Vitamin D: Nature’s Boon to us

The newest superstar supplement  (and I must say, I’m on board with the bandwagon) is vitamin D, which isn’t a vitamin at all as it can be synthesized by the body (when the skin is exposed to sunlight) – it’s actually a prohormone. Nonetheless, vitamin D is important to many bodily functions and research is finding that many Americans are deficient in it, which may be contributing to chronic diseases.

Vitamin D refers to a group of fat-soluble secosteroids responsible for enhancing intestinal absorption of calcium, iron, magnesium, phosphateand zinc. In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol). Cholecalciferol and ergocalciferol can be ingested from the diet and from supplements. Very few foods contain vitamin D; synthesis of vitamin D (specifically cholecalciferol) in the skin is the major natural source of the vitamin. Dermal synthesis of vitamin D from cholesterol is dependent on sun exposure (specifically UVB radiation).

Vitamin D from the diet or dermal synthesis from sunlight is biologically inactive; activation requires enzymatic conversion (hydroxylation) in the liver and kidney. Evidence indicates the synthesis of vitamin D from sun exposure is regulated by a negative feedback loop that prevents toxicity, but because of uncertainty about the cancer risk from sunlight, no recommendations are issued by the Institute of Medicine (US), for the amount of sun exposure required to meet vitamin D requirements. Accordingly, the Dietary Reference Intake for vitamin D assumes no synthesis occurs and all of a person’s vitamin D is from food intake, although that will rarely occur in practice. As vitamin D is synthesized in adequate amounts by most poeple exposed to sunlight.

A diet deficient in vitamin D in conjunction with inadequate sun exposure causes osteomalacia (or rickets when it occurs in children), which is a softening of the bones. In the developed world, this is a rare disease. However, vitamin D deficiency has become a worldwide issue in the elderly and remains common in children and adults. Low blood calcidiol (25-hydroxy-vitamin D) can result from avoiding the sun. Deficiency results in impaired bone mineralization and bone damage which leads to bone-softening diseases.

Vitamin D - Natures Boon to us

Benefits of Vitamin D


Vitamin D

  • Helps calcium absorption from the gut and maintains normal blood levels of calcium and phosphorus. If not enough calcium is absorbed from the intestines, the body will take calcium from the bones to normalize blood levels – which we obviously don’t want!
    • Without adequate vitamin D and calcium, only 10-15% of dietary calcium and 60% dietary phosphorus is absorbed
  • Prevents rickets (soft bones) in children, osteomalacia (weak bones) and osteoporosis in adults [see above mechanism]
  • Recent research indicates that adequate stores of vitamin D may play a role in preventing many chronic diseases and conditions including cancer, hypertension, diabetes, allergies in children, multiple sclerosis
    • One study reported that postmenopausal women who increased their vitamin D intake by 1100 IU of vitamin D3 reduced their relative risk of cancer by 60 to 77%
    • Several studies have linked vitamin D deficiency and colon, prostate, breast ovary and esophageal cancer, with blood levels >20ng/mL reducing the risk by as much as 30-50% according to one study
  • Likely plays a role in optimizing immune function
  • May help prevent cardiovascular disease by inhibiting inflammation [chronic inflammation is a risk factor for heart disease]

Those that may be at risk of deficiency: elderly, obese individuals, dark skinned individuals, lack of exposure to sunlight, exclusively breast fed infants, diets that avoid dairy/egg products, those with limited sun exposure, after gastric bypass surgery, hospitalized patients.

Specific disease states that increase the risk of vitamin D deficiency include cystic fibrosis, inflammatory bowel disease, celiac disease, diabetes, pancreatic disease, kidney disease, cardiovascular disease, and liver disease

The test: Ask your doc to check 25hydroxyvitamin-D – there are a few different lab values they can check, but this is best indicator of vitamin D status in the body as it reflects the amount of vitamin D produced by the body and consumed (not in body tissues however).

How much do you need?

The Institute of Medicine recently came out with new [controversial] recommendations for vitamin D and calcium:

  • 0-12 months — 400 International Units (IU)
  • 1-70 years — 600 IU
  • >70 years — 800 IU

Many other health professionals (MD’s and RD’s) agree that this isn’t enough to do all the amazing things listed above. I get that the IOM is playing it safe, but with 30-50% of the general population being deficient, and the tolerable upper limit (maximum amount considered safe) being 4000 IU/day, supplementing 1000-2000 IU per day is my general recommendation for teenagers on. If you’re deficient [which I encourage all my patients to get checked] you actually would need 50,000 IU per week for about eight weeks and then a maintenence dose of 50,000 IU per month thereafter.

Benefits of Vitamin D

Sources of Vitamin D

Your body makes vitamin D when the skin is exposed to sunlight. However, it can be difficult to obtain the necessary amounts based on many variables affecting the amount synthesized including: season, length of exposure, sunscreen, skin color (melanin content – the more this pigment you have, the darker your skin is and more difficult to synthesize vitamin D), and time of day. Some researchers suggest that 5-30 minutes of sun exposure without sunscreen from 10:00 AM and 3:00 PM at least twice per week to the face, legs, arms or back should be adequate. However, you won’t find many health professionals recommending 60+ minutes of sunscreenless exposure per week due to risks for melanoma (skin cancer).

The best natural food source of vitamin D3 is fatty fish and some mushrooms contain D2. Fortified milk contains about 100 IU per 1 cup – meaning to meet the IOM’s recommendations, you would need to drink 6 cups per day (even of skim milk, that’s an extra 480 calories per day, or almost +1 pound per week – we won’t even talk about if it’s not skim milk); to meet my recommendations, 10-20 eight ounce glasses of milk per day!

Understanding Benefits of Vitamin D

Test Results on Vitamin D

Per the National Institute of Health, here’s what your blood test results mean:

<11 ng/mL (Deficiency) —  Rickets in infants and children

<15 ng/mL (Insufficient) — Inadequate for bone and overall health

>30 ng/mL (Sufficient) — Proposed as desirable level and disease prevention

>200 ng/mL (Intoxication) — Considered potentially toxic

Many experts recommend blood levels closer to 50-75ng/mL for optimal health.

D2 or D3?

Vitamin D2 (ergocalciferol) comes from yeast, while Vitamin D3 (cholecalciferol) is found naturally in cod liver oil and oily fish such as salmon and can be obtained from sheep’s wool. Studies have had varied results, but many tend to think D3 is more effective at raising blood levels of vitamin D. However, if you are a vegan/vegetarian, D2 may be a better option and will still have positive effects.

Note: Make sure to take your vitamin D supplements with a meal containing fat – it is a fat soluble vitamin meaning that it needs fat to be absorbed.

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