As many as 77 percent of people diagnosed with cancer take dietary supplements, according to the Leukemia & Lymphoma Society. But do supplements really help those with blood cancers, or can any hurt? While some supplements may improve polycythemia vera (PV) symptoms or reduce risks for complications, others have the potential to cause harm.

Many dietary supplements containing vitamins, minerals, and herbs are available without a prescription. Some may be marketed as having benefits to prevent or treat cancer or reduce cancer treatment side effects. It’s very important to follow your doctor’s advice about which supplements to take and avoid — your doctor understands the details of your health condition best.

Continue reading to learn more about five supplements that may help people living with PV and three supplements that you may be safer avoiding.

Supplements With Potential Benefits

If you’re living with PV, you may have symptoms linked to increased inflammation such as itching, joint pain and swelling, and fatigue. Currently, there aren’t any clinical trials specifically investigating how certain supplements may help people with PV. However, some supplements with effects on red blood cell (RBC) production, and those with anti-inflammatory properties have shown potential benefit for some people with PV.

In a 2017 survey from the Mayo Clinic Survey Research Center of more than 1,300 people with myeloproliferative neoplasms (MPNs), 72 percent of people reported using an over-the-counter (OTC) supplement.

Although some supplements may be helpful, you shouldn’t use them as a replacement for your usual PV treatment. Before you start taking any supplements, check with your doctor to make sure it’s safe for you.

1. Vitamin D

Vitamin D is an important vitamin that plays a role in several body functions, such as:

• Calcium absorption
• Regulation of cell growth
• Inflammation
• Immune system function

Vitamin D deficiency is a common health problem. Around 30 percent to 50 percent of the world’s population has vitamin D levels that are too low. Vitamin D deficiency may be even more common in people with PV. A 2020 study found that two-thirds of people with the condition had a vitamin D deficiency.

Because vitamin D can affect blood cell growth, researchers are studying its usefulness in treating different types of blood cancers, such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML).

Researchers think that vitamin D may help reduce the production of excess RBCs in people with PV. Studies in mice have found that vitamin D can block one of the processes that cause excess RBCs — the Janus kinase/signal transducers and activators of the transcription (JAK/STAT) signaling pathway. The JAK/STAT pathway may be altered in people with PV who have a mutation (gene variant) in a protein called Janus kinase 2 (JAK2). A mutation in JAK2 can make developing blood cells extra sensitive to growth factors, resulting in an overproduction of many blood cells.

More studies are needed to find out whether the same is true in humans. However, vitamin D supplements may have other health benefits, including preventing osteoporosis (bone thinning) and possibly reducing the risk of dying from some cancers.

2. Omega-3 Fatty Acids

Omega-3 fatty acids are healthy fats that can be found in foods like fish and flaxseed. Supplements with omega-3 fatty acids include:

• Fish oil
• Cod liver oil
• Krill oil
• Algal oil (a plant-based source made from algae)

If you have PV, too many RBCs can increase your risk of blood clots, heart attack, and stroke. Some studies have found that taking an omega-3 supplement may lower your risk of blood clots, heart disease, and death from heart disease.

While there haven’t been any clinical trials in humans, a study in mice in Lipids in Health and Disease found that omega-3 fatty acids can affect how blood cells develop. More studies are needed to see how this supplement may be used to treat PV and other blood disorders.

3. Curcumin

Curcumin comes from the spice turmeric. It’s known for its antioxidant and anti-inflammatory effects. You can find curcumin in many different forms, such as tablets, capsules, ointments, and drinks.

In addition to its anti-inflammatory properties, curcumin may prevent the production of excess blood cells. A 2019 laboratory study using cells with a JAK2 mutation found that curcumin blocked the JAK/STAT pathway. These results are promising, but clinical trials are needed to see if curcumin has the potential to treat PV.

Curcumin is generally recognized as safe by the United States Food and Drug Administration (FDA) and is usually well-tolerated by most people who take it.

