You’ve likely heard about vitamin D’s important role in maintaining strong bones and teeth. But it also plays several other important roles to keep your body healthy – including the function of your gut.
As part of our research on how a dietary fiber supplement affects bone mass in children and adolescents, the MetA-Bone Trial, we are also studying gut health.
For this study, we recruited 213 children and adolescents from South Florida, primarily Hispanics, though some were Black. Before having them start taking the fiber supplement, we measured their vitamin D levels to ensure they had adequate amounts. Surprisingly, we found that 68% of these children had suboptimal vitamin D levels.
Considering South Florida is an area with plenty of sunshine year-round, this was both startling and concerning. While vitamin D can be obtained from foods, most people in the U.S. get this vitamin primarily from skin exposure to sunlight. For youth approaching or experiencing puberty – a period of profound physiological changes, including rapid changes in bone mass – vitamin D deficiency could lead to several health issues.
Connection between vitamin D and health
Vitamin D is involved in so many bodily functions because there are vitamin D receptors in different organs. These receptors act like docking stations for vitamin D to bind to and trigger different effects in the skin, intestine, bone, parathyroid gland, immune system and pancreas, among others.
Vitamin D regulates calcium levels in the body, which is key for not only building and maintaining bone mass but also the basic functioning of the nervous system.
Vitamin D also stimulates cell differentiation, a process in which cells become specialized to carry out specific functions. It is also essential to insulin secretion to control blood sugar levels, blood pressure regulation, muscle repair and regeneration, immune function and nutrient absorption, among many other functions.
Vitamin D and gut health
The vitamin D receptors in your gut improve calcium absorption and strengthen your intestinal barrier.
The intestinal barrier is a layered wall that allows your gut to absorb nutrients and keep out harmful bacteria. This wall is composed of intestinal cells and proteins called tight junctions that act like bricks sealing these cells together. Tight junctions play an important role in maintaining the structure of your intestinal barrier.
Vitamin D receptors help your gut produce tight junctions to maintain your intestinal barrier. Research suggests that vitamin D deficiency reduces production of the receptors the nutrient binds to, subsequently reducing the seal of the intestinal wall. This weakening of the gut barrier may allow substances from the intestine to pass into the blood, causing inflammation. Disruption of the intestinal barrier is linked to many diseases, including liver disease, Type 1 diabetes, obesity and gastrointestinal conditions such as celiac disease, inflammatory bowel disease and colon cancer.
After discovering that so many of the participants in our MetA-Bone Trial had suboptimal vitamin D levels, we became interested in understanding how this nutrient might be affecting their gut health. For this, we also measured the strength of their intestinal barrier and associated this to their vitamin D levels in blood.
We found that children with suboptimal vitamin D levels had a higher risk of damaging their intestinal barrier compared with children with optimal vitamin D levels. This finding suggests that even in healthy children, suboptimal levels of vitamin D may compromise the gut and potentially increase the risk of developing chronic diseases at an early age.
Getting enough vitamin D
Vitamin D deficiency is highly prevalent in the U.S. and around the world. Roughly 15.4% of children and adolescents in the U.S. were vitamin D deficient in 2017. While vitamin D deficiency has slightly decreased over time in the general U.S. population, it remains high among teens, especially children with darker skin.
How can you ensure you are getting enough of this important nutrient?
Only a few foods naturally contain vitamin D. For example, vitamin D is naturally found in fatty fish – such as trout, salmon, cod and tuna – egg yolks and mushrooms. Vitamin D can also be found in many fortified foods, such as dairy products like milk and cheese, plant-based milks, breakfast cereals, some orange juice brands and infant formulas. Dietary supplements are also good sources of vitamin D.
For most people in the U.S., Sun exposure is their main source of vitamin D. However, how much Sun exposure you need depends on several factors, such as the melanin content of your skin. Melanin is a pigment that protects your skin from ultraviolet radiation. People with more melanin – and therefore darker skin – produce less vitamin D from Sun exposure than those with less melanin and may thus require longer Sun exposure to meet minimum requirements.
Since excessive ultraviolet radiation is associated with skin cancer, clinicians typically recommend you meet your vitamin D requirements through foods and beverages. For healthy children and adults, the recommended dietary allowance of vitamin D is 600 IU, with an age-based upper limit of no more than 1,000 to 4,000 IU. You can usually meet this through a healthy diet that includes a variety of whole and unprocessed foods.
Researchers continue to uncover the extensive benefits of vitamin D in the body, supporting its indispensable role in nutrition and health. For growing children and adolescents, enough vitamin D is important for healthy development.
Jacqueline Hernandez is Assistant Professor of Dietetics and Nutrition, Florida International University. Cristina Palacios is Professor and Chair of Dietetics and Nutrition, Florida International University.
The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.
© The Conversation
24 Comments
virusrex
One important clarification is that the article clearly says the levels in the patients studied are "suboptimal" while the headline call them "deficient" which is not the same thing.
This is important because the problems with deficiency are not all the same, and there is a huge difference between what levels can cause bone development problems and which can cause gut problems as in this study. This is why sometimes it is found that supplementation has no real effect on something where vitamin D is involved, (like bone density or respiratory infections) the levels in the patient can be "suboptimal" and still be enough to support those functions without problems.
