Carbs, cholesterol and the lipid hypothesis

One of the most entertaining depictions I’ve seen of the whole cholesterol debate, from Fat Head. It explains how the lipid hypothesis (saturated fat = heart disease) gained popularity, and shows how inflammation in arteries causes plaque, not cholesterol. Essential viewing for those being told to cut fat from their diets.


Excellent as this segment is, I found the film as a whole  disappointing. Too much of it is a somewhat clumsy diatribe against Morgan Spurlock’s Supersize Me. It does make good and important point: how did Spurlock manage to consume 5000+ cal/day eating McDonalds? Even eating 3x day super-sized meals (which he ate 9x in the month covered by the film) doesn’t add up to the daily total. A Double Quarter Pounder with cheese is ‘only’ 730 calories (there’s no mention that I could see in either film of the Chicken Selects Premium Breast Strips, which clocks in at 1270 calories, or the Deluxe Breakfast at 1220). Tom Naughton, Fat Head’s film-maker, was unable to access Spurlock’s food log, but suggests that the balance was made up by adding sugary drinks – and in the film Spurlock indeed seems to be carrying two cups with many of his purchases (Chocolate Triple Thick Milkshakes between meals would certainly do it: 1,160 cals each). Which makes sugar the culprit rather than the more photogenic burgers.

Naughton did, it must be said, succeed in losing weight over the course of his film by eating only McDonald’s. That doesn’t make it a recommended diet, but it raises uncomfortable questions, as the film says, for people who blame fast foods – and the people who eat them – for the cultural rise in obesity. It offers a few alternative theories for that trend: the downward change in the US definition of ‘obese’, the percentage rise in the US of populations genetically prone to higher body fat, the increase in sedentary behaviour (this after previously citing Gary Taubes’ finding that exercise – though recommended for all kinds of reasons – does not play a part in weight loss), the higher average age of the population,  the increase in snacking, and the increase in consumption of sugary drinks. And both films rightly point to carbs and sugar as being in excess in fast foods.

 

Obesity: So many causes, so few solutions

SugarGood to see The Lancet looking critically at obesity – which will cripple public health systems in the years to come, through its association with diabetes, cancers and other chronic conditions.  Sugar taxes, the article notes, are not the only solution. (Personally I think they’d be a helpful start, given the rampant consumption of needlessly sweetened foods and beverages in the Western world. On the other hand, added sugars are only part of what the body metabolizes as sugar: processed carbohydrates are surely having an equal effect, and are harder for consumers to recognize as problematic.) Clearly dietary, environmental, commercial, metabolic, microbial and lifestyle causes and solutions need urgent study by government funders and health researchers.

The UK report referenced in The Lancet’s article, Sugar Reduction: The Evidence for Action (October 2015) lays bare a number of relevant issues and is worth a read. But even it ultimately bangs its head on the desk in dismay: no easy solution, it says. “No single action will be effective in reducing sugar intakes. This is too serious a problem to be solved by approaches that rely only on individuals changing their behaviour in response to health education and marketing, or the better provision of information on our food.”

To put it mildly, as the Lancet does:
“Obesity needs much more serious attention than countries and global health organisations are currently prepared to give.”

Gutsy bacteria

Missing MicrobesThe human microbiome is hot stuff these days. Hard to imagine we have only gained some understanding of its existence and importance since the Human Microbiome Project kicked off in 2008. Beneficial gut bacteria, it turns out, are very hard to study because they live an anaerobic (oxygen-free) life in our intestinal tract. It was only when their DNA could be studied (metagenomics) that we began to understand how big a deal they were in human health. A very big deal indeed, as they are thought to number in the trillions. Our understanding of their diverse identities can barely be described as sketchy.

I’ve been browsing my way through Missing Microbes. I love this book. Its author, Martin Blaser, is an MD who has been researching a much discussed bacterium, Heliobacter Pylori, for over 30 years. H. pylori, which has colonized the human gut for more than 50,000 years, was determined by the winners of the 2005 Nobel Prize in Physiology to be the cause of peptic ulcers which had previously been ascribed to stress. The bacterium has also been associated with stomach cancer.

But Blaser also believes H. pylori plays an important immunological role, and that our all-out antibiotic assault on it may be costing us in more ways than the increasing rates of antibiotic resistance which the Nobel winners had also predicted. Blaser and others speculate that since its loss in Western populations correlates to increases in autoimmune disorders, there may be more to this ancient bacterium that has for so long co-existed in the human gut. Adults who lack H. pylori may also be more susceptible to reflux (GERD) and heartburn that can themselves lead to esophageal cancers. And there is some evidence that it protects against allergies and asthma in childhood.

Blaser has a lot to say about antibiotic use in modern medicine as well as modern farming, and how these have contributed to making the modern microbiome a biological desert, and landed humans in a completely new and dangerous medical landscape.

As his book’s subtitle suggests, Blaser believes that antibiotic use has contributed to many of our modern ills.  His work on antibiotics and obesity suggested that antibiotics administered in childhood may have the same effect farmers look for in their meat animals: accelerated growth, making them taller and fatter.

