Vitamin Culture Part II: The Efficacy of Vitamins
Vitamin Culture Part II: The Efficacy of Vitamins
March 4, 2024
Joy Stepinski, MSN, RN-BC
Last month we looked at the historical perspective of vitamins, which gave insight into the lack of regulation and oversight of vitamin manufacturing. Additionally, we considered fortification and enrichment of food with synthetic supplements. This month we will delve into some of the research findings to determine the reported efficacy of vitamins.
First, let’s briefly explore vitamin use in our modern culture. In an article published in JAMA (Journal of the American Medical Association), results from the National Health and Nutrition Examination Survey provide awareness of current practice [1]. Among surveyed nonpregnant adults, 52% of participants used at least one dietary supplement in 30 days, and 31% used a multivitamin-mineral supplement. The treatment reasons selected were designated as overall health and wellness, and to accommodate for lack of nutrition.
According to the JAMA authors, the US Preventative Services Task Force commissioned a review of supplementation efficacy, particularly concerning the benefits for cardiovascular disease and cancer (the top two causes of death) and overall mortality. The findings concluded insufficient evidence to support the benefits of supplementation with multivitamins for either cardiovascular disease or cancer. There was no benefit of vitamin E supplementation. Furthermore, there was a risk of harm with synthetic beta-carotene (the carotenoid that gives plants an orange pigment and transforms into vitamin A in the body). Beta-carotene was found to cause an increased risk of lung cancer among smokers or people with asbestos exposure. The potential for adverse effects exists for vitamin supplementation. For example, vitamin A can reduce bone mineral density and vitamin D can cause kidney stones. The authors stated that “the USPTF concludes that the evidence is insufficient to determine the balance of benefits and harms of supplementation with single or paired nutrients for the prevention of cardiovascular disease or cancer.”
Vitamin C is a popular supplement equated with good health because of its high level of antioxidants. In one study, researchers compared the antioxidant activity of Red Delicious apples to that of a vitamin C supplement [2]. In the research findings, the authors concluded that 100 grams of apples with their skin intact, or approximately ½ cup of sliced apples, are equivalent to 1,500 mg of vitamin C. The standard oral supplement dose is 50 to 200 mg daily [3], a small fraction of whole apple benefits. Additionally, the research included applying apple extracts to cancer cell lines. Again, apples with their skin in place significantly reduced tumor cell growth, with the rate corresponding to the amount applied. While the study was conducted in a lab, the authors felt the results could pertain to real-life examples. Whole fruit was more effective in these experiments than the vitamin supplement.
Another use for vitamin C is the prevention of the common cold. Research investigating the prophylaxis and treatment of the common cold used approximately 30 individual studies [4]. The findings showed that regular consumption of vitamin C may reduce the duration of cold symptoms, but would not decrease the severity or prevent the common cold. The only exception was a small benefit found in athletes. High doses of vitamin C started after a cold onset showed no consistent effect. A separate Cochrane study [5] likewise concluded that “routine vitamin C supplementation is not justified” because the vitamin does not decrease the incidence of colds in the general population. Vitamin C is not without side effects, which include gastrointestinal symptoms (i.e., abdominal cramps, heartburn) [4].
Often the consumption of vitamins is equated to dementia prevention and the maintenance of cognitive health. Authors of a Cochrane systematic review [6] gathered findings from 28 clinical trials that investigated the outcome of vitamins on cognition with a comparison group of participants who did not take the vitamins. Included were 14 clinical trials with 28, 000 participants involving B vitamins (folic acid, vitamin B6, and vitamin B12) and 8 clinical trials to vitamins linked with antioxidants, such as beta-carotene, vitamin A, vitamin C, and vitamin E (47,000 participants).
Other smaller trials investigated complex multivitamins, vitamin D, zinc, and copper. The overall findings of the study demonstrated that middle-aged and senior adults did not receive any benefit in protecting cognition with vitamin or mineral supplementation. Vitamin C may have a small long-term benefit of low certainty, according to a study with 5 to 10 years of use.