In this aspect the finding of this study is important because (if replicated) it can indicate problems that are specially sensitive to these levels and that can be improved even on people that have enough vitamin D to avoid other kinds of conditions.
Raw Beer
68% of the 213 children and adolescents recruited for their study had suboptimal vitamin D levels. But later on the article states: "Vitamin D deficiency is highly prevalent in the U.S. and around the world. Roughly 15.4% of children and adolescents in the U.S. were vitamin D deficient in 2017."
So the headline is accurate, many children (~15.4%) are deficient in vitD. It is not referring to the 68% suboptimal in their study.
Raw Beer
These are all things I mentioned here countless times since the start of the pandemic, but was always summarily dismissed by the usual propharma members. People with darker skin were greatly affected by Covid; I'm sure many lives could have been saved if this information was widely disseminated during the pandemic. Unfortunately, we could only hear or read about it on the "conspiracy" and "bro-science" websites...
Raw Beer
Having suboptimal (not just deficient) levels adversely affects immune function. So most people would benefit from increasing their levels.
I have come across a number of studies showing that sun exposure provides additional benefits, compared to supplementation. The Medcram Youtube channel does a good job describing this.
I generally make an effort to get some sun exposure when possible, but trying to avoid it around noon. And I supplement when I can't get much sun.
virusrex
Still worth of clarifying since this can be misinterpreted (or misused by bad actors) to pretend the suboptimal levels are enough to produce negative effects all around, not just on the specific mechanism found here.
Not at all, you misrepresented the actual information to pretend any level below suboptimal would necessarily have a negative effect on immunity against covid or other respiratory infections, this has been proved false scientifically, that is why your claims could be dismissed, because the best available evidence refutes them.
Yet the experts contradict you and consider vitamin D supplementation only helpful on people that have clinical signs of deficiency, not just laboratory levels below what is considered normal, once again not all physiological process require the same minimum amount of vitamin D.
This is precisely because of their lack of reliability and the fact that they routinely choose to hide scientific information that contradict what brings these sites profits.
And how is the cost benefit considering the higher risks of cancer? that is explicitly in the comment you quote because it is a very important consideration, even if marginal benefits could be obtained, this becomes invalid if the risks are much higher. Since it is relatively easy to get Vitamin D from normal nutrition this is obviously the much better option, all theoretical benefits without the extra risks.
Youtube channels are not scientific studies.
Raw Beer
It's a doctor showing us several actual peer-reviewed studies.
Raw Beer
Yeah, the quote says that "excessive ultraviolet radiation is associated with skin cancer."
All those recommending sun exposure clearly say to avoid excessive exposure, and to avoid exposure around noon.
Raw Beer
No, experts now recommend aiming for optimal levels, not just to overcome deficiency. Including those consulted for the above article.
virusrex
None that you have brought to prove your point, a doctor is not the one making claims here, you are.
And exposition lead to excessive ultraviolet radiation, that means that increasing exposition can only come with higher risks of exposition and cancer (yes even if not done at noon). This is a cost that can make a marginal benefit irrelevant, specially when the same benefit can be obtained by following a healthy diet instead. No extra risks, all the benefits.
The article is not the one claiming that suboptimal levels of vitamin D have clinical significance for respiratory infections, you were the one making that claim even when it is refuted scientifically. It is fine and everything to have good levels of vitamin D, but to say that this would have made people without clinical signs of deficiency have better outcomes for covid is not supported by evidence, in fact it is contradicted by evidence that prove that supplementation did not bring added benefits for patients suffering from covid.
Nibek32
A majority of Americans are both obese and quite unhealthy. The standard American diet (SAD) is to blame. This is what happens when you let food and medical corporations dictate your health recommendations.
No money to make with healthy people.
virusrex
"Medical corporations" recommendations are perfectly valid and are (generally speaking) the same as in Japan, that people systematically try their best to ignore these recommendations do not make the recommendations wrong, that is a terribly irrational argument.
Lots of money actually, people like remaining healthy and doctors still get their salaries supporting this, I mean, it is not like doctors in Japan are poor, right?
Nibek32
@virus
I’m not talking about Japan. I’m talking about the US.
Japan’s system is not as broken, and people are much healthier.
virusrex
But the recommendations from the "medical corporations" about what constitutes a healthy diet are (again, in general) the same, that means that blaming those recommendations is not logical, because that would necessarily mean that Japan would be in even worse condition because the population listen to those recommendations even more than in the US.
The point is that in the US the population do not have healthy diets as recommended by the doctors. So you can blame food corporations as much as you want (and many other factors, from cultural to genetic and social) but not what the doctors recommend.
Jay
Ridiculous. The “recommendations” you’re defending -the ones pushed by medical corporations and government food pyramids - are directly influenced by lobbyists from Big Ag, Big Sugar, and ultra-processed food conglomerates. These are the SAME geniuses who told people in the 80's and 90s to eat 6–11 servings of grains per day and avoid fat like it was plutonium.
