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After the merry Christmas holidays and the high spirits of Hogmanay and Ne’er Day in Scotland, January stretches out, dark, drab and driech. February too promises precious few fine days, although the longer daylight hours are cheering.
It is time for those at work and home to hunker down, and for snowbirds to fly out of blizzard-blasted northern states and Canada, past chilly Virginia to the warm blanket of southern Florida.
Young Rose-breasted Grosbeak. Courtesy Geoff Giles
Birds too are on the move. The neotropicals headed further south several months ago, although a few hardy individuals stayed on in our Williamsburg area through the light snows and recent ice-storm. How would they manage without the hospitality of feeder stations in gardens and yards? Every year, there are reports of a hummingbird and a tanager lingering here in mid-winter, and a Rose-breasted Grosbeak visited a friend’s garden this month. I wonder if these vagrants are seasonally disoriented or knowingly hanging around avian soup kitchens, but they are thrilling sights for being among our most colorful birds.
A flock descending in the backyard like a sudden squall can lift a brow leaning at the computer for a welcome moment of respite from concentrated work. Mostly American Robins and occasionally Red-winged blackbirds or grackles, they are probably not the residents of other times of year for those birds have temporarily gone to more southerly neighborhoods. The winter relatives have come down from the north to feast on left-over berries of holly, wax myrtle, and red cedar. Why the locals moved away before emptying their larder puzzles me, but the policy helps the migrants who replace them. The wrens, nuthatches and chickadees seen at this time of year may also be newcomers, but I like to think my special friends, the cardinals and bluebirds, stay with us the year round. But how could I know unless I banded them?
Small bird feeder – fat, grain and seeds
We only see White-throated Sparrows and Dark-eyed Juncos in the coastal plain in winter. They skulk around the shrubbery, ignoring the gardener at work nearby, and take turns to peck suet on the feeder. Juncos are nick-named ‘snowbirds’ because they are regarded as harbingers of hard weather. In the mountains above 3,000 feet, they are the only birds you can count on seeing throughout January. The deer have no choice but to stay the year round, and many animals perished of starvation in the very hard winter five years ago. Bears are safe from the elements while torpid in their dens. Most other birds and critters move down the valleys to better pickings around creeks or to even further afield. But you can tempt some of them to stay.
The Big Feeder
Last fall, I hauled 200 pounds of whole corn and chicken scratch in a barrel 20 feet up in the low canopy between two trees. The job needed a hand winch and a block and tackle. Under a hole in the base of the barrel, a small propeller spins automatically every 12 hours, scattering grain in a 50 foot radius for six seconds. A gamecam monitors the area and a motion detector rings in the house 100 feet away to tell me when to grab binoculars. But the hefty feeder was not installed for the benefit of viewers; it feeds the hungry while I am away, and only needs replenishing every two months.
Winter trees are wisely bare and silent, but this helps me to see further into the woods. The season is not dead; wildlife are coming to their Time Square.
In the past few hours, several deer came to nibble grain. Four ruffed grouse in cuddly feather balls strutted around, and two fox squirrels, so much larger and more handsome than gray relatives, darted back and forth with grain to a hiding place. And there was rarely a moment when small birds were absent. There was no fighting over food and, despite the bitter cold, most visitors were in mated pairs. A pineal gland tells them the time of year. I recorded a mother bear grubbing under the feeder with two adorable cubs, but now she may be dreaming of spring with a tiny newborn pup or two attached to her teats. January is hard, but has its compensations, and is full of distant anticipation.
Next Post: The Soda File
Virginia Nature Journal for January
Who knows about Fructose?
Lucas Cranach (1526). The Courtauld Gallery (extract)
Was it a sweet or sexy temptation?
The apple that Eve plucked
from the tree was sweeter than honey, or to be perfectly accurate it had relatively more of the sweeter stuff than in honey. Apples contain more fructose than glucose, and fructose is much sweeter than either glucose or sucrose (the sugar in our pantry).
Aside from the creation story, the other theory predicts that some plants acquired an advantage by evolving biochemical pathways that generated more flavorsome sugar, like fructose, in their ripening fruit. Being more attractive to eaters, helped to disperse seeds to places where they could thrive. Eve is in the apple, as fructose.
‘Fructose’ has a healthy ring, from its Latin root for ‘fruit.’ We were advised to eat an apple a day to keep the doctor away, and fructose was recommended for people with diabetes because it has a low glycemic index. But it may not be such a good prescription, and has been losing its salubrious cachet ever since high fructose corn syrup was introduced forty years ago. Glucose still glitters, which is a differentiation that seems odd at first sight because the two molecules have the same number of carbon, hydrogen and oxygen atoms.
Glucose + Fructose = Sucrose
Having identical chemical formulas does not make them the same. They are no more the same substance than genetically identical twins are the same person. Glucose and fructose are monosaccharide sugars forming in equal amounts when their parent molecule, sucrose, is digested by enzymes breaking its oxygen bridge apart. The two ‘baby’ sugars have different shapes, but when it is their turn to be digested they generate the same number of calories. But not all calories are equal.
Shape matters. Consider another sugar-lover. When yeast cells feed on the sugary mixture in unfermented grape ‘must’ they mostly prefer glucose, and as alcohol increases in the liquor more undigested fructose is left behind. That can make a wine too sweet for taste. Vintners are therefore choosy because some strains of yeast have a greater affinity for fructose which makes a drier product. Not all yeasts are equal.
Of these twins, only glucose is essential for life, although we don’t need to eat it raw because it is created by digestion of more complex carbohydrates and fats. We manage perfectly well without fructose in our diet too. Even sperm, which are nourished in fructose-rich semen, are equally satisfied when provided with only glucose.
More interestingly, our body handles the two sugars very differently. Glucose is rapidly absorbed into the bloodstream from the small intestine via a special transporter (GLUT4). It then races through the liver for delivery to every corner of the body. Under strict control by the hormone, insulin, glucose provides fuel for metabolism and growth in cells, and any surplus is converted to fat and stored in adipose tissue.
On the other hand, fructose is absorbed slowly from the gut and by a different transporter (GLUT5), and even more poorly in infants where it can cause diarrhea. Once it reaches the hepatic portal vein it stops at the liver where it is taken up into cells by a process that doesn’t involve insulin. Once inside, it is handled differently to glucose, forming glycerol as a backbone for making triglycerides. Several studies have shown that fructose-rich diets raise both triglyceride levels and LDL small particles while lowering HDL-cholesterol, which are thought to be unhealthy signs. Since fructose is lipidinous, it potentially contributes to metabolic syndrome, including diabetes and obesity, and there is additional evidence of a role in fatty liver, gout, and inflammatory conditions. Eve was wise to offer Adam only one apple.
Until a little over a century ago, dietary sugar could only be afforded by the wealthy and powerful. No longer. Growing up with cheap and omnipresent sugar, it is easy to equate abundance with beneficence. The longest aisles in supermarkets are stacked with sodas and sports drinks full of sugars, and rows of ‘healthy’ apple juice contain a whopping 100 grams of fructose per liter. Those are the most visited aisles in stores, and conveniently located near cash registers.
Longest aisle in the supermarket
At home, grocery products lining pantry and fridge shelves are also saturated with sugars. But it’s hard to know how much sugar we consume by reading labels. How can we accurately compare it in different foods or brands when labels describe amounts as ‘serving sizes’ instead of ounces or grams? How much sugar is added versus natural? How much is glucose versus fructose versus sucrose? As consumers buy more processed foods instead of using raw ingredients for home cooking we are locked into choices made by manufacturers. They spoon in the sugar to increase shelf-life and palatability (Eve’s temptation).
I know how hard it is to resist sweet stuff, and harder still to give up. Perhaps fructose is hardest of all, being so sweet and stealthy. Our gut absorbs it more rapidly as we become used to it, and it doesn’t suppress the hunger hormone (ghrelin) as glucose does. We get hooked, without being satisfied.
When we were introduced to tea and coffee as children our ration was a measly half-teaspoon of sugar to make them more palatable. As soon as we started savoring the beverages, mother weaned us off the sugar, and a few weeks later the sweetness was so repellent that if we sipped Dad’s tea by mistake it made us heave. It took much longer to adjust him to unsweetened drinks. In that age, when sweetness was well-regarded in every way, children could surprise visiting aunts and uncles by teasing them: “We are teatotal, and saving our sugar ration for chocolate!”
It is now cool to cut sugar and worry about fructose, and the stigma is sticking. Robert Lustig has over five million viewers for his YouTube diatribe against fructose, and Michelle Obama was quoted as saying,”Our kids don’t choose to make food products with tons of sugar and sodium in supersized portions, and then to have those products marketed to them everywhere they turn.” We must stop blaming the fat boys and girls in class for being gluttons. With choices made for them and sweet temptations at every turn, they are casualties of a food and drinks industry focused on annual financial performance. And since the FDA is unlikely to regulate sugar in foods, the sweet tide continues to rise.
High fructose corn syrup is gradually replacing sugar from cane and beet because it is so cheap. Produced by industrial hydrolysis of starch, HFCS55 and HFCS42 are the main products for foods and beverages, while HFCS90 finds specialty uses. The number represents the percentage, so the fructose hit in HFCS is similar to 50 in granulated pantry sugar. There are important differences, however, in the source, process, farm acreage, economic and environmental impacts of subsidized corn for HFCS.
While HFCS is regarded as a new dietary demon, we have been exposed to fiendish fructose for eons, although not in any quantity until recent generations. It is unavoidable, but lower exposure through smaller serving sizes, home cooking, dilution of fruit juices, etc. can be managed over time because there is no physical addiction to sugar. Perhaps it will become the new tobacco.
Animal studies show that it would take an impossibly large serving of fructose to kill us, but that doesn’t deny a toxicity that is cumulative and insidious over time. Even the most benign substances that life depends on, like water and oxygen, can harm us when we are overexposed to them.
I imagine a naïve man visiting the seaside for the first time. He sets up his deckchair on the beach at the low water mark so his toes are wetted by a gentle ripple at the ocean edge. Two hours later, he is enjoying the warm water washing around his calves while he is engrossed in an anthology of Robert Browning. When five more hours have gone by, the soothing water is up to his waist and the open book flops on his chest at the Paracelsus poem as he dozes off. But after ten hours, a wave splashing his face wakens him, but too late to swim back.
Perhaps the metaphor is too strong, but Paracelsus would argue otherwise. He was a sixteenth century doctor and the father of toxicology. A great deal of nonsense has been attributed to him, but he rightly pointed out that “the poison is in the dose.”
Next Post: Virginia Nature Journal for January
Posted in Biomedical
Tagged fructose, Paracelsus, Robert Lustig, sugar diet
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Sweet and Sickly
Everything in moderation, including moderation. That’s Wilde … but did he really mean everything, including sugar, or was Oscar teasing us? What would he say since we consume immoderate amounts of the sweet stuff? And does it matter anyway?
Sugar for a man-year
Some twenty years ago, I asked my students in Edinburgh to keep a food diary for their physiology class. Two weeks later they calculated their daily average rations of protein, fat, carbs, and micronutrients. Some of the young men consumed half of their carbs as sugar—equivalent to a 3 lb bag (1.4 kg) every week—mainly in candies, cakes, sodas, juices, bread, processed foods, and, of course, ad libitum volumes of beer. At that rate they swallowed four tons of refined sugar in a lifetime, contributing over 20 % to their total calories. The women consumed rather less of everything, but some were nonetheless so shocked that they abruptly changed their food choices, and sugar was first for the axe.
Scotland has been the land of “bread and buns” since Greenock became a Sugaropolis on the River Clyde. Ships docking after plying the Atlantic trade route from the West Indies provided a bustling trade that made sugar cheap enough for everyone to afford to excess. You can find it added to most things on your pantry and fridge shelves—from apple juice to zucchini in cans—often unnecessarily or excessive. Sugar consumption boomed throughout much of the Western World, and there was hardly ever a whimper of reproach.
Why would anyone protest? Isn’t a sweet gift a token of love? Parents, friends, and guests would buy candies, chocolate, ice cream, and candy floss (“candy cotton”) for us children, and more recently (if only in Scotland), deep fried Mars bars with a whopping 1,000 sweet, greasy calories. We were told that candy was good because it “gave us energy” (as if we were not hyperkinetic enough), and no one accused the gift-bearer of harming children. It was good for school dentists too, who labored like road workers inside our gaping mouths with jackhammers and caterpillar excavators. Ever since Queen Elizabeth I smiled a row of blackened stumps, “British teeth” have been synonymous with crumbling ruins for North American dentists.
