Top 10 Cancer Fighting Supplements: Evidence Based Literature Review (2025)
Can certain foods lower your cancer risk? Are some foods increasing it without you realizing? What about vitamin and mineral supplements—do they help prevent cancer, or could they actually increase your risk?
The term "anti-cancer supplements" can be misleading. While some nutrients support the body in cancer prevention or treatment, others may interfere with therapies or even pose risks.
This guide compiles over 500 scientific references on cancer, diet, and supplements—helping you navigate the facts with confidence.
Understanding Supplements and Cancer: What You Should Know
- Dietary supplements are not regulated like medications. Unlike prescription drugs, supplements aren’t rigorously tested by the FDA for safety or effectiveness before hitting the market.
- Not all supplements are beneficial. While some may support health, others could interact with cancer treatments or cause unwanted side effects.
- Choosing the right supplement can be overwhelming. With thousands of options available, knowing where to start can be a challenge.
Should You Take Supplements During Cancer Treatment?
If you're considering supplements, always consult your doctor first—especially since some may interfere with medications or ongoing treatments.
How to Interpret Scientific Research
Not all studies carry the same weight. Here’s how research ranks in terms of credibility:
- Meta-analysis and systematic reviews – The highest level of evidence, as they analyze and combine data from multiple RCTs and studies to identify overall trends and draw more reliable conclusions.
- Randomized controlled trials (RCTs) – The gold standard, providing the strongest evidence.
- Small human studies – Can offer insights, but results are less reliable.
- Animal studies (mice/rat models) – A step closer to understanding effects in living organisms.
- Lab studies (cell cultures) – Useful for early discoveries but not directly applicable to humans.
What This Article Covers
We’ll explore dietary supplements that may help prevent cancer or aid recovery during treatment, along with the latest research and studies. New findings emerge constantly, so staying informed is key.
Let’s dive into the science and separate the myths from the facts!
- Top 10 Cancer Fighting Supplements
- Vitamin D3 and K2
- Turmeric (Curcumin)
- Fish Oil (Omega-3 Fatty Acids)
- Vitamin C
- Magnesium and Molecular Hydrogen
- Green tea (EGCG)
- Quercetin
- Melatonin
- Garlic (Allicin)
- Probiotics and Microbiome
- 3 Supplements That May Increase Cancer Risk
- Nicotinamide Riboside supplements and Cancer
- Conclusion
1. Vitamin D3 and K2
- This large-scale review looked at diverse populations — The data covered various groups and nationalities, including women in the U.S. Midwest, Danish adults with a family history of cancer and Canadians living in high-altitude areas. The participants had different health statuses as well — some had colorectal cancer, or a documented vitamin D deficiency. Others were also given a vitamin D supplement.
- While the participants varied in health status and genetic risk, a consistent pattern emerged — The researchers found that the lower your vitamin D levels, the higher your risk of developing colon cancer. On the flip side, people with adequate or optimal levels of vitamin D had dramatically lower rates of cancer.
- Unfortunately, majority of people today have very low levels of this vital nutrient — A recent study that looked at the vitamin D status of more than 5,600 adults found that 37.6% had vitamin D insufficiency (blood levels between 20 and 30 ng/mL), while 42% were severely deficient (blood levels lower than 20 ng/mL) in this nutrient.
- A landmark 1996 study found that women with the highest vitamin D intake had a 58% lower risk than those with the lowest intake.
- A 2021 meta-analysis found a 39% lower risk of colorectal cancer in people with higher blood levels of vitamin D. The researchers also noted that when vitamin D levels were monitored over time, those who maintained higher levels had a 20% lower chance of developing colorectal cancer down the line.
- A Canadian study found that supplementing with vitamin D reduced the incidence of precancerous polyps — by 33% for all polyps and 43% for high-risk ones. These polyps often go on to become cancer if not addressed early, so this kind of intervention has massive implications.
- The Iowa Women's Health study found that women who took vitamin D with calcium saw a 15% drop in colorectal cancer risk compared to those who didn't take any supplements.