Be honest and admit these guidelines weren’t built on health - they were built on lobbying. And no, Japan’s relatively better health isn’t thanks to those guidelines - it’s because the traditional diet here is nothing like the ultra-processed, seed-oil-soaked sludge pushed over there.
And saying “Americans just don’t follow the recommendations” misses the point: the recommendations themselves are flawed. People aren’t thriving when they do follow them - they’re getting sicker.
You want health? Ditch the corporate guidelines and eat REAL, ancestral food. The medical-industrial complex isn’t in the business of prevention - it’s in the business of "managing" disease, ie a band-aid fix. And we’re absolutely RIGHT to call that out.
Raw Beer
But for some time (decades), doctors have been recommending avoiding the sun, and to always use sunscreen. That recommendation is best avoided, as long as you avoid excessive exposure.
virusrex
Baseless accusations that you keep repeating as an excuse for not having arguments nor evidence, the same as flat earthers and creationists do when confronted the same.
The recommendations are the same as in Japan and many other countries yet obesity is not a problem, this simple fact disproves the false claim that the recommendations are the problem, after all since the Japanese do eat much more accordingly then the country should have a much bigger problem right?
Grains are a perfectly good source of nutrients, and excess of fat is a well known factor of risk for cardiac health, the current recommendations are still valid and you have never provided any scientific argument to refute them, a balanced diet without excess of anything is still key to a good health.
You are not refuting the argument, you are just explaining how the Japanese adhere better to the recommendations. You just disproved your own argument.
You have never provided any scientific reference that says the current recommendations (that explicitly say the less ultraprocessed food is better) are wrong, just claim they are wrong as if you had presented anything or had a valid appeal to authority, this is of course not the case.
No, that is not best avoided, there is no problem avoiding sunlight and using sunscreen, after all this guarantees a lower risk of skin cancer, and you can get all the vitamin D you need from a healthy diet. All the benefits, none of the risks. This of course in no way demonstrates any dietary recommendation in the US (or the rest of the world) is wrong.
Nibek32
@jay
SPOT ON!
Raw Beer
Being fat is a risk factor, but not dietary fat (except seed oils).
Many of the dietary recommendations from the "respected institutes of medicine" are making people fat.
virusrex
That is completely incorrect, the cardiologists have clearly and unequivocally proved that dietary fat (nothing special about seed oils) do contribute to cardiac problems, the nail in the coffin comes from the intervention studies where statins (that work lowering cholesterol) clearly improved cardiac health, at this point there is no sense in negating this, it is as irrational as believing all the medical organizations of the world are in some impossible global conspiracy.
Jay
Not sure what this flat-earther nonsense is about but I think it proves there isn't much substance in your argument. The traditional Japanese diet emphasizes unprocessed, seasonal foods - fermented vegetables, fatty fish, organ meats, and broth-based dishes. The moment heavily-processed Western food began penetrating Japan's market? Obesity and chronic disease started rising. So no, the “recommendations” aren’t saving them - they’re surviving in spite of them.
And refined grains offer very minimal nutrient density compared to animal-based foods. Even whole grains can’t match the bioavailability or completeness of nutrients from meat, eggs, and organ foods. The truth is, grains became dietary staples because they were cheap and easy to store - NOT because they were ideal for human health.
As for fat being a risk factor for heart disease - what century are we living in? The “saturated fat kills” narrative has been collapsing for over a decade. Multiple large-scale studies and meta-analyses (including in The Lancet and AJCN) have shown no consistent link between saturated fat intake and heart disease. The real villains? Industrial seed oils, processed sugar, and chronically elevated insulin levels - exactly the kind of damage you get from FOLLOWING conventional dietary guidelines.
And NO, saying “everything in moderation” is not a good statement when the food conglomerate definition of “moderation” includes highly addictive, inflammatory ultra-processed junk... the framework is broken from the start.
Raw Beer
Yeah, I read that countless times, that saturated fat is associated with higher LDL, which is associated with increased risk of cardiovascular disease. But experts looking at the evidence are finally increasingly giving up on the idea of LDL having a causative role in CVD.
virusrex
No, that is completely false, you keep making this claim but when challenged to bring any institution of medical science that support this claim you have never brought any. Because there is none.
I mean, you are not going to expect people to believe every single respected institution of health in the whole world is in a conspiracy to lie about it, right? the only logical conclusion is that dietary fat should be limited, and that there is no special danger from oils produced from seeds.
Wick's pencil
Well, maybe it's time for the institution of medical science to keep up with the data. What Rawbeer and Jay wrote is what the data shows.
Maybe the institutions of medical science are involved in a "conspiracy" to focus on profits over health.
virusrex
It was very simple to show it was not, at all. This explain why the experts of the whole world are not even remotely likely to be wrong, while the people that contradict them use false arguments and terribly flawed references because there is nothing actually reliable supporting their claims.
The same excuse of flat earthers that blame all the institutions of planetary science of being involved in a conspiracy to focus on profit over disclosing the real shape of the planet.
Beyond what is believable, specially looking at the absolute lack of evidence brought to prove the opposite point.