Analysis by Dr. Joseph Mercola
June 26, 2025
Story at-a-glance
· New research involving over 1.3 million people
shows that higher blood levels of vitamin D are linked to up to 58% lower risk
of colorectal cancer, especially in women
· A whopping 80% of adults are either deficient or
insufficient in vitamin D, which significantly increases their risk of
developing colorectal cancer over time
· Vitamin D helps slow cancer cell growth, support
gut health, and reduce inflammation — factors that are all important in
preventing tumor formation in the colon
· Getting regular sun exposure or supplementing with
vitamin D has been shown to reduce the risk of polyps and tumors, even in
people with a genetic risk for colon cancer
· Testing your vitamin D levels and correcting
deficiencies through sunlight, supplements, or food is one of the most powerful
and low-cost ways to reduce your colon cancer risk
Colorectal cancer is one of the most prevalent
types of cancer today, particularly in Western countries where modern,
processed-food diets have become the norm. Every year, 1.2 million cases of
colorectal cancer are diagnosed worldwide, and around 930,000 people succumb to
this disease.1 It's
the second most common cancer affecting men, and ranks as the third most common
cancer in women.2
Some of the early symptoms of colorectal cancer
include abdominal discomfort, blood in the stool, fatigue, and unexplained
weight loss. However, these symptoms are usually dismissed until the disease
has progressed, and it's too late.
Now, research has highlighted a powerful yet often
overlooked factor that will help protect against this lethal disease — vitamin D.
Video Link: https://youtu.be/V6DkfXJuhAw
New Data Shows Vitamin D
Plays a Bigger Role in Colon Cancer Prevention
A comprehensive
analysis published in the journal Nutrients in April 2025 has discovered a
fascinating but substantial link between vitamin D and colorectal cancer (CRC).
The researchers reviewed and analyzed data from 50 separate studies involving
over 1.3 million participants to determine how much vitamin D impacts your risk
of developing colorectal cancer.3
•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.
"Maintaining optimal vitamin D
levels and adequate dietary intake is crucial in preventing CRC and improving
patient prognosis," the researchers
said.
•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.4
Mónika Fekete, Ph.D., a professor in the Institute
of Preventive Medicine and Public Health at Semmelweis University and the
study's lead author, commented:
"While vitamin D is not a
substitute for screening or a healthy lifestyle, it is an important and
relatively modifiable factor worth paying attention to — especially in
individuals at higher risk of deficiency, such as older adults, people with
limited sun exposure, those with darker skin, or individuals with chronic
illnesses."5
More Notable Highlights from the Featured Study
This new research makes it clear that if you're not
paying attention to your vitamin D status, you're missing out on one of the
simplest and most powerful tools available to reduce your risk of colon cancer.
Below are some of the compelling findings from the featured analysis that point
to vitamin D as a key factor in reducing your risk of colorectal cancer.
•A landmark 1996 study found that women with the highest vitamin D
intake had a 58% lower risk than those with the lowest intake.6
•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.7
•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.8
•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.9
•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.10
How Does Vitamin D Affect
Your Colorectal Cancer Risk?
Vitamin D is a
fat-soluble nutrient your body naturally synthesizes when your skin is exposed
to sunlight. As I've noted in previous articles, it plays an essential role in
your bone health, immunity, and brain function, including mood regulation.
•Vitamin D's
role in cancer protection — Vitamin D acts by attaching to vitamin D
receptors (VDR) found in your cells, including your colon cells. When this
occurs, a series of signals are released that affect how your cells grow,
develop, and survive.11 However, having poor vitamin D levels weakens
these protective effects, allowing abnormal colon cells to survive and multiply
instead.12
•Another vital
purpose of vitamin D — Animal studies have also found that vitamin D
helps delay some age-related changes by activating another important pathway
via the vitamin D receptor. This pathway involves a molecule called Nrf2, which
plays a crucial role in protecting your body from oxidative stress and DNA
damage — two factors that are commonly linked to the development of cancer.13
•Vitamin D also
supports the health of your intestinal lining — The colon is
constantly regenerating itself, and this requires precise communication between
your cells. Vitamin D ensures that this process runs smoothly. According to one
research:
"Vitamin D
and its nuclear receptor (VDR) regulate intestinal barrier integrity, and
control innate and adaptive immunity in the gut. Metabolites from the gut
microbiota may also regulate expression of VDR, while vitamin D may influence
the gut microbiota and exert anti-inflammatory and immune-modulating
effects."14
Vitamin D Has Protective
Effects Against Other Cancers, Too
In general,
cancer now ranks as the second-leading cause of death worldwide, after
cardiovascular disease.15 As the featured analysis and the supporting
studies it investigated discovered, it's clear that optimizing your vitamin D
levels is a key strategy to reduce cancer deaths. However, health officials
rarely acknowledge its importance. In fact, there are multiple ways by which
vitamin D helps protect against cancer, such as:16
•Inhibiting
cancer cell growth — It targets different stages of cancer
development and progression. This includes the
initiation, growth and spread of cancer cells.