Raw Mars bar before deep frying
Apart from the black mark of caries, ‘sweetness’ has resonated in our language for centuries with everything wholesome and beautiful— a sweet girl/ boy/ spirit/ victory/ life/ air/ scent/ friendship. And Hamlet’s mother in her adieu, “Sweet to the sweet, farewell.”
Sweetness and sugar are interchangeable and both sound positive in almost every way, including financially. Sugar futures are safe bets for investors because the commodity reaches multiple markets—food, drink, fuel. And when Great Grandpa Francis took a retirement job as chairman of the International Sugar Council he was in a sweet spot. Harrowing memories of slave labor had faded, and there were none of the modern worries about environmental and nutritional impacts.
Neither did our doctors ever condemn a sweet tooth, as far as I can remember. However, unknown to us and yet not far from home there was a maverick fighting a single-handed battle against sugar interests.
A book pulled from the dustbin
John Yudkin (1910- 1995), a London professor of physiology, published Pure, White and Deadly in 1972 (Sweet and Dangerous in the USA). The title reads like an Agatha Christie arsenic plot, but his book claimed that sugar is a slow poison, and that did not endear him to his profession or the industry. They strenuously barred him from guest lectureships and expert panels, although with typical British understatement, he wrote that, “relations with one or two friends in industry have occasionally become rather strained.” He also had the rare distinction of his book being condemned even before it was published: “(this book) is science fiction … and for your dustbin” (The World Sugar Research Organization). The criticism must have pained him, because he was a “jolly man” according to one of my colleagues.
If World Sugar represented the bitter enemy in industry, Ancel Keys at the University of Minnesota was his bête noire in academia (blogpost December 21, 2014). After President Dwight Eisenhower suffered a series of heart attacks in 1955, American epidemiologists focused on the growing epidemic of heart disease, and Dr. Keys led the campaign against saturated dietary fat and for lowering blood cholesterol. Keys made the front cover of Time magazine and leaves a legacy of official dietary advice and food choices in our supermarkets.
Yudkin was a rare critic of Keys’ famous Seven Countries study of health and diet, and much else that claimed to prove a case against animal fat. He argued that the choice of countries was arbitrary, and sometimes the link with disease and obesity was stronger with sugar than fat. Moreover, the Canadian Inuit and African Masai subsisted on high fat diets (>50% of calories) consisting of meat, blood, blubber, and milk without developing heart disease, or at least until they adopted a Western diet. It was a similar story for Sephardic Jews before and after migration from Yemen to Israel. And the acclaimed Mediterranean diet, which is poor in ‘bad fats’ and rich in ‘good’ ones, happens to be low in sugar.
Rather accusingly, he said the low fat bandwagon was based on the elementary error of assuming that a correlation proves causation, and after it started rolling it was propelled by vested interests. As far as I know, he never met its architect, Ancel Keys, which was probably merciful because they might have come to blows, verbally if not worse. The bitterness went deeper than an esoteric tiff between academics because Keys had brought round his government, much of the medical profession, and the food industry to his cause. If he was wrong, there was blood on his hands—bad dietary advice to the nation would fail to roll back the tide of heart disease, and this has not happened after fifty years. As if to rub salt in a wound, Yudkin showed the correlation with disease is better for TV ownership, which is not as ironic as first sight. Heart disease is associated with all the hallmarks of affluence—sedentary lifestyle, obesity, smoking, fatty and sugary diets. The story is complex.
Perhaps he deliberately exaggerated as prophets are wont to do. He had to struggle to get attention from a profession and authorities who had turned their backs on him. Not only did he single out sugar as a chief cause of the triad of heart disease, obesity, and adult-type diabetes, but claimed it might be responsible for a mixed bag of gout, diverticulitis, dermatitis, duodenal ulcers, vision problems, and even cancer. In claiming sugar was the bogeyman of so many ailments he gave opponents a better chance to ridicule him. He wasn’t taken seriously until after his death, when another outsider stepped forward to carry the baton.
Gary Taubes in a New York Times magazine article (July, 2002) asked, What if fat doesn’t make you fat? Like his predecessor, he thought the triad was more likely caused by hormonal changes.