North American children are typically exposed to around 17 courses of antibiotics by the time they are 20, and another 13 by the time they are in their 30s. This doesn’t include the antibiotics they may receive from their mother through the placenta or breast milk, nor those consumed in drinking water, milk and meat. Children born of C-sections are also deprived of protective maternal bacteria from vaginal birth, and subject to direct or indirect antibiotics.

We don’t know yet what will be the long term effects of so many antibiotics on a developing brain and immune system in children, nor on public health as a whole. There are a lot of troubling correlations: people who used antibiotics in the month before a salmonella outbreak in Chicago got sicker than those who didn’t. Exposure of children to broad-spectrum antibiotics in the first two years of life (notably –mycin drugs) is associated with lifetime obesity. A Swedish study found a clear association between celiac disease onset following antibiotic use. Antibiotics impair our ability to excrete estrogen, leading to the modern ills of estrogen dominance (which affects men and children as well as women). Even short courses of antibiotics may permanently change our unique, personal microbiome, and there is no known way to permanently reinstate what’s been lost – even if we knew what that was.

Not all beneficial bacteria – or, like H. pylori, those that demonstrate amphibiosis, being sometimes beneficial and other times not – can be re-colonized into the human gut over the long term. H. pylori, for example, which is not just one but a family of microbes, is acquired in infancy and childhood in conditions that typically no longer exist in the Western world. (Blaser stresses replacing the term “infection” with “colonization” when speaking of our microbes. Since we have co-existed with some – like H. pylori – for millennia, the only thing we know for sure is that we don’t fully understand our biological history with them.)

Meanwhile, says Blaser, we can start by avoiding antibiotics wherever possible, particularly broad-spectrum ones that cause too much collateral damage. Avoiding c-section births except in medical emergencies, and re-evaluating the prophylactic use of antibiotics where c-sections are required would help protect children. Discussing with a pediatrician whether antibiotics are the appropriate first course of treatment for childhood ailments  is crucial. Lobby for policies preventing the use of antibiotics in farming and meanwhile avoid conventionally raised meat and dairy. He’s lukewarm on probiotic supplements, prebiotics, and their hybrid synbiotics, mainly because we simply don’t know which bacteria are crucial, and there is little research and no standards for production. Fecal transplants are helpful for some conditions (but not DIY versions where the donor has not been screened for medical risks to the recipient).

Meanwhile, the research into this essential biological mystery is exploding in the scientific world. Let’s hope we can get enough scientific leverage on political will to reverse some of the excesses of antibiotics before we’ve killed off all that aids us.

New Frontiers in Fibre

New Frontiers in FibreI spent Thursday afternoon at at St Thomas’ Hospital, attending #BNFNewFibre, a British Nutrition Foundation half day seminar on dietary fibre research. In four short hours we heard from eight nutrition academics and researchers studying new uses for fibre.

The European Food Safety Authority (EFSA) has deemed specific forms of fibre may be recommended for maintaining cholesterol levels, maintaining normal bowel function, reducing post-prandial glycemic levels, increasing fecal bulk and reducing intestinal transit time.

It is the term “fibre” that is problematic, though: soluble vs insoluble; dietary vs functional; whole food sources vs manufactured, extracted and refined, and so on. Since many health claims do not specify the precise type of fibre they are talking about, it is difficult to make sweeping conclusions about intake and effect.

And of course, we are each biochemically unique, the health of our microbiome affected by many factors (age, genetics, pregnancy, lactation, environment, dietary habits, medical conditions and interventions, antibiotic use, etc) not all of which we can control or even identify. These same factors determine our need for fibre, which feeds the hundreds of different strains of beneficial bacteria throughout the length of our digestive system.

We have only identified some 200 unique strains, and 600,000 unique microbial genes, so we have barely begun to learn the position and role these play within our metabolism.

We don’t yet have a good understanding of how fibre works in the microbiome to protect against cardiovascular disease or increase calcium uptake (to protect against osteoporosis), or how it may interact with bile acids, in gene expression or in immune support. Research suggests it may increase satiety, leading to weight loss or protecting against obesity.

Fibre is often included in health advice (either avoiding or adding to the diet) for treatment or prevention of a whole array of medical conditions (colorectal cancers, enteral feeding, irritable bowel disease, irritable bowel syndrome, diverticulitis, radiation toxicity, constipation..)

The speakers whirled through dozens of studies in these areas – published and in process – and left us with the unsurprising conclusion that fibre studies are maddeningly difficult to do with accuracy and consistency (humans being maddeningly diverse in their habits and behaviour, subjects being less than numerous in many studies due most likely to the expense of dietary research, and the very nature of fibre which differs greatly in its chemical composition and effects in the body). And that much more needs to be known.

All this was discussed in the context of last year’s daunting Scientific Advisory Committee on Nutrition (SACN) recommendations which propose raising the already unattained 18g recommended daily fibre consumption to 30g/day for British adults (in Canada it’s 38g for men under 50 or 25 for women).