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

Adding daily multivitamins to the supplement stash is a popular path to take on the journey to better health and wellness. But should you?

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 (MVM) provide a means to fill in the gaps. According to the National Institutes of Health, one-third of Americans include MVMs in their wellness routine.

According to the Nutrition Business Journal's Supplement Business Report 2022, the U.S. market for dietary supplements, including vitamins, minerals or both, grew to $59.9 billion in 2021. Popular kitchen-cabinet staples are vitamin D and omega-3 fatty acids. Yet, according to the Centers for Disease Control and Prevention, MVMs are the top supplement choice for all age groups. MVMs earned $8 billion in sales, 37% of total dietary supplement sales in 2020, per the NIH.

a woman reading the back of a pill bottle while grabbing a glass of water

While many brands promote MVMs for energy, athletic performance and immunity, general health and disease prevention are the primary reasons people take them routinely, per a 2017 review published in Nutrition. A regular eating pattern full of whole grains, lean protein, fruits, vegetables, nuts and seeds may make a MVM unnecessary. Keep reading to learn more about multivitamins and what happens to your body when taking a multivitamin daily.

What Is a Multivitamin?

Multivitamin mineral supplements are dietary supplements that contain unique 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 dosages. While the average person looks to multivitamins to get ahead of their health, other groups may be at high risk for poor nutrition and 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, a registered dietitian nutritionist at Graciously Nourished.

What Happens When You Take It Every Day

You May Have Better Immune Function

Zinc, vitamin C and vitamin D play significant roles in maintaining a 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, which happens 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 a small 2020 study published in Nutrients, 42 older adults were randomly placed into two groups, with 21 in one group receiving a MVM and the other 21 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.

Moreover, vitamin D is often studied for its benefits in regulating gut function, per a 2020 article published in the American Journal of Physiology-Gastrointestinal and Liver Physiology. When lacking, it can cause inflammation, potentially driving chronic diseases. The 2020-2025 Dietary Guidelines for Americans specifically label vitamin D as a nutrient of public health concern, since recommended intakes can be challenging to achieve.

You Might Experience Gastrointestinal Symptoms

Taking your daily multivitamin could cause tummy troubles, depending on the levels of nutrients it possesses. "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 Melissa Mitri, M.S., RD, of Melissa Mitri Nutrition.

In a multivitamin, the following vitamins and minerals could create gastrointestinal symptoms in high doses.

  • Iron: diarrhea, nausea, vomiting and constipation
  • Magnesium: diarrhea, nausea, abdominal cramps
  • Vitamin C: diarrhea, nausea, abdominal cramps
  • Zinc: nausea, gastric distress, vomiting and loss of appetite
  • Calcium: constipation

If you're planning to take a multivitamin, Mitri recommends looking for nutrients close to 100% of the RDA. Sticking to multivitamin brands that don't overload you with nutrients is key to lessening stomach upset.

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 Mitri. A 2020 study published in Nutrition & Metabolism investigated MVM supplementation in 82 healthy, active adults, with 40 receiving a placebo and 42 receiving a MVM. After one month, they found MVM increased carbohydrate breakdown in males after 10 minutes of exercise and increased energy expenditure. Females taking MVMs reported reduced stress and lower mental tiredness; after 30 minutes of exercise, they were less physically tired. Furthermore, some deficiencies, such as iron deficiency, can drop your energy levels, causing you to feel sluggish and tired. This study also saw higher ferritin (a measure of iron stores) levels after supplementing with MVM for a month.

You Might Have A Healthier Pregnancy

Prenatal vitamins are MVMs that help 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. Birth-givers and babies are at a high risk of nutrient deficiencies, and about 28% of pregnancies become iron deficient in the last trimester. Data, such as a 2021 publication in Nutrients, supports that MVM supplementation in pregnancy may reduce the chances of pregnancy complications such as anemia, intellectual disability, gestational diabetes, autism and neural tube defects. The American College of Obstetrics and Gynecology encourages 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 positively influence psychological challenges. A 2019 study published in Current Developments in Nutrition randomized 66 college students into two groups, a placebo group and an MVM group. After 30 days, the group taking a daily MVM experienced a significant drop in anxiety. An additional 2021 study of 30 people with anxiety, published in Frontiers in Psychiatry, found that high doses of vitamin D effectively improved anxiety symptoms.

You Might Have Sharper Brain Function

According to the National Institute on Aging, forgetfulness, poor focus and trouble learning are typical signs of aging. Emerging research suggests multivitamins may help counteract these challenges by sharpening your brain function. A 2022 study published in Alzheimer's & Dementia split 2,602 adults into three groups. One group took a 500-milligram cocoa extract supplement, one took a placebo, and the last took an MVM. After following all groups for three years, researchers found that daily MVM supplementation improved brainpower through executive function. Executive function aids in memory, attention, planning and focus. No significant differences were seen in the cocoa and placebo groups.

What to Look for in a Multivitamin

Always speak with your health care provider before starting a new supplement. They have a better idea of your medical history and health needs to help you make the best choice for yourself. Before adding more vitamins to your supplement stash, here are some things to consider.

Choose Nutrients You May Lack

Depending on your lifestyle or health issues, you may be fully aware of the nutrients you lack. 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. Or, take an iron supplement separately as prescribed by your doctor," says Lorencz.

Stick to Certified Supplements with Safe Ingredients

Some supplements may contain contaminants like heavy metals. To avoid tainted supplements, look for signs on the label that they have been verified. "When choosing a multivitamin, look for the USP or NSF third-party seal of approval on the bottle. This ensures the product contains what it said it does and is held to the highest quality standards," says Mitri. You can also narrow your search by avoiding supplements that give an oversupply of 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.

The Bottom Line

What happens to your body when you take a multivitamin every day could vary from renewed energy to more brainpower. While the research on multivitamins continues, daily multivitamins may not benefit everyone. The truth is that 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. Talk to your medical provider about supplementation options if you have a poor appetite, digestion problems, food allergies or a new pregnancy.

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