Unrealistic Hypothetical Curves For Risk Of Vitamin D Deficiency And Excess
The fundamental assumption is that, for all nutrients, there is a wide gap between risk of nutrient inadequacy and the risk of nutrient excess . The flat section of the graph is entirely hypothetical and may or may not be relevant to vitamin D. A wide gap between adequate and excessive intake is used to justify why committees that evaluate nutrient requirements are usually different and separate from the committees that evaluate excess . A narrow gap would force committees to balance risks and benefits, instead of addressing each without regard for the other.
To date, committees that address the issue of vitamin D safety have failed to address the possibility that a narrower minimum risk zone might be appropriate. The current dilemma with respect to vitamin D is how to deal with a UL that is 50 mcg/d in light of accumulating evidence that the total daily adult requirement may be 100 mcg/d .
Vitamin D Upper Levels: Review Of Potential Indicators And Selection Of Indicators
Few studies have been designed to specifically evaluate the safety of vitamin D intake, and there is not general agreement about the intake levels at which vitamin D may cause harm. A recent National Institutes of Health conference highlighted the lack of knowledge about mechanisms of action and toxic forms of the vitamin as well as the many limitations in the available evidence. Conference participants noted that available randomized controlled trials designed to illuminate health benefits likely underestimate the true potential for risk because: for ethical reasons, adverse outcomes are secondary outcomes, studies are of relatively short duration, adverse outcomes are not always adequately monitored or completely reported, and adverse outcomes generally lack adequate statistical power for detection . Further, inclusion and exclusion criteria prevent persons at greatest risk from being study participants .
Q: Do Some People Naturally Have Lower Vitamin D Levels Than Others
A: People with darker skin pigmentation tend to have lower levels, as do people who use sunscreen, dont spend much time outdoors, or are overweight or obese. This is because vitamin D is fat soluble, so it gets trapped in fatty tissue and cant be used by the body as it should be. Gastrointestinal surgery, like gastric bypass, makes it difficult to absorb vitamin D. And as we age, we dont absorb vitamin D well, and we produce less.
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What Are The New Dris For Calcium
The DRIs for calcium are based on evidence related to bone health, largely from the results of calcium balance studies. Calcium balance, which can be positive, neutral or negative, compares total calcium intake with urinary and fecal excretion of calcium. It is used to determine the accumulation and level of bone mass.
|Adequate Intake rather than Recommended Dietary Allowance.|
The IOM report states that there are no additional health benefits associated with calcium intakes above the level of the new RDA.
Total calcium intake should remain below the level of the new UL to avoid possible adverse effects. Long-term intakes above the UL increase the risk of adverse health effects, such as kidney stones.
The Final Verdict On Vitamin D
No bones about it, the endocrinologists we interviewed agree with our dermatologist.
“Just being outdoors, you get a fair amount of sun exposure and some sun-related generation of vitamin D, says Dr. Insogna. Because skin cancer, particularly melanoma, can be such a devastating disease, it’s best to use sunblock when outdoors in strong sunlight for any prolonged length of time. Because this may limit the amount of vitamin D you get from sun exposure, make sure your diet includes sources of vitamin D from foods or supplements, he says.
Both your skin and your bones will thank you.
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Experts Reassess Upper Limit Of Vitamin D Intake
Vitamin D plays a crucial role in dietary calcium absorption and maintenance of blood calcium levels, both of which have a direct effect on bone health. Recent studies show that vitamin D may help prevent colon cancer1 and diabetes2 among other things.
The Food and Nutrition Boards current upper limit of vitamin D3 of 50 ìg per day was calculated based on 10-year old data. Researchers reviewed the most recent vitamin D studies to determine if the current upper limit should be raised in order to get the most benefit out of vitamin D supplementation.
In order to do this, they compared the results of more than 20 individual studies involving vitamin D3 supplementation. They gave preference to studies where the amount of vitamin D3 supplementation was correlated with 25-hydroxyvitamin D and calcium blood concentrations. Hypercalcemia, measured by elevated blood calcium, was selected as the measure of vitamin D toxicity. Hypercalcemias clinical manifestations include pain, conjunctivitis, anorexia, fever, chills, thirst, vomiting, and weight loss.
It should be noted that the researchers concluded that other possible side effects of vitamin D supplementation, i.e. kidney stones and cardiovascular disease, were not a problem at this level.
Hathcock, John N., et al. Risk assessment for vitamin D. The American journal of clinical nutrition 85.1 : 6-18.
Posted August 5, 2008.
Good Sources Of Vitamin D
From about late March/early April to the end of September, most people should be able to make all the vitamin D they need from sunlight.
The body creates vitamin D from direct sunlight on the skin when outdoors.
But between October and early March we do not make enough vitamin D from sunlight. Read more about vitamin D and sunlight.
Vitamin D is also found in a small number of foods.
