Name:
A 30-Year-Old on Vitamins
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A 30-Year-Old on Vitamins
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Upload Date:
2022-02-28T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
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CATHY: Hi, welcome to Harrison's Podclass, where we discuss important concepts in internal medicine. I'm Cathy Handy.
CHARLIE: And I'm Charlie Wiener,
CHARLIE: and we're coming to you from the Johns Hopkins School of Medicine.
CATHY: Welcome to Episode 36: A 30-Year-Old on Vitamins.
CHARLIE: Here's the question. A 30-year-old woman expresses the desire to maintain a healthy lifestyle and has a focus on preventive health. She believes that she can prevent illness, and specifically cancer, through ingesting supplements and antioxidants. When reviewing her current intake, you determine that she's taking vitamin A 20,000 IU daily, and she's been taking that dose for about the past 12 months. Cathy, what do you think of that dose of vitamin A?
CATHY: Well, vitamin A-- which is labeled in international units, you will see it often referred to as IU-- so, the highest daily dose recommended in adults is 10,000 IU/day, so, she's taking twice the recommended dose, which I would not advise. I'd want to also know about any side effects, since she's been on this high dose for a year now.
CHARLIE: What kind of things would you be looking for when you ask about side effects?
CATHY: So, thinking about symptoms of chronic vitamin A toxicity, it can be varied and may involve many organ systems. The more common ones that I think about are dry skin, cheilosis, glossitis, vomiting, alopecia, bone demineralization, and pain. You can also get hypercalcemia, lymph node enlargement, hyperlipidemia, and especially in a young woman, you can get amenorrhea. Vitamin A intoxication can also cause increased intracranial pressure with pseudotumor cerebri and even liver fibrosis with portal hypertension.
CHARLIE: Wow, with all those side effects, what are the perceived benefits of this higher dose of vitamin A?
CATHY: Well, it's one of the fat-soluble vitamins, along with vitamin C, D, and E, and it's vital for normal development of the visual, immunologic, reproductive, and musculoskeletal symptoms. And vitamin A deficiency was a common cause of childhood blindness until supplementation became the norm. Vitamin A also has antioxidant properties, and this is the major rationale for why its use as a supplement has grown in recent years.
CHARLIE: And people are thinking that the antioxidant effects can benefit their risk of cancer and cardiovascular disease, right?
CATHY: Right. But you definitely would not want to take supplements at this high dose.
CHARLIE: Okay. So, the question asks: What advice can you give her regarding this dose? Option A says, chronic ingestion of this dose of vitamin A could be associated with an increased risk of lung cancer, even in non-smokers. Option B says, chronic ingestion of this dose is associated with yellowing of the skin but not the sclera. Option C says, she should discontinue this dose prior to attempting a pregnancy, as this dose could lead to an increased risk of spontaneous abortions and congenital malformations, including craniofacial abnormalities and valvular heart disease.
CHARLIE: And option D says, this dose is the highest daily recommended dose that is proven to be safe without toxicity.
CATHY: Well, we already eliminated option D because it's above the highest daily recommended dose. So, let's go through the other answer choices. So, question A asks about ingestion in association with increased risk of lung cancer in non-smokers. So, this is wrong. Now, there are conflicting data between observational studies which suggest the benefit in clinical trials, but there were two large prospective clinical trials of beta‐carotene and vitamin A looking specifically on lung cancer incidence.
CATHY: One was published in 1994 and the other in 1996, both in the New England Journal of Medicine. And both of these trials were done in male smokers because of the high incidence of lung cancer, and the goal or the major outcome of the study was to see if supplementation would decrease the risk of cancer. But both of the studies actually did not meet their primary endpoint, and they actually suggested a higher increased risk of lung cancer in those who are on supplementation.
CATHY: The more recent study that was done in 1996 looked at over 18,000 people who were at risk for lung cancer-- again, male smokers-- and found that after four years of vitamin A supplementation there was no benefit and possibly adverse effects on the risk of cancer and cardiovascular disease. But, again, these studies were both done in smokers, so the benefit or harm in terms of lung cancer risk in non-smokers, who at baseline are at a lower risk of lung cancer, has not been rigorously studied, so, we really cannot say for sure if she would gain any benefit or if non-smokers in general would gain any benefit from vitamin A supplementation.
CHARLIE: Okay, so that paradoxical increase is kind of interesting. We eliminated option A. What about the other choices? Option B asks about yellowing of the skin.
CATHY: So, option B refers to carotenemia, which is a condition that's associated with yellowing of the skin but not of the sclera. This condition is associated with the ingestion of over 30 mg of beta-carotene on a daily basis for a prolonged period of time. And beta-carotene is an organic compound found in plants and fruits, and it's a precursor to vitamin A. Children fed large amounts of carrots may develop the yellow tinge of the skin, but beta-carotene shouldn't be found in the supplement she's taking.
CATHY: So, she's really not at risk of carotenemia from her excessive use of the vitamin A supplement. So, we can rule this option out.
CHARLIE: The distinction about the sclera is important because in jaundice the sclerae are involved, right?
CATHY: Right. That's correct.
CHARLIE: Okay. So, that leaves us with option C which must be the correct option and talks about pregnancy and vitamin A.
CATHY: Yes. So, C is the correct choice. So, excess vitamin A in pregnancy can result in spontaneous abortion and congenital malformations, including craniofacial abnormalities and valvular heart disease.
CHARLIE: So, it's important that pregnant women be advised to not take excessive doses of vitamin A, right?
CATHY: Right. So, the highest daily recommended dose in adults is 10,000 IU/daily and most prenatal vitamins have about 2,000 IU, which is what you would be prescribing for pregnant women. So, more than that you would want to try and avoid your patients against.
CHARLIE: Alright. Let me just-- before we close, toss in a little bit of historical tribute for you. It was interesting that Arctic explorers who were ingesting polar bear liver developed vitamin A toxicity, and some of them actually died. We have subsequently found out that polar bear liver is enriched in vitamin A for reasons that I don't understand. But the natives who hunted polar bears and cherished the meat knew that they had to avoid liver because it was toxic. Acute vitamin A toxicity manifests as increased intracranial pressure, diplopia, vertigo, seizures, and death can occur.
CATHY: Glad I stay away from polar bear liver.
CHARLIE: Okay. So, the teaching point of this case is that high doses of vitamin A supplementation have not been demonstrated to provide any clinical benefit and, importantly, can be associated with toxicity. The toxicity is most dire in pregnant women, which can include the development of spontaneous abortion, congenital malformations in the fetus, including craniofacial abnormalities and valvular heart disease.
CATHY: And to read more about this, you can go to Harrison's chapter on General Considerations in Clinical Medicine. ♪ (music) ♪