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My favourite hot chocolate milk with rum ! |
I was intrigued by the late Professor Jane Plant’s
inspiring story on how she beat cancer by giving up dairy products. Her story and her books can be found in
various websites. When Daily Telegraph published her story in 2014, the article
triggered numerous complaints and she was being accused of misleading women by
falsely suggesting a link between breast cancer and dairy products. Mind you,
we are talking about the multi-million farming business here!
(http://www.telegraph.co.uk/foodanddrink/healthyeating/10868428/Give-up-dairy-products-to-beat-cancer.html).
Well, in my opinion, she was just sharing what she has
experienced and how giving up dairy products improved the prognosis of her
breast cancer. Similarly, in my case, having to live with benign breast disease
with multiple cysts for a couple of years and how a simple dietary change
within a short period of time gave me a diagnosis of breast cancer! I guess we
missed out something there.
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Deliciously crazy french onion soup with lots of cheese! |
A large number of studies have investigated the relation
between dairy food consumption and breast cancer risk, unfortunately with
conflicting results. Some studies were well-designed but some have obvious
flaws. Most cancer-related organizations prefer to take the middle path by
saying there were no significant relationship between dairy products intake and
cancer.
Nevertheless, there are studies that positively link
dairy products intake and risk of cancer worthy of attention!
- In an ecologic study from 1916-1975 where data obtained
from the Norwegian Cancer Registry were analysed to compare risk of breast
cancer among women who went through the period before, during, or after World
War II, breast cancer risk in 1975 was found to be 2.7-times higher than in
1916. This risk has been associated with changes of life style factors after
World War II including milk intake (Tretli and Gaard 1996).
- In another prospective study to examine the
relationship between energy and fat consumption and the risk of breast cancer
among 25,892 Norwegian women, women consuming 0.75 L or more of full-fat milk
daily had a relative risk of 2.91 compared with those who consumed 0.15 L or
less (Gaard et al. 1995).
- Data from the Nurses' Health Study II found that women
who ate red meat and two or more servings of high-fat dairy products (whole
milk or butter) every day had a higher risk of breast cancer before menopause (Cho et al. 2003).
- A study and a mean follow up of 11.8 years on 1893
women diagnosed with early-stage invasive breast cancer from 1997 to 2000
concluded that intake of high-fat dairy was related to a higher risk of
mortality after breast cancer diagnosis (Kroenke et al. 2013).
- In another recent large Swedish cohort study among
people with lactose intolerance, it was demonstrated that people with lactose
intolerance and low consumption of milk and other dairy products had a
decreased risk of breast, lung, and ovarian cancers (Ji et al. 2015).
- An increased ovarian cancer risk was observed for
whole milk consumption and lactose intake among African-American women in a
population-based case-control study (Qin et al. 2016).
- A study to
assess differences in dietary intakes in breast cancer survivors and women
without a history of breast cancer revealed that survivors tend to consume less
dairy products, animal protein, total protein, and calcium, but more legumes,
non-citrus fruit, and carbohydrates (Lay et al. 2016).
- Experiments carried out in the laboratory indicated
that consumption of commercial whole and non-fat milk for 20 weeks doubled the
incidence chemical-induced mammary tumors in rats (Qin et al. 2007).
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Cheese, glorious cheese...... |
A variety of mechanisms suggesting ways dairy products
influence breast cancer risk was hypothesized. For example, the presence of components such
as calcium, vitamin D, insulin-like growth factors (Ma et al. 2001, Qin et
al. 2009), conjugated linoleic acid (Voorrips et al. 2002), and estrogenic hormones (Brinkman et al. 2010) are thought to be contributing to the risks.
- The Melbourne Collaborative Cohort Study, which
included women from Australia, New Zealand, the United Kingdom, Italy, and
Greece, found that dairy intake was statistically significantly related to
higher levels of estradiol and free estradiol (Brinkman et al. 2010).
- Since estrogens are considered the major etiologic
pathway to breast cancer, the influence of dairy intake on estrogens should be
strongly considered in understanding how dairy would affect breast cancer–specific outcome (Kroenke et al. 2013).
Recently, more defined molecular mechanisms were
proposed. To appreciate the mechanisms behind milk-induced cell proliferation
and growth, we need to understand briefly the role of FTO gene, the microRNAs
(miRNAs) found in cow’s milk and the mTORC1 signalling pathways.
- FTO (fat mass- and obesity-associated) gene is widely
expressed in a variety of human tissues and is detected in the brain,
pancreatic islets, and the liver (Frayling et al. 2007,
Bodo C. Melnik 2015). The FTO gene has been recognized to play a crucial role in the
early-life determination of body weight, body composition and energy balance (Sebert et al. 2014).
- FTO plays a predominant role in DNA demethylation and
m6A-dependent mRNA demethylation (Frayling et al. 2007,
Gerken et al. 2007, Jia et al. 2011). FTO-mediated demethylation of
mRNAs increases transcriptional activity and generates mRNA splice variants
that are critically involved in adipogenesis (Zhao et al. 2014), appetite control (Jia et al. 2011), and mTORC1 activation (Gulati et al. 2013,
Han et al. 2012). It is important to note that mTORC1 activation eventually leads to
cell growth and proliferation and is known to be a marker in breast cancer.
- In addition, FTO promotes transcription and increases
genomic transcriptional activity, a requirement for postnatal growth and
lactation coordination.
- FTO also plays a critical role in milk production. The
mRNA of prolactin, the most important hormone promoting lactation, is regulated
via m6A methylation which was dependent on FTO activity (Bian et al. 2015,
Carroll et al. 1990).
Enhancing both milk quality and quantity is a major
selection criterion for the genetic improvement of livestock. High performance
dairy cows with higher milk yield have an enhanced expression of miRNA-29 (Bian et al. 2015). MiRNAs are non-coding RNA molecules that regulates gene expression.
- Abundance of miRNA-29s increases both bovine FTO mRNA
and protein levels of these cells (via inhibition of methylation).
- DNA methylation is a process which methyl groups are
added to DNA, and if the methyl groups are located at the genes, then the genes
will not be transcribed or translated into proteins. On the other hand, demethylation
is a process that removes the methyl group from the DNA.
- Bovine miRNA-29s, which are identical with human
miRNA-29s, and bovine FTO mRNA, which is highly homologous (similar) to human
FTO mRNA, are taken up by humans via the uptake of milk exosomes by human
macrophages ( a type of immune cell) (Bian et al. 2015).
- In milk, miRNAs are encapsulated in exosomes which are
highly resistant against harsh degrading conditions and thus, facilitating
uptake by endocytosis. MiRNAs of commercial cow´s milk are known to survive processing
such as pasteurization, homogenization and refrigeration (Howard et al. 2015).
- MiRNAs are known to be absorbed from cow milk and
affect gene expression in peripheral blood mononuclear cells of human subjects (Baier et al. 2014). Since, the majority of bovine miRNAs have nucleotide sequences
complementary to human gene transcripts; the absorbed miRNAs are likely to regulate
human genes (Baier et al. 2014).
In short:
- Milk stimulates the expression of FTO, which functions
as a critical amplifier of the transcriptional machinery for postnatal growth.
- Milk activates the nutrient-sensitive kinase
mechanistic target of rapamycin complex 1 (mTORC1), which induces
mTORC1-dependent translation, a crucial requirement for cell growth and
proliferation (B. C. Melnik 2015).
- mTORC1 activation eventually leads to increased growth
and proliferation and is known to be a marker in certain cancers.
- Milk proteins are a rich nutrient source of
branched-chain essential amino acids (BCAAs) and glutamine which also play an
important role in FTO expression and mTORC1 activation (Lenders et al. 2009,
Millward et al. 2008).
- In comparison to human breast milk, equivalent volumes
of cow´s milk transfer three times more BCAAs to the human and thus may overstimulate BCAA-driven FTO and mTORC1
activation, both of which triggers cell growth (B. C. Melnik 2015).
In my humble opinion, if you have benign breast
diseases, you may want to seriously considering limiting dairy products from
your diet. I wished I knew this earlier, but I am definitely not crying over
spilled milk!
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Blissful ice cream......sigh... |
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