- The Danish "Diet, Cancer and Health" study (one of the major ones included) found that vitamin D offered even stronger protection in people with a high genetic risk of colon cancer. That means if you've got a family history of this disease, optimizing your vitamin D status isn't just helpful — it could be life-saving.
The cancers for which the most human data are available are colorectal, breast, prostate, and pancreatic cancer. Numerous epidemiologic studies have shown that higher intake or blood levels of vitamin D are associated with a reduced risk of colorectal cancer (R). In contrast, the Women’s Health Initiative randomized trial found that healthy women who took vitamin D and calcium supplements for an average of 7 years did not have a reduced incidence of colorectal cancer (NEJM 2006). Some scientists have pointed out that the relatively low level of vitamin D supplementation (10 μg, or 400 IU, once a day), the ability of participants to take additional vitamin D on their own, and the short duration of participant follow-up in this trial might explain why no reduction in colorectal cancer risk was found.
Studies also show a link between vitamin D deficiency and cardiovascular disease, diabetes, and cancer (Sizar, 2020).
In 2016, a landmark study published in PLOS ONE found that women over 55 with blood concentrations of vitamin D higher than 40 ng/ml, had a 67% lower risk of cancer compared women with levels lower than 20 ng/ml.
- fatty fish
- egg yolks
- fortified milk
Research has shown that once you reach a minimum serum vitamin D level of 40 ng/mL (100 nmol/L), your risk for cancer diminishes by a whopping 67%, compared to having a level of 20 ng/mL or less.
The connection was strongest for lung and prostate cancers.
There’s more: A study published in the International Journal of Oncology found that cancer cells grow more slowly in lung cancer patients treated with vitamin K2.
A previous study found the same effect with leukemia patients. Vitamin K2 also safely suppressed growth of hepatocellular carcinoma, a common and deadly type of liver cancer, by blocking cell replication and triggering apoptosis. (source)
Vitamin K also slashed the risk of liver cancer coming back, in a group of patients who had experienced remission. Here’s the story. . .
Sixty-one liver cancer patients were declared free of cancer following surgery. Thirty-two of them received a vitamin K2 analogue, whereas 29 received placebos. The cumulative survival rates for the patients who received menatetrenone were 100% at 12 months, 96.6% at 24 months, and 87.0% at 36 months; and the corresponding survival rates for patients in the control group were 96.4%, 80.9%, and 64.0%, respectively (P = 0.051). (source)
A disorder previously nicknamed “pre-leukemia” called Myelodysplastic syndrome (MDS) often leads to full-blown leukemia, with all its disastrous consequences. In MDS, the bone marrow churns out young white blood cells instead of mature ones. But vitamin K treatment can induce apoptosis, and cause MDS cells to differentiate into healthy, mature white blood cells that can help your immune response, even in the face of full-blown leukemia. (source)
Vitamin K2 combined with vitamin D3 may be even better. In a recent study, it more than doubled the response rate of patients with low white blood counts, boosting it from 13 percent to 30 percent.
Vitamin K may also help against non-Hodgkin lymphoma, stomach, nasopharynx, and oral cancers. (source)
Buying Guide: Most vitamin D3 supplements include vitamin K2. Click here to buy vitamin D3 and K2.
2. Turmeric (Curcumin)
- blocking cancer cells from multiplying
- killing colon, breast, prostate, and melanoma cancer cells
- slowing tumor growth
Unfortunately, while there's some curcumin in whole turmeric, there's not enough in the regular spice to achieve clinically relevant results. The turmeric root itself contains only about 3% curcumin concentration. Another major limitation of curcumin as a therapeutic agent is that it is poorly absorbed. When taken in its raw form, you're only absorbing about 1% of the available curcumin.
"Studies on the effect of curcumin on cancer and normal cells will be useful for the ongoing preclinical and clinical investigations on this potential chemo-preventive agent."
