Is dairy ‘cancer food’?

Is dairycancer food’?
Is dairy ‘cancer food’? asks WDDTY rhetorically in its “special report” by an unnamed writer.

Based on the opinions of a “cancer expert” who is not an oncologist, is no longer GMC registered and sells supplements, a notorious crank with a history of misleading claims, and arm-waving appeals to “every expert” which are not backed up by evidence of consensus of expert opinion, a favourite bogeyman of “nutritionists” is asserted to be a cause of cancer.

Where sources are cited, they fail to back the text supposedly based on them. For example, a source that states a risk from high but not low-fat dairy intake is stated as evidence that dairy per se increases risk.

2013-11_15Is dairy ‘cancer food’?

Author not identified

“In my view, anyone with cancer should give up dairy completely,” says Dr Patrick Kingsley, British cancer expert and author of The New Medicine. From Tokyo to Arizona, every expert who focused on cancer and nutrition repeated the same mantra: Give up dairy.

Patrick Kingsley is not an oncologist. he is not GMC registered. He is a proponent of his self-originated “new medicine” and a vendor of alternative treatments. Support for his claims to expertise and the validity of his treatments comes primarily in the form of books authored by himself. He appears to have no peer-reviewed publications indexed by PubMed.

Searches of common databases and information resources reveals no consensus n favour of dairy exclusion among dieticians or oncologists. The primary search term linking cancer and dairy is a study finding slightly elevated risk of prostate cancer associated with dairy consumption, which acknowledges that it cannot unpick the effects of dairy from the role of calcium in vitamin D metabolism (see below).

British scientist Jane Plant was 42 years old when she first noticed a lump in her breast; six years later, the disease had spread to her lymph system and she was left with a lump “the size of half a boiled egg” protruding from her neck. Plant’s situation, deemed terminal, rapidly turned around when she decided to cut out dairy.

Within days the malignant lump on her neck began to shrink and, within six weeks, it had vanished completely. That was 25 years ago—it hasn’t returned since.

The idea of a metastatic malignancy that was cured in weeks by simply excluding dairy from the diet, is implausible. No sources are provided for the claim.

Jane Plant is a geologist and geochemist, not a medical scientist.

New evidence From Kaiser Permanente research division, which tracked nearly two thousand breast cancer survivors for up to 12 years, shows that women who continue eating dairy after their  breast cancer has
been diagnosed are 49 per cent more likely to die from their cancer (and significantly more likely to die from any cause) than women who cut such foods from their diet.1

Reference 1: J Natl Cancer Inst. 2013 May 1;105(9):616-23. High- and low-fat dairy intake, recurrence, and mortality after breast cancer diagnosis. Kroenke CH, Kwan ML, Sweeney C, Castillo A, Caan BJ.

BACKGROUND: Dietary fat in dairy is a source of estrogenic hormones and may be related to worse breast cancer survival. We evaluated associations between high- and low-fat dairy intake, recurrence, and mortality after breast cancer diagnosis.

RESULTS: In multivariable-adjusted analyses, overall dairy intake was unrelated to breast cancer-specific outcomes, although it was positively related to overall mortality. Low-fat dairy intake was unrelated to recurrence or survival. However, high-fat dairy intake was positively associated with outcomes. 

CONCLUSIONS: Intake of high-fat dairy, but not low-fat dairy, was related to a higher risk of mortality after breast cancer diagnosis (emphasis added)

The claim that cancer outcomes are significantly worse in women who consume dairy products is specifically refuted by this study. It finds, however, an association between high fat dairy (i.e. more of the oestrogenic hormones in dairy fat) and mortality.

This would be a good reason to switch to lower fat dairy products and a terrible reason to exclude dairy, especially for post-menopausal women at risk of osteoporosis.

“There is now consistent and substantial evidence that the higher the milk consumption of a country, the greater their breast and prostate cancer risk,” says British nutritionist and author Patrick Holford.

Patrick Holford qualified as a psychologist, has no legitimate qualifications in diet, is a vendor of supplements, an HIV-AIDS denialist and promotes quack ideas such as hair analysis.

According to 2008 figures, the incidence of breast cancer for women in China was 21.6 for every 100,000 people, while in America the rate is 76, in the UK it’s 89.1 and in France—a country famous for its love affair
with butter and cream—it’s 99.7.2 These differences cannot be reduced to genetics, as migrational studies reveal that when Chinese and Japanese people move to the West, their rates of breast (and prostate) cancer go up.

This is an example of the post hoc fallacy. There is no proven causal relationship.

Reference 2: http://globocan.iarc.fr/factsheets/cancers/breast.asp#INCIDENCE

Compare this with a list of countries by milk consumption. Fourth highest milk consumption per capita is India. India has well below average breast cancer incidence. While a link is possible, it is not supported by these figures.

