The liabilities of excess sugar in the prevailing modern diet are by now common knowledge.
With rare exception, debate on the matter is limited to whether sugar is a, or the, delivery vehicle for the grave toll of modern eating.
For what it’s worth, I am emphatically in the former camp, having asserted to anyone who would listen across an expanse of decades that no one thing is wrong with the modern diet, and no single nutrient fixation will remedy it. Rather the contrary, sequential preoccupation with any given nutrient scapegoat or savior while neglecting the quality of overall diet has taken us from one dietary boondoggle to the next. There is more than one way to eat badly; we seem committed to exploring them all.
For human health, we need a balanced assembly of wholesome foods- not just the avoidance of something toxic in excess. From the perspective of planetary health, the case against animal foods in general and beef in particular is most salient. Ultra-processed foods have been implicated in weight gain, and in an array of other ills burgeoning with percussive regularity in the scientific literature. Our food- or the willfully addictive junk that all too often masquerades as food- is, indeed, killing too many of us, and a comprehensive overhaul of diet quality is in order.
In such a context, there is a valid case for particular attention to sugar. In diets made up of far too many empty calories, sugar is a singular source. In a population epidemically prone to obesity, insulin resistance, type 2 diabetes, and excess inflammation- sugar is implicated in all of those crimes against the human condition. And, with singular efficacy, sugar propagates its own excessive intake by stimulating the human appetite center as nothing else does. The food industry knows this and exploits it quite profitably. We know it, too, veil it as we may in the coy guise of ‘sweet tooth.’ Feed one of those, and it grows into all the menace of a fang.
So, the case for displacing sugar from our diets is clear. For those habituated to a particular level of sweetness, such displacement without dissatisfaction has generally meant replacement, and that in turn has meant sugar substitutes, alternatively known as non-nutritive sweeteners (NNS), artificial sweeteners (AS), no-calorie sweeteners, and so on. Enter a new study in the prestigious journal, Cell, that implicates such NNS in many of the same and most serious transgressions as those of sugar itself. What now, are we to do?
I will answer that, but first some particulars of the new study, which I found to be unusually compelling. With an elegant, rigorous, multicomponent approach (reminiscent of a Yale doctoral dissertation I evaluated many years ago, and that earned its author High Honors), the research team in question demonstrated both the what, and the how, of NNS harms. First, using the standard randomized trial design, they demonstrated that NNS- notably sucralose and saccharin- impaired glycemic responses in healthy adults without prior intake of these compounds. As impairment of glucose/insulin metabolism is among the particular concerns attached to sugar, discerning this effect with common replacements raises the obvious issue of swapping a pot for a kettle.
The researchers further demonstrated that the four NNS studied- the two above, along with aspartame and stevia- all induced changes in the microbiome. Finally, they transplanted the microbiomes of affected humans into germ-free mice (mice bred and raised to be free of all bacterial exposure, and lack a microbiome)- and reproduced the same metabolic effects in the mice, indicating that disruption of the microbiome is the causal pathway to impairments in glucose and insulin metabolism.
The bottom line here is that NNS do at least some of the harms they are expressly intended to mitigate. As indictments go, that’s pretty harsh.
To be clear, though, this was a short-term study and the longer-term effects are only inferable, not known. Participants were chosen to be free of prior exposure to NNS, which is exception rather than norm in modern societies, and might skew the results one way or another. Individual responses to NNS varied, and responses to different NNS varied as well, with less overt harm seen with stevia and aspartame than with saccharin and sucralose. And finally, the detrimental effects of NNS observed here were not compared quantitatively to those of various sugars, and thus a net benefit is by no means precluded. When one’s only options are frying pan or fire, the frying pan has relative virtues.
But those are not the only options. I had qualms about NNS before there was worrying research on the topic, and there has been worrying research long before now. My concerns were, and are, rooted in sense- to which science is always playing catch-up.
First, it made sense that if the sweetness of sugar stimulated appetite, and a desire for ever more sweetness in the diet, that comparable sweetness imparted by other compounds might confer similar effects. The perception of sweetness is a particular chemosensory response in the brain, via taste buds, no matter the agent. It stands to reason that effects might be shared among compounds that share in producing this stimulus.
Second, NNS are by definition non- nutritive, and not a normal component of human food. The introduction of non-food chemicals, whether from tree leaf or test tube, into the realm of human comestibles invites a nod at the law of unintended consequences. As we learn ever more about the delicate balance of the microbiome and its vulnerability to disturbance by means of diverse dietary exposures- all the more so.
Which brings us back to: what now? My favored approach- personally, and across a 30-year expanse of patient care- is attention to stealth sugar, and taste bud rehab. Stealth sugar is sugar processed into diverse foods not appreciably sweet, from salad dressings to salty snacks, nut butters to pasta sauces. This list is all but endless, and the aggregate grams of sugar it can add to one’s daily diet is impressive. Fortunately, there are alternative products in all such categories without the added sugar- recognizable to all with a bit of food label literacy. By making such substitutions, innumerable grams of sugar may be backed out of the daily diet before ever adjusting the foods where sweetness matters most.
Just as higher intake of sugar begets a higher threshold for satisfaction, so does a lower intake reduce that threshold. This is very analogous to any other habit-forming substance; the more you get, the more you need, and to some extent, vice versa. By dialing down exposure to sugar, sensitivity to sweetness is dialed up in tandem. Food and drink that was pleasantly sweet before starts to be too much so- and that is an invitation to make further adjustments there. Soda can transition to seltzer; desserts and breakfast items can be half as sweet and just as good. It’s a process made in steps, each supporting the next.
The net effect is what I have long called “taste bud rehab.” Delicious is whatever we decide it is, and that decision is much predicated on the familiar. Bathe your taste buds in copious sugar all day, they expect it, want it, need it. Disabuse them of this, however, and a far greater native sensitivity to sugar reawakens. You need less; you want less. Taste bud rehab is not about trading off pleasure for health; it’s about investing just a bit of time and effort in a process that lets you love, and prefer, the very foods that love you and your health back.
None of this- not the new study, not my take- precludes selective use of NNS in an effort to reduce sugar intake, particular during a transition period. Perfect should never be made the enemy of good.
However, real food, mostly plants is the foundation of any good diet, and it is overall diet quality that most reliably predicts the health outcomes that matter most to us all. In a diet of actual, wholesome foods- there is little to no place for non-nutritive chemical compounds of whatever origin.
At best, the new study issues a precaution about undue reliance on NNS. Fortunately, the important task of reducing sugar to the minimal place it should claim in your overall diet can be achieved with or without them. Displacing sugar does not depend on replacing it.
David L. Katz, MD, MPH, FACPM, FACP, FACLM, is the Founding Director (1998) of Yale University’s Yale-Griffin Prevention Research Center, and former President of the American College of Lifestyle Medicine. He has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both preventive medicine, and nutrition. He has made important contributions in the areas of lifestyle interventions for health promotion; nutrient profiling; behavior modification; holistic care; and evidence-based medicine. David earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates.