What Happens to Your Body When You Take a Multivitamin Every Day

Eating a healthy diet is the ultimate path to optimal nutrition. For those who may fall short on critical nutrients, multivitamins and multivitamin-mineral supplements (MVMs) provide a means to fill in the gaps. Nearly one-third of Americans include MVMs in their wellness routine. Multivitamin/mineral supplements are dietary supplements that contain combinations of vitamins, minerals or both, with each nutrient helping to meet a dietary need. Available in various forms—such as capsules, gummies and liquid—MVMs are usually taken once a day, though some may recommend multiple daily doses. While many brands promote MVMs for energy, athletic performance and immunity, the primary reasons people take them routinely are general health and disease prevention.

While the average person looks to multivitamins to get ahead of their health, some groups may be at higher risk for poor nutrition and thus have a greater need for them. "For most people, a multivitamin isn't necessary, but for some, like older adults, people who are experiencing low appetite or difficulty eating a balanced diet, from an illness or even pregnancy, a multivitamin can help fill in nutrition gaps," says Kelsey Lorencz, RDN. Keep reading to learn more about multivitamins and what happens to your body when you take a multivitamin daily.

Why We Love Multivitamins

You May Have Better Immune Function

Zinc, vitamin C and vitamin D play significant roles in maintaining healthy immune function. Lacking these nutrients makes it harder for your body to fight illnesses. That's because zinc and vitamin C deficiencies can cause oxidative stress when antioxidants and free radicals in the body are off their balance, leading to inflammation and disease. Vitamin C is more than a vitamin; it's also an antioxidant that helps remove harmful free radicals that can wreak havoc on immune health.

In one small study, older adults were randomly placed into two groups, with half receiving an MVM and the other half receiving a placebo. After 12 weeks, the researchers found that MVM supplementation improved blood levels of zinc and vitamin C; however, there weren't any improvements in markers of immune function.

Vitamin D is often studied for its role in regulating gut function. When lacking, it can cause inflammation, potentially driving chronic diseases. Vitamin D is a nutrient of public health concern, since recommended intakes can be challenging to achieve. This is partly because our bodies produce vitamin D when we're exposed to a certain level of sunlight—so if you're not exposing your skin to the sun long enough, your body won't produce it. Some foods also contain vitamin D, but unless you're eating a lot of them, you might not be getting enough of this vitamin.

You May Boost Your Energy Levels

"People who begin to supplement with a multivitamin and have a specific deficiency may feel a difference in their energy level, but it's not guaranteed," says Melissa Mitri, M.S., RD.

One study investigated MVM supplementation in healthy, active adults, with 42 receiving an MVM and 40 receiving a placebo. After one month, they found that the MVM increased energy expenditure and carbohydrate breakdown in males after 10 minutes of exercise.

Females taking MVMs reported reduced stress and lower mental tiredness; after 30 minutes of exercise, they were less physically tired.

Some deficiencies—such as iron—can drop your energy levels, causing you to feel sluggish and tired. This study also found higher levels of ferritin (a measure of iron stores) after supplementing with MVM for a month.

For most people, a multivitamin isn't necessary, but for some, like older adults, people who are experiencing low appetite or difficulty eating a balanced diet, from an illness or even pregnancy, a multivitamin can help fill in nutrition gaps.

You Might Have a Healthier Pregnancy

Prenatal vitamins are MVMs that support the developing baby's cells, tissues and organs. Folic acid, iron, DHA, choline and iodine—vital nutrients every pregnancy needs—are found in many prenatal vitamins. Pregnant women and babies are at a high risk of nutrient deficiencies, and about 28% of women become iron-deficient in the last trimester.

MVM supplementation in pregnancy may reduce the baby's chances of anemia, intellectual disability, gestational diabetes, autism and neural tube defects. The American College of Obstetrics and Gynecology (ACOG) recommends taking prenatal vitamins before and during pregnancy.

