Metabolical

I read the book Metabolical (2021), by Doctor Robert Lustig, in August of 2024. It was long and dense with facts and analysis. Some parts were not entirely clear. I never saw any citations. Overall, it was still a decent book.

He starts off by claiming that health in the West, and especially in the UK and the US, is diminishing. This requires some parsing of the statistics. It is not enough to say that the number of heart attacks has increased per capita, since modern technology allows people for the first time in history to survive their first few heart attacks. Instead, he claims that there are indeed more first heart attacks. It’s not enough to say that cancer diagnosis per capita is rising, since we are diagnosing cancer earlier and earlier, meaning people have more years to live post-diagnosis, and because people are living longer in general, even long enough to get cancer, which is very much an age-related disorder. Instead, he claims that cancer rates are rising even among children, and after taking into account early diagnosis. Also, while it is true that people are living longer than they were a century ago, those extra years are less healthy ones by other metrics. I’m not sure what to think.

He then goes on to claim that the entire medical establishment is focused on treatment rather than cure or prevention. This has been my impression as well. My hunch is that it has a lot to do with the causes of many diseases being too unsettled, controversial, and mysterious to properly advise on how to prevent them. He admits this is part of the problem, though he still thinks that most chronic diseases are at least partly caused by metabolic dysfunction brought on by sugar and that at least on this point doctors should be more focused on diet than on prescribing yet more pills.

From there, he gets into the three main points of the book: Avoid fructose. Eat fiber. Avoid processed food. So long as those three stipulations are met, we are free to choose our personal diets as we like. He supports both veganism and keto.

Allegedly, fructose is literally poison in too many ways to keep track of, not all of them clear to me. From what I was able to pick up on, it seems to contribute to perforation of the intestine (“leaky gut” syndrome), suppress the enzymes that bring glucose into the mitochondria and burn it, are not useful for conversion into amino acids (unlike glucose), increase free radical production at rates much higher than glucose, and increase glycation at rates much higher than glucose. The only thing it is good for is that it can be burned for the same number of calories as other sugars (4kcal/gram). The worst part is that while every cell in the body takes in glucose, only liver cells and muscle cells can take in fructose. However, if they do not burn it all up immediately, it gets converted into fat within the cells. This ectopic fat (fat outside of the designated adipose tissue) leads to insulin resistance, in turn leading to many other problems, though exactly how was not clear to me. High levels of glucose, while still problematic, do not lead to this same problem, since the liver will turn it into starch instead of fat, something I thought only plant cells did.

I still do not have an overall picture of the insulin system, and this book barely helped. Over the past five years, I have collected many individual pieces of the puzzle, but there are many pieces missing, and some of them are contradictory. I was hoping this book would explain. It did not, but it did teach me many new facts: Three hormones are involved in the feeling of hunger. Ghrelin is secreted by the stomach and tells the brain when it is empty. Leptin is secreted by the adipose tissue and tells the brain when it is full. Insulin is secreted by the pancreas and does very many things. It tells every cell in the body to open up to incoming blood glucose. It tells the adipocytes to stop releasing fat. It inhibits the leptin signal to the brain. It also promotes blood vessel wall muscle growth (raising blood pressure), and reduces the ability of the kidneys to remove salt (also raising blood pressure). While a necessary molecule, too much insulin over too long a time is not good.

Something Doctor Lustig repeats over and over is: Protect the liver. The liver can be damaged by many things. Iron is one of them, yet we need some iron for other body processes. An excess of branched amino acids is another. For those actively building lots of muscles, these amino acids are necessary, but any excess goes to the liver and destroys it. Omega-6 fatty acids are another. These are compounds used in the cell membranes of some plants, but risky for animals like us to incorporate in large numbers. We need omega-3 fatty acids. Excess glucose is another. The worst thing for our livers by far (except for alcohol) is fructose.