When glucose is absorbed into the bloodstream it stimulates insulin secretion from the pancreas. Insulin keeps glucose in check by a ‘handshake’ with a receptor on cells that opens a gate for glucose to enter where it is burnt for energy or stored as fats, to excess if sugar and insulin remain high. How the metabolic balancing act leads to a spectrum of disease is still being worked out, but its disorders seem to be related to the aging process. While studying worms in her lab at the University of California, Cynthia Kenyon found that insulin-like genes switched on by a sugary diet shorten their lifespan. After her discovery, she switched to a low glycemic diet.
Mother’s rule at the meal table was wiser than she knew. My brothers and I regarded the savory course as something to struggle through before we were rewarded with a sweet dessert. We were never allowed to reverse the order. The protein and fat lying heavy in our stomachs when the sugar came down the chute delayed gastric emptying, slowing its path into the small intestine for absorption and curbing a rush of glucose into the blood. Likewise, she forbad candy between meals, which avoids an unnecessary glucose spike, although her rationale was to dodge the dentist.
Yudkin also admitted struggling with a sweet tooth when young and an expanding waistline in mid-life. He slimmed by switching to a low-carb diet, which was a long time before we heard about the Atkins diet. But he wasn’t the pioneer of low carbs; that credit belongs to a Victorian Londoner, who, as a coffin-maker, knew something about corpulence. William Banting (1796-1878) found a low-carb diet helped him to slim, and he broadcast his discovery in a book that sold well, if not in medical circles. By an odd twist of history, one of his descendants won the Nobel Prize in 1923 for the discovery of insulin. Banting’s formula was close to the modern paleo diet, which I will return to in another blogpost.
Yudkin might chuckle now that sugar is portrayed as the new tobacco. You know the climate of science has changed when America’s First Lady and Dr. Oz have taken theories on board, even if the originator is forgotten.
But how could so many experts be so wrong for so long? Science is the most objective path to knowledge, but still a human endeavor. When a complicated case is heard in the court of science the judgment depends not only on the evidence presented but on the outcome of a clash between the prosecutor and defending attorney. Ancel Keys would have made a very persuasive trial lawyer and, more importantly, nutritional science makes hard cases.
Nutrition has been called kitchen science as one of the softer life sciences. It may look like a pure, white meringue with a hard crust, but squeeze it and you find a soft, gooey center. The more complicated the subject the greater the uncertainty, and the chemical complexity of food is compounded by the genetics and lifestyles of diners. And unlike testing a new drug, it is almost impossible for a study to strictly control the diet of its subjects long enough to reveal divergences in health. Consequently, we have a smorgasbord of slimming diets and food fads which are hard to prove or dismiss.
I favor Michael Pollan’s commonsense philosophy: “Eat food/ Not too much/ Mostly vegetables” (In Defense of Food). He applauds food that is not highly processed, farming practices with environmental integrity, and diets based on moderate food choices that reduce glycemic carbs. But it may not have appealed to Oscar Wilde who loved sweetmeats, and his father, Dr. Sir William Wilde, made his fortune in the sugar industry.
Next Post: Who knows about Fructose?
Posted in Biomedical
Tagged Ancel Keys, Atkins diet, Gary Taubes, John Yudkin, low carb diet, Michael Pollan, Oscar Wilde, Sugar industry, William Banting
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Where the Bee Sucks
There are compensations of being cooped up indoors in wintertime. Bilbo Baggins looked forward to the long evenings in his hole at Bag End when he could relax in an armchair toasting his feet in front of a blazing fire. It’s a time of greater idleness and harder to rouse oneself even for a few steps from a comfort zone to the pantry for a snack. And bee colonies are likewise.
As the outside temperature falls below freezing, they huddle deep inside their hive to maintain a remarkable 90 °F. (32°C.). The workers who labored so hard on warm days earlier in the year are now idlers that rarely bother to snack, and no longer share their precious honey stores with drones that died off in the fall. The queen is at the quiet center of the bee-ball. She has stopped laying eggs, and won’t resume until February when the colony must expand rapidly for the coming nectar flow.
Cosy-up in the comb
Honey stores gradually run down over the cold season. On warm days, a few workers head out to forage for the few hours before sundown, but it is a risky business because if nectar and pollen are scarce the flights may have a negative energy balance. Bee colonies often perish from starvation at the end of winter, just a few days or weeks before food is plentiful again.