•Preventing cancer spread — It has antimetastatic effects, meaning it
stops cancer cells from spreading from the original tumor site to other areas
of the body. This is useful
for improving survival rates, as metastasis is often responsible for many
cancer fatalities.
•Stopping tumor
formation — Vitamin D is anti-tumorigenic; it helps prevent tumors from
forming or growing by inducing cancer cell death, blocking cell cycle
progression, or blocking pathways that trigger tumor growth.
A 2023 review published in the Journal of Steroid
Biochemistry and Molecular Biology highlighted some of the types of cancer that
vitamin D could help prevent, such as:17
·
Breast
·
Prostate
·
Bladder
·
Glioblastoma
·
Melanoma
·
Squamous cell carcinoma
·
Ovarian
·
Multiple myeloma
·
Osteosarcoma
·
Head and neck
The study also highlighted the role of genetic
differences in the VDR that could influence breast cancer risk. Read more about the
findings here — "More Evidence Showing Vitamin D Combats Cancer."
Sunlight — Mother Nature's Vitamin D Factory
While some amounts of vitamin D are found in foods
like fatty fish, liver, and egg yolks, the ultimate way to boost your levels of
this nutrient is through mindful and appropriate sun exposure.
•When sunlight hits your skin, it
produces a type of vitamin D called cholecalciferol — It's far different from vitamin D2, which is
what you get from plant sources like mushrooms and yeast. D3 is actually more
effective at increasing blood levels. On a typical sunny day, your body may
produce up to 25,000 international units (IU) of vitamin D.18
•How much sun is enough? Ideally, you must expose your bare skin to direct
sunlight daily. Gauge how long to stay under the sun safely by doing this
simple test — Pay close attention to your skin for any sign of pinkness. The goal is to stay just below the point where your
skin starts to turn slightly pink. If your skin turns red, it's a sign of
damage, not benefit — get out of the direct sun immediately.
•Your body cannot get too much vitamin
D from sun exposure — Your body stops making vitamin D
when you've got enough, so you can't overdo it from sunlight alone. However, if
you have darker skin, you'll need to spend more time in the sun to produce the
same amount of vitamin D as someone with lighter skin.
•An important caveat about sun exposure
— If you're still consuming a
processed food diet loaded with vegetable oils or seed oils, then sun exposure
will work against you. This is because seed oils are packed with linoleic acid (LA), which then accumulates in
your skin.
When the LA in
your skin interacts with the UV rays from the sun, it triggers inflammation and
DNA damage. To avoid this, I recommend avoiding direct sunlight during peak
hours until you've eliminated seed oils for at least six months.
•Additional
reminders on sun exposure — In some cases, it's impossible to completely
avoid peak sunlight during the period when you're purging LA from your diet. If
this is the case, it's best to follow protective measures:
◦Take 12
milligrams of astaxanthin daily — This will enhance your skin's UV resistance.
◦Apply
niacinamide (vitamin B3) cream before and after sun exposure.
◦Take a baby
aspirin — This will
help prevent LA from converting to harmful oxidized linoleic acid metabolites
(OXLAMs). Ideally, take the aspirin 30 minutes to
one hour before sun exposure.
•A strategy to speed up LA removal from
your skin — One interesting discovery I
recently made was that there's a way to quicken up the pace by which your body
purges LA embedded in your skin. This is by ingesting a special fat called
pentadecanoic acid or C15:0, found in raw, grass fed milk.
I recommend getting at least 2 grams of C15:0 per
day, which will significantly speed up LA clearance from your body from two to
three years to 12 to 18 months. My article, "The Fast-Track Path to Clearing
Vegetable Oils from Your Skin" will give you more
insightful details about C15:0.
However, not everyone has access to sunlight at all
times. For example, people who live in far northern regions have very few
months of peak sunlight. In this case, a vitamin D3 supplement is the best
alternative.
Get Tested to Ensure You're
Meeting the Ideal Levels for Cancer Prevention
Measuring your
vitamin D level, ideally twice a year, is the only way to determine if you're
getting enough sun exposure and/or taking the right amount of vitamin D3
supplement.
•What's the
optimal level for cancer prevention? Ideally,
you must aim for between 60 ng/mL and 80 ng/mL. The cutoff for sufficiency is
around 40 ng/mL. In Europe, the measurements you're looking for are 150 to 200
nmol/L and 100 nmol/L, respectively.