Adulterated milk

But the problem may have more to do with the state of today’s store-bought milk, and our obsession with ‘low-fat’ rather than with dairy per se. For instance, when scientists look for the link between dairy and prostate cancer, they find that the risk is higher only with low-fat milk, which delivers too high levels of calcium and strips out the protective anticancer effects of conjugated linoleic acid (CLA),a powerful anticarcinogen.3

Reference 3: Am J Clin Nutr. 2005 May;81(5):1147-54. Dairy, calcium, and vitamin D intakes and prostate cancer risk in the National Health and Nutrition Examination Epidemiologic Follow-up Study cohort. Tseng M, Breslow RA, Graubard BI, Ziegler RG.

CONCLUSIONS: Dairy consumption may increase prostate cancer risk through a calcium-related pathway. Calcium and low-fat milk have been promoted to reduce risk of osteoporosis and colon cancer. Therefore, the mechanisms by which dairy and calcium might increase prostate cancer risk should be clarified and confirmed. (emphasis added)

This finding is inconsistent with the breast cancer finding, and is stated by the authors to be a weak finding (“may increase risk”) which requires further analysis to unpick the different factors involved, including the roles of calcium and vitamin D.

Why milk might feed cancer

CLA also protects against the most cancer accelerator: insulin-like growth factor 1, or IGF-1. The hormone naturally circulates in our blood and, like cortisol, progesterone and oestrogen, it’s necessary—it’s in mother’s milk to ensure the baby grows, and levels of IGF-1 rise in puberty to stimulate the growth of breasts. As we grow older, levels naturally drop off. That is, unless you’re a dairy lover.

This appears to be addressed by reference 1: it is related to fat content not dairy per se.

“We certainly know that people who consume a lot of dairy products will have higher levels of IGF-1,” says Patrick Holford.

“It simply does what it’s meant to do—stimulate growth. It also stops overgrowing cells from committing suicide, a process called ‘apoptosis’.”

Besides breast cancer, elevated IGF-1 levels have been linked to increased risks of colorectal, breast, pancreatic, lung, prostate, renal, ovarian and endometrial cancer.4 In fact, men with the highest IGF-1 levels quadruple their risk of prostate cancer 5

Reference 4: Recent Pat Anticancer Drug Discov. 2012;7:14–30. Insulin-like Growth Factor: Current Concepts and New Developments in Cancer Therapy Erin R. King, MD, MPH and Kwong-Kwok Wong, PhD

A somewhat puzzling source as it is reviewing patent reports related to IGF-1.

Reference 5: Science. 1998 Jan 23;279(5350):563-6. Plasma insulin-like growth factor-I and prostate cancer risk: a prospective study. Chan JM, Stampfer MJ, Giovannucci E, Gann PH, Ma J, Wilkinson P, Hennekens CH, Pollak M.

“Identification of plasma IGF-I as a predictor of prostate cancer risk may have implications for risk reduction and treatment” – the source mentions dairy only once, as a citation to Am. J. Epidemiol. (2007) 166 (11): 1270-1279. Calcium, Dairy Foods, and Risk of Incident and Fatal Prostate Cancer The NIH-AARP Diet and Health Study, Park et. al. which states: “Although the authors cannot definitively rule out a weak association for aggressive prostate cancer, their findings do not provide strong support for the hypothesis that calcium and dairy foods increase prostate cancer risk.”

A search for each of the cancer types listed plus dairy, taking the first obvious peer-reviewed study for each:

  • Colorectal cancer: “Milk intake was related to a reduced risk of colorectal cancer” – J Natl Cancer Inst. 2004 Jul 7;96(13):1015-22. Dairy foods, calcium, and colorectal cancer: a pooled analysis of 10 cohort studies.
  • Breast cancer : As above, a risk associated with high but not low-fat dairy produce
  • Pancreatic cancer: “Total meat, red meat, and dairy products were not related to risk” – Am. J. Epidemiol. (2003) 157 (12): 1115-1125. Dietary Meat, Dairy Products, Fat, and Cholesterol and Pancreatic Cancer Risk in a Prospective Study Michaud et. al.
  • Lung cancer: No obvious significant studies, but dairy farmers have lower lung cancer incidence.
  • Prostate cancer: As above, weak evidence of increased risk, uncertain at this stage whether it is dairy specific or related to calcium / vitamin D link
  • Ovarian cancer: “Overall, no associations were observed for intakes of specific dairy foods or calcium and ovarian cancer risk” – Cancer Epidemiol Biomarkers Prev. 2006 Feb;15(2):364-72. – Dairy products and ovarian cancer: a pooled analysis of 12 cohort studies. Genkinger et. al.
  • Endometrial cancer: “Total dairy intake was not significantly associated with risk of preinvasive endometrial cancer. [W]e observed a marginally significant overall association between dairy intake and endometrial cancer” – Int J Cancer. 2012 Jun 1;130(11):2664-71. Milk, dairy intake and risk of endometrial cancer: a 26-year follow-up. Ganmaa et. al.

