Are You Sure That’s Good For You? Pros and Cons of 10 Common Breast Cancer Supplements

What’s our best advice when it comes to choosing supplements? It’s a bit on the boring side: talk to your doctor. There are a lot of folks out there who claim to know about miracle vitamins or oils or supplements, and it’s vital that someone going through cancer treatment talk to their medical team before trying anything new. Some supplements can interact negatively with cancer treatment.

Our advice may not be as flashy as claims of a tumor-fighting compound available at the grocery store, but we’ll stick with our boring advice just like we’ll stick with wearing bike helmets and seatbelts.

But there are vitamins and compounds that cancer patients hear a lot about, and you likely have questions. We’ve gone ahead and compiled a list of ten common supplements and the pros and cons of each. Make sure to do your homework before giving these a try!

1. Vitamin C

The Pros
Vitamin C, in addition to possibly reducing the length of colds, is used to prevent heart attacks and strokes, osteoarthritis, and eye problems. Vitamin C may also lower the risk of lung cancer, digestive cancers, and even breast cancer.

According to, vitamin C cannot treat or prevent cancer, but healthy diets that include fruits and vegetables that contain vitamin C have been linked to reduced cancer risk.

The Cons
The recommended daily allowance (RDA) of vitamin C is 75mg for women and 90mg for men. A good diet should provide more than enough vitamin C on its own as one orange supplies about 70mg, and making sure to consume five servings of fruits and vegetables each day can easily put you over 200mg.

High doses of vitamin C (over 2,000 milligrams a day) can cause diarrhea, gas, and upset stomach. The vitamin can interact negatively with blood thinners, and high doses may reduce the effectiveness of chemotherapy and radiation.

2. Calcium

The Pros
Calcium is especially important for women to promote bone health and prevent osteoporosis and it can guard against the bone weakening that happens with some chemotherapy medications. Calcium may also protect against the bone loss associated with the use of aromatase inhibitors (drugs that stop the production of estrogen). Some studies have shown that calcium and vitamin D can make breast cancer less likely to spread.

The Cons
Having too much calcium can cause the excess to build up in the blood and cause hypercalcemia, which can inhibit kidney function and mineral absorption. The Mayo Clinic recommends that women between the ages of 19 and 50 have between 1,000 and 2,500mg of calcium a day, and women 51 and older should take in between 1,200 and 2,000mg. Additional intake does not provide additional benefits. If you eat a calcium-rich diet (with foods like dairy products, dark green vegetables, sardines, and salmon), eat foods fortified with calcium, and take a calcium supplement, you may exceed the upper limit of the recommended amount.

3. Vitamin D

The Pros
Vitamin D helps the body absorb calcium and is therefore important for bone health, especially for those taking aromatase inhibitors or undergoing bone-weakening types of chemotherapy. Calcium and vitamin D together may help protect against breast cancer. Some foods, like milk and cereal, are fortified with vitamin D, and it’s found naturally in fish and eggs. Our bodies also produce vitamin D when we’re exposed to the sun (though long-term exposure to the sun can be damaging, so be careful).

The Cons
More than 2,000 international units of vitamin D a day can cause hypercalcemia and cause calcium deposits to form over time. High doses may also cause kidney stones, nausea, vomiting, and weakness. But 2,000 international units is quite a lot—a typical multivitamin contains 400 units. The recommended daily amount for people younger than 50 is 200 units, 400 units for people ages 50 to 70, and 600 units for those 71 and older.

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Katie Taylor started writing in 5th grade and hasn't stopped since. Her favorite place to pen a phrase is in front of her fireplace with a cup of tea, but she's been known to write in parking lots on the backs of old receipts if necessary. She and her husband live cozily in the Pacific Northwest enjoying rainy days and Netflix.
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