Archive for the ‘Vitamin D’ Category

Vitamin D Deficiency

Sunday, November 15th, 2009

Here is an email exchange I recently had:

November 06, 2009

Hi Jack,

I’ve been vegan for almost two years and am wondering about a skin condition I recently developed. I have a red flaky patch of skin right below the corner of my lip and above both eyelids. The patch is not itchy or yellowish, so I suspect it is not eczema. I am wondering if the patches are the result of a vitamin deficiency. I used to take a multivitamin, but I quit taking it because my skin took on a yellowish hue, especially in the winter when I eat more squash (and my doctor thought I might be getting too much beta-carotene). I now only take a B-complex vitamin. Is it possible that the skin patches are a sign that I’m not getting enough of a particular vitamin?

My response:

A lack of vitamin D can cause psoriasis in some cases, but other than D and B-vitamins, which it sounds like you are good on, I don’t know what it might be or if it is likely to be nutrition-related. It’s definitely not a common complaint I hear from people who are vegan.

November 14, 2009

Dear Jack,

I saw my primary care doctor this week and she speculated that I might have a vitamin D deficiency. I began taking supplements and going outside for 30 minutes a day around noon. The patches have all but disappeared in a matter of days. Just wanted to let you know in case you ever come across any other individuals with the same condition. I have since read more about the health problems associated with vitamin D deficiency, and I am thankful my deficiency manifested itself in a way that I was able to take notice and do something about it.

Addendum Nov 15, sent from a different reader:

I had ‘eczema’ for years every winter and when I started taking Vitamin D2, 2000 IU, it went away for good. I also had my 25-hydroxy-Vitamin D level tested and it was at the very lowest end of normal…. Any skin condition that’s worse in the winter (where UV is low in the winter) I would suspect Vitamin D deficiency.

Carrot Juice and Sunburn

Wednesday, October 28th, 2009

I was corresponding with JoAnn Farb who told me something interesting she has noticed about carrot juice protecting against sunburn:

“I discovered on several occasions that drinking large amounts of carrot juice and/or to a lesser extent — simply eating huge amounts of raw greens, reduces any observable changes in skin color (burning or tanning) when exposed to sun.

“I first noticed this on a canoe trip — years ago — I should have burned — was not using sunscreen and everyone else who didn’t use it did burn badly. But I had been drinking lots of carrot juice every day before hand. Then again in Australia, in January, in Sydney on the beach, Sarina [her daughter] was one year old at the time and pretty much nursing for all her calories. Each day over the noon hour I took her to the beach and let her crawl around naked — and I was in a swim suit. At first I just did ten minutes and then we put full clothing on. Each day I saw no burn and no tan. I increased the time more — until we were fully exposed for well over an hour and saw absolutely no reactions on our skin. There were juice bars everywhere; I was drinking two to three large glasses of fresh carrot juice every day.

“I have certainly had my share of sunburns at other times, from much less exposure, but have tested this repeatedly. Not only will carrot juice protect me and my family from sunburns, but if we have not been drinking carrot juice and do happen to burn, we will drink large amounts right away and the burn fades quickly.”

I have long known about the orange tint that people who drink a lot of carrot juice can get, but I was not aware of any sunburn protection. I checked it out and found research showing that beta-carotene does protect against sunburn:

Köpcke W, Krutmann J. Protection from sunburn with beta-Carotene — a meta-analysis. Photochem Photobiol. 2008 Mar-Apr;84(2):284-8. Epub 2007 Dec 15.

The study found that taking beta-carotene for 10 weeks, in amounts of about 57 mg per day, protected against sunburn. One cup of carrot juice has about 22 mg of beta-carotene.

The researchers said the SPF of beta-carotene was about 4. They thought the benefit from beta-carotene could be due to its antioxidant potential or interference in other parts of the biochemical pathways leading to sunburn.

JoAnn went on to ask:

“I have always wondered, since Michael Hollick mentions the pinking of the skin as a way to get an indication of how much vitamin D one is potentially making, does consuming all this carrot juice in some way inhibit vitamin D production? Or is the pinking of the skin merely a general way to gauge melanin amounts but otherwise not really related to biosynthesis of D?”

I’m afraid I do not know the answer to this and I could not find any research on it. I did, however, find one study in which higher intakes of beta-carotene were associated with less bone mineral loss in the elderly:

Sahni S, Hannan MT, Blumberg J, Cupples LA, Kiel DP, Tucker KL. Inverse association of carotenoid intakes with 4-y change in bone mineral density in elderly men and women: the Framingham osteoporosis Study. Am J Clin Nutr. 2009 Jan;89(1):416-24. Epub 2008 Dec 3.

