Should You Be Taking Vitamin Supplements?

Vitamins were among the most exciting discoveries of the early 20th century. Since then, however, doctors have been expressing a lot of skepticism about the value of taking vitamin supplements. A pronouncement in 2022 from the United States Preventive Services Task Force (USPSTF) continued that tradition. Readers are curious about the potential value of supplements for specific purposes, such as preventing cataracts.

Can Taking Vitamin Supplements Help You Avoid Cataracts?

Q. As a registered dietician, I have been amazed at the number of people who get less than the recommended daily intake of vitamin C. I recently read a research article suggesting that higher vitamin C intake is associated with lower risk of cataracts. I wonder whether eye doctors ever recommend this crucial nutrient as a preventive strategy.

A. We tracked down the research you located in Acta Ophthalmologica (May, 2016).  The authors reviewed the scientific evidence and concluded that high vitamin C intake “is associated with a reduced risk of cataract, especially in America and Asia.” They advocate for vitamin C as a “primary prevention of cataract.”

Many ophthalmologists do recommend the AREDS formulas to slow the progression of macular degeneration. These supplements contain 500 mg of vitamin C, which is substantially higher than the RDA. For men, that is 90 mg a day, while for most women it is 75 mg. You can learn more about strategies to maintain eye health from our Show 1402: How You Can Protect Your Precious Eyesight and Keep Your Eyes Healthy.

Research on the Value of Multivitamins:

Despite the lack of enthusiasm from some healthcare experts, evidence is building that older people who take multivitamins may be slowing cognitive decline. The COSMOS trial (Cocoa Supplement and Multivitamin Outcomes Study) was a large, randomized controlled trial involving more than 20,000 participants for five years (American Journal of Clinical Nutrition, June 2022). The researchers had focused most of their attention on cancer and cardiovascular outcomes. Volunteers taking multivitamins (Centrum Silver daily) were less likely to develop lung cancer. There were no significant changes in the risk of heart attacks, strokes or other types of cancer.

Do Multivitamins Help Preserve Memory?

The investigators also included cognitive tests on three different subsets of COSMOS participants. In the first one, reported last spring, 3,500 older individuals took online cognitive tests at the beginning and yearly during the trial for a total of three years. Those taking multivitamins performed significantly better than those on placebo for immediate recall (American Journal of Clinical Nutrition, May 24, 2023).

The researchers concluded:

“Daily multivitamin supplementation, compared with placebo, improves memory. Multivitamin supplementation holds promise as a safe and accessible approach to maintaining cognitive health in older age.”

Global Cognition Improves; Executive Function Doesn’t:

Now, results from two other groups in COSMOS have been analyzed. Even more important, a meta-analysis covers results from all three of these investigations (American Journal of Clinical Nutrition, Jan. 18, 2024). Some of these volunteers were tested in the clinic (COSMOS Clinic), some online (COSMOS Web) and some were evaluated each year over the phone (COSMOS Mind). The results were broadly consistent among these different groups. People taking multivitamins scored better over the years than those on placebo. The benefit overall could be compared to a two-year delay in cognitive aging. Not all aspects of cognitive function got the same boost. Episodic memory improved quite a lot, while executive function (the ability to plan and prioritize) did not.

We should point out that multivitamins are not a magic bullet against cognitive decline. To preserve brain power, people should probably also be getting adequate sleep, physical activity and a healthful diet rich in vegetables and fruits. To learn more about this holistic approach, you may wish to listen to our interview with Dr. Dale Bredesen. It is Show 1269: How the First Survivors of Alzheimer’s Saved Their Brains.

USPSTF Threw Shade on Taking Vitamin Supplements:

The USPSTF did not consider cognitive function when it published a review of the evidence on vitamins and minerals against heart disease or cancer (JAMA, June 21, 2022). The authors reviewed 84 studies including people with no known cardiovascular problems or cancer at the outset. They also had no vitamin or mineral deficiencies. In this population, multivitamins were linked to a small but statistically significant drop in the risk of cancer, including lung cancer. On the other hand, beta carotene was associated with a higher risk of lung cancer as well as death from cardiovascular diseases.

The USPSTF presented this evidence to support its recommendations, also published this week (JAMA, June 21, 2022). The committee recommends that people avoid taking beta carotene or vitamin E supplements. In its view, the evidence is not adequate to recommend either for or against multivitamins or other supplements to prevent cancer or heart disease.

Exceptions Worth Knowing:

We are not convinced, however, that taking vitamin supplements is always a bad idea. One study showed that vitamins can actually help reduce the risk of certain chronic diseases. There are also some medications that may increase our need for vitamins. That may tip the balance in favor of supplements.

Do Vitamin Supplements Lower the Likelihood of Autoimmune Disorders?

Autoimmune disorders are common, affecting tens of millions of Americans. Rheumatoid arthritis, psoriasis, lupus, Graves’ disease, Hashimoto’s and polymyalgia rheumatica, among others, all count. Now results from a five-year randomized controlled trial indicate that supplements of vitamin D and omega 3 fatty acids reduce the risk for developing autoimmune disease.