Another thing he repeats over and over is: Feed the gut. This brings me to his fiber theory. Fiber provides no calories to us, but it is important for digestion. There are two kinds of fiber. Insoluble fiber creates a lattice in the gut while the globular, soluble fiber plugs the holes in the lattice, trapping other compounds such as sugar or starch away from digestive enzymes. This means that anything thoroughly mixed with fiber is digested slowly, absorbed slowly, travels further down the intestine before being absorbed, and therefore gives the gut microflora the first crack at it. By keeping our bacteria well-fed, we ensure they do not try to eat our intestines, contributing to “leaky gut,” which causes myriad troubles all over the body, including an autoimmune disease where the body attacks its own digestive tract, potentially leading to even more troubles. Well-fed helpful bacteria are also better able to limit the growth of any foreign bacteria we eat, keeping us from getting sick.

After fructose, his archnemesis is processed food, but he doesn’t even make an attempt to define it until two-thirds of the way through the book. Here are some of the things he says about processed food:

“If you take processed food out, you’ve lowered salt and sugar, and you wouldn’t need the medicine.” – page 42

“In particular, we’ve learned that sugar, the main component of processed food…” – page 151

“Processed meats are laden with nitrates…” – page 154

“Processed food is dangerous because of the lack of fiber…” – page 154

“…processed food won’t ferment.” – page 256

My problem here is that “processed” is too vague a term. Cutting, cooking, and freezing are all processes. Sometimes I lack the time, patience, or equipment to do these. What difference does it make if I do this myself or let the producer do it for me ahead of time so I can just pop it in the microwave? Do I really have to pluck my own chickens and pick my own fruit? Finally, on page 242, we get seven criteria for what makes a food processed:

Processed food is mass-produced, consistent batch to batch, consistent country to country, uses specialized ingredients from specialized companies, and consists of pre-frozen macronutrients. All of these sound like this is exactly what we want, and I am surprised that freezing is not considered a process. Processed food also must stay emulsified so that the fat and water do not layer out and it must have a long shelf life or freezer life. I understand that if there are specific emulsifiers or preservatives that science has shown to be harmful, then we can talk about those, but to be against all processed food simply by virtue of being “processed” doesn’t make sense.

Speaking of specific compounds, chapter 20 covers some of those. Diacetyl is a flavor enhancer that causes damage to both lungs and liver. Potassium bromate strengthens dough, but also causes cancer. Lecithin, polysorbate, carboxymethylcellulose, and carrageenan are emulsifiers that keep fat and water bound together, but for this very reason they are also able to damage the mucus layer protecting the intestine from digesting itself and allowing the bacteria or large molecules into the blood. Watch out for all these things in the ingredients list, possibly under other names. The most dangerous compounds are nitrates, nitrites, and trans fats, but each of these have been banned.

I notice he never mentions artificial sweeteners, extracts, MSG, or dyes. Instead, he mentions things that have either been banned or that I never see listed. This book is not the one to read if you are looking out for specific ingredients to avoid.

Other compounds will not be in the ingredients list because they are given to the living organisms before they are food. Among these are pesticides, herbicides, hormones, and antibiotics. Hormones given to promote growth of livestock have been implicated in epidemics of breast growth in children – more than once. Antibiotics given to livestock to prevent disease have been suspected of killing the beneficial gut microflora of those who eat them. Thus, it is not only processed food that is suspect, but whole food as well.

Of course, watching what we eat does us no good if there is food fraud. Sometimes companies lie about what they’ve put in it. To minimize the risk of fraud, avoid foods with large numbers of ingredients and large numbers of contributors and middlemen to its production. While it is possible that your bottle of olive oil might be diluted with some other oil, it is even more likely that the traces of olive oil in your herb-infused crackers came from another company the cracker company chose based solely on price, not on verifiable quality. In other words, the more processing, the greater the risk of fraud. Also, the more processing, the harder time laboratories have to detect fraud. Doctor Lustig cites no evidence to show that fraud occurs or that it occurs often, but it still seems like good common-sense advice.

