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Breast cancer: Common deficiencies of a few nutrients increase the risk of breast cancer and lethal metastases

Breast cancer: Common deficiencies of a few nutrients increase the risk of breast cancer and lethal metastasesBreast cancer is very common in the Western world and modern society. The disease is thought to be associated with lifestyle factors and lack of essential nutrients. For instance, it has been known for a long time that lack of vitamin D increases the risk of breast cancer. According to a new study that is published in the science journal Endocrinology, there is also a link between lack of vitamin D and the development of metastases in the lungs. Previous research also shows that the widespread deficiency of selenium, iodine, omega-3 fatty acids, and melatonin can increase the risk of breast cancer but supplements can help prevent the disease and possibly be used as add-on therapy.

Breast cancer is the most common cancer among women. Although treatments have improved a lot in recent years, it still hasn’t been possible to bend the curve. On the contrary, far more women in northern Europe, USA, and Canada contract breast cancer compared with women in Asia and Africa. The difference primarily has to do with the Western lifestyle, which is supported by the fact that Asians and Africans have a higher breast cancer rate if they move to Europe or the United States.
Although some women are genetically prone to get breast cancer, it is often dietary and lifestyle factors that trigger the disease. It takes many years for breast cancer to develop, which is why it is relevant to look closer at why vitamin D, selenium, iodine, omega-3 fatty acids, and melatonin have a positive impact both as a preventative measure and as add-on therapy.

  • One in nine Danish women contracts breast cancer
  • The curve has not been bent
  • Lifestyle and lack of nutrients play a determining role

Vitamin D

The sun during the summer period is our main source of vitamin D. Our modern way of living where we spend far too much time indoors, the dark winter period, ageing, having dark skin, being overweight, or having diabetes are all factors that contribute to the big problem with around one billion people worldwide being vitamin D-deficient.
Vitamin D has several cancer-preventive functions and it has been known for a long time that lack of vitamin D increases your risk of breast cancer and other cancer types.
On the other hand, vitamin D supplementation can slow down the development of breast cancer and metastases in the lungs, according to a new mouse study that is published in Endocrinology.
Here, the scientists found that vitamin D regulates certain chemokines (C CXCL12/CXCR4) and signal pathways that are involved in the spread of breast cancer.
Lack of vitamin D worsens the prognosis for post-menopausal women that have been diagnosed with the disease, according to a study of Brazilian women. The study is published in the North-American science journal Menopause. The scientists found that women with insufficient levels of vitamin D in their blood tended to get larger lumps in their breasts and had more metastases. Also, a higher number of their lymph nodes were attacked.
Lack of vitamin D is also associated with elevated estrogen levels, which can cause breast cancer cells to grow. A study from Fred Hutchinson Cancer Research Center in Seattle, USA, shows that daily supplementation with 50 micrograms of vitamin D for a year can lower estrogen levels in the blood and reduce the risk of breast cancer. This is even the case with overweight women who often have higher estrogen levels in their blood.
The need for vitamin D varies from person to person and depends on genetic factors, sun exposure, skin color, age, BMI, and chronic diseases.
EU’s Scientific Committee on Food has set 100 micrograms as the daily safe upper intake level for vitamin D for adults.
In any case, it is vital to optimize blood levels of vitamin D. One of the leading vitamin D scientists, Professor Cedric F. Garland from the University of California, San Diego School of Medicine in the United States, headed a study in which he observed that blood levels of vitamin D must be at least 60 ng/ml in order to prevent breast cancer.
Several meta-analyses have shown that high-dosed vitamin D supplements not only lower the risk of breast cancer and other cancer forms, they even improve the chance of surviving if you have been diagnosed with the disease. It is therefore vital to make sure to get enough vitamin D throughout life in order to maintain optimal blood levels of the nutrient.
Because vitamin D is lipid-soluble it is best to take the nutrient in soft capsules with oil, as this helps the body absorb and utilize the vitamin.