•Adjust your
levels depending on your test results — Once you've confirmed
your vitamin D levels via testing, adjust your sun exposure and/or vitamin D3
supplementation accordingly. Then, remember to retest in three to four months
to make sure you've reached your target level.
•Optimize other
nutrients to help meet your levels — Remember to balance
your vitamin D3 with calcium, magnesium, and vitamin K2 through your healthy
diet.
•If you're
supplementing with vitamin D3, here's a tip — Take it with a meal
that has some healthy fat, like grass fed butter or tallow. Since vitamin D is
fat-soluble, this will help your body absorb it.
Your Gut Health — Another
Vital Factor to Reduce Your Colon Cancer Risk
Vitamin D, or
the lack of it, is indeed a key factor that increases your risk of colon
cancer, but there's another major aspect that many people are ignoring until
it's too late — their gut health.
There's
actually a significant connection between the state of your gut microbiome and
colorectal cancer risk, particularly the composition of the food you eat. Your gut is a fascinating, complex ecosystem
teeming with trillions of bacteria, both helpful and harmful. These tiny residents play a
crucial role in digestion, nutrient absorption and even your immune system.
But when you
consume a poor, nutritionally deficient diet loaded with ultraprocessed junk
foods high in vegetable oils and LA, not only are you hampering the growth of
good bacteria, but you're also nourishing the pathogenic bugs. This disruption
in the gut microbiome leads to an inflammatory environment, increasing the risk
of colon cancer.19
Hence, you must
take the necessary steps to protect your gut health. Read my article "Unveiling the Link Between Ultraprocessed Foods and Colon Cancer" for more
information.
Frequently Asked Questions
(FAQs) About Vitamin D for Colorectal Cancer Prevention
Q: How does vitamin D
help protect against colorectal cancer?
A: Vitamin D plays a direct
role in cell regulation. It slows the growth of abnormal cells,
encourages unhealthy cells to die, reduces inflammation in the gut, and helps
maintain the health of the intestinal lining — all of which are key in
preventing cancer from developing or progressing.
Q: What vitamin D
level is considered protective against colon cancer?
A: For
cancer prevention, aim for blood levels of 60 to 80 ng/mL. Levels below 30
ng/mL are considered low, and anything under 20 ng/mL is classified as
deficient. Most adults fall below these thresholds, putting them at unnecessary
risk.
Q: Does vitamin D reduce
the risk of colon polyps, too?
A: Yes. One Canadian study
found that supplementing with vitamin D reduced all colon polyps by 33%, and
high-risk polyps by 43%. These types of growths are often
precursors to cancer, so reducing them is a major step in prevention.
Q: Is sun exposure enough to meet my vitamin D
needs?
A: Sunlight
is the most effective way to make vitamin D naturally, but only if you're not
loaded with seed oils, which cause skin damage. If sun exposure isn't
possible — due to location, skin tone, or season — a vitamin D3 supplement is
recommended.
Q: Who is most at risk
for vitamin D deficiency and colorectal cancer?
A: Older adults, people with
darker skin, those with chronic illness, or anyone with limited sun exposure
are more likely to be deficient. If you have a family history of colorectal
cancer, optimizing your vitamin D levels becomes even more important.
Sources and References
·
1 WHO, Colorectal Cancer, July 11, 2023
·
2 Nutrients. 2025
Apr 15;17(8):1351
·
3, 5, 12 Prevention, April 22, 2025
·
4 J Cachexia Sarcopenia Muscle. 2025 Mar 31;16(2):e13778
·
6 Journal of the National Cancer
Institute, Volume 88, Issue 19, 2 October 1996
·
7 Critical Reviews in Food Science and
Nutrition, Volume 63, 2023 - Issue 1
·
8 Preventive Medicine, Volume 135, June 2020, 106072
·
9 Nutrition and Cancer, Volume 71, 2019
- Issue 5
·
10 PLOS One, February 3, 2020
·
11, 13 Ageing Research Reviews, Volume 87, June 2023, 101923
·
14 Acta Histochem
Cytochem. 2020 Jun 16;53(3):33–42
·
15 J Thorac Dis.
2017 Mar;9(3):448–451
·
16, 17 The Journal of Steroid Biochemistry and Molecular Biology, Volume 231,
July 2023, 106308
·
18 J Steroid
Biochem Mol Biol. 2019 May:189:228-239
·
19 Gut 2025;74:586-602
Source: https://articles.mercola.com/sites/articles/archive/2025/06/26/vitamin-d-helps-lower-risk-of-colorectal-cancer.aspx?cid_source=takecontrol&cid_medium=email&cid_content=art1HL&cid=20250726_TC
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