For decades, advice to ward off heart disease has promoted a diet low in saturated fat and cholesterol as a means of keeping blood cholesterol levels in check.
A study published today in the Journal of the American Medical Association suggests there's something else we need to do – scale back our intake of added sugars.
Folks with the highest – versus the lowest – intake of refined sugar had higher blood triglycerides (fat) and triple the risk of having a low level of HDL (good) cholesterol.
While it's long been know that carbohydrates can boost heart-disease risk by altering blood lipid levels, this is the first study to investigate the link between added sugars and blood lipids.
Added sugars are defined as those put in during food processing and preparation to enhance flavour, add texture and assist browning. On ingredient lists they go by many names, including corn syrup, dextrose, high-fructose corn syrup, fruit juice concentrate, glucose-fructose, honey and sucrose to name just a few.
In today's study, researchers from Emory University, Atlanta examined sugar intake and blood lipid levels in 6,113 men and women aged 18 and older. Participants were grouped by their intake of added sugar, with the lowest group consuming up to 5 per cent of daily calories and the highest 25 per cent or more of daily calories.
As sugar consumption climbed, levels of HDL cholesterol fell. Compared with low sugar consumers (5 per cent of daily calories or less), those whose diets contained the most were three times more likely to have a low level of HDL cholesterol.
Cholesterol needs to be piggy-backed on carriers called lipoproteins in order to circulate in the bloodstream. In the case of HDL cholesterol, it's transported on particles called high-density lipoproteins. HDL cholesterol is called "good cholesterol" because it picks up excess cholesterol in the body and disposes of it through the liver.
Having a low HDL cholesterol level is associated with a greater risk of heart disease. Risk is increased if HDL cholesterol is less than 1 millimole per litre (mmol/L) in men and less than 1.3 mmol/L in women. (Women generally have higher levels than men because estrogen increases HDL cholesterol.)
LDL cholesterol, on the other hand, moves through the bloodstream on low-density lipoproteins. It's referred to as "bad cholesterol" because it sticks to artery walls, causing a build-up of fatty plaques. Over time, this causes thickening and narrowing of the arteries. The study found no relationship between sugar intake and LDL cholesterol.
It did, however, reveal higher blood triglyceride levels among those who consumed the most sugar. Triglycerides are made in the liver from the foods you eat. A blood triglyceride level higher than 1.7 mmol/L is considered elevated and usually means you eat more calories than you burn or you drink too much alcohol.
It's not completely understood how excess sugar wreaks havoc on blood lipids. Studies suggest fructose, found in large quantities in nearly all added sugars, has something to do with it. Fructose has been shown to increase the liver's production and release of triglycerides and to impair the body's ability to clear fat from the bloodstream.
It's estimated that the average Canadian consumes about 16 teaspoons of added sugar per day, about 13 per cent of our daily calories. According to the American Heart Association, that's too much.
In August last year, the association released a statement encouraging Americans, who swallow 22 teaspoons of sugar each day, to limit added sugars more than any previously issued guidelines. (The U.S.-based Institute of Medicine suggests a sugar limit of 25 per cent of energy while the World Health Organization recommends we limit added sugars to 10 per cent of daily calories.) The AHA advised adults to cut added sugars to 5 per cent of daily calories – roughly five teaspoons (80 calories worth) for women and nine teaspoons (144 calories) for men.
The Heart and Stroke Foundation of Canada doesn't give a specific guideline for added sugar intake. Nor does Health Canada, advocating moderation instead.
There are reasons beyond heart health to reduce sugar intake. Excessive sugar intake, especially from sweetened beverages, has been linked with higher calorie intake, higher body weight, and lower intake of vitamins and minerals.
The biggest culprits for added sugars are soft drinks and sweets. But added sugar also lurks in a surprising number of everyday foods such as breakfast cereals, salad dressings, frozen dinners, pasta sauces, soy milk, even peanut butter and bread.
To sleuth out hidden sugars, read nutrition labels. The Nutrition Facts box discloses the grams of sugars contained in one serving of the food (4 grams of sugar is equivalent to one teaspoon). Keep in mind, however, that these sugar numbers don't differentiate between added sugars and naturally occurring sugars (such as fruit or milk sugars).
To find added sugars, you need to read the ingredient list too. You might be surprised to see how many different types of refined sugars are added to one product.
The following tips will help you curb your intake of added sugars:
– Limit sugary drinks. Replace soft drinks, fruit punch, iced tea and Vitaminwater with water, low-fat milk, vegetable juice or tea.
– Satisfy your sweet tooth naturally. Choose fruit, yogurt or homemade smoothies over candy, cakes, cookies and pastries.
– Choose breakfast cereals that have no more than 6 to 8 grams of sugar per serving. Exceptions include cereals with dried fruit.
– When buying packaged baked good or cereal bars, choose products with no more than half the total carbohydrate from sugars.
– Sweeten foods with spices instead of sugar. Add cinnamon to hot cereal, a dash of vanilla to lattes, and grated fresh ginger to fruit and vegetables.
– Reduce sugar in recipes. As a rule, you can cut the sugar in most baked goods by one-third.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.