reduces chronic inflammation (Calton et al., 2015), which is associated with most current diseases.
Blood Testing
Thankfully, detecting a vitamin D deficiency is simple.
Common causes of this deficiency include:
Limited sun exposure
Obesity (Cordeiro et al., 2018)
Age (the older you are, the lower the synthesis)
Dark skin
Alcohol consumption
Certain medications
But with a straightforward blood test, you can find out your levels, with normal levels considered above 30 ng/ml.
Effect of Cooking Methods on Vitamin D Content
Overview of Cooking Methods and Vitamin D Retention
Cooking methods can significantly impact the retention of vitamin D in food.
The choice of cooking technique, temperature, and duration all play a role in preserving or degrading vitamin D content.
Understanding these factors is crucial for maximizing the nutritional benefits of vitamin D-rich foods.
Grilling and Oven Cooking: Effective Preservation Methods
Grilling and oven cooking are among the most effective methods for preserving vitamin D content in foods.
These methods maintain lower internal temperatures and avoid excessive moisture loss, which helps retain the vitamin D content (Kamel et al., 2024) (Sridonpai et al., 2022).
For example, grilled fish and mushrooms have been shown to retain high levels of vitamin D after cooking.
Frying and Boiling: Higher Risk of Vitamin D Loss
Frying and boiling, on the other hand, are associated with higher losses of vitamin D.
The high heat and water involved in these methods can degrade the vitamin, especially in fatty fish and mushrooms (Kamel et al., 2024) (Sridonpai et al., 2023).
However, some studies suggest that frying can still retain a significant portion of vitamin D if done at moderate temperatures and for shorter durations (Saghafi et al., 2018) (Zareie et al., 2019).
Stir-Frying and Baking: Moderate Retention
Stir-frying and baking fall somewhere in between, offering moderate retention of vitamin D.
These methods balance heat and moisture, making them suitable for preserving vitamin D in foods like mushrooms and fish (Sridonpai et al., 2023) (Cardwell et al., 2023).
Thermal Stability of Vitamin D in Fortified Foods
Fortified foods, such as vegetable oils and milk, have shown good stability of vitamin D during cooking.
For instance, vitamin D3 in fortified canola oil retains up to 87.4% of its content during normal cooking processes (Saghafi et al., 2018) (Zareie et al., 2019). Similarly, vitamin D2 in fortified milk remains stable during pasteurization and boiling (Kaushik et al., 2014) (Syama et al., 2019).
Comparison of Dietary Sources versus Supplements for Vitamin D Levels
Dietary Sources: Natural but Limited
Dietary sources of vitamin D, such as fatty fish, mushrooms, and fortified foods, provide a natural and sustainable way to improve vitamin D levels.
However, the amount of vitamin D obtained from these sources is often limited, especially in populations with restricted dietary preferences or inadequate access to fortified products (Calvo et al., 2005)(Zittermann & Pilz, 2017).
Supplements: the Most Effective
Vitamin D supplements are a highly effective way to achieve optimal levels, particularly in individuals with deficiency.
Studies have shown that supplements can significantly raise serum 25-hydroxyvitamin D levels, especially in deficient populations (Mashhura, 2022) (Barake et al., 2010).
Clinical Practice Guidelines
In 2024, the Endocrine Society issued a new clinical practice guideline (Demay et al., 2024) aimed at addressing vitamin D requirements to prevent diseases in the healthy population.
It suggests empirical (without prior testing) vitamin D supplementation only for:
People aged 1 to 18 years: the recommended dose is approximately 1,200 IU daily.
Adults under 50 years: the recommended dose is 600 IU daily.
Adults over 75 years: to reduce the risk of mortality. The recommended dose is approximately 900 IU daily.
Pregnant women: to reduce the risk of complications. The recommended dose is approximately 2,500 IU daily.
People with prediabetes: to reduce the risk of developing type 2 diabetes. The recommended dose is approximately 3,500 IU daily.
This guideline was widely criticized for not supporting routine screening for 25(OH)D in the general population and not including other population groups that could also benefit from vitamin D supplementation.
In contrast, a review published in the journal Nature (Bouillon et al., 2022) recommends:
Correcting vitamin D deficiency in all individuals who have it (which requires testing)
A daily dose of 2,000 to 4,000 IU as safe for the adult population
Combining Vitamin D With Vitamin K2
Given the variety of opinions and recommendations, you should consult your doctor.
If vitamin D supplementation is indicated in your case, it would be ideal to combine it with vitamin K2.
Together, they:
Increase bone mineral density (Kuang et al., 2020) by directing calcium to your bones.
Reduce the risk of coronary artery disease (Li et al., 2023)(Geleijnse et al., 2004) by preventing calcium buildup in arteries.
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To your zenith within,
Sara Redondo, MD
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I was low on D for years and had no clue. Love how you break it down. It's clear, grounded, and actually useful.
Vitamin D also helps the immune system to be more alert/active/powerful. I take vit D because I had a blood test and it found out I was low on that level. But then again in the UK there's not much sun as in other parts of the world. Good and informative article.