The sweet danger of sugar, Harvard Health publishing
In the American diet, the top sources of added sugar are soft drinks, fruit drinks, flavored yogurts, cereals, cookies, cakes, candy, and most processed foods. But added sugar is also present in items that you may not think of as sweetened, like soups, bread, cured meats, and ketchup.
The result: we consume way too much added sugar. Adult men take in an average of 24 teaspoons of added sugar per day, according to the National Cancer Institute. That's equal to 384 calories.
"Excess sugar's impact on obesity and diabetes is well documented, but one area that may surprise many men is how their taste for sugar can have a serious impact on their heart health," says Dr. Frank Hu, professor of nutrition at the Harvard T.H. Chan School of Public Health.
In a study published in 2014 in JAMA Internal Medicine, Dr. Hu and his colleagues found an association between a high-sugar diet and a greater risk of dying from heart disease. Over the course of the 15-year study, people who got 17% to 21% of their calories from added sugar had a 38% higher risk of dying from cardiovascular disease compared with those who consumed 8% of their calories as added sugar.
"Basically, the higher the intake of added sugar, the higher the risk for heart disease," says Dr. Hu.
How sugar actually affects heart health is not completely understood, but it appears to have several indirect connections. For instance, high amounts of sugar overload the liver. "Your liver metabolizes sugar the same way as alcohol, and converts dietary carbohydrates to fat," says Dr. Hu. Over time, this can lead to a greater accumulation of fat, which may turn into fatty liver disease, a contributor to diabetes, which raises your risk for heart disease.
Consuming too much added sugar can raise blood pressure and increase chronic inflammation, both of which are pathological pathways to heart disease. Excess consumption of sugar, especially in sugary beverages, also contributes to weight gain by tricking your body into turning off its appetite-control system because liquid calories are not as satisfying as calories from solid foods. This is why it is easier for people to add more calories to their regular diet when consuming sugary beverages.
"The effects of added sugar intake — higher blood pressure, inflammation, weight gain, diabetes, and fatty liver disease — are all linked to an increased risk for heart attack and stroke," says Dr. Hu.
Sugars and health, Cambridge University Press
There is a longitudinal study using data from a subgroup of the large American survey National Health and Nutrition Examination Survey. This study reported that risk of cardiovascular disease (CVD) increased with increasing added sugars intake and the risk was significant at levels of added sugar intake above 15 % of total energy. There were very few participants with added sugars intake of less than 5 % of total energy. Due to the lack of systematic reviews on risk of CVD it is necessary to look at systematic reviews of added sugars intake and markers of CVD such as body fatness. A review of randomized controlled trials assessing differences in body fatness between diets high and low in added sugars found that diets high in sugars increased body fatness although few of the trials included were more than 8 weeks in duration. The difference in levels of added sugars varied between studies but the pooled estimate indicated that the difference in body fatness was 0·75 (95 % CI 0·30, 1·19) kg. The mechanism for this increase in weight gain is most likely due to increased energy intake with a diet higher in free sugars. In the Carbohydrates and Cardio-metabolic Health report by the Scientific Advisory Committee on Nutrition a review of similar trials and energy intake reported that energy intake was 1275 (95 % CI 889, 1660) kJ higher on the diet higher in free sugars. A review of trials that replaced free sugars with other types of carbohydrate and therefore did not change the energy content of the diet reported no differences in body weight between the groups. More research is needed to determine the mechanisms and how the metabolic impacts of specific sugars increase risk of obesity and 2DM.
One of the largest sources of free sugars is sugar sweetened beverages (SSB). SSB are the largest contributor of free sugars in children and adolescents in the UK and the second largest contributor in adults ranging from a contribution of 25 % of NMES in adults to 40 % in adolescents. Mean daily intakes of NMES from SSB are therefore about 20 g/person, which does not include sugars from fruit juices. Intakes are larger in the USA and higher in lower income families. There are health concerns that high intakes of sugars from SSB increase risk of weight gain and 2DM.
A number of systematic reviews of the effect of SSB on weight and BMI have been published. The most recent of these is the review by Malik, which included ten trials (the strongest study design to determine causality) published up to 2013. For adults they included six results from five trials measuring the effect on weight of adding SSB to the diet. Although the trials varied in length and intakes of SSB, all the trials reported higher weight with higher intakes of SSB. The pooled estimate indicated that weight was increased by 0·85 (95 % CI 0·5, 1·2) kg with higher SSB consumption. The results for children were not as clear cut. Although all five trials indicated that a lower SSB intake reduced weight the pooled estimate was not statistically significant for children. The differences in findings could be due to the differences in the trial methods used for children. All five trials in children measured the effect on weight of reducing SSB in the diet unlike the trials in adults which measured the effect on weight of adding SSB to the diet. This is an important difference, which may be due to ethical constraints in studies involving children and young people. Many of the other systematic reviews that have been published also report that high intakes of SSB increase weight but they had mixed results as to whether these increases were statistically significant or not. They all included a large number of cohorts and cross-sectional studies and very few trials and are therefore more prone to bias.
Evidence on risk of 2DM with higher intakes of sweetened drinks from trials is scarce and therefore the evidence provided here is based on longitudinal cohorts. A systematic review of cohorts (of at least 3 years in duration) that was included in the Department of Health review of carbohydrates and cardio-metabolic health reported a 20 % increase in risk of 2DM with each portion (330 ml) sweetened drink. Imamura et al. reported similar results of an 18 % increase in risk with one portion of sweetened drink and took this a step further and reported the population attributable fraction for 2DM from SS. The population attributable fraction was higher in the USA but in the UK, they estimated that 79 000 new cases of type 2 diabetes in the UK over the next 10 years will be attributable to SSB consumption equivalent to a population attributable fraction of 4 (95 % CI, 2, 6) %.
The connection between sugar and disease, CNN health
Evidence of a link between free sugar and cancer has been limited and controversial, and needs more research, the study’s authors said. But the finding, according to the study, could be explained by the known effects of sugar on weight: High sugar consumption has been associated with obesity, which is a strong risk factor for various cancers. The same goes for cardiovascular disease.
“Added sugar intake can promote inflammation in the body, and this can cause stress on the heart and blood vessels, which can lead to increased blood pressure,” behavioral scientist Brooke Aggarwal told CNN in February. Aggarwal, an assistant professor of medical sciences in the cardiology division at Columbia University Irving Medical Center, wasn’t involved in the study.
Highly processed foods, which can have lots of free sugar, have been found to increase inflammation, a risk factor for depression.
“Whole food carbohydrates take longer to break down into simple sugars, and a part of them — the fiber — can’t be broken down at all,” Adam told CNN in February. “This means that whole, intact grains don’t cause the same spikes in blood sugar that we experience when we eat simple sugars. Blood sugar spikes trigger insulin spikes, which can destabilize our blood glucose and … be the underlying cause of health problems in the long run.”
Yes, too much sugar is bad for our health, The University of Sydney
Most of the concern about excess sugar consumption has been focused on weight gain, and rightly so. Our livers can turn sugar into fat. Too much sugar – and too much soft drink, in particular – can cause fat to be deposited on our waist. This is known as visceral fat.
Visceral fat is especially harmful because it increases the risk of heart disease and type 2 diabetes, even when blood sugar levels are higher than normal.
But what does the science say about sugar and the raft of other conditions we see in the headlines every other week? Let’s look at two examples: dementia and cancer.
Dementia
Dementia is an umbrella term for brain disorders that cause memory loss, confusion and personality change. It’s the greatest cause of disability among older Australians and the third-biggest killer. Alzheimer’s disease is one type of dementia.
The research does not show that sugar causes dementia. But there is emerging research that suggests high-sugar diets may increase the risk of developing the disease. What we can say is that there is a link between high-sugar diets and dementia, but we don’t have evidence to show that one causes the other.
A 2016 New Zealand study of post mortems on human brains assessed seven different regions of the brain. The researchers found that the areas of greatest damage had significantly elevated levels of glucose (sugar). Healthy cells don’t usually have elevated levels of glucose.
This was also found in a separate analysis of post-mortem brain and blood samples from Baltimore in 2017. Using blood samples collected from the patients over a 19-year period before they died, the brain glucose concentration at death was found to be highest in those with Alzheimer’s disease. What’s more, this glucose level had been slowly increasing for years.
The levels of blood glucose were not indicative of diabetes. So otherwise healthy people could have rising levels of glucose in the brain well before any obvious signs of disease prompt any action.
Together, these studies tell us that the brains of people with Alzheimer’s disease struggle to metabolize sugar for energy. The changes in the brain seem to be linked to persistent increases in blood glucose over a long period of time. And the damage to brain cells is occurring well before overt symptoms of Alzheimer’s appear.
We don’t know if simply consuming high amounts of sugar results in the build-up of glucose in the brain. But other research also supports this theory.
A recent analysis of more than 3,000 people found that those who drink sugary beverages were more likely to have smaller brains and perform worse on a series of memory tests.
The researchers calculated that consuming one to two or more sugary drinks per day could be equivalent to up to 13 years of additional brain ageing. And a separate analysis of soft drink versus fruit juice reported similar affects.
Cancer
Cancer is a condition in which the cells in the body mutate and rapidly multiply. It’s Australia’s second biggest killer and will affect half of Australians if they live to 85.
There is no evidence that sugar causes cancer, but there are at least two ways in which they are linked.
First, if you are overweight or obese, you have an increased risk of developing 11 different types of cancer. Consuming too much sugar (and too many kilojoules overall) leads to weight gain, which increases the risk of cancer.