Vitamin D’s cancer preventive properties:

  • Regulates gene activities by way of on-off switches
  • Regulates cell growth
  • Regulates estrogen levels
  • Boosts the immune system and helps it destroy abnormal cells
  • Counteracts inflammation that causes oxidative stress in the cell


Selenium supports around 30 selenium-dependent enzymes (selenoproteins) that control cellular energy turnover and a host of other functions. Differences in selenium blood levels have been observed between breast cancer patients and healthy controls long before the disease has surfaced. It is therefore reasonable to believe that selenium has potential for long-term prevention. An estimated one billion people globally are believed to lack selenium, primarily because of selenium-depleted farmland and altered dietary habits. Over the past decades, the widespread selenium deficiency has been linked to the increased rate of breast cancer and other cancers. The risk of dying of cancer is also greater if you lack selenium.
A Polish population study that is published in the journal Nutrients showed that having higher blood selenium levels increases your chances of surviving breast cancer after 10 years. In an earlier Swedish study, it was seen that the quartile of breast cancer patients with the highest selenium levels in their blood (≤ 100 µg/L) had better odds of surviving compared to the quartile with the lowest selenium levels (≥ 81 µg/L).
Both the Polish and the Swedish studies support earlier studies showing that selenium has a cancer preventive effect.
The farmland in Europe is low in selenium and even though fish and shellfish are considered good selenium sources, research has shown that even if you consume seafood five days a week, you don’t get enough of the nutrient. The research was carried out in collaboration with scientists from the Danish Cancer Society.
The recommended selenium intake is 50-70 micrograms per day but this is not enough to saturate selenoprotein P, a selenoprotein that is used as a marker of the body’s selenium status. In order to properly saturate this selenoprotein you need more than 100 micrograms daily
Most selenium studies carried out on humans have used doses of around 100-200 micrograms. It is best to take selenium yeast with many different selenium species, as this gives the same variety of different selenium types as you get by eating a varied diet. The European Food Safety Authority (EFSA) has established a safe upper intake level of 300 micrograms daily.

Selenium’s cancer preventive properties

  • Regulates cell growth
  • Supports powerful antioxidants (GPX) that protect the cells’ DNA and mitochondria against free radicals
  • Repairs DNA damage
  • Inhibits the formation of new blood vessels in tumors (anti-angiogenesis)
  • Helps diseased cells self-destruct (apoptosis)
  • Contributes to a well-functioning immune disease
  • Counteracts inflammation
  • Neutralizes environmental toxins such as mercury


Iodine is important for the body’s metabolism. Our ability to utilize iodine is disturbed by environmental toxins such as fluoride compounds, chlorine, and bromine, which therefore increase our need for iodine. Iodine’s ability to protect against breast cancer is demonstrated in animal studies. Epidemiological studies of population groups that have higher iodine intake than others show that they have a lower risk of developing breast cancer.
Iodine protects against breast cancer by regulating the estrogen balance and the MCF7 gene in breast cancer cells, according to a study that is published in International Journal of the Medical Sciences. The researchers behind this study therefore suggest that iodine is relevant as add-on therapy in the pharmacological treatment of hormone-dependent breast cancer. Besides the thyroid gland, ovaries contain large amounts of iodine, which means that an iodine deficiency may result in changes in the ovaries’ estrogen production and changes in the estrogen receptors in breast cells.
American scientists have found that women living in iodine-deficient states produce more estrogen. Also, cells in their breast tissue increase their estrogen sensitivity. Both factors are known to increase the risk of breast cancer.
The thyroid gland, the breasts, the prostate, the colon, and the nervous system contain tissues that convert the omega-6 fatty acid AA (arachidonic acid) into delta-iodolactone. This particular iodine compound causes cancer cells and worn-out cells to self-destruct in an essential process called apoptosis. However, cancer cells are only able to perform apoptosis if there is enough iodine.
It appears that lack of dietary iodine may be a factor that contributes to the widespread breast cancer incidence.
There is iodine in fish, shellfish, seaweed, algae, fish sauce, and eggs. At one point when the iodine intake in Denmark was below the official recommendation, mandatory iodine-enrichment of table salt was introduced. Since then, the iodine intake has increased a little but it is still too low.
It is also a problem that many people prefer sea salt or Himalayan salt. While these salt sources contain more minerals, they don’t contain as much iodine as regular table salt. It is therefore important to make sure to get iodine from other sources. One should also avoid eating table salt that contains anti-caking agents such as aluminum that can have a negative effect on the nervous system and reproductive properties. Choose mineral salt that contains iodine plus sodium and magnesium.
The recommended daily intake for iodine (in Denmark) is 150 micrograms for adults but some people may need more. The European Food Safety Authority (EFSA) has established a safe upper intake level of 600 micrograms. Healthy people should try to get more iodine from fish, shellfish, and seaweed that produces quite a lot of iodine in the form of iodides.

