Low-carb, high-protein eating may curb cancer risk

Hitherto known mostly as a weight-loss method, low-carb eating may also protect us against cancer. A new study highlights how heavy intakes of sugar and refined carbohydrates typical of the industrialised Western diet could be a factor fueling the worldwide cancer epidemic.

The study, published next month in Cancer Research, indicates that eating a low-carbohydrate, high-protein diet may reduce the risk of cancer and slow the growth of tumors already present.

Although the study was conducted in mice, its authors said the findings are relevant to humans:  “The fact that human blood glucose can be significantly reduced with low-carbohydrate diets, and the association of many cancers with high blood glucose levels, suggest that our findings are very relevant to human cancers, particularly cancers that have been associated with higher blood glucose and/or insulin levels, such as pancreatic, breast, colorectal, endometrial and esophageal cancers.”

Cancer cells need significantly more glucose than healthy cells to grow and thrive. Restricting carbohydrate intake can significantly limit blood glucose and insulin, a hormone that is released in response to rising blood glucose and that promotes tumor growth in both humans and mice.

For the study, Gerald Krystal of the British Columbia Cancer Research Centre and his team implanted various strains of mice with human or mouse cancer cells and assigned them to one of two diets. The first diet, a typical Western diet, contained about 55% carbohydrate (mostly sucrose, or table sugar), 23% protein and 22% fat. The second contained 15% carbohydrate (mostly in the form of starches that were about 70% amylose, a more slowly digested sugar typically found in whole grains, legumes, bananas, sweet potatoes, radishes and parsnips), 58% protein and 26% fat.

The low-carb mice exhibited lower blood-glucose and insulin levels and their tumor cells grew consistently slower than in those fed the high-carbohydrate western diet. They also had lower lactate levels – a chemical that fuels cancer growth and metastasis.

In addition, mice genetically predisposed to breast cancer were put on the two diets and almost half of those on the Western diet developed breast cancer within their first year of life while none on the low-carbohydrate, high-protein diet did. Only one mouse on the Western diet reached a normal life span (approximately two years), with 70% dying from cancer. Only 30% of those on the low-carbohydrate diet developed cancer and more than half of them reached or exceeded their normal life span.

In addition to lowering blood glucose levels, a low-carbohydrate, high-protein diet can both boost the immune system’s ability to kill cancer cells and prevent obesity. “Certain amino acids (i.e., arginine and tryptophan) play a very important role in allowing killer T cells to kill tumor cells,” says Krystal.

Moreover, high protein diets lead to more rapid satiety, which reduces obesity. “Obesity has a dramatic effect on cancer incidence, likely, at least in part, by increasing chronic inflammation,” he explains.

All this doesn’t mean we need to banish carbohydrates forever; however, we need to differentiate between less-healthy carbohydrates that cause a sharp increase in blood glucose and healthier carbs with a gentler glycemic impact.

The former include starchy foods like baked goods made with white flour, potatoes and white rice – all of which make up a large proportion of the calories a typical Westerner eats every day.

The latter tend to be unrefined, natural foods such as vegetables, fruits, legumes, nuts or whole grains that are converted more gradually into blood glucose. (Similar to the carbs the healthier mice ate.) These foods also generally contain important anti-cancer plant chemicals; thus they play an important role in an anti-cancer diet. In Zest for Life I recommend that people stick to low-glycemic carbohydrates – especially non-starchy vegetables – and eat protein with every meal to keep blood glucose levels stable.

Does increasing protein intake mean eating more meat? Such a conclusion could be problematic, for red and processed meats are thought to increase the risk of colorectal cancer. (See this post.) My view is that we should eat some high-quality protein at every meal, but should aim to vary its sources as much as possible, alternating between fish, white and occasional red meat, eggs, legumes, nuts and minimally processed soy foods; Dr Krystal  uses whey protein isolate powder to boost his protein intake.

It’s worth noting that the low-carb, high-protein diet tested in this study is also low in fat (26%, as compared with around 35% in the traditional Mediterranean diet and 50% in the Atkins diet).  While hungry, captive mice will eat this kind of diet, humans struggle to stick to low-carb, low-fat diets for long. (A recent survey found that 80% of Dukan dieters regained the weight they had shed on this low-fat, high-protein regimen within three years.)

“It is likely that we could still attain very beneficial effects if we raised the fat slightly and reduced the protein slightly,” says Dr Krystal. Such a diet (say 20% carbohydrate, 40% fat and 40% protein) would also be easier to maintain than the 15% carb, 25% fat and 60% protein model used in the mouse studies, he says.