- fortified foods such as some fat spreads and breakfast cereals
Another source of vitamin D is dietary supplements.
In the UK, cows’ milk is generally not a good source of vitamin D because it is not fortified, as it is in some other countries.
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What Vitamin D Dosage Is Best
Vitamin D is commonly known as the sunshine vitamin.
Thats because your skin makes vitamin D when it is exposed to sunlight .
Getting enough vitamin D is important for optimal health. It helps maintain strong and healthy bones, aids your immune system and may help protect against many harmful conditions .
Despite its importance, roughly 42% of people in the US have a vitamin D deficiency. This number rises to a staggering 82.1% of black people and 69.2% of Hispanic people .
There are several other groups of people that have higher vitamin D needs because of their age, where they live and certain medical conditions.
This article will help you discover how much vitamin D you need daily.
What Research Gaps Were Identified
The IOM expert committee identified areas where further research would help improve the determination of reference values in the future. A total of 22 major research needs were identified and are summarized in Table 9-1 of the report. The general categories of information gaps are:
- Data on the physiology and metabolism of calcium and vitamin D
- Data on health outcomes and adverse effects related to calcium and vitamin D
- Data on dose-response relationships between intakes of calcium and vitamin D and health outcomes
- Evidence to judge independent effects of calcium and vitamin D
- Information on the impact and role of sun exposure relative to vitamin D
- Standardized and consistent data on calcium and vitamin D intakes
- Exploration of methodologies for synthesizing evidence
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The New Safe Upper Limit Still Too Low
There is no record of anyone, anywhere, ever becoming vitamin D toxic from sunshine alone. So we can be pretty sure that even 20,000 IU of vitamin D3 daily is not toxic for a healthy adult.
In fact there has never been a case of vitamin D toxicity at anything less than 30,000 IUs of vitamin D daily.
In the light of modern research, widespread vitamin D deficiency and epidemic levels of vitamin D-related diseases, an upper limit for vitamin D of just 4000 IU is still much too low.
- It does not allow people who are seriously vitamin D deficient to quickly restore their vitamin D levels to healthy levels.
- Some people cannot maintain even an adequate vitamin D blood level on 4000 IU per day
Vitamin D, toxicity only occurs when a very large accumulation of the vitamin has been taken into the body , in excess of the bodys requirement.
Up to that point, even very high daily doses of vitamin D3 carry little risk for people in good health, even though repeated daily for several weeks.
If you are uncomfortable about taking the higher doses of vitamin D required to reach optimum vitamin D levels, then you may be reassured by the IOMs Safe Upper Limit.
After all, if the IOM thinks you will be quite safe taking 4000 IU of vitamin D per day, you can be pretty sure its O.K!
But even 4000 IU may not be the right dose for you, if you are aiming for optimum vitamin D. It could be too high, and it could be too low, depending on your own Personal Vitamin D Dosage.
Want to know more?
Is Vitamin D Vegan
Vitamin D3 has historically been made from lanolin extracted from sheep wool, but recently, a vegan/vegetarian form has become available. This version is extracted from lichen and it is called Vitashine. This product is also sugar, wheat, gluten, and dairy-free.
Vitamin D2 supplements, made by irradiating mushrooms, are also vegan/vegetarian-friendly.
Studies have shown that D3 increases blood levels of vitamin D more significantly than D2.
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Recommended Daily Intakes And Upper Limits For Vitamins And Minerals
See Your Nutritional Requirements
The table below provides the daily intakes of vitamins and minerals by age, gender, and life stage based on the latest Recommended Daily Allowances and Adequate Intakes , as well as Tolerable Upper Intake Levels developed by National Academies of Sciences, Engineering, and Medicine.
- ULs from Dietary Reference Intakes : Tolerable Upper Intake Levels, Vitamins from the National Academies
Vitamin D Supplement Safety
Your body produces vitamin D when exposed to the sun, but many people may not get enough due to a variety of factors. Because of this, people often turn to vitamin D supplements. Unfortunately, it isnt uncommon for people to overdo it.
A 2017 study published in The Journal of the American Medical Association found that between 1999 and 2014, there was an increase in the number of American adults taking daily vitamin D supplements of 1,000 IU or more. Of these, 18% exceeded 1000 IU each day and 3% took more than 4,000 IU per day, which may place them at a higher risk of experiencing some adverse effects related to excessive vitamin D.
In most cases, you can get all of the vitamin D you need naturally without supplementation through sun exposure and diet. A 15-minute walk outside each day with your extremities exposed can boost vitamin D production. .
Eating foods that are naturally high in vitamin D or are fortified with the nutrient can help. Foods you can eat to boost your vitamin D levels include:
- Fortified milk, yogurt, or juice
- Fatter fish such as tuna or salmon
If you do decide to take a vitamin D supplement to correct a deficiency or because you are unable to get an adequate amount through sunlight and diet, always follow your doctor’s guidelines and do not take more than recommended amounts.