So the boldly asserted claim of a strong link with numerous specific cancers, not backed by references to sources, is contradicted where sources address the question directly.

However, the claim that dairy increases risks of these cancers is stated as fact (again without sources) by  Vegan International Voice for Animals, and contradicted with allusions to sources but no specific references by The Dairy Council, whose summaries are in line with the studies listed above.

In general, claims that milk is a significant and substantial risk factor for cancers are linked primarily to sites with an ideological commitment to reduced dairy consumption or other alternative diet and health claims.

But what about bones? 

We’ve been repeatedly told that drinking milk builds strong bones, yet clinical research tells a different story. One study, which followed more than 72,000 women for 18 years, showed no protective effect of increased pasteurized milk consumption on fracture risk.

The source of this figure is Am J Clin Nutr. 2003;77:504–511. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women Diane Feskanich, Walter C Willett, and Graham A Colditz. This refers to post-menopausal women; as it notes: “A review of the literature concluded that there is no clear benefit of higher milk or dairy food intake on bone mass or fracture risk in women > 50 y of age but that a benefit is seen in women < 30 (37)”

The WDDTY article appears to be using the bait-and-switch tactic of conflating two cohorts (pre- and post-menopausal women)with different risk and benefit profiles.

Could eating your greens provide better protection?

A report from the US Nurses’ Health Study found that those eating a serving of lettuce or other green leafy vegetables every day cut the risk of hip fracture in half compared with eating only one serving a week.6

Reference 6: Am J Clin Nutr, 1999; 69: 74–9 Vitamin K intake and hip fractures in women: a prospective study. Feskanich D, Weber P, Willett WC, Rockett H, Booth SL, Colditz GA.

CONCLUSIONS: Low intakes of vitamin K may increase the risk of hip fracture in women. The data support the suggestion for a reassessment of the vitamin K requirements that are based on bone health and blood coagulation.

This applies to post-menopausal women, for whom dairy is not found to be protective.

A much later and wider-ranging study is Health Technol Assess. 2009 Sep;13(45):iii-xi, 1-134. Vitamin K to prevent fractures in older women: systematic review and economic evaluation. Stevenson M, Lloyd-Jones M, Papaioannou D.:

CONCLUSIONS: There is currently large uncertainty over whether vitamin K1 is more cost-effective than alendronate; further research is required. It is unlikely that the present prescribing policy (i.e. alendronate as first-line treatment) would be altered.

This suggests that sources may have been selected to serve an agenda rather than on the basis of the best and most current research.

Dark leafy greens not only provide calcium, but are also a potent source of vitamin K, which helps in calcium regulation and bone formation. There’s another benefit to choosing non-dairy foods. “Eating nuts, seeds and greens gives you the right balance of calcium and magnesium, but you don’t get that balance in dairy products,” says Holford. For those considering switching to soy milk, you might be interested to hear how it is made. According to Dr Al Sears, a physician with extensive experience in natural healthcare, it involves “washing the beans in alkaline or boiling them in a petroleum-based solvent; bleaching, deodorizing and pumping them full of additives; heat-blasting and crushing them into flakes; and then mixing them with water to make ‘milk’.”

This rather transparent dig at soya milk is no doubt entirely unrelated to the fact that in the US soya is routinely sourced from GM crops. Surely it would be entirely out of character to attack an entire food source on the basis of an instinctive dislike for genetically modified crops.

Thankfully there is a plethora of options available for the non-dairy consumer today, ranging almond milk to raw truffle chocolate.

Thankfully there is no credible evidence that any such thing is required, as fake milk products tend to be an acquired taste.

What Doctors Don't Tell You
Why don’t doctors tell you that cutting out dairy will prevent or cure cancer?

Because there’s no good evidence it will.

3 thoughts on “Is dairy ‘cancer food’?”

  1. Be careful. Holford’s suggestion about the high incidence of Ca Breast in France tallies with the evidence regarding a high dairy-fat diet as noted above. Note that he’s got that bit right

    1. Up to a point correlation is not causation. As noted, India has the fourth highest dairy consumption in the world but well below average breast cancer rates – and I don’t think India does low-fat dairy half as much as the US or UK.

      The answer is almost certainly “I think you’ll find it’s a bit more complicated than that”.

  2. Pingback: Daily Overload – News in short (14-11-2013) « The Skeptical Bear

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