Ever since the French sailors, weakened by scurvy, lost control of the seas to the British navy which was scurvy-free by vitamin C in the lime juice added to their daily ration of grog (hence the name “Limeys”), vitamins have been a subject of great interest and, even now, a lot of mystery. Everyone agrees that a little bit of them is essential for good health, but even two-time Nobel Prize winner Linus Pauling couldn’t convince all of us that a lot of vitamin C could cure a cold. (1)
Vitamin D is currently the most popular vitamin to study because of some past research suggesting that vitamin D protects us from heart disease, particularly the elderly. A 2012 survey reported that about 20% of respondents were taking vitamin D supplements (multivitamin supplements were not included). Supplemental vitamin D AND supplemental calcium have long been touted for preventing loss of bone density, or osteoporosis, especially in post-menopausal women.
It is clear that Vitamin D deficiency can cause growth retardation and bone disease, particularly in the first years of life. It is a bit unclear as to how much of vitamin D we need. The American Academy of Pediatrics recommends vitamin D supplements of 400 units a day for breast-fed babies. Recommendations for minimum doses in other than infants range from 400 units to 2000 units a day. It is said to be almost impossible to be “vitamin deficient” on a normal diet nowadays, but certain very restricted vegan diets can cause some problems in rare cases. Also, studies of Northern urban children (less sun exposure) revealed “low” Vitamin D blood levels which stirred up a lot of discussion about its significance and about “what level was normal”. Too much of most vitamins can’t really hurt you too much. Most “excess” of vitamins ingested ( the amount over the minimum required to prevent a deficiency disease) just ends up in the toilet via your urine.
A recent systematic review of a large number of peer-reviewed research studies on the use of supplemental Vitamin D to reduce the risk of cardiovascular disease was recently published. (2) This meta-analysis (our trade name for such huge reviews) of 21 randomized clinical trials with over 83,000 participants (mean age, 65) followed for 1 to 12 years showed that using a variety of Vitamin D supplements did NOT lower the risk for myocardial infarction, stroke, cardiovascular-related deaths, or all-cause deaths. This is “the best evidence to date that fails to support use of vitamin D supplementation for lowering cardiovascular risk.” (3)
Of course, the results of that meta analysis was muddied just a bit by another meta analysis of 52 clinical trials with over 75,000 participants (mean age, 74) with 1 year follow-up which showed that Vitamin D supplements was associated with 4 per 1000 persons fewer deaths from cancer in a small sub-group of participants. (4) To further confuse the issue, it was noted that this small but significant difference occurred in only those people taking the D³ form of oral Vitamin D, not those taking the D² form. But, this review also revealed no cardiovascular benefits.
What about effects of vitamin D supplements on bone-density? If the recommended daily dose of vitamin D is from 400 to 2000 units, what if we took twice that? About 3% of U.S. adults take over 4000 units of vitamin D daily. A Canadian randomized study of 311 adults with pre-study normal vitamin D blood levels took either 400, 4000, or 10,000 units per day of supplemental vitamin D for three years. Bone density actually DECREASED in those taking the higher doses. Also, the vitamin D blood levels in those taking the 400 units (recommended minimum) did not increase above normal. “The findings point to no benefit for bone integrity—and even harm—with high dose vitamin D supplementation in patients with adequate vitamin D blood levels.” (5)
In today’s blog I offer evidence-based skepticism about the benefits of both vitamin C and vitamin D supplements. In my last blog I cautioned against vitamin E . . .at least the inhaled form. Is there a vitamin F supplement to continue my progression? Yes, there is! Vitamin F is an outdated term for omega-3 and omega-6 fatty acids, but I think I’ll let that subject “sleep with the fishes” for the moment.
References
1. “Vitamin C and The Common Cold”, Linus Pauling, 1970 and 1976.
2. JAMA Cardiology 2019 Aug; 4:765
3. NEJM Journal Watch cardiology,vol.39, Oct. 2019)
4. NEJM 2019;380:33
5. JAMA 2019Aug27;322:736
HUB's LIST of medical fun facts 