The beekeeper who stole most of the honey hoarded last summer must replace it. Trading sugar for honey seems good to him. But the sugar-water that was welcome in warmer months needs lots of energy from beating wings to evaporate it, and can increase the danger of condensation inside the hive. So we give candy to the bees, and why not at Christmas?
On a warm Christmas Day like today there was no danger of chilling the bee-ball when I lifted the inner cover to check the girls. I took a bar of candy out of Santa’s sack and rested it on the frames of empty honeycomb. The candy was home-made by boiling concentrated sugar with a few drops of essential oils until it caramelized and set into solid bars. It’s toffee for bees. A few lethargic workers crawled from their warm place to inspect the treat. Last year, I tested whether they could tell the difference between refined sugar and non-caloric artificial sweetener, because some people find it difficult. Of course bees aren’t so easily fooled. They know that real sugar is vital for survival, but it’s a different story for our species.
Next Post: Pure and Poisonous
A Merry Christmas to my readers
A Healthy Oil Change
Smoke curling out of an open window or from under a car hood is a bad omen, and smoky chimneys and cigarettes emit toxins. It often means bad news, and we made a metaphor of it, There’s no smoke without fire. But occasionally it seems almost wholesome.
I used to enjoy it gently billowing over a wok before I threw vegetables on the hot oil to stir-fry. Perhaps smoke from cooking is welcome because the kitchen is a sanus sanctuarium— provided the oil doesn’t catch fire! I wonder if different notions about smoke rarely cross-fertilize because they are processed in separate registers on the right and left sides of my brain. No doubt there’s a lot more mental subtlety involved, but one day when smoke from a wok on the kitchen hob made me cough my right brain woke up to ask why. Wasn’t it a healthy smoke? And, if not, what kind of chemical brew was I creating?
It’s a question that has been studied more by biological chemists than you might think from the few media reports, although some food warriors have posted smoke signals. When I started reading tidbits from scientific journals I understood why.
When any kind of vegetable oil is heated a chain reaction starts to evolve aldehydes like acrolein, 4-hydroxynonenal, and a bevy of other unfamiliar molecules. Heated above the ‘smoke point,’ the rates of reactive aldehyde formation climb ever higher. Some of these molecules are known mutagens that can form adducts with DNA, making them candidate carcinogens. Polyunsaturated fatty acids in oils recommended by the authorities are more vulnerable to oxidation than the monounsaturated types because they have more double bonds. Saturated fat, which by definition have none of them, are much more stable. Suddenly, it dawned on me that home cooking can make my home more polluted than the street at rush hour.
Good, bad or ugly fats?
If vapor was the sole danger I could avoid it by turning up the extractor fan, but my meal was bathing in a toxic slush. Since higher temperatures and long cooking times increase the problem, I wondered how many times cooking oil is re-used at the fast food joint where I sometimes buy a burger and fries? I also thought about my neighbor who saves oil from his deep fryer after cooking a Christmas turkey? Perhaps it’s safer dining at home.
Restaurant chains can reduce oil oxidation under a blanket of non-reactive nitrogen, or at least test the quality of any reused oil, but home cooks don’t have that option until there is a mass spectrometer for the kitchen countertop. Meantime, we blithely follow recipes regardless of chemistry, and have to rely on our senses and common sense for safe cooking.
The first precaution is to watch for smoke, which is a warning that the oil has spoiled and should be replaced. The second is to sniff over the pan because an acrid smell points to acrolein in the vapor. And the final test is to taste the oil.
Smokey wok
When I compared several cooking oils by heating them to 400 °F. (204 °C.), the extra virgin olive oil and walnut oil were smoking before they reached this temperature, and their fruity notes were gone and tasted bitter. These oils had already gone bad. But refined oils like canola had higher smoke points, and though they started tasteless they remained that way. Lastly, I opened a large bottle of olive oil which had just passed its sell-by date. Since it smelled rancid, oxidation was happening at room temperature and, reluctantly, it had to go. Vegetable oils are a kitchen doctor’s dilemma that Mum never had to worry about. How did it happen?