Omega-3 and other fats

Oily fish and different types of omega-3 lower the risk of developing breast cancer, according to a Polish study that is published in In Vivo. The study included 201 Polish women with freshly diagnosed breast cancer and a control group with 201 healthy women matched for age. Using a standardized diet questionnaire and interviews, the scientists mapped out the diet and lifestyle habits of the participants.
It turned out that the women with the highest consumption of dietary fat, where fat accounted for more than 10 percent of their total energy intake, had a significantly lower risk of developing breast cancer compared with the women who got very little dietary fat. Women who hardly ever ate fish and were overweight had a greater risk of developing breast cancer compared with the women who were slender and ate more fish. The scientists concluded that a relatively high intake of fats lowers the risk of developing breast cancer, especially the omega-3 fatty acids from oily fish. An American mouse study has demonstrated that a diet rich in omega-3 fatty acids significantly lowers the risk of injected breast cancer cells attaching to the mammary glands of the mice. Moreover, the risk of cancer cells spreading to other organs was also reduced in the group of mice that was fed a diet rich in omega-3 fatty acids, and they lived longer than the mice who got a diet rich in omega-6.
There were mice in the omega-3 group that did not even get breast cancer and apparently were able to destroy the injected breast cancer cells. The mice that got a diet rich in omega-3 also had less inflammation. According to the scientists, this may mean that omega-3 fatty acids help to suppress the type of inflammation that triggers the rapid development and spread of tumors. The American study is published in Clinical and Experimental Metastasis.
The results of the two studies fit in nicely with other studies showing that fish oil consumption during pregnancy and in the childhood helps suppress the development and spread of breast cancer cells later in life.
It is important to maintain an optimal balance between omega-3 and omega-6 fatty acids. Consuming too much omega-6 from plant oils, margarine, chips, and industrially processefoods destroys the delicate balance and sets the stage for low-grade chronic inflammation. This is not something one notices but the condition results in oxidative stress that is very bad for your health.

  • Choose oily fish such as herring, anchovies, salmon, mackerel, and trout from clean and pure waters
  • Try to avoid predatory fish like tuna that tend to contain too much mercury and other hormone-disrupting chemicals
  • High-quality fish oil supplements are a good alternative for people who do not like oily fish or simply don’t eat enough


Melatonin is primarily known as a sleep hormone but studies show that the compound prevents cancer in a variety of different ways. Melatonin is produced in the brain’s pineal in response to nightfall. With increasing age, this gland starts to calcify and shrink, causing our melatonin synthesis to decrease. At the age of approximately 60, a person’s melatonin production will have dropped by around 50 percent compared with when that person was in his or her twenties. It continues to drop.
For decades, scientists have pointed to the link between decreasing melatonin production in senior life and the fact that the risk of breast cancer and other cancers goes up. Lack of daylight, overexposure to light from the screens of electronic devices (blue light), stimulants, medicine, air travel across time zones, and electrosmog can also lower the body’s natural melatonin production.
Nightshift work can increase a woman’s risk of breast cancer by up to 40 percent, according to Johnni Hansen, a senior scientist working with the Danish Cancer Society.
There is possibly a relation between low melatonin levels and breast cancer. Melatonin inhibits the production of the type of estrogen that is involved in hormone-sensitive breast cancers. A study carried out on mice shows that melatonin supplementation can lower the risk of cancer. The scientists believe melatonin has several important functions. It is an antioxidant, it regulates the hormone balance, it supports the immune defense, and it counteracts unwanted inflammation. Although no human studies are able to show that melatonin can prevent cancer at this point, it appears that melatonin supplements are able to postpone the ageing process.
There are also promising results of studies where cancer patients have been given supplements of melatonin. Standard cancer therapy includes chemotherapy and radiation. According to a Danish research article published in Ugeskrift for Læger (the journal of the Danish Medical Society), melatonin supplements are able to boost the anti-cancer effect of chemotherapy and reduce many of the side effects. By combining chemotherapy with melatonin, it is possible to increase the odds of surviving cancer from 28.4 percent to 52.2 percent over a one-year period. The positive effect of melatonin in cancer confirms earlier studies from abroad.
No matter what, it is always important to get a proper night’s sleep to support the body’s natural melatonin production. If you have problems with falling asleep or if you sleep poorly, you should do something to solve the problem. In many cases, it is caused by a lack of melatonin.
If the common tips and advice for better sleep fail to work, try taking a melatonin supplement to compensate for the lack of melatonin in your body. Most tablets contain 3 mg of melatonin and should be taken approximately one hour before going to bed (unless directed to do otherwise).