Again, the ancestral Mediterranean diet may offer the best solution: it is rich in low-glycemic vegetables and fruits, provides plenty of protein through fish, lean meat, legumes and nuts, offers healthy fats in the form of olive, nut and fish oils and is low in sugar and refined grains.

Best of all, it is simple and tasty, making it a pleasure to follow long-term.

Am I a Food Fascist?

It's not often that I am called a "Food Nazi," but it happened last week - for the first time - after I published this post relating my decision to bake "Faux-reo cookies" for my daughter, rather than buy her a packet of mass-produced Oreos.

Apparently, some people get upset when you suggest that feeding children high-sugar confections is a bad idea. The vehemence of two commenters' reactions - accusing me of "food Nazism," and predicting that my daughter will develop an eating disorder because I limit her intake of junk food - prompted some reflection.

Returning briefly to the "Oreo episode:" I did not heavy-handedly overrule my daughter's wish for the branded article. I simply told her that I had gone to the supermarket to buy the cookies she had requested, saw that they contained lots of unhealthy ingredients and asked her how she would feel if we baked a batch of healthier cookies instead.

Her response was highly enthusiastic. Like many children, she loves to bake with mommy, an activity that is often curtailed by lack of time on my part. She was delighted at the prospect of not only getting a sweet treat closely resembling Oreo cookies, but also spending "quality time" with me.

Meanwhile, I would like to reassure the commenter who fears that a lack of junk food will turn my daughter food-phobic. The "no junk food" rule in our home means no sugary breakfast cereals, no pre-made meals, no candy, no factory-made cookies and cakes and no soft drinks.

This is because my kids - and most others - inevitably get regular doses of junk outside the home, at friends' houses and birthday parties, for example. On family outings, we will occasionally let them have an ice cream or a non-caffeinated soft drink as a rare treat. In restaurants, they are allowed dessert and any of the "kiddie treats" handed to them. A few years ago, even our dentist handed them candy after their first dental check-up, as a reward for having caries-free teeth! (Prompting confused head-shaking from my children.)

At home, however, we have learned that letting even occasional junk foods creep in simply opens the door to endless begging for more, and so we put a stop to it some years ago. For breakfast we eat home-made porridge with chopped nuts, Bircher muesli with fresh fruit and whole milk yogurt, fruit and nut smoothies, a variety of eggs served alongside mashed sweet potatoes, or whole grain toast topped with sardines, cheese or nut butter. The children drink water or herbal tea sweetened with honey. Lunch is eaten at school (and is generally moderately nutritious as best). On weekends, at home, lunch or dinner will feature fish, meat or pulses with salad and/or vegetables and water.

We do eat desserts at home (fruit cobblers, tarts and compotes, egg puddings, etc.), cakes (cheesecake, chocolate cake, apple cake, etc.) and cookies, but these are home-made (often together with the kids) and usually contain whole grain flour and half (or less) the sugar of their store-bought counterparts.

This blog isn't about feeding kids, it's about dietary cancer prevention. So why am I yammering on about what I feed my offspring?

Because teaching children about healthy food choices, and showing them how to prepare delicious home-made alternatives to unhealthy branded foods is one of the most important gifts we can offer them for a long life of good health. (That cancer prevention starts in the womb and that childhood eating patterns influence our chances of developing cancer later in life, was illustrated eloquently by Ricardo Uauy, Professor of Public Health Nutrition at the London School of Hygiene and Tropical Medicine, in this fascinating presentation at the 2010 World Cancer Research Fund conference.)

As long as they are young and consume the majority of their meals at home, we can influence our children's taste buds and shape their metabolism in beneficial ways. It can only be hoped that that they will continue to eat this way once they fly the coop.

So to those of you who worry that I am raising a generation of orthorexics (i.e., people who obsess compulsively about eating only healthy foods), let me reassure you: I am anything but an austere food-fundamentalist. My children know that outside the home, they can make their own food choices. As my story above about the dentist confirms, junk food has an amazing power to find kids; you don't need to help them look for it.

Meanwhile, at home we revel in growing and gathering our food, preparing it and eating it. Ketchup and mayonnaise? French fries? Salad dressings? Oreo cookies? Hamburgers and hot dogs? We make ‘em all - and so can you!

Faux-reo cookies: kids like real food if you dare serve it to them!

My daughter's friends have recently begun bringing sweet snacks to school to brighten the mid-morning recess of this poor child, whose mother (me) deprives her of junk food. Oreo Cookies, now available in even the smallest of French supermarkets, have become my daughter's favorite snack, so much so that she recently asked for a packet of them for her ninth birthday.