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What Is A Low Vitamin D Level
There is a bit of controversy regarding what is considered a low vitamin D level between different expert organizations. A vitamin D level measures levels of 25D in the blood .
Most experts recommend:
- Levels of 20-50 nanograms/milliliter of 25D: Sufficient
- Levels of 12-19 ng/ml: Borderline
- Levels of less than 12 ng/ml: Deficient
However, not everybody agrees, and some organizations suggest different cut-off values.
The Institute of Medicine states:
- Levels above 20 ng/ml: Sufficient
- Levels below 20 ng/ml: Deficient
Note that several members of the IOM committee publicly stated that over screening for vitamin D deficiency was a problem which typically resulted in unnecessary treatment. They were not in agreement with a cut-off level of 20 ng/ml for deficiency and recommended a lower level of 12.5 ng/ml.
The Endocrine Society states:
- Levels above 30 ng/ml: Sufficient however, some assays are inaccurate and levels of 40-60 ng/ml better guarantee sufficiency
- Levels of 21-29 ng/ml: Insufficient
- Levels below 20 ng/ml: Deficient
Talk to your doctor about what he/she considers to be a low vitamin D level.
Food Choices To Fill Calcium Shortfalls3
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How Do I Know If I Have Vitamin D Deficiency
Vitamin D deficiency is measured with a blood test that measures 25D. This is the form of D3 that has undergone conversion by the liver although it is still inactive and requires further conversion by the kidneys to active vitamin D3, 1,25D.
The reason 25D is measured is because it is the most stable form of D3. It is also the most abundant form and lasts several weeks in the body. It is a good representation of how much vitamin D has been obtained from both diet and sun exposure.
Conversely, 1,25D only lasts for a few hours in the body and levels are a thousand-fold less than those of 25D. Our body also has a way of increasing the production of active D3 by the kidneys during times of deficiency and insufficiency, so a blood test for 1,25D may appear normal or elevated even when your actual levels of vitamin D are low. However, in some disorders of calcium metabolism, the 1,25D test may be used.
25D levels will tell your doctor if you are deficient in vitamin D, borderline, sufficient, or vitamin D toxic.
See the flow chart above for an overview of the different forms of vitamin d.
Calcium Upper Levels: Review Of Potential Indicators And Selection Of Indicators
Excess calcium intake from foods alone is difficult if not impossible to achieve. Rather, excess intakes are more likely to be associated with the use of calcium supplements. However, the potential indicators for the adverse outcomes of excessive calcium intake are not characterized by a robust data set that clearly provides a basis for a doseresponse relationship. The measures available are confounded by a range of variables including other dietary factors and pre-existing disease conditions.
The classic toxicity state of hypercalcemia is seen with either calcium or vitamin D excess, although it appears that the symptoms of hypercalcemia are manifested at relatively lower intake of calcium compared with vitamin D, for which high intakes are required to reach a toxic state. In the discussions below, hypercalcemia, as well as, hypercalciuria is described first as general conditions associated with the toxicity of either nutrient, followed by a discussion of adverse outcomes associated with excess calcium intake.
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How Much Is Too Much
Because vitamin D is a fat-soluble vitamin, it can build up in the body. So it is possible to get too much of it.
The National Institutes of Health says these are the upper limits per day for vitamin D:
- Birth to 6 months: 25 mcg
- Babies 7-12 months: 38 mcg
- Children 1-3 years: 63 mcg
- Children 4-8 years: 75 mcg
- Children 9-18 years: 100 mcg
- Adults 19 and older: 100 mcg
- If pregnant or breastfeeding: 100 mcg
“There is a potential to cause harm if you overdose on supplements above 4,000 IU/day, but there is no fear of overdosing from the sun, because your skin acts like a regulatory system, only allowing production of the amount of vitamin D you need,” says Patsy Brannon, PhD, a Cornell University professor of nutritional sciences who served on an Institute of Medicine committee that reviewed vitamin D recommendations.
Vitamin D Benefits And Warnings
Although the research is still hazy, some people will benefit from taking vitamin D supplements, along with sufficient calcium intake, to promote their bone health. But they don’t require large amounts of vitamin D to get the benefit. “More is not necessarily better. In fact, more can be worse,” says Dr. Manson. For example, a 2010 study published in JAMA showed that intake of very high doses of vitamin D in older women was associated with more falls and fractures.
In addition, taking a supplement that contains too much vitamin D can be toxic in rare cases. It can lead to hypercalcemia, a condition in which too much calcium builds up in the blood, potentially forming deposits in the arteries or soft tissues. It may also predispose people to painful kidney stones.
If you’re taking vitamin D supplements, the take-home message is moderation. Taking too much can limit the benefits of the sunshine vitamin.
Selected food sources of vitamin D
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