Diet habits and lifestyle

Unhealthy diets, lack of nutrients, overweight, physical inactivity, ageing, and too little sleep all increase the risk of cancer. Also, alcohol is the cause of around 3 percent of breast cancer cases in Europe. Alcohol causes even more cases in Denmark because Danish women drink more.
A Danish woman is 4-5 times more likely to develop breast cancer than a Chinese or Japanese woman and our large consumption of dairy products is believed to play a major role in that, simply because milk is not part of Asian diets. Milk contains hormones such as estrogen and IGF-1 that promote growth, even the growth of cancer cells.
For example, the Nurses’ Health Study from Harward University shows that pre-menopausal women with elevated levels of IGF-1 in their blood are seven times more likely to get breast cancer compared with women who have low IGF-1 levels.
There can be several reasons why Asian diets lower the risk of breast cancer. They contain more fish and seaweed that provide vitamin D, selenium, iodine, and omega-3. And it has been demonstrated that Asian women are substantially more likely to get breast cancer if they start eating European or American diets.
One should also pay attention to hormone replacement therapy (HRT) and hormone-disrupting chemicals in the diet and surrounding environment. It is known that ionizing radiation such as X-rays can cause breast cancer.

Factors that increase your risk of breast cancer

  • Lack of vitamin D, selenium, iodine, omega-3 fatty acids, and melatonin
  • Chronic inflammation
  • Lack of sleep
  • Overweight
  • Hormone-disrupting chemicals
  • Hormone supplements after menopause (products with estradiol)
  • Birth control pills and hormonal coils (IUS) slightly increase the risk
  • Alcohol
  • Ionizing radiation


Jiarong Li et al. Vitamin D regulates CXCL12/CXCR4 and epithelial-to-mesenchymal transition in model of breast cancer metastasis to lung. Endocrinology 2021 March

The North American Menopause Society (NAMS). Obesity and vitamin D deficiency may indicate greater risk for breast cancer. ScienceDaily 2018

University of California – San Diego. Greater Levels of vitamin D associated with decreasing risk of breast cancer. 2018

De Sousa Almeida-Filho B et al. Vitamin D is associated with poor breast cancer prognostic features. J Steroid Biochem Mol Biol 2017

Mark Szwiec et al. Serum Selenium Level Predicts 10-Year Survival after Breast Cancer. Nutrients, 8 March, 2021

Rosewell Timmerman, Stanley Omaye. Selenium´s Utility in Mercury Toxicity: A Mini-Review. Scientific Research. 2021

Lutz Shomburg. Dietary Selenium and Human Health. Nutrients 2017

New Links between selenium and cancer prevention. HRB. December 2017

Rychlik W. The need for iodine supplementation. OMS 12.06.2017

Frederick R. Stoddard et al. Iodine Alters Gene expression in the MCF7 Breast Cancer Cell Line: Evidence for an Anti-Estrogen Effect of Iodine. International Journal of Medical Sciences. 2008

Dorota Dydjow-Bendek and Pawel Zagozdzon. Total Dietary, Fatty Acids, and omega-3/omega-6 Ratio as Risk Factors of Breast Cancer in the Polish Population – a Case-Control study. In Vivo January-February 2020

Sarawoti Khadge et al. Long-chain omega-3 polysaturated fatty acids decrease mammary tumor growth, multiorgan metastatis and enhance survival. Clin Exp Metastasis. 2018

Vinter, Anna Gry, Mogens Helweg Claësson: Melatonins indvirkning på immunsystem og cancer. Ugeskrift for Læger 2015

Sanches-Barcelo EJ et al. Melatonin uses in oncology: breast cancer prevention and reduction of the side effects of chemotherapy and radiation. Expert Opin Investig Drugs 2012

Wang YM et al. The efficacy and safety of melatonin in concurrent chemotherapy or radiotherapy for solid tumors: a meta-analysis of randomized controlled trials. Cancer Chemother Pharmacol. 2012

Ane Bodil Søgaard, Karen Østergaard, Troels V. Østergård. Mælk og sundhed: Hvad er det du drikker.

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