AS A SUGAR LOVER, I have tried to ignore the increasingly negative publicity about its health hazards until I recently read about possible effects on the aging brain. And then when I started to pay attention to ingredients labels, I was shocked to find how mistaken I’d been–for example, about my favorite San Pellegrino “sparkling grapefruit beverage,” just water, right?–and began to choose my sugary treats more carefully.
Although there is still no definitive evidence that sugar causes change in the brain, recent evidence suggesting that dysfunctions associated with diabetes–hyperglycemia, hypertension, insulin resistance and elevated cholesterol–might also contribute to dementia has led some experts to call Alzheimer’s “Type 3 diabetes” (that is, a third type of diabetes, one that affects the brain). Damage to blood vessels from hyperglycemia, resulting for example in retinopathy, is seen as an early indicator that sugar affects the brain.
Increased blood sugar levels were associated with higher risk of dementia in a 2013 study of about 2,000 adults across the country, average age 76, most of whom did not have diabetes. The study, published in the New England Journal of Medicine, established “for the first time, convincingly, that there is a link between dementia and elevated blood sugars in the non-diabetic range,” according to study author Dr. David Nathan, director of the Diabetes Center at Mass General Hospital; and that the higher the blood sugar, the higher the risk of dementia.
This research “offers more evidence that the brain is a target organ for damage by high blood sugar,” UCLA endocrinologist Medha Munshi, another study author, told the New York Times. “And everyone is still working on the ‘why’.”
Insulin, the hormone that controls blood sugar levels, also strengthens synaptic connections between brain cells, thereby enabling the formation of stronger memories. In a 2012 study at UCLA, rats that consumed large quantities of fructose developed insulin resistance that affected synaptic activity in the brain and impaired cognition. This study suggested that the effects of sugar on nerve cells’ ability to communicate “could have repercussions in how well we remember instructions, process ideas and handle our moods,” according to Fernando Gomez-Pinilla, PhD, who suggested that while insulin in the body controls blood sugar, it may play a different role in the brain.
And then there’s inflammation, which has been linked to progressive damage in the brain. Even mild elevations of blood sugar over time can increase the ability of blood sugars to bind with proteins, in turn increasing the production of inflammatory chemicals – although it’s still unclear whether inflammation can cause dementia.
Attaching sugars to the proteins in collagen and elastin can also spur aging effects on the skin. And excess sugar may also be implicated in bone health as it can inhibit calcium absorption and deplete phosphorus, which facilitates the absorption of calcium.
The FDA recommends that no more than 10 percent of one’s daily diet should come from sugar – about 12.5 teaspoons or 50 grams/day — including not just the fructose and glucose in white table sugar (sucrose), but coconut sugar, agave and corn syrup as well as fruit juice, honey and other sugary foods. Confusion arises, however, when quantities of “natural” and “added” sugars are combined, both in recommendations and in food ingredients labels (see examples from my kitchen in list below). The FDA has said it would like to change the labels to distinguish between the two. While some dieticians argue that our bodies don’t differentiate among kinds of sugars, others point out that added sugars represent “empty” calories devoid of nutrients, while foods like milk and fruit containing natural sugars are nutrient-dense, providing calcium, protein, vitamins and/or dietary fibers. The World Health Organization also recommends a 10 percent cap on sugars but excludes those in fresh fruits, vegetables and milk.
While much remains tentative and unclear about sugar risks and recommendations, everyone seems to recommend consuming less sugary food and drink. “Sugar detox” appears in the title of at least three books featured on Amazon. In a UCLA study showing actual improvement in mental function (see MyLittleBird story on reversing memory loss) for subjects who selected among 36 changes to make in their lives (including eliminating gluten, red meat, etc.), “eliminating simple carbohydrates” is listed as #1.
Coke (12-ounce can) – 39 grams of sugar
Tropicana Pure OJ (8 oz) – 22 grams
San Pellegrino grapefruit-flavored (11.15 ounce-can) 35 grams
Ocean Spray Cranberry (10 oz) – 35 grams
2% milk (1 cup) – 13 grams
Gingerale (Canada Dry) (10 ounces) – 29 grams
Raisin Bran (“365” Whole Foods brand) (1 cup) – 15 grams
Raisin Bran Crunch (Kellogg’s brand) (1 cup) – 19 grams
Lucky Charms (General Mills) (1/2 cup) – 10 grams
Frosted MiniWheats (Kellogg’s) (21 biscuits) – 11 grams