Vitamin A: A Neglected Nutrient by Many Vegans?

Vitamin A is found only in animal products, but the body can create it out of carotenoids, like beta-carotene.

When I first got involved in vegan nutrition, vitamin A was considered a non-issue because we assumed most vegans would easily get enough beta-carotene with any sort of varied diet to cover our needs.

But in 2001, the Food and Nutrition Board (FNB) doubled the amount of beta-carotene they said was enough to meet vitamin A needs. According to the FNB, this change was based on “data demonstrating that the vitamin A activity of dietary β-carotene is one-sixth, rather than one-third, the vitamin activity of purified β-carotene in oil (1).”

They go on to say:

“This change in bioconversion means that a larger amount of provitamin A carotenoids, and therefore darkly colored, carotene-rich fruits and vegetables, is needed to meet the vitamin A requirement. It also means that in the past, vitamin A intake has been overestimated.”

This change mostly flew under the radar, but it made a significant difference in how easy it would be to get enough beta-carotene.

I recently became more concerned about vitamin A, quite literally, by accident. Early last Fall, I twice got up in the middle of the night and walked straight into my bedroom door that was halfway open, face-first!

Over the previous year or so, I had slacked off on vitamin A, relying only on a bit of shredded carrots on salad and mangoes on most days. In mid-November, I decided I needed to make a real effort to add more yellow vegetables to my diet and started eating sweet potatoes every day. A few weeks later, I realized that I had been having no trouble seeing the bedroom door at night. I wondered if there was a connection to what seemed to be my improved night vision.

In checking out whether it was likely that my apparent change in night vision was possibly caused by eating more beta-carotene, I was reminded that vitamin A metabolism is involved with immune function. When vegans get sick easily, I tell them to think about more zinc or protein, neglecting any concern about vitamin A. (Interestingly, vitamin A metabolism appears to rely on zinc.)

Vitamin A deficiency symptoms begin with night blindness, and if it progresses, can lead to the more severe eye problems of corneal ulcers, scarring, and blindness (2). Vitamin A is also important for growth and development in infants and children, and for red blood cell formation (2).

Because I suspect that many vegans might not be giving vitamin A any thought, I decided to make this post and add some information to Vitamin A at VeganHealth.org. That link has a chart showing which foods are high in carotenoids. I would encourage everyone to check the chart to make sure they are getting enough. And you might save yourself a few bumps on the noggin!

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References

1. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: The National Academies Press, 2001. | link

2. Vitamin A. Linus Pauling Institute. Accessed 1/25/2013. | link

4 Responses to “Vitamin A: A Neglected Nutrient by Many Vegans?”

  1. Carry Says:

    You’ve got me really intrigued… I was under the impression that Vit A and beta-carotene supplements bordered on dangerous. And that a diet with lots of fruits and vegetables (containing carotenoids and phytochemicals) was the best.

    In Finnish trials, using beta-carotene supplements failed to prevent lung cancer, and there was actually an increase in cancer in those who took the supplement. This study was halted when the physician researchers discovered the death rate from lung cancer was 28 percent higher among participants who had taken the high amounts of beta-carotene and vitamin A. The death rate from heart disease was also 17 percent higher in those who had taken the supplements compared to those just given a placebo. Another recent study showed similar results, correlating beta-carotene supplementation with an increased occurrence of prostate cancer. Furthermore, a meta-analysis of antioxidant vitamin supplementation found that beta-carotene supplementation was associated with increased all-cause mortality rate.

    As a result of these European studies, as well as similar studies conducted here in the United States, articles in the New England Journal of Medicine, the Journal of the National Cancer Institute, and the Lancet all advise people to stop taking beta-carotene supplements.

    In humans, excess vitamin A is potentially a problem, even in ranges not normally considered toxic. One study found that subjects with a vitamin A intake in the range of 1.5 mg had double the hip fracture rate of those with an intake in that range of .5 mg. For every 1 mg increase in vitamin A consumption, hip fracture rate increased by 68%. Vitamin A supplementation has also been associated with a 16% increase in all-cause mortality.

