Should You Take a Supplement or Enjoy the Sunshine? Answers to Vitamin-D Questions.

Supplementing Your Diet with Vitamin D: Questions and Answers.
By Tanya Wilson

If you are considering a vitamin D supplement as an adjunct to healthy weight loss, or simply as part of a healthier diet, here are some commonly asked questions and answers. We hope you find this list helpful

What are some risk factors for vitamin D deficiency?

Milk allergy and lactose intolerance.

Digestive disorders, such as Crohn’s disease or celiac sprue.

Strict vegetarian diet.

Very low-fat diets or taking fat-blocking medications:

Some dietary fat is required in the gut for Vitamin D to be digested and absorbed by the body. See below for which medications and fat-blockers.

Naturally darker skin pigmentation:

Higher levels of melanin are thought to block UV radiation and thus interfere with vitamin D synthesis in the skin. It is important to note that there are a few studies that contradict this.

Obesity:

Studies have shown obese people (those with BMI of 30 or above) tend to have lower levels of vitamin D in their blood. The exact reasons for this are still being studied, but it could be because the excess fat tissue stores and locks in the vitamin, keeping it from entering circulation in the blood.

Age 50 years and older:

As we age, the skin’s ability to synthesize vitamin D weakens, and the kidneys are less able to convert vitamin D into its active hormone form.

Limiting sun exposure:

This includes those who spend a lot of time indoors, cover their arms and legs when outside, or consistently use sunscreen.

Living in a northern climate:

Picture a line running from northern end of California to Boston. At this line, UV radiation from sunlight is insufficient for natural production of vitamin D from November to Febuary. As you go further north, this time period can last as long as six months.

How can you produce Vitamin D naturally through sunlight?

There isn’t enough scientific data available to establish exact guidelines for the amount of sun exposure needed to produce adequate levels of vitamin D in the skin naturally. The following are just general guidelines, always keep in mind that too much sun exposure can do much more harm than good.

5-30 minutes of sun exposure (UV radiation) between 10 a.m. and 3 p.m., twice a week should be adequate. This is with face, arms, legs or back exposed, without sunscreen.

Commercial tanning beds which emit 2-6% UVB radiation are also effective for natural vitamin D synthesis.

Sunshine filtered through glass windows is not effective- UV radiation will not penetrate glass.

Complete cloud cover and shade can reduce UV rays by 50-60%.

Sunscreens of SPF-8 and above will interfere with natural production of vitamin D in the skin.

What is the daily requirement for vitamin D?

No strict dietary requirements are established, instead there is a very light, very conservative estimate called “adequate intake” or AI. This is because vitamin D can be synthesized in the skin and because there is still debate as to just how much is enough, and how much is too much.

Adequate Intake is the Same for Men and Women:

0 -13 years: 200 IU (5 mcg)

14-18 years: 200 IU (5 mcg)

19-50 years: 200 IU (5 mcg)

51-70 years: 400 IU (10 mcg)

71 + years: 600 IU (15 mcg)

Maximum Intake of Vitamin D:

2000 IU (50mcg) for both males and females over age 13

Can you get too much vitamin D?

You cannot get too much through sun-exposure. Natural vitamin D synthesis is self-limiting; Once it reaches a certain concentration in the skin, it starts breaking down.

BUT, you can possibly get too much as a diet supplement.

By ingesting vitamin D, you’re bypassing the skin and its self-limiting mechanism. Since D is a fat-soluble vitamin, the excess won’t be broken down and flushed out of your system via the kidneys. Instead, the body ferrets it away into existing fat tissue so levels may build up; however vitamin D toxicity is uncommon.

Are there side effects from too much vitamin D?

Symptoms of vitamin D toxicity include:

nausea, vomiting, poor appetite, constipation, weakness, severe weight loss, confusion, abnormal heart rhythm, higher likelihood of kidney stones

Can vitamin D interact with other medications?

Yes. Always check with your physician and pharmacist before considering any dietary supplement, whether it’s for weight loss or any other reason.

Here are a few examples:

Vitamin D supplements can interfere with these medications:

Calcium Channel-Blockers

Thiazide Diuretics

Lanoxin (Digoxin)

These medications can interfere with vitamin-D absorption/use by the body:

Corticosteroid medications (prednisone)

Cholestyramine, also called Questran, LoCholest, and Prevalite

Phenobarbital

Phenytoin (Dilantin)

Cimetidine (Tagamet)

Fat blockers can interfere with the absorption of Vitamn D:

Fat Blockers (Orlistat, also called Xenical and Alli)

If you are using a fat-blocker:

For vitamin D to be absorbed a small amount of fat is needed, or it just passes through. Many doctors recommend a supplement if you are on one of these weight loss aids; however it’s unclear how effective supplementation is in this situation.

In this case, you should check with your physician about spending a few minutes in the sun instead and having your blood levels checked.

The latest research associates low vitamin D levels with poorer weight loss rates, and less abdominal fat loss while on a low-calorie diet.

What foods contain vitamin D?

Not many. The foods highest in vitamin D are generally fish, particularly salmon, mackerel and tuna, or fish livers (an acquired taste…). Much smaller amounts can be found in egg yolk, beef liver, some mushrooms, and cheeses.

In fact, vitamin D in the typical Western diet comes mainly from fortified dairy products. This is why individuals who are lactose-intolerant, suffer milk allergies, or are on a strict vegan diet are at risk for deficiency.

Here are some examples for comparison:

Cod liver oil, 1 Tbs. = 1,360 IU

Vitamin-D fortified Milk = 98 IU

Salmon, cooked (3.5 oz) = 360 IU

Tuna, canned in oil (3 oz) = 200 IU

Egg (whole) = 20 IU

Swiss Cheese (1 oz) = 12 IU

Lastly, vitamin D absorption is not enhanced by calcium.

It’s the other way around- vitamin D helps with the absorption of calcium. Therefore, if you’re considering a vitamin D supplement of 2000 units, you do not have to increase your calcium intake to “keep up” with that. If you want a more potent supplement, vitamin D3 (cholecalciferol) will raise blood levels of vitamin D more effectively than vitamin D2 (ergocalciferol).

As always, consult with your physician before starting a new weight loss regimen or taking any supplements, including vitamins.

To learn more about what vitamin D is, its connection to other illnesses, and adding it to a healthy diet plan, Vitamin D for Quick Weight Loss

Reference:

National Institutes of Health, Dietary Supplement Fact sheet: Vitamin D.