The VITAL Trial:

The VITAL study included more than 25,000 adults. It asked whether vitamin D or omega-3 supplements could lower the chance of heart disease or cancer. The results were disappointing (New England Journal of Medicine, Jan. 3, 2019). Reductions in cancer and heart disease were modest and not significant.

The scientists didn’t stop there, however. During the study, they collected data allowing them to evaluate a link with autoimmune conditions. Analysis shows that people taking vitamin D3 for five years were about 22 percent less likely to get a diagnosis of an autoimmune disease (American College of Rheumatology, Nov. 4, 2021). For omega-3 supplements, the drop in diagnosis was around 18 percent.

Lead author Dr. Karen Costenbader noted in reporting the study that

“there are no other known effective therapies to reduce the incidence of autoimmune diseases.”

To us, that suggests taking vitamin supplements is valuable. However, that hasn’t always been the conventional view.

Are Vitamin Supplements a Waste of Money?

For nearly 40 years, there was a consensus among health professionals that most people should not be taking vitamin supplements. Their view has been that this does no more than lead to expensive urine.

Just Eat a Well-Balanced Diet:

The standard advice is to eat a well-balanced diet. No one can argue with that sentiment, but what does it mean? A well-balanced diet is rarely defined beyond a vague idea of eating your vegetables. The USDA suggests that people should eat between five and nine servings of vegetables and fruits daily. For a person who consumes 2,000 calories a day, that works out to around two and a half cups of veggies and two cups of fruit a day. In reality, not many Americans actually manage that many servings of produce.

As a result, many people fall short on the vitamins and minerals they need for good health. This is especially true for people who take medications on a regular basis. The consequence is that many should be taking vitamin supplements, or possibly minerals.

What Minerals Might You Need?

Magnesium is an essential mineral that is frequently low in American diets. The best sources are green leafy vegetables, nuts, fruits such as figs or raspberries and various types of beans.

Do Medications Affect Magnesium Levels?

Even people who do eat fruits and vegetables could still find themselves in trouble if they must take certain pills for heartburn or high blood pressure, for example. Acid-suppressing drugs like esomeprazole (Nexium), lansoprazole (Prevacid) and omeprazole (Prilosec) limit magnesium absorption. ACE inhibitors such as enalapril or lisinopril deplete magnesium and zinc. So do thiazide diuretics like hydrochloriothiazide (HCTZ).

Low magnesium levels have been linked to depression, diabetes, high blood pressure, heart disease and arrhythmias. Symptoms include insulin resistance, severe menstrual cramps, leg cramps, fatigue and migraine headaches.

Think About Zinc:

A word about zinc: most people don’t think about it very much. Low levels can lead to changes in the senses of taste and smell, slower wound healing, diarrhea and hair loss.

Who Should Be Taking Vitamin Supplements with Vitamin B12?

Vitamin B12 is another critical nutrient that may be affected by medication. This vitamin is found in meat, fish, poultry, dairy products and eggs, so people following vegetarian and vegan diets may come up short. The acid-suppressing medications mentioned above can also interfere with vitamin B12 absorption. That’s because the stomach needs acid to absorb vitamin B12 adequately. Older people, whose stomach acid production often drops dramatically, are at risk of vitamin B12 insufficiency.

In addition, the diabetes drug metformin can also lead to inadequate vitamin B12. More than 80 million prescriptions for metformin are dispensed annually. That doesn’t include millions more for combination diabetes drugs like Janumet that include metformin.

Certain antibiotics such as doxycycline, ciprofloxacin and co-trimoxazole can also affect vitamin B12 absorption.

Vitamin B12 deficiency can lead to serious complications such as neuropathy, which can cause burning, tingling and numbness. Low levels can also contribute to cognitive impairment and mood disorders. People who must take such medicines should ask their doctors to monitor their vitamin B12 levels periodically.

More Research on the Benefits of Taking Vitamin Supplements:

There are studies going back several years demonstrating that vitamin supplements can be helpful in certain situations that may be relevant for you. We got this question from a reader in 2014:

Q. Is it true that taking vitamins is a waste of money since they do not improve our health?

A. An editorial in the Annals of Internal Medicine (Dec. 17, 2013) titled “Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements” makes this argument. We don’t entirely agree, however.

Some studies have shown that certain vitamins can improve cognitive function, reduce the risk of cancer or lower the chance of getting cataracts (JAMA, Jan. 1, 2014 & Nov. 14, 2012; Ophthalmology, Feb. 2014).

Learn More:

You can learn more about the pros and cons of nutritional supplements and the interactions of drugs and nutrients from Fortify Your Life: Your Guide to Vitamins, Minerals, and More. The author is Dr. Tieraona Low Dog, one of the country’s leading experts on dietary supplement and integrative medicine.