I don’t know what to think of all this, but where he really starts to go off the rails is his take on food groups and labeling. He acts as if he doesn’t understand the difference between a food group and a nutrient class, saying inane things such as fruit juice not being a fruit (because the sugar is freed from its fiber matrix, making it as bad as soda). I always knew that fruit juice was full of sugar, which some people thought was unhealthy, but it was still considered fruit. Not all fruits are equal. He gets all uptight because some language in an official document was changed from “eat less than” to “don’t eat more than.” Isn’t that the same thing? He insists that sugar in nutrition labels should be measured in teaspoons and not grams to be less confusing to the average person, but knowing the visual size of a teaspoon means nothing if you don’t know how much you should be eating in the first place, which one can learn in either format, so what difference does it make? He insists that listing added sugar is important, before finally admitting on page 328 that it is the total amount of sugar that is important. He calls out vague and misleading phrases in advertising such as “helps build strong bodies,” “natural,” “GMO-free water,” and “evaporated cane juice,” but given how confused the average person is about everything and how diverse the language is between different groups of people, I can’t say with certainty that companies are doing wrong to use such phrases. Some people do indeed need to be assured that their water contains no GMOs and call evaporated cane juice what most of us would call molasses.

He even goes so far as to declare sugar a non-food. According to him, salt and fat are foods, but caffeine, alcohol, and sugar are addictive drugs. I do see his point. Ethanol is commonly understood to be a (mild) poison, yet we can metabolize it for calories (7kcal/gram). Fructose is commonly understood to be a source of food calories (4kcal/gram), yet we are gradually learning it acts in many ways like a mild poison. Both ethanol and fructose have been consumed since antiquity and have important places in cultural rituals, such as Passover (wine) and birthday parties (cake). They are more alike than different. However, does this really mean that fructose is a drug? Or does it mean that ethanol is food?

The book is more than nutrition advice. It also dives into the money and politics behind American food policy. Allegedly, Kellogg invented cereal because he was a Seventh-Day Adventist who believed that consuming meat aroused sinful passions, especially lust, and also dulled the mind to the point that one could not understand and accept the saving Gospel. Allegedly, the link between sugar and cavities was certain before dentists realized they were losing business and so created the bacterial theory. Later, fluoridated toothpaste and drinking water offered some limited protection from cavities, yet dentists went along with it anyway. Contrary to popular belief, the pharmaceutical industry might actually be anti-vaccine, since seventy-seven of the eighty-nine proposals for a COVID-19 vaccine came from universities, not corporations. I don’t know what to think, and I don’t really care about the complex mix of motives institutions might have for their positions; it’s too easy to dismiss truth because our teachers might have ulterior motives for spreading it. I care about what the science says.

So, if doctors are focused on treatment and our food supply is tainted, what can we do about sickness prevention? Chapter 9 tells you what to look for in your blood tests to diagnose yourself and how to change your diet. It’s far too complex to repeat here, so you’ll have to buy the book yourself. In fact, it is so complex, I still can’t keep it straight myself.

The final chapters contain his manifesto for public policy change. He suggests taxing soda and using the money to subsidize water. He suggests having food companies pay for our health care, incentivizing them to deliver healthy food. Alternatively, he suggests that insurance companies buy our groceries, only covering what they approve of. This will cost more on groceries in the short run, but less on health care in the long run, no matter who is paying. Finally, he calls for educating the public that there is no biological requirement for sugar, for requiring that nutrition labels include how much sugar has been added separate from total sugar, for a ban on advertising sugary foods on television and at sports events, for a ban on loss leading of processed food, for a tax on sugar, and for an end to food subsidies that distort the market and keep sugar cheap.

Finally, I got to what really interests me and why I bought the book: the biochemistry!

