Archive for the ‘Beta-carotene’ Category

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.

What Supplements Do I Take?

Tuesday, October 27th, 2009

Updated September 2013

Every month or so, someone reads my recommendations for vegans, checks out some vegan multivitamins, and then writes me asking about the high levels (many times the RDA) of some individual vitamins in many of the vegan multivitamins.

B vitamins (including folic acid) and vitamin C can be very high in multivitamins. There are concerns that taking folic acid could be linked to cancer, but this connection is far from proven. In the meantime, limiting folic acid is prudent. [A meta-analysis from 2013 found no link between folic acid and cancer in the many clinical trials that have been performed using large amounts of folic acid. (1)] I’m not aware of any risks in taking B vitamins and vitamin C in the amounts found in typical vegan multivitamins.

There is also evidence that taking vitamin A (as retinol, retinyl palmitate, or retinyl acetate) can cause osteoporosis at typical amounts of 1,500 mcg (5,000 IU) found in vitamins. Vitamin A as carotenoids does not cause osteoporosis and is what is typically found in vegan vitamins. See Vitamin A at the Linus Pauling Institute for more info.

I thought it might interest readers to hear what supplements I take:

Calcium & Zinc: In the morning, I drink calcium-fortified soy milk and take a 25 mg zinc supplement (I break a 50 mg supplement in half). In the evening, I take one-half of a Trader Joe’s Ca/Mg/Zn supplement which provides 250 mg of calcium, 125 mg of magnesium, and 3.25 mg of zinc. I take it for the calcium and zinc.

Vitamin B12: I take half of a Trader Joe’s High Potency B “50” tablet every morning and evening. This provides 50 µg of vitamin B12. I also suspect I can use a bit extra riboflavin which this provides.

Iodine: I take a 225 µg kelp tablet about once every 3 days. I hardly ever eat seaweed.

Vitamin D: During the warmer months (when sunburn is possible) I get out in the sun a lot, probably too much. During the colder months, I take a vitamin D supplement of 1,000 IU each day. Vitamin D2 supplements should be fine. I had my vitamin D levels tested in September of 2011 and they were at 34 ng/ml (84 nmol/l).

Vitamin A: I am pretty good about eating yellow vegetables or drinking carrot juice every day.

Omega-3s: I am a bit of an anomaly and do not adhere to my own recommendations. Around 2002, I had my blood clotting time tested. Being a vegan, I wanted to make sure I was getting enough omega-3s and that my blood wasn’t clotting too fast. Well, it turned out that it was actually clotting a bit too slowly. I had been taking one teaspoon of flaxseed oil per day for a couple years and decided to stop supplementing. I have had my clotting time tested a number of times since then and it is always a bit slower than normal. So for omega-3s, I will take a DHA tablet once in awhile, but by no means as often as I recommend for other vegans.

Creatine: I am a recreational weightlifter, lifting three times per week with short but intense workouts. For a long time, I supplemented with creatine off and on, but I think I’m finally done with that. It might benefit elite vegetarian athletes, but I did not find any consistent enough results to justify the cost or bother.

Reference

1. Martí-Carvajal AJ, Solà I, Lathyris D, Karakitsiou DE, Simancas-Racines D. Homocysteine-lowering interventions for preventing cardiovascular events. Cochrane Database Syst Rev. 2013 Jan 31;1:CD006612. | link

Vitamin A

Monday, April 13th, 2009

A nutrient not many people think a lot about is vitamin A. I just updated VeganHealth.org with the vitamin A content of various plant foods. Take a look there and make sure you’re getting enough!