3. Fish Oil (Omega-3 Fatty Acids)
The research was presented April 4, 2022 at the annual Experimental Biology meeting in Philadelphia. The animal model showed that omega-3 fatty acids helped promote the cancer-fighting activities of immunotherapy and anti-inflammatory therapy.
Make sure you buy high-quality omega-3 fatty acid supplements, meaning that the omega-3 fatty acids are pure and have not oxidized much (having low “TOTOX” value).
TOTOX value stands for total oxidation value. The omega 3 fatty acids EPA and DHA from fish oil are highly sensitive to oxidation. This means that they are rapidly affected by contact with oxygen. Oxidised fatty acids are not beneficial to our health. For this reason, a good fish oil supplement has a low TOTOX value. The maximum TOTOX value is set at 26 by the Global Organization for EPA and DHA omega-3.
4. Green Tea (EGCG)
However, the National Center for Complementary and Integrative Health (NCCIH) state that studies of green tea and cancer in humans have so far produced inconsistent results.
5. Vitamin C
*Umbrella review: An umbrella review, or a review of reviews, is a systematic review that only considers other systematic reviews as an eligible study type for inclusion.

There's still no evidence that vitamin C alone can cure cancer, but researchers are studying whether it might boost the effectiveness of other cancer treatments, such as chemotherapy and radiation therapy, or reduce treatment side effects.
There are still no large, controlled clinical trials that have shown a substantial effect of vitamin C on cancer, but some preliminary studies do suggest there may be a benefit to combining standard treatments with high-dose IV vitamin C."
6. Magnesium and Molecular Hydrogen
An analysis of the prospective, Swedish Mammography Cohort (JAMA 2005), evaluated 61,433 women aged 40 to 75 without a history of cancer for a mean follow-up of 14.8 years. The highest quintile of magnesium intake was associated with a significantly lower risk of CRC compared with the lowest quintile. This benefit was observed for both colon and rectal cancers.
A case-control study evaluated 2204 subjects from the Tennessee Colorectal Polyp Study (2007), which demonstrated that increasing total magnesium intake was significantly associated with decreasing risk of CR.. The highest tertile of dietary magnesium intake (>298 mg/day) was significantly associated with reduced risk of CRC in an age-adjusted model.
A study of 140,601 postmenopausal women from the Women’s Health Initiative (2015) with an mean follow-up of 13 years demonstrated a significant reduction in CRC risk with the highest quintile of total magnesium intake compared with the lowest quintile of magnesium intake. The benefit was driven by colon cancer, with a trend for rectal cancer.
Magnesium and Pancreatic Cancer
A study of 66,806 subjects aged 50 to 76 at baseline from the Vitamins and Lifestyle cohort (Nature 2015) evaluated magnesium intake and the incidence of pancreatic cancer during a mean follow-up of 6.8 years. Subjects with magnesium intake below the recommended dietary allowance were more likely to develop pancreatic cancer, particularly in those whose intake was less than 75% of the recommended dietary allowance. In this study, a 100 mg/day decrease in magnesium intake resulted in a 24% increase in risk of pancreatic cancer.
7. Melatonin
8. Quercetin
2022 - A paper published in August 2022 in Nutrition Research analyzed the pro-apoptotic effect that quercetin has on aging cells. The paper reviewed preclinical and early phase data using quercetin as a senolytic agent and found the data showed it was effective in “preventing or alleviating cancer formation.”
The authors reviewed the importance of cellular aging in the development of cancer cells and the effect that quercetin may have on the suppression of cancer cell proliferation.
Cellular senescence is a dynamic and multi-step process that is associated with alterations in metabolic activity and gene expression. This can compromise tissue regeneration and contribute to aging. On the other hand, by removing senescent cells, age-related dysfunction can be attenuated and potentially extend the lifespan.
This study published in 2017 in Oncology Reports took things a step further, finding that quercetin induced cancer cell death in nine types of cancer, including prostate cancer, colon cancer, and breast caner.
