Corn Oil and Cancer?

The benefits of corn oil keep rolling in. In a new study by Stephen Freedland's group at Duke, feeding mice a diet rich in butter and lard didn't promote the growth of transplanted human prostate cancer cells any more than a low-fat diet (1).

Why do we care? Because other studies, including one from the same investigators, show that corn oil and other industrial seed oils strongly promote prostate cancer cell growth and increase mortality in similar models (2, 3).

From the discussion section:

Current results combined with our prior results suggest that lowering the fat content of a primarily saturated fat diet offers little survival benefit in an intact or castrated LAPC-4 xenograft model. In contrast to the findings when omega-6 fats are used, these results raise the possibility that fat type may be as important as fat amount or perhaps even more important.

There's a large body of evidence implicating excess omega-6 fat in a number of cancer models. Reducing omega-6 to below 4% of calories has a dramatic effect on cancer incidence and progression*. In fact, there have even been several experiments showing that butter and other animal fats promote cancer growth to a lesser degree than margarine and omega-6-rich seed oils. I discussed that here.


* The average American eats 7-8% omega-6 by calories. This means it will be difficult to see a relationship between omega-6 intake and cancer (or heart disease, or most things) in observational studies in the US or other industrial nations, because we virtually all eat more than 4% of calories as omega-6. Until the 20th century, omega-6 intake was below 4%, and usually closer to 2%, in some traditional societies. That's where it remains in contemporary traditional societies unaffected by industrial food habits, such as Kitava.

Magnesium and Insulin Sensitivity

From a paper based on US NHANES nutrition and health survey data (1):

During 1999–2000, the diet of a large proportion of the U.S. population did not contain adequate magnesium... Furthermore, racial or ethnic differences in magnesium persist and may contribute to some health disparities.... Because magnesium intake is low among many people in the United States and inadequate magnesium status is associated with increased risk of acute and chronic conditions, an urgent need exists to perform a current survey to assess the physiologic status of magnesium in the U.S. population.

Magnesium is an essential mineral that many people apparently don't get enough of. One of the many things it's necessary for in mammals is proper insulin sensitivity and glucose control. A loss of glucose control due to insulin resistance can eventually lead to diabetes and all its complications.

Magnesium status is associated with insulin sensitivity (2, 3), and a low magnesium intake predicts the development of type II diabetes in most studies (4, 5) but not all (6). Magnesium supplements largely prevent diabetes in a rat model* (7). Interestingly, excess blood glucose and insulin themselves seem to reduce magnesium status, possibly creating a vicious cycle.

In a 1993 trial, a low-magnesium diet reduced insulin sensitivity in healthy volunteers by 25% in just four weeks (8). It also increased urinary thromboxane concentration, a potential concern for cardiovascular health**.

At least three trials have shown that magnesium supplementation increases insulin sensitivity in insulin-resistant diabetics and non-diabetics (9, 10, 11). In some cases, the results were remarkable. In type II diabetics, 16 weeks of magnesium supplementation improved fasting glucose, calculated insulin sensitivity and HbA1c*** (12). HbA1c dropped by 22 percent.

In insulin resistant volunteers with low blood magnesium, magnesium supplementation for four months reduced estimated insulin resistance by 43 percent and decreased fasting insulin by 32 percent (13). This suggests to me that magnesium deficiency was probably one of the main reasons they were insulin resistant in the first place. But the study had another very interesting finding: magnesium improved the subjects' blood lipid profile remarkably. Total cholesterol decreased, LDL decreased, HDL increased and triglycerides decreased by a whopping 39 percent. The same thing had been reported in the medical literature decades earlier when doctors used magnesium injections to treat heart disease, and also in animals treated with magnesium. Magnesium supplementation also suppresses atherosclerosis (thickening and hardening of the arteries) in animal models, a fact that I may discuss in more detail at some point (14, 15).

In the previous study, participants were given 2.5 g magnesium chloride (MgCl2) per day. That's a bit more than the USDA recommended daily allowance (MgCl2 is mostly chloride by weight), in addition to what they were already getting from their diet. Most of a person's magnesium is in their bones, so correcting a deficiency by eating a nutritious diet may take a while.

Speaking of nutritious diets, how does one get magnesium? Good sources include halibut, leafy greens, chocolate and nuts. Bone broths may also be a source of magnesium. Whole grains and beans are also fairly good sources, while refined grains lack most of the magnesium in the whole grain. Organic foods, particularly artisanally produced foods from a farmer's market, are richer in magnesium because they grow on better soil and often use older varieties that are more nutritious.

