Perhaps because of the pandemic, we often hear questions about whether our long-standing health regimens are as effective as we have believed them to be. One example is multivitamins, a dietary supplement used by about one-third of American adults, according to the National Institutes of Health, but which has caused confusion in recent years. According to one source, up to 86% of adults take vitamins or supplements, but only 21% have documented vitamin deficiencies. We spoke to health experts about whether we need to take vitamins, what changes we feel when we do, and how long the changes last.
“Whether or not you benefit from taking a multivitamin depends entirely on whether or not you have a vitamin deficiency,” says Samuel Mathis, MD, MPH, a board-certified family medicine physician and assistant professor in the Department of Family Medicine at the University of Texas Medical Branch.
“Vitamins alone tend to cause side effects more frequently due to their higher concentrations.”
Samuel Mathis, MD, MBA
Board Certified Family Physician, Assistant Professor, and Associate Director of Medical Student Education Programs at the University of Texas Medical Branch
Despite their popularity, multivitamins have no concrete evidence that they prevent or reduce the risk of major diseases. Instead, many experts have consistently maintained that a healthy diet can naturally meet vitamin needs. Julia Zumpano, RD, a registered dietitian at the Cleveland Clinic’s Center for Human Nutrition, evaluates her patients’ diet and supplement intake before recommending a multivitamin. “Basically, [multivitamin] “Multivitamins aren’t harmful, but they may be unnecessary given your current diet and supplement intake,” says Zumpano, so be sure to talk to your healthcare provider to determine if taking a multivitamin is right for you.
Below, both Dr. Zumpano and Dr. Mathis discuss what happens to your body when you start taking vitamins, who benefits most, and possible side effects.
Multivitamin Basics
A multivitamin is a supplement that usually comes in tablet, capsule, or liquid form and contains a variety of essential vitamins and minerals (often vitamins A, C, D, E, and K, plus minerals such as calcium, magnesium and zinc). While the ingredients in multivitamins may vary, their purpose is to provide a convenient way to get nutrients that you may not be getting enough of through your diet alone.
Zumpano works with patients at the Cleveland Clinic who may be undergoing treatment and therefore have a variety of unique nutritional needs. With this deep expertise, Zumpano universally recommends choosing a multivitamin that:
- By gender
- By age
- Verified by Third Party Testing
- Harvard Health also recommends choosing vitamins that have the United States Pharmacopeia (USP) seal of approval on the label, which guarantees that the multivitamin contains the ingredients and amounts listed on the label.
What happens when you first start taking vitamins?
When you start taking vitamins, your results will vary depending on your specific nutritional needs, your body’s ability to absorb nutrients, and the type of vitamin you start taking. “People who are deficient in vitamin C will see immediate benefits from taking vitamin C,” says Dr. Mathis. People who are deficient in vitamin C will see improvements in fatigue, skin conditions, and immune function.
“With other vitamins and minerals, the effects are slower and less noticeable,” says Dr. Mathis.
To improve absorption, several factors must be considered.
- Take vitamins with meals: Taking vitamins with a meal enhances absorption. This is especially true for the fat-soluble vitamins A, D, E, and K, which need to be consumed with fat to dissolve properly. According to some sources, 5 to 10 grams of fat is ideal to ensure your body absorbs all the nutrients. Think two eggs, two slices of cold salmon, or a few bites of avocado.
- Choosing the right vitamin form for better bioavailability“Bioavailability” refers to the percentage of nutrients that are absorbed from the diet and used for normal body functions. Some vitamins are better absorbed and used by the body than others. For example, vitamin D3 is typically absorbed more efficiently than vitamin D2.
- Addressing digestive issues that may interfere with nutrient absorption: Digestive disorders such as lack of stomach acid, celiac disease, and inflammatory bowel disease can interfere with your body’s ability to absorb vitamins and minerals from food and supplements. Managing these conditions can help improve nutrient absorption and ensure your body receives the full benefit of the vitamins you’re taking.
How long does it take for vitamins to start working in your body?
“Some vitamins can take four to six weeks to show any effect or benefit,” says Dr. Mathis.
On the other hand, it may take up to two to three months for you to see the benefits of a multivitamin, depending on how well the supplement is absorbed by your body, says Zumpano.
Dr. Mathis suggests that patients should take at least a month to evaluate whether a vitamin or supplement is working. After this time, he says, it might be worth taking a break and comparing the effects of taking the supplements with those of not taking them (with your doctor’s permission, of course).
What happens to your body when you take a daily multivitamin?
Taking a daily multivitamin can help maintain health and prevent nutritional deficiencies, especially if your diet doesn’t provide all the nutrients you need. Many long-term users report fewer colds due to the immune-boosting effects of vitamins like C and E. Additionally, continued intake of vitamins B12 and D can support bone health and nerve function.
What side effects can I experience when I start taking a new vitamin?
Possible side effects when starting a new vitamin will vary depending on which vitamin you’re taking. “With multivitamins, some people may experience changes in bowel habits or stomach upset,” Dr. Mathis notes. And, “When taking vitamins on their own, side effects tend to occur more frequently due to the higher concentrations.” This may sound familiar if you’ve started taking certain supplements, like magnesium or iron.
Common side effects when starting to take a new vitamin include:
- abdominal pain
- nausea
- diarrhea
- constipation
- Changes in urine color
Additionally, certain vitamins can increase your risk of certain health problems. For example, taking large amounts of vitamin C has been shown to increase your chances of developing kidney stones.
Zumpano lists some less common but important side effects to watch out for, including headache, redness of the skin, itchiness, rash, anxiety, and allergic reactions. If you experience any of these symptoms, discontinue use and consult your healthcare provider immediately.
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