In a moment of weakness, I made my way to the supermarket to purchase said cookies. Although I have a strict "no junk food" rule, I didn't want to seem like a food fundamentalist. I mean: one packet of Oreos - no big deal, right?

As I lifted the packet off the shelf, I couldn't help glancing at the ingredients and my heart sank. According to manufacturer Nabisco, these edible food-like discs contain (in this order) "sugar, enriched flour (wheat flour, niacin, reduced iron, thiamine mononitrate, riboflavin, folic acid) high oleic canola oil and/or palm oil and/or canola oil and/or soybean oil, cocoa (processed with alkali), high fructose corn syrup, cornstarch, leavening (baking soda and/or calcium phosphate), salt, soy lecithin, vanillin - an artificial flavor, chocolate."

 

As a rule, I avoid buying anything that lists sugar as its first ingredient. In my children, it causes highly-strung, jittery behavior followed by tearful irritability. In me, it causes the above symptoms plus bloating, exhaustion and sugar cravings. Sugar is not a food; it is at best a condiment. As a first ingredient, it's a no-no.

Next ingredient: enriched flour. Sounds nice: "enriched." How thoughtful of them to put all those extra nutrients in. But what it really means is: "We've taken all the natural goodness out of this grain when we refined it and now we're putting four vitamins and one mineral back in." Of course, this denatured flour bears little resemblance to the vast panoply of nutrients available from whole, unrefined grains.

As for the fats: why won't the manufacturer say which fats they used the day the cookies were made? Doesn't this vague list of oils, selected at the manufacturer's discretion, open the door to the cheapest, lowest-grade processed fats available on any given day?

Although scientists continue to argue about the health effects of dietary fats, few would dispute that denatured, mass-produced factory oils are unlikely to offer health benefits, and may well contain inflammation-fueling omega-6 fatty acids and trans fats.

Next ingredient: cocoa. This at least is healthy, right? Well, yes, when it's "raw" (i.e. naturally fermented, dried, defatted and ground into a powder), cocoa is chock-full of plant chemicals called procyanidins, thought to have powerful antioxidant, anti-inflammatory and tumor-growth-inhibiting properties.

However, the industrial process of "dutching" (i.e. treating cocoa with an alkalizing agent to modify its color and give it a milder flavor) sharply reduces the polyphenol content in cocoa. One study found that 60 per cent of natural cocoa's original antioxidants were destroyed by even light dutching, and 90 per cent were destroyed by heavy dutching.

High-fructose corn syrup, the next ingredient, doesn't offer much more hope of sustenance to my growing child. Along with sugar (above) it can disrupt blood-sugar metabolism, feed cancer cells (see this post) and contribute to weight gain - especially around the middle, the least healthy place to carry extra fat.

As for baking soda - sorry to be a party pooper, but researchers recently found that when combined with cocoa, the latter's polyphenol content is sharply reduced. One study found that in chocolate cakes leavened with baking soda, the amount of procyanidins declined by 84 per cent; the same recipe prepared with baking powder showed no loss at all.

Dispirited by my Oreo fact-finding mission, I decided I'd rather be branded a boring old food purist than feed my daughter a concoction of cheap sugars and fats. I replaced the cookies on the supermarket shelf, drove home and Googled "Homemade Oreo cookies".

And this is what I found: a fabulous recipe by French Laundry chef Thomas Keller. I made a few adjustments to the ingredients, swapping soured crème fraiche for heavy cream, reducing the amount of white chocolate, swapping baking powder for baking soda, whole spelt flour for white wheat flour, using raw cocoa and scraping a vanilla bean into the cream.

I also simplified the cookie-shaping: instead of rolling out the very sticky dough (which required angelic patience), I pinched off small portions of dough, rolled them into balls, placed them on the paper-lined baking tray and flattened them into discs with my fingertips - less precise, but mercifully quick.

Don't get me wrong; these cookies *do* contain sugar, fats and calories aplenty and are not something to eat every day. But I take comfort from the fact that all the ingredients are natural, minimally processed and - apart from the sugar - contain useful nutrients. They also taste amazing, the crunchy, bitter cookie contrasting beautifully with the sweet, sticky cream inside.

Best of all, my daughter loved them! "They don't look so great, but they taste much better than the real ones," my daughter opined. She took a few cookies into school the next day for her friends to taste. To my great surprise, they agreed with her. Guess who gets to provide the next round of Faux-reos at recess?

Photograph courtesy of "C" at www.projectmcb.com