A second, more direct pathway linking sugar to cancer is the capacity for sugar to stimulate insulin secretion. This is a potent hormone signal for cell growth. Cancer cells also rely on sugar for energy to fuel their continual growth.
This suggests that independent of any change in your weight, consuming too much sugar may increase your risk of developing cancer.
But we need to be cautious about the quality of data available directly linking cancer to sugar consumption.
A recent study of 35,000 people, for instance, reported a link between higher obesity-related cancer risks and heavy consumption of soft drink. But the authors point out that it was impossible to specifically separate drinking soft drinks from other unhealthy behaviors, such as smoking or lower levels of physical activity.
12 Ways Too Much Sugar Harms Your Body, WebMD
Weight Gain
Sugar-sweetened beverages are a big source of added sugars for Americans. If you drink a can of soda every day and don’t trim calories elsewhere, in three years you’d be 15 pounds heavier. Putting on too much weight can lead to problems like diabetes and some cancers.
Heart Disease
One in 10 Americans gets 1/4 or more of their daily calories from added sugar. If you eat that much, one study found that you’re more than twice as likely to die from heart disease than someone who gets less than half as much. It’s not clear why. It could be that the extra sugar raises your blood pressure or releases more fats into the bloodstream. Both can lead to heart attack, stroke, and other heart diseases.
Diabetes
Sugary drinks in particular can boost your odds for type 2 diabetes. That can happen because when sugar stays in your blood, your body may react by making less of the hormone insulin, which converts the food you eat into energy. Or the insulin doesn’t work as well. If you’re overweight, dropping even 10-15 pounds can help you manage your blood sugar.
High Blood Pressure
Usually, salt gets the blame for this condition, also called hypertension. But some researchers say another white crystal -- sugar -- may be a more worrisome culprit. One way they believe sugar raises blood pressure is by making your insulin levels spike too high. That can make your blood vessels less flexible and cause your kidneys to hold onto water and sodium.
High Cholesterol
Sugary diets are bad for your heart, regardless of how much you weigh. They can:
- Raise your so-called "bad" (LDL) cholesterol and lower the "good" (HDL) kind.
- Hike blood fats called triglycerides and hinder the work of an enzyme that breaks them down.
Liver Disease
Most packaged foods, snacks, and drinks are sweetened with fructose, a simple sugar from fruits or veggies like corn. Your liver turns it into fat. If you regularly pump fructose into your body, tiny drops of fat build up in your liver. This is called non-alcoholic fatty liver disease. Early diet changes can reverse it. But over time, swelling and scarring can damage your liver.
Cavities
You know sugar rots your teeth. How? It feeds the bacteria in your mouth, which leave behind acid that wears away your tooth enamel. Sugary drinks, dried fruits, candy, and chocolate are common offenders. Sour candies are among the worst. They’re almost as acidic as battery acid! If you eat tart treats, rinse your mouth with water afterward or drink some milk to neutralize the acid.
Poor Sleep
Too much sugar during the day can mess with your blood glucose levels and cause energy spikes and crashes. You may struggle to stay awake at work or doze off in class at school. In the evenings, a bowl of ice cream or cookies can pump you with sugar that can wake you up at night. It also can cut short the time you’re in deep sleep. So, you may not wake up feeling refreshed.
ADHD
It’s a common perception that sugar worsens the symptoms of attention deficit hyperactivity disorder. But the link is unproven. More studies knock down the theory that sugar causes or worsens ADHD than support it. We don’t know exactly what leads to ADHD, but your genes probably play a large role.
Mood Problems
Feeling down? Your sweet tooth may be part of the problem. Several studies have linked sugar and mental health problems. One of the latest showed that men who ate more than 66 grams of sugar a day -- almost double what’s recommended -- were 23% more likely to be diagnosed with anxiety or depression than men who ate 40 grams or less. Too much sugar could fuel depression through swelling, or inflammation, in your brain, which is more common in people with depression.
Gout
You may know that you can get this painful arthritis from eating too much red meat, organ meats, and lobster. The same goes for fructose. It can make uric acid build up in your blood, which in turn forms hard crystals in your big toe, knees, and other joints.
Kidney Stones
You get these when chemicals in your pee turn into solid crystals. Your body flushes out some kidney stones without much pain. Others can get stuck in your kidney or another part of your plumbing and block urine flow. Too much fructose -- from table sugar, high-fructose corn syrup, or processed foods -- raises your chances for kidney stones.
Aging
Sugary drinks may add years to your biological age. DNA called telomeres cap the end of your chromosomes to protect them from damage. Longer is better. Shortened telomeres may go hand in hand with age-related diseases like diabetes. One study found that people who drink 20 ounces of soda a day have shorter telomeres. Researchers figure that’s like adding more than 4 years to the age of your cells.