The problem with seeds such as grains, beans and nuts is that they also contain phytic acid which prevents the absorption of magnesium and other minerals (16). Healthy non-industrial societies that relied on grains took great care in their preparation: they soaked them, often fermented them, and also frequently removed a portion of the bran before cooking (17). These steps all served to reduce the level of phytic acid and other anti-nutrients. I've posted a method for effectively reducing the amount of phytic acid in brown rice (18). Beans should ideally be soaked for 24 hours before cooking, preferably in warm water.

Industrial agriculture has systematically depleted our soil of many minerals, due to high-yield crop varieties and the fact that synthetic fertilizers only replace a few minerals. The mineral content of foods in the US, including magnesium, has dropped sharply in the last 50 years. The reason we need to use fertilizers in the first place is that we've broken the natural nutrient cycle in which minerals always return to the soil in the same place they were removed. In 21st century America, minerals are removed from the soil, pass through our toilets, and end up in the landfill or in waste water. This will continue until we find an acceptable way to return human feces and urine to agricultural soil, as many cultures do to this day****.

I believe that an adequate magnesium intake is critical for proper insulin sensitivity and overall health.


* Zucker rats that lack leptin signaling

** Thromboxane A2 is an omega-6 derived eicosanoid that potently constricts blood vessels and promotes blood clotting. It's interesting that magnesium has such a strong effect on it. It indicates that fatty acid balance is not the only major influence on eicosanoid production.

*** Glycated hemoglobin. A measure of the average blood glucose level over the past few weeks.

**** Anyone interested in further reading on this should look up The Humanure Handbook

Lindeberg on Obesity

I'm currently reading Dr. Staffan Lindeberg's magnum opus Food and Western Disease, recently published in English for the first time. Dr. Lindeberg is one of the world's leading experts on the health and diet of non-industrial cultures, particularly in Papua New Guinea. The book contains 2,034 references. It's also full of quotable statements. Here's what he has to say about obesity:

Middle-age spread is a normal phenomenon - assuming you live in the West. Few people are able to maintain their [youthful] waistline after age 50. The usual explanation - too little exercise and too much food - does not fully take into account the situation among traditional populations. Such people are usually not as physically active as you may think, and they usually eat large quantities of food.

Overweight has been extremely rare among hunter-gatherers and other traditional cultures [18 references]. This simple fact has been quickly apparent to all foreign visitors...

The Kitava study measured height, weight, waist circumference, subcutaneous fat thickness at the back of the upper arm (triceps skinfold) and upper arm circumference on 272 persons ages 4-86 years. Overweight and obesity were absent and average [body mass index] was low across all age groups. ...no one was larger around their waist than around their hips.

...The circumference of the upper arm [mostly indicating muscle mass] was only negligibly smaller on Kitava [compared with Sweden], which indicates that there was no malnutrition. It is obvious from our investigations that lack of food is an unknown concept, and that the surplus of fruits and vegetables regularly rots or is eaten by dogs.

The Population of Kitava occupies a unique position in the world in terms of the negligible effect that the Western lifestyle has had on the island.

The only obese Kitavans Dr. Lindeberg observed were two people who had spent several years off the island living a modern, urban lifestyle, and were back on Kitava for a visit.

I'd recommend this book to anyone who has a scholarly interest in health and nutrition, and somewhat of a background in science and medicine. It's extremely well referenced, which makes it much more valuable.

Thank You

I'd like to extend my sincere thanks to everyone who has supported me through donations this year. The money has allowed me to buy materials that I wouldn't otherwise have been able to afford, and I feel it has enriched the blog for everyone. Here are some of the books I've bought using donations. Some were quite expensive:

Food and western disease: health and nutrition from an evolutionary perspective. Staffan Lindeberg (just released!!)

Nutrition and disease. Edward Mellanby

Migration and health in a small society: the case of Tokelau. Edited by Albert F. Wessen

The saccharine disease. T. L. Cleave

Culture, ecology and dental anthropology. John R. Lukacs

Vitamin K in health and disease. John W. Suttie

Craniofacial development. Geoffrey H. Sperber

Western diseases: their emergence and prevention. Hugh C. Trowell and Denis P. Burkitt

The ultimate omega-3 diet. Evelyn Tribole

Our changing fare. John Yudkin and colleagues


Donations have also paid for many, many photocopies at the medical library. I'd also like to thank everyone who participates in the community by leaving comments, or by linking to my posts. I appreciate your encouragement, and also the learning opportunities.