    Here are some studies, supporting the above:
    Whiting SJ. Lemde B. Excess retinol intake may explain the high incidence of osteoporosis in northern Europe. Nutr Rev. 1999. 57(6): 192-195.
    Melhus H. Michaelson K. Kindmark A. et al. Excessive dietary intake of vitamin A is associated with reduced bone mineral density and increased risk of hip fracture. Ann Intern Med. 1998.129(10): 770-778.
    Omenn GS. Goodman GE. Thornquist MD. Et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. New England Journal of Medicine. 1996. 334(18): 1145-1149.
    Mayne ST. Beta-carotene, carotenoids, and disease prevention in humans. FASEB. 1996;10(7):690-701.
    Goodman GE. Prevention of lung cancer. Current Opinion in Oncology 1998;10(2):122-126.
    Omenn GS, Goodman GE, Thornquist MD, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. New England Journal of Medicine 1996;334(18);1150-1155. Hennekens CH, Buring JE, Manson JE, et al.
    Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease. New England Journal of Medicine 1996;334(18):1145-1149.
    Albanes D, Heinonen OP, Taylor PR, et al. Alpha-tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta-carotene cancer prevention study: effects of base-line characteristics and study compliance. Journal of the National Cancer Institute. 1996;88(21):1560-1570.
    Rapola JM, Virtamo J, Ripatti S, et al. Randomized trial of alpha-tocopherol and beta-carotene supplements on incidence of major coronary events in men with previous myocardial infarction. Lancet 1997;349(9067):1715-1720.
    D Bjelakovic G, Nikolava D, Gluud LL, et al. Antioxidant supplements for prevention of mortality in healthy participants and patient with various diseases. Cochrane Database Syst Rev 2008;16(2):CD00776.
    Kolata G. Studies Find Beta Carotene, Taken by Millions, Can’t Forestall Cancer or Heart Disease. New York Times, Jan. 19, 1996.
    Bjelakovic G et al. Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases. Cochrane Database Syst Rev. 2008 Apr 16;(2):CD007176.
    Hennekens CH. Buring JE. Manson JE. et al. Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease. New England Journal of Medicine. 1996. 334(18): 1145-1149.
    Albanes D. Heinonen OP. Taylor PR, et al. Alpha-tocopherol and beta-carotene supplements and lung cancer incidence in the alpha-tocopherol, beta carotene cancer prevention study: effects of base line characteristics and study compliance. Journal of the National Cancer Institute. 1996. 88(21):1156-1570.
    Rapola JM, Viramo J, Ripatti S. et al. Randomized trial of Alpha-Tocopherol and Beta-Carotene supplements on incidence of major coronary events in men with previous myocardial infarction. Lancet. 1997. 349(9067): 1715-1720.

  2. Jack Norris RD Says:

    Carry,

    Good reminders. I’m not suggesting people take beta-carotene supplements, just get it through foods. That said, I don’t know that the amount of beta-carotene in a typical multivitamin is dangerous. I would try to avoid pre-formed vitamin A or retinol supplements.

  3. Joe Says:

    As a concerned non-RD vegan, I just want to make sure I understand what you are suggesting better: When you said you added more “yellow vegetables” to your diet, what did you actually eat? You mentioned adding more sweet potato, which I know is supposed to help with Vit. A needs, but does that count as a yellow vegetable? What vegetables did you have in mind (yellow corn, squash, yellow bell peppers)?

  4. Jack Norris RD Says:

    Joe,

    I meant sweet potatoes and carrots. Technically, potatoes are vegetables and corn is a grain (and corn is not high in beta-carotene). You can see a list of the foods high in beta-carotene (most of which are “yellow vegetables”) here:

    http://veganhealth.org/articles/vitamina

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