4. Green Tea

Green tea is a popular beverage, and green tea extract can be used as a dietary supplement. Researchers have studied its potential benefits in preventing heart disease, some types of cancer, and inflammatory conditions.

Many of the benefits of green tea are associated with the presence of powerful antioxidants called polyphenols. These chemicals can help stop the formation of free radicals, which can cause cell damage.

Green tea may have benefits beyond its anti-inflammatory and antioxidant properties. A study in rats from the European Journal of Nutrition found that green tea was associated with a lower amount of iron and a lower percentage of RBCs. Aluminum found in green tea may be responsible for the decrease in iron levels. This is because aluminum can compete with iron during the production of RBCs. Clinical trials are needed to find out if green tea may be helpful for people with PV.

5. N-Acetylcysteine

N-acetylcysteine (NAC) is a medicine that’s used to treat acetaminophen (Tylenol) poisoning. As a supplement, it can have antioxidant and anti-inflammatory properties, which may make it useful in treating medical conditions involving inflammation.

A study in mice in the journal Blood found that NAC may help prevent blood clots in people with PV. While these results are promising, clinical trials in humans are needed to find out if NAC can improve PV symptoms.

Supplements With Potential Dangers

If you have PV, your doctor may ask you to avoid some common vitamins and minerals because they can encourage the production of RBCs. Before you take any supplement, check with your doctor to make sure it doesn’t contain an ingredient you should avoid.

1. Iron

Iron is a mineral your body uses to make hemoglobin — the protein that carries oxygen in your RBCs. Many people first diagnosed with PV have an iron deficiency — meaning their iron levels are too low. However, iron deficiency may actually be the goal of some treatments for people with PV because it limits how many RBCs your body can make.

Iron is available in many different kinds of supplements — including many multivitamins. Make sure you check the label of your vitamins and supplements to see if they contain iron.

2. Vitamin C

Vitamin C — also known as ascorbic acid — is a nutrient that’s found in many different fruits and vegetables. If you take a vitamin C supplement or eat foods high in vitamin C along with iron-rich foods, you can increase the amount of iron your body absorbs. Talk to your doctor about how much vitamin C you should consume each day.

3. B Vitamins

Vitamins B12 and B9 (also known as folic acid) are used to make RBCs. People with PV often have high vitamin B12 and low folic acid levels. If you take a supplement with vitamin B12 or folic acid, it may cause increased RBC production.

Treatment of Polycythemia Vera

You should never use supplements to replace your doctor-recommended PV treatment. Only FDA-approved medications and treatments for PV are evaluated for safety and effectiveness. Dietary supplements don’t have the same strict requirements as approved treatments. Additionally, there aren’t any clinical trials that show any supplement is safe or effective for PV.

Talk to your doctor about proven treatments for PV.

FDA-approved treatment options for PV and its symptoms include:

• Phlebotomy — Regular blood withdrawals can reduce your blood volume and excess blood cells.
• Low-dose aspirin — This can lower your risk of blood clots.
• Medications to reduce RBCs — These include hydroxyurea (Droxia, Hydrea, Siklos), interferon alpha, ruxolitinib (Jakafi), and busulfan (Myleran).
• Drugs to reduce itching — These include antihistamines like loratadine (Claritin) and antidepressants like fluoxetine (Prozac).
• Bone marrow transplant — This procedure involves replacing your bone marrow with healthy cells from your own body or a donor.

Before you start taking any new supplement, you should talk to your doctor about the possible benefits, side effects, and drug interactions with your current treatment. Make sure your doctor has an up-to-date list of everything you take, both OTC and prescription, on file.

Talk With Others Who Understand

On myMPNteam, the social network for people living with myeloproliferative neoplasms and their loved ones, more than 3,600 members come together to ask questions, give advice, and share their stories with others who understand life with MPNs.

Do you take one or more dietary supplements for your PV? Have you discussed them with your doctor? Share your experience in the comments below, or start a conversation by posting on your Activities page.