These are a small sampling of studies that show limited efficacy with synthetic vitamins. Vitamins appear to have little benefit on cardiovascular disease, cancer, dementia, and the common cold for the general population. In fact, in one study, Red Delicious apples were superb to a vitamin C supplement [2]. As T. Colin Campbell writes in the book Whole: Rethinking the Science of Nutrition, vitamin C in one apple likely does not explain its full antioxidant potential [7]. Instead, Vitamin C, in combination with other compounds, promotes the apple’s beneficial properties.
Vitamins are an essential part of health decisions, just like a prescription drug. While some vitamins have benefits for limited circumstances, careful consideration is important. When thinking about taking a vitamin, some questions to consider are:
1. What is the long-term health outcome that results from taking the vitamin? Will it correct the problem or condition of which it is intended?
2. What are the side effects?
3. Do the risks (i.e., side effects or adverse effects) outweigh the benefits?
4. How does taking a synthetic vitamin compare with a diet rich in plant food? Is a vitamin consumed simply to avoid healthy eating?
5. What is the frequency of the deficiency that the vitamin is trying to correct? In other words, in modern culture, we rarely see Rickett’s or scurvy, which are two diseases of vitamin deficiency that are no longer prevalent.
In his book, Campbell describes that nutrients rarely act alone [7]. The amount of nutrient available to the body (bioavailability) is influenced by different vitamins and minerals. For example, calcium reduces the bioavailability of iron, while beta-carotene increases the bioavailability of iron. Researchers have found that many nutrient pairs influence each other (i.e., vitamin E and selenium, vitamin E and vitamin C, vitamin E and vitamin A), which subsequently play a large role in the immune system [8]. When a supplement is taken, that particular vitamin or mineral may help the immune system. However, there is a possibility that immune function may be suppressed.
Furthermore, the body is designed so that it extracts nutrients that are needed without human thinking required to calculate a specific amount. For example, the body extracts the nutrients it requires from one fruit. However, when eating a second fruit, the body may not need to acquire the same amount. There is not a linear relationship between the amount of nutrients consumed and the amount that the body uses. Campbell states [7] “Our bodies have evolved to eat whole foods, and can therefore deal with the combinations and interactions of nutrients contained in those foods” (p. 71)
These are some of the important considerations when taking vitamins, as well as other supplements. Assumptions that vitamins are effective are not necessarily reflected in the health literature. Furthermore, they may cause unwanted side effects. While consuming isolated nutrients to address health issues may not solve a certain problem, overall lifestyle can make an enormous impact. Consuming primarily plant food, exercising regularly, decreasing stress levels, losing weight, and staying hydrated are all areas of important focus.
References
1. Mangione, C. M., Barry, M. J., Nicholson, W. K., Cabana, M., Chelmow, D., Coker, T. R., ... & US Preventive Services Task Force. (2022). Vitamin, mineral, and multivitamin supplementation to prevent cardiovascular disease and cancer: US preventive services task force recommendation statement. JAMA, 327(23), 2326-2333. https://doi.org/10.1001/jama.2022.8970
2. Eberhardt, M. V., Lee, C. Y., & Liu, R. H. (2000). Antioxidant activity of fresh apples. Nature, 405(6789), 903-904.
3. Drugs.com. (2023). Ascorbic acid dosage. https://www.drugs.com/dosage/ascorbic-acid.html
4. Heimer, K. A., Hart, A. M., Martin, L. G., & Rubio-Wallace, S. (2009). Examining the evidence for the use of vitamin C in the prophylaxis and treatment of the common cold. Journal of the American Association of Nurse Practitioners, 21(5), 295-300. https://doi.org/10.1111/j.1745-7599.2009.00409.x
5. Rutjes, A. et al. (2018). Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.CD011906.pub2
6. Hemilia, C. (2013). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, 1. https://doi.org/10.1002/14651858.CD000980.pub4
7. Campbell, T. C. (2014). Whole: Rethinking the science of nutrition. BenBella Books.
8. Kubena, K. S., & McMurray, D. N. (1996). Nutrition and the immune system: a review of nutrient–nutrient interactions. Journal of the American Dietetic Association, 96(11), 1156-1164.