You May Be Less Anxious

The unfortunate reality is that mental health issues are rising today. The good news is that more research continues to emerge on how nutrition can influence psychological challenges.

A review study found that consuming adequate B vitamins and probiotics can reduce depression and anxiety symptoms, and may help with sleep. The study looked at B vitamins as a complex, meaning it did not differentiate specific B vitamins like niacin or B-12. You will find B-complex vitamins in an MVM, and you may also find one with added probiotics.

Additionally research has found that high doses of vitamin D effectively improved anxiety symptoms.

You Might Have Sharper Brain Function

Forgetfulness, poor focus and trouble learning are typical signs of aging. Emerging research suggests that multivitamins may help counteract these challenges by sharpening your brain function.

In a study on supplementation and brain function, researchers split 2,602 adults into three groups. One group took a 500-milligram cocoa extract supplement, one took an MVM, and the last took a placebo. After following all groups for three years, researchers found that daily MVM supplementation improved executive function, which aids in memory, attention, planning and focus. No significant differences were seen in the cocoa and placebo groups.

Potential Side Effects You Should Know About

Taking your daily multivitamin could cause tummy troubles, depending on the nutrients in it. "If you are taking [multivitamins] in large doses and your body doesn't need the extra, you may experience mild side effects such as nausea or stomach upset," says Mitri.

The following vitamins and minerals in multivitamins could create gastrointestinal symptoms in high doses.

• Iron: diarrhea, nausea, vomiting, constipation

• Magnesium: diarrhea, nausea, abdominal cramps

• Vitamin C: diarrhea, nausea, abdominal cramps

• Zinc: nausea, gastric distress, vomiting, loss of appetite

• Calcium: constipation

How Much Can You Take?

When dosing a multivitamin, it's best to stick with the recommendations on the bottle.

Depending on the type of vitamin—tablet, gummy, chewable, etc.—the dosage can vary.

Dosage may also vary depending on the age of person consuming the multivitamin.

Is a Multivitamin Safe for Everyone?

Some supplements do not mix well with certain medications or medical conditions, so always speak with your health care practitioner before starting a new supplement. They can evaluate your medical history and health needs to help you make the best choice for yourself.

If you're planning to take a multivitamin, Mitri recommends looking for nutrient levels close to 100% of the recommended dietary allowance, as opposed to ones that go way over the RDA. Sticking to multivitamin brands that don't overload you with nutrients is key to lessening stomach upset.

What to Look For in a Multivitamin

Depending on your lifestyle or health issues, you might be lacking some nutrients. For example, vegetarians and vegans are prone to deficiencies in iron and vitamin B12.

"Pay attention to the specific nutrients you may fall short on. Many people can use a daily boost of nutrients like vitamin D and iron. If these nutrients are a concern for you, make sure your multivitamin has vitamin D3, the most absorbable type, and contains iron, since not all multivitamins do," says Lorencz. "Or take an iron supplement separately, as prescribed by your doctor."

Some supplements may contain contaminants like heavy metals. To avoid tainted supplements, look for signs on the label that state they have been verified. "When choosing a multivitamin, look for the USP or NSF independent verification seal of approval on the bottle," says Mitri. "This ensures the product contains what it said it does and is held to the highest-quality standards."

You can also narrow your search by avoiding supplements that oversupply some nutrients. "Look for ingredients that meet as close to 100% of the RDA for that nutrient as possible and are free from additives and fillers," Mitri adds.

Our Expert Take

What happens to your body when you take a multivitamin every day can vary from renewed energy to more brainpower. While the research on multivitamins continues, daily multivitamins may offer little benefit if you're a healthy eater. Eating a wide variety of healthy foods is the first-line approach to supplying your body with the nutrition essentials. A regular eating pattern full of whole grains, lean protein, fruits, vegetables, nuts and seeds may make an MVM unnecessary. Talk to your medical provider about supplementation options if you have a poor appetite, digestion problems, food allergies or a new pregnancy, or if you're thinking about becoming pregnant.