Calories are not calories: That is, what you eat is not what your body gets out of it. Without sufficient levels of vitamins and minerals, even sugar will pass right through you without being absorbed. With enough fiber, as much as thirty percent of calories will be eaten by gut bacteria before we have a chance to get to it. It takes calories to digest food, and the amount depends on what the food is made of. At the cellular level, it takes calories to prepare molecules for burning. Fat loses 2-3% to this process. Carbohydrates lose 6-8%. Proteins lose 25%. Triglycerides containing omega-3 fatty acids effectively have zero calories because they are never burned, but stored away to build cell membranes from. Trans fats also have zero calories because our bodies don’t know what to do with them at all, so they just sit around and clog arteries.

Protein is not protein: Not all proteins have the same proportions of amino acids. Of the 20 amino acids the body uses, 11 of them it can make itself from other compounds. The other 9 come directly from food. Of these, tryptophan is the hardest to come by. Furthermore, the amino acids that make up muscle protein (what most of us eat) are toxic to the liver, even though we need them to build our own muscles.

Carbohydrates are not carbohydrates: Glucose and fructose have immensely different effects on the body. Sucrose breaks down into equal amounts of glucose and fructose, while lactose breaks down into equal parts glucose and galactose. Starch breaks down into glucose alone, and thus pasta is safer than sweets.

Starch isn’t starch: Linear starch (found in legumes) has two ends for enzymes to snip glucose units from. Branched starch (found in wheat, rice, and potatoes) has many ends, meaning it breaks down faster and causes blood sugar spikes.

Fiber isn’t fiber: Grains that have been ground no longer have insoluble fiber of the correct size to be useful, even if it is chemically identical. Processed foods that have had fiber added cannot possibly have it fully mixed at a microscopic enough level to be useful. Natural fruit keeps its sugars safely locked inside a fiber matrix. Fruit juice and flour does not. Thus, whole grain bread is no better than white bread.

Triglycerides aren’t triglycerides. Saturated fats from animals are better than unsaturated oils from seeds, but oils from fruit (such as avocadoes and olives) are okay. Unsaturated fats can be transformed into trans fats with enough heat, but saturated fats never can be, because having hydrogen bonded to every site where hydrogen could bond means no weak spots.

Saturated fats aren’t saturated fats. Even-chain fatty acids (from meat) are processed everywhere in the body, but odd-chain fatty acids (from milk) are processed in the liver. There is some evidence that milk protects the liver, although there is otherwise no need for adults to be drinking milk.

Cholesterol isn’t cholesterol. Not only is there a difference between HDL and LDL, but there is a difference between LDL and LDL. LDL-C is correlated with heart disease only at very high levels, and negatively correlated with heart disease at moderate levels. Yet, all LDLs are measured together and a statin is prescribed to lower them when too high, but statins don’t even work on LDL-C anyway.

Glucose spikes are not insulin spikes. This is largely because fructose also raises insulin, but also because of lag and pancreatic abnormalities.

Body fat isn’t body fat. A while ago, the medical community figured out that height mattered and used BMI instead of weight. Doctor Lustig prefers to use waistline as a rough metric because it is the ectopic fat and visceral fat, rather than the subcutaneous fat, that matters.

More things to worry about:

Beyond its main points, the book is packed with many anxiety-inducing factoids. Olive oil can be turned into trans fat by cooking with it at too high a temperature. Antibiotics can survive in meat and kill your beneficial bacteria in your gut, allowing “bad” bacteria to take over. Low stomach acid reduces the ability to absorb vitamin B12. Lack of sleep increases ghrelin, leading to hunger. Stress increases cortisol, leading to insulin resistance. Caffeine makes fructose worse. Wheat contains 700 antigens that some people have sensitivities too; it’s not just about gluten. Bottle-fed babies don’t work their mouths as hard, leading to different oral architecture later in life, possibly leading to sleep apnea and mouth-breathing. Breeding tomatoes for sweetness has reduced lycopene levels. Breeding grapes for sweetness has reduced vitamin C levels. Mother’s blood sugar levels determine the number of fat cells baby will be born with and retain throughout life. Monoculture agriculture depletes the soil and requires more fertilizer.