It appears that in this case, beta-carotene was not noticeably interfering with any vitamin D formation in these people, though this is a very indirect way to try to answer that question.

Vitamin D in Older People

Tuesday, May 19th, 2009

Nothing major, but I just updated the vitamin D page of with results from a study on vitamin D supplementation in older people. It’s short, so I will just cut and paste it here.

Older People

As mentioned in the recommendations, elderly people need 30 minutes a day of direct sunlight in order to produce adequate vitamin D.

A 2009 study from Ireland showed that people aged 64 years or older needed 15 mcg (600 IU) per day to bring vitamin D levels from an average of 55 nmol/L to 74 nmol/L. The researchers estimated that it would take about 40 mcg (1600 IU) per day to raise 97.5% of the participants’ vitamin D levels to 80 nmol/L.

Although some researchers recommend maintaining vitamin D levels at 80 nmol/L, there is not enough evidence to know that there is much of a difference between 74 and 80 nmol/L. For this reason, the recommendation of 25 mcg (1,000 IU) should suffice for people aged 64 and older.

Upper Body Exercise & Bone Density

Thursday, May 7th, 2009

It has long been thought that exercise is good for bones because the stress stimulates the bones to become stronger. Heavier people generally have higher bone mineral density (BMD), presumably due to the higher stress put on their bones.

Some time ago, I was giving a talk and mentioned that exercise is good for bones. Someone asked if you need to exercise your upper body in order for bones in your upper body to benefit from exercise. I didn’t know the answer; it didn’t seem unreasonable to me that any exercise could stimulate increased BMD via hormones circulating throughout the entire body.

I finally got around to looking into it today. I found a number of abstracts of experiments and meta-analyses looking at whether exercise improves BMD. Most indicated that exercise does improve BMD in certain spots, especially the hip and spine.

I only found one study that compared upper body exercise to lower body exercise:

Winters-Stone KM, Snow CM. Site-specific response of bone to exercise in premenopausal women. Bone. 2006 Dec;39(6):1203-9. Epub 2006 Jul 28.

People who did upper and lower body exercise had more improvement in their lower back BMD compared to people who only did lower body exercise. Unfortunately, it appears that they didn’t measure the spine in the upper back or other upper body areas which would have been interesting information.

This is just one study and I don’t think it’s conclusive, but so far it appears that at least some of your bones will benefit from doing upper body resistance exercise in addition to lower body exercise.

More Vitamin D – Interview with Michael Holick

Thursday, April 30th, 2009

I just read a very engaging article about vitamin D (and that is saying a lot, I find most nutrition articles to be drowse-inducing). It is an interview with one of the world’s foremost vitamin D experts, Michael Holick. It is free on the web here.

A quick summary of the main points:

– 30 to 80% of the US population is vitamin D deficient.
– Vitamin D can protect against cancers, autoimmune diseases, infections, and bone problems.
– If you live north of Atlanta, your skin can’t make vitamin D from November through March.
– Both children and adults need 1,000 IU a day to keep their vitamin D levels above 30 ng/ml (about 75 nmol/L), which is the most healthy level.
– You need massive amounts of vitamin D to overdose. 5,000 IU per day, indefinitely, is probably safe.
– Vitamin D2 is as effective as D3.
– The sun is the most efficient way to receive vitamin D and may have important health benefits beyond vitamin D production.

For sun exposure, Dr. Holick says:

“I typically recommend people go out for a period of time—depending on the time of the year, the time of day, the latitude, and the degree of skin pigmentation—if you know you’re going to get a mild sunburn after 30 minutes, I typically recommend about 10, no more than 15, minutes of arms and legs exposure, or if you’re in a bathing suit, abdomen and back exposure as well, 2 to 3 times a week. Always wear sun protection on your face because that’s the most sun-damaged area and it’s only about 9% of your body surface, so it doesn’t provide you with that much vitamin D. Go out, enjoy yourself, get some sensible sun exposure, then put sunscreen on if you plan to stay out for a longer period of time. People with a higher degree skin pigmentation, such as African Americans, are walking around with an SPF of 8 to 15. That’s why they need to be exposed for much longer periods of time and why people of color are at especially high risk of having vitamin D deficiency.”

Vitamin D in Seventh-day Adventist Vegetarians

Tuesday, April 28th, 2009

I have just updated with info on vegetarians’ vitamin D levels from the Adventist Health Study-2 which were recently released.

The good news is that vegetarians were no worse off than non-vegetarians. The bad news was that many of them were deficient, especially African Americans.

You can read more here.

And make sure you are following the vitamin D recommendations.