Vitamins and dietary supplements can help you get the micronutrients your body needs to stay strong during a cancer diagnosis, but when it comes to breast cancer treatment, it’s important to discuss safety and appropriate use with your doctor first.

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Breast cancers begin in any tissue of the breast. They’re one of the most common types of cancer among women, according to the American Cancer Society (ACS), but they can affect anyone.

Many supplements are safe to take during breast cancer treatment and recovery, but not all products are appropriate or recommended for use. Discussing your vitamins and supplements with your doctor or breast cancer specialist is an essential part of achieving the best outcome possible.

Vitamin D

Vitamin D is a key component in maintaining bone health and supporting immune function. It helps your body absorb calcium, which is important to keep your bones and teeth strong.

Your doctor may recommend a vitamin D supplement because certain breast cancer treatments can promote bone loss and increase your risk for osteoporosis. Some animal studies suggest higher levels of vitamin D and calcium may reduce the chance breast cancer will spread to other areas of the body like the bones.

One study from 2016 found vitamin D deficiency increased the risk of breast cancer’s spread or metastasis.

Vitamin D also supports mental health function and may help reduce symptoms of anxiety or depression in some people with a cancer diagnosis.

Vitamin C

Vitamin C is purely obtained through your diet. It’s a vitamin and an antioxidant. An antioxidant is a molecule that helps prevent cellular damage from particles called “free radicals.”

Some research suggests vitamin C can be a powerful supportive therapy in breast cancer treatment. A review from 2020 showed vitamin C, in a high dose intravenous (IV) form, had significant anti-inflammatory and anti-cancer benefits without interfering with certain treatments and some chemotherapy agents.

Other research cautions against the use of vitamin C during breast cancer treatment, particularly during chemotherapy. Results in 2019 from a large clinical trial indicated participants taking vitamins A, C, and E before and after chemotherapy treatment were more likely to experience a recurrence of cancer. Researchers attributed this to antioxidants promoting cell repair even in cancer cells.

How you obtain vitamin C may also matter. A review of studies from 2020 indicated only vitamin C from food sources, and not vitamin C in supplement form, was associated with reduced breast cancer risk and mortality.

B vitamins

There are eight B vitamins, each with specific functions, but they all work together to help maintain your neurological function, energy levels, and cellular metabolism.

The effectiveness of B vitamins during cancer treatment is varied across different cancer types. When it comes to breast cancer, research review data from 2023 notes certain B vitamins like B6, B9, and B12 may have protective features and may help reduce nerve pain from chemotherapy treatments.

B12, however, in the 2019 clinical trial research was shown as a supplement associated with a higher rate of breast cancer recurrence and increased mortality in chemotherapy treatment.

Minerals, like vitamins, are also micronutrients. Unlike vitamins, however, minerals are inorganic compounds. They’re not produced by living organisms and are naturally occurring elements found in the earth’s crust.

Calcium

In combination with vitamin D, calcium can be an important part of maintaining your bone health during breast cancer treatment. Calcium is also important to processes in your body related to muscle contraction, nerve communication, blood pressure, and blood clotting.

While some preliminary studies, human and animal, have indicated calcium may help reduce a person’s risk for breast cancer, more research in humans is necessary to determine if there are true protective benefits. Currently, there is no evidence that shows calcium can prevent breast cancer.

Selenium

Selenium is a trace mineral, meaning your body needs very small amounts for optimal function. It’s an antioxidant, and it promotes immune health as well as thyroid hormone metabolism in addition to its cellular restoration benefits.

A cohort study from 2021 looking at 10-year survival rates in breast cancer found they were significantly better among people with higher selenium levels. Research authors recommended more studies to prove the validity of selenium supplementation for breast cancer outcomes.

Zinc

Zinc is another trace mineral and is highly involved in proper enzyme function. It helps your body regulate a spectrum of physiological reactions in everything from digestion and metabolism to nerve function.

Not only does zinc support your immune function and wound healing, but it also has antioxidant properties and supports hormonal balance.

In breast cancer, zinc pathways are being investigated as potential therapeutic targets in emerging therapies. According to a different research review from 2023, imbalances in zinc levels in the body can contribute to tumor growth. However, that does not necessarily mean that zinc supplementation will affect cancer growth or development.

More research is necessary to establish any potential benefits specific to breast cancer progression and treatment.

Omega-3 fatty acids are a type of fat molecule used by your body for a variety of functions. Omega-3 fatty acids promote immune function and can help reduce inflammation, two benefits that may support your current cancer treatments.

Research from 2023 suggests eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), 2 specific types of omega-3 fatty acids, may help reduce chemotherapy side effects and improve overall breast cancer survival rates.

Omega-3 fatty acids come from foods like fish, walnuts, soy, and flaxseed, but they can also be taken in supplement form. Recommended doses vary depending on your age and gender but are typically under 1.4 grams (g) a day. Exceeding 3 g a day can increase the risk of adverse reactions.

Omega-3 fatty acid supplements were also noted in the large clinical trial research from 2019 as associated with an increased risk of cancer recurrence and mortality during chemotherapy treatment.

If you’ve been diagnosed with breast cancer, discuss all your supplements with your doctor or breast cancer specialist. This includes supplements you’re currently on and vitamins or supplements you’re considering taking.

The research on using vitamins and supplements in breast cancer is mixed. Current guidelines from the American Cancer Society (ACS) and the National Cancer Institute advise caution when taking these products during breast cancer treatment.

Certain vitamins and dietary supplements can affect how well cancer treatments work, and too-high doses can have serious negative side effects. To ensure your safety, many experts recommend getting your micronutrients from foods rather than commercial additives.

Nutritional support can help keep your body energetic and strong when it comes to treating breast cancer, but that does not mean you should start taking handfuls of supplements.

While research suggests certain vitamins and other micronutrients may have beneficial effects on cancer treatment and prevention, there is also a growing body of literature that suggests some supplements may negatively affect your breast cancer outcome or treatment success.

Before starting any dietary supplement, discuss the pros and cons with your doctor or breast cancer specialist.