Vitamin D, technically not a vitamin, but a steroid hormone is produced out of cholesterol when your skin is exposed to the sun. Vitamin D was identified by Adolf Windaus, who was awarded the Nobel Prize for Chemistry in 1928. The discovery was a key factor in the eradication of rickets. The importance of Vitamin D has also been found to have many more benefits than bone health. It also has anti-inflammatory properties and helps form ‘killer cells’ which support the immune system. A deficiency is Linked to many diseases from diabetes to neurological conditions, e.g. dementia, heart disease, and cancers. In fact Low levels of vitamin D increase the risk of dying from all causes by 150%
There are actually two main forms found in the diet: Vitamin D3 (cholecalciferol): Found in some animal foods, like fatty fish and egg yolks.Vitamin D2 (ergocalciferol): Found in some mushrooms.
Of the two, D3 (cholecalciferol) is the one we’re interested in, because it is almost twice as effective at increasing blood levels of vitamin D as the D2 form.
The conversion of vitamin D happens first in the liver and then in the kidneys before it becomes the compound that is biologically active: calcitriol.
ARE WE GETTING ENOUGH?
Unfortunately there is a deficiency in D in the vast majority of the US population.
A study published Archives of Internal Medicine suggest up to ¾ USA adults not getting enough.
Why a deficiency pandemic?
Well best source of D is sunshine. For thousands of years our ancestors lived in the sun., then 50,000 years ago we migrated north. Working indoors, then moved to cities where buildings blocked sunshine and traveled by car then start to wear sunblock. But the problem is many sunscreens block UVB needed for vitamin D production (and UVB doesn’t cause melanoma UVA does)
What are some vitamin D foods?
It isn’t easy to get enough vitamin D from your diet. While fortified vitamin D foods such as milk and cereals are available, most provide vitamin D2, a form which is much less well utilized by the body than D3.
The best dietary sources include sockeye salmon, tuna, mackerel and sardines, eggs. Also mushrooms IF grown in light. (most are commercially grown in the dark).
As we know the best source is sunlight so daily exposure is helpful.
HOW do we balance sun exposure?
Estimate the amount of time it would take for your skin to turn pink – or slightly, but noticeably darker – in the sun. Then reduce that time by 50 percent if you have fair skin, 25 percent for darker skin, and get that amount of exposure between 11 a.m. and 3 p.m. two to three times per week.
Can WE OVERDOSE?
Despite the fact that more people are now taking vitamin D supplements, it’s rare to find someone with very high blood levels of this vitamin.
One recent study looked at data from more than 20,000 people over a 10-year period. It found that only 37 people had levels above 100 ng/ml (250 nmol/l). Only one person had true toxicity, at 364 ng/ml (899 nmol/l) (8).
In one case study, a woman had a level of 476 ng/ml (1,171 nmol/l) after taking a supplement that gave her 186,900 IU of vitamin D3 per day for two months (9).
This was a whopping 47 X the generally recommended safe upper limit of 4,000 IU per day.
The woman was admitted to the hospital after she experienced fatigue, forgetfulness, nausea, vomiting, slurred speech and other symptoms (9).
Although only extremely large doses can cause toxicity so rapidly, even strong supporters of these supplements recommend an upper limit of 10,000 IU per day (3).
Although many symptoms of excessive vitamin D are attributed to high blood calcium levels, some researchers suggest that mega doses may lead to low levels of vitamin K2 in the blood (18).
One of vitamin K2’s most important functions is to keep calcium in the bones and out of the blood. It’s believed that very high vitamin D levels may reduce vitamin K2 activity (18, 19).
To protect yourself against bone loss, avoid taking excessive vitamin D supplements and take a vitamin K2 supplement. You can also consume foods rich in vitamin K2, such as grass-fed dairy and meat.