Vitamin D requirements are highly Individual - vitamin D status is dependent on numerous factors, such as your skin color, your location, and how much sunshine you're exposed to on a regular basis. The ONLY way to be sure, is to get your blood level tested.
Your body stores vitamin D for a few weeks / months - if you get enough sun exposure during the summer months, you may have enough for the winter too, but most people in the U.S.would benefit from supplemental vitamin D during winter.
Conventional (woefully deficient) RDAs:
• 400 IU for infants, children and adolescents |
• 200 IU for adults up to age 50 |
• 400 IU for adults aged 51 to 70 |
• 600 IU for seniors over 70 |
Since the RDA for vitamin D was set in 1997 at 400-600 IU (International units), there have been more than 3000 studies finding that this level is barely sufficient to even prevent rickets (weakened bones) and does nothing to protect from cancer, heart disease and infections. To get a feel for vitamin D amounts, realize that under ideal conditions it is frequently possible to generate ~ 20,000 IU of vitamin D by exposing your skin to the sun.
Recommended daily vitamin D Intake for OPTIMAL health is 35 IU's of vitamin D per pound of body weight. Based on the most recent research E.g. For a 40# child, the recommended average dose would be 1,400 IU /day, and for a 170# adult, the dose would be nearly 6,000 IU's.
Blood CALCIDIOL levels
We are designed to be in the sun - ideally, we can produce vitamin D3 from UV-B spectrum sunlight acting on the skin which converts cholesterol precursor(7-DHC) in the skin into D3. UV-B rays occur when the zenith angle of the sun is > 45°, typically 10am to 2pm, and depends on latitude and season. Obtaining sun at these times optimizes skin's vitamin D production, whilst minimizing UV-A damage to skin.
A light skinned person needs at least 30 minutes of ~ 1/3 body (arms, lower legs, face, hands) exposure, without sunscreen, and with clear skies (Up to 1 or more hours may be needed for darker skinned people and the elderly).
For more information on how to effectively and safely obtain vitaminD3 by exposing skin to sunlight:
The "Sunbath"- as vitamin D Therapy"
Food Sources of vitamin D3
Food Source of vitamin D2
Sun-exposed / dried mushrooms can provide a significant source of D2 Sun-exposed, sliced and dried mushrooms retain their high vitamin D2 content for many months and provide a good, NATURAL, supplemental source those who do not see the sun too much during that e winter months.
Mushrooms in Sunlight - Significant provitamin D2 Source
Vitamin D from Supplements / Fortified Foods
Fortified whole-fat milk. 1 cup whole milk (vitamin D added, look for the D3 form, not D2) -98 IU
D2 vs. D3. The two manufactured forms typically used to fortify food, such as milk, orange juice, bread and cereals, and used in vitamin supplements are:
Studies conclude that vitamin D3 is considerably more potent than D2 (conservatively stated at 4 times more potent). In one particular study, although both D2 and D3 initially produced a similar rise in blood CALCIDIOL, after 3 days it then fell rapidly to baseline within 14 days, while D3 treated people continued to rise to a peak by 14 days, and then stayed high. Armas LA et al, D2 is much less effective than D3 in humans. J Clin Endocrinol Metab 2004;89:5387-91] Abstract/FREE Full Text
It is suggested that this reflects the different affinities of D2 and D3 for the vitamin D binding protein. Also, D2 is broken down more rapidly than D3, and has a shorter shelf-life. One study estimated D2 at 20-40% as efficient as D3 at raising blood CALCIDIOL levels. Trang HM, Cole DE, Rubin LA, Pierratos A, Siu S, Vieth R: Evidence that vitamin D3 increases serum 25-hydroxyvitamin D more efficiently than does vitamin D2. Am J Clin Nutr 1998, 68:854-858. PubMedAbstract | PublisherFullText
Since the drug companies have a license for the use of the patented D2 form of D, expect to find that form in prescription supplements.
Due to many factors, vitamin D Dosage is highly individual and the only way to know for sure if you are getting the right amount is to test your blood CALCIDIOL (25(OH)D) level
Age | Dosage |
Under 5 | 35 IU/#/day |
Age 5-10 | 2500 IU |
Age 18-30 | 5000 IU |
Pregnant Women |
5000 IU |
( 1 µg vit. D = 40 IU )
The vitamin D council recommends ~ 4000 IU from dietary intake in the absence of UV-B light
It is important to realize that vitamins A and D work hand-in-hand. Both protecting and supporting one another. Human studies not taking this into account produce skewed results, and animal studies show that even moderate amounts of vitamin D (from any source)increases the body's need for vitamin A. Vitamin A will help protect you from an excess of vitamin D. The best food source of vitamin A is beef liver, at least 3-4 oz eaten once per week. Alternatively, take 50,000 units of vitamin A concentrates from fish once or twice a week; Beta-carotene does not provide enough vitamin A to balance vitamin D.
Effectiveness of vitamin D supplementation requires the simultaneous / balanced dietary inclusion of calcium, magnesium, phosphorus, and vitamin K :
You need the right fats for efficient use of vitamin D
VITAMIN D toxicity is considered to exist when one has very high blood levels of vitamin D and calcium AND calcium deposits in soft tissues. Studies on this complex subject are much debated, and it is difficult to draw solid conclusions. To avoid toxicity, it would seem that VITAMIN D levels need to be in the "just right" range, neither too little, nor too much. Evidence also suggests vitamin D toxicity may result from a relative deficiency of vitamins A and K. Symptoms of vitamin D toxemia, such as excessive calcium levels, are not generally observed until CALCIDIOL levels reach ~150 ng/mL. Koutkia P, et al, 2001. Note: Robert Heany reports toxicity at 250 nmol/ L, which is 100 ng / mL, produced from >10,000 IU D / day.
Overdose of vitamin D from the sun is prevented by two inbuilt mechanisms:
CALCITRIOL [1,25(OH)D], the active form of vitamin D DOES NOT provide a satisfactory indication of a person's vitamin D status. Its best evaluation and the "gold-standard" is obtained from the circulating CALCIDIOL [25(OH)D] level.
Recommended Testing Lab - Lab Corp in the US; if the test is done by Quest Diagnostics Lab, then divide your result by 1.3 to get the "real" number.
Ng / ml vs. nmol/l -ng / ml are the units of measure in the U.S., However, much of the world uses nmol/l. Test results measured in nmol/l, are multiplied by 2.5 to get ng/ml.
Normal vs. Optimal CALCIDIOL Levels
25 (OH) D CALCIDIOL LEVELS |
|||
Deficient |
Optimal |
With Cancer |
Too High |
<50 ng/ml |
50-65 ng/ml |
65-90 ng/ml |
>100 ng/ml |
Barger-Lux MJ, Heaney RP, Dowell S, Chen TC, Holick MF: Vitamin D and its major metabolites: serum levels after graded oral dosing in healthy men. Osteoporos Int 1998, 8:222-230. PubMed