As heart disease grew to epidemic proportions, the American nutritionist, Ancel Keys, led a charge against saturated animal fat over fifty years ago. He was followed by an omnibus of researchers, medical societies, and government officials who transformed the national diet which we still have (but I won’t say enjoy). The arguments were based on apparently unassailable reason and facts—energy-rich fat makes us fat, and dietary cholesterol deposits in atheromatous plaques. Clinical surveys (occasionally) helped to prove the low fat revolution was sound.
Which cooking oil?
But when animal fats were thrown out of the diet the food industry had to fill the gap. Where would the missing calories come from, and what would replace the fat needed as shortening for pastries, cookies, etc? The industry turned to vegetable oils rich in polyunsaturated fats. This decision seemed a safe bet, especially because they were already marketed as margarines created by chemical conversion of liquid oils to partially hydrogenated trans fats. These products had the dual virtues of remaining solid at room temperature (like butter) and having a high smoke point for deep-frying (like lard or beef tallow). As the demand for more vegetable oils bloomed, farmers sowed fields with ever larger crops of rapeseed and soybean. However the safety of trans fats was not sufficiently scrutinized until recently when were they banned in restaurants, food labeling was mandated and the F.D.A. posted a health warning. The complex mixture of unnatural isomers in trans fats are implicated in a wide range of diseases, and now it’s their turn to be condemned.
The food industry is reluctant to return to animal fat because of the legacy of research stretching back to Dr. Keys and the stamp of officialdom. Although a search for substitutes continues, refined vegetable oils have found a new role in deep frying. They are presented as a healthy choice because they don’t raise the ‘bad’ type of cholesterol (LDL), although a rather weak predictor of heart disease in most people. You seldom read about the downside.
The public continues to be subjected to a vast dietary experiment that fails to conquer cardiovascular disease, which still beats cancer to the top of the C.D.C. list of causes of mortality. Switching from animal fat to trans fat and from trans fat to refined vegetable oils have been hailed, in turn, as advances in public health, but we may have ended up with a new cancer risk, or at least a concern that deserves more research. Moreover, as dietary calories from fat have declined over the years they have been replaced by refined carbohydrates, which are now held responsible for obesity and diabetes emerging in children. It’s hard to grasp the scale of disease, disability, and death that can be traced back to dietary recommendations over the last two generations.
I hope people are thinking more about their diet, and listening less to official prescriptions. The relationship between our food and health is far more complicated than the experts were wont to believe. I hope that people fret less about fat in their diet than about the environment in which crops are grown and farm animals are husbanded. There are far too many vested interests in our food choices. Mum’s cooking probably wasn’t as unhealthy as the next generation assumed when they squirmed at the larded memory. I’m sure her pastry, cakes, and cookies tasted better than those served today.
I have turned the tables on cooking fats and oils at home. Margarine and polyunsaturated spreads are out, butter is in. Butter can be good even at high temperatures if the solids and water are removed by clarification. And if lard ever reappears on supermarket shelves I may pull out one of Mum’s old recipes.
For high temperature cooking, I often use refined oils, like safflower, which have high smoke points; olive oil and tasty nut oils are reserved for salad dressing and other cool uses. The pros and cons of different oils otherwise confuse me because the composition of healthy fatty acids (usually meaning omega-3s) and antioxidants vary with the source, season, and storage conditions. Of course, we choose those that taste best (the unprocessed kinds), but I am more focused now on safe cooking to avoid nasty radicals generated by oxidation. And I am more careful about storage conditions, meaning for shorter periods in the cool and dark. I even squeeze drops of vitamin E from capsules into bottles of vegetable oil to help preserve them.
These concerns about dietary fats are new to me, though they shouldn’t be. As long ago as the late 1950s, Denham Harman (1916-2014), a gerontologist at the University of Nebraska, was expressing doubts about the wholesale adoption of vegetable oils in the national diet. As a former chemist at Shell Oil, he knew that unsaturated fats are unstable and susceptible to oxidation. In one of my books published in the 1990s (Cheating Time), I mentioned his free radical theory of how oxidized lipids cause cell aging and disease. But the penny didn’t drop in a lifetime of cooking until I leaned over a smoky wok one day.
[In coming weeks I will post about sugar and salt]
Next Post: Where the Bee Sucks
Posted in Biomedical
Tagged Ancel Keys, lipid oxidation, polyunsaturated fats, saturated fats
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Roger musing about Peace with Nature 