Then there are the random comments that make me question his judgment. There is neither the quantity nor quality of them that warrants tossing the whole book out, but I point them out as a lesson to authors not to make the same mistakes.

On page 232, he states, “Galactose is an essential component of certain fats in the brain called cerebrosides and ceramides.” I thought fats were three hydrocarbon chains linked by a glycerol bridge, whereas monosaccharides were circular molecules with a carbon-hydrogen-oxygen ratio of 1:2:1. It doesn’t make sense for galactose to be a “component” of fat. Did he mean it was a precursor molecule? It is things like this that make it hard for me to see the big picture of how it all fits together.

On page 245, he states, “Trans-fats are calories, but not food.” This contradicts what he says elsewhere about trans fats not being used by the body and therefore not having calories. Did he mean that they have calories when oxidized in the laboratory? That’s confusing.

On page 360, he calls sugar, coffee, corn, cocoa, and even crude oil hedonic commodities. What does he mean by that? Is oil hedonic? Is it hedonic to be able to get to work on time and not freeze to death in winter? On page 379, he claims that it is the hedonic actor that drives the epidemics of processed food, opiates, and guns. Gun epidemic? What is he even talking about? Is there an epidemic of guns? What does that mean? Are guns hedonic? Is it hedonic to want to protect ourselves from murderers, rapists, and fascists?

On pages 18-19, he said, “Obamacare…hasn’t solved any of these issues, because it isn’t addressing the root cause of the problem. Then there was Trump’s response, which hoped to solve the problem by letting sick people die.” Here he assumes motives when all Trump did was convince congress to end the mandate portion of Obamacare, reversing many problems while making none of them worse. Could he have done more to help people? Maybe, but he was dealing with many issues and can’t do much on his own without congressional approval. I find it bizarre that in the midst of a paragraph criticizing both Obamacare and Medicare-for-all, including criticism of the cost, that one would not claim Trump an ally. It is little throwaway comments like these that make me think Lustig is completely out of touch with reality. On medicine, I have no expertise and have to trust his, but when it comes to politics, we are on my turf.

Will this book change habits? Probably not. As he acknowledges himself, people are often too busy and too tired to prepare a proper meal and will just reach for something quick. With rising rent prices, many people are living in vans and eating from cans. Visiting multiple grocery stores a week is too inconvenient. It is often difficult to know what ingredients are in the food. Not all foods are available to us and not all available foods are affordable. Furthermore, the science isn’t settled yet. Lustig himself admits on pages 58-60 that studies are difficult, expensive, and fraught with many forms of bias, since many of them rely on patient recall of what they have been eating. Can we trust anything in this book at all?

There are also too many tradeoffs. Limiting this argument to just what I saw in the book, I have determined that we are screwed either way. This is a fallen world and not our final home. Some processing is good. Lustig admits that milk is the one thing that should be processed (pasteurization). Preservatives are bad, but so is spoilage. Smoking meat is the traditional preservative, but also carcinogenic. BPAs in cans protect the food from metal contamination, but can also be poisons themselves. Farming without preservatives or pesticides means more food waste and higher food prices. Pureed baby food means less chance of choking, but also means weaker jaws and trouble chewing later in life. Cooking food leads to glycation products, but raw food allows the ingestion of living pathogens and parasites. Which is worse? Lustig offers the compromise of fermented foods, but I simply can’t take seriously anyone that thinks sauerkraut is food. It’s literally garbage. I would rather be sick.

Overall, this was a stressful book to read. Everything I love the most is poisoning me. Telling me I have to work harder at preparing my own food and suggesting I might eat sauerkraut wears me out. I need some sugar. I wasn’t planning on it, but after plowing through this exhausting book, I need to relax with a Dunkin Donuts Signature Latte and some pastries. I’ll see you later.

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