In another 2017 study, researchers gave quercetin to mice with tumors. Researchers found that mice in the quercetin-treated group showed delayed tumor growth, no significant changes in daily behavior, significantly better survival ratings, and increased rates of cell death.
9. Garlic (Allicin) and Onion
One study of 543,220 participants found that those who ate lots of Allium vegetables, such as garlic, onions, leeks and shallots, had a lower risk of stomach cancer than those who rarely consumed them (Source).
A study of 471 men showed that a higher intake of garlic was associated with a reduced risk of prostate cancer (Source).
Several clinical studies have found an association between garlic intake and a lower risk of certain types of cancer.
10. Probiotics and Microbiome
Indeed, as reported in Nature, a 2015 study found that while microbe-free mice failed to respond to treatment with checkpoint inhibitors, mice given Bacteroides fragilis fared much better. Other researchers have had similar findings, showing Bifidobacterium improves the effectiveness of cancer immunotherapy in lab animals — again by triggering a more robust response by specific anticancer immune cells.
As you might expect, antibiotic treatment has been found to worsen response to immunotherapy, likely because antibiotics indiscriminately kill all gut bacteria, thereby ridding your body of many really important immune helpers. Importantly, even cancer therapies that do not rely on the activation of your immune response typically fail unless you have the appropriate gut microbes. (source)
For example, certain chemotherapy agents actually rely on gut microbes to eradicate the tumor directly. In other instances, the microbes' influence on cancer is related to their ability to influence gene expression alter the stability of your genes.
Avoid Taking These 3 Supplements Too Casually as They May Increase Cancer Risk
Additionally, a systematic review and meta-analysis published in Nutrients in 2022 established a 16 percent increase in lung cancer risk associated with beta-carotene supplementation, with smokers and asbestos workers facing an even greater risk of 21 percent.
The U.S. Preventive Services Task Force (USPSTF) recommends against using beta-carotene supplementation for the prevention of cardiovascular disease (CVD) or cancer.
A study published in 2023 by Newcastle University in the UK found that eating more carrots is related to a reduced incidence of cancer, but taking beta-carotene had no such effect.
Vitamin E
The USPSTF does not recommend using vitamin E supplements to prevent CVD or cancer, citing a comprehensive analysis of nine randomized trials that demonstrated no benefits.
Although vitamin E is a good antioxidant, too much of it can cause gastrointestinal bleeding and other conditions, Dr. Tzung-Hai Yen, a professor in the Department of Nephrology and director of the Clinical Poison Center at Chang Gung Memorial Hospital in Taiwan, told The Epoch Times.
This is especially the case for people with chronic diseases, Yen said. They need to be more cautious because many health products might not suit them. They should first seek advice from a physician before taking vitamin E supplements.
Vitamin B in High Doses
Published in the Journal of Clinical Oncology, this study involved 77,118 Americans aged 50 to 76 and found that men supplementing with either vitamin had a 30 to 40 percent increased risk, particularly among smokers.
However, there was no association between vitamin B6, B9 (folic acid), and B12 supplementation and lung cancer risk in women. Data showed that the participants’ intake of both B6 and B12 far exceeded the U.S. government’s recommended daily intake of 1.3 mg/day and 2.4 mcg/day.
Supporting evidence from a case-control study with 5,183 case-control pairs published in the International Journal of Cancer linked higher vitamin B12 levels with an increased overall lung cancer risk. The study also analyzed genetic data from 29,266 lung cancer cases and 56,450 controls and reached the same conclusion.
Nicotinamide riboside supplements and Cancer
Conclusion and Key Takeaways
- Although this is a comprehensive guide, please do not consider this guide as personal medical advice, but as a recommendation for use with professional providers. Consult with your doctor and discuss with her/him.
- Our aim here isn't to replace your doctors' advice. It is intended as a sharing of knowledge and information. Do take note that most strategies are not 100% protective against cancer. It's a continuous struggle between the immune system and the cancer cells.
Nutrition and Cancer: Foods, Supplements, Diet and Lifestyle Strategies (2025 Guide)
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