- There are many mixed opinions in nutrition science.
- Dozens of studies are published every week, but most of them are of a low quality.
- The studies most commonly promoted by the media are test-tube studies, animal studies or observational studies.
- These studies have limited value on their own, and their results often completely contradict each other.
- This has caused a lot of confusion about what constitutes evidence-based nutrition.
- However, there are a few facts in nutrition that are truly backed by strong evidence.
- These are supported by systematic reviews, meta-analyses or randomized controlled trials — the best types of studies we have.
Here are 7 nutrition facts that are supported by strong evidence.
1. Low-Carb Diets Promote Weight Loss
Low-carb diets are undeniably effective for losing weight, although the mechanism behind it is hotly debated.
They have been shown to produce results equal to or better than low-fat diets in studies lasting anywhere from 6 weeks to 2 years.
In fact, a detailed analysis of 17 randomized controlled studies found that overall, low-carb diets led to greater weight loss and reduction in heart disease risk factors, when compared to low-fat diets.
Low-carb diets appear to be particularly beneficial for people with metabolic syndrome, who carry excess weight around the middle and are at an increased risk of diabetes.
In a 12-week study of men with metabolic syndrome, the low-carb group lost nearly twice as much weight as the low-fat group. They also had a 20% average decrease in abdominal fat, compared to 12% in the low-fat group.
In many studies, the low-carb groups were allowed to eat unlimited protein and fat. One of the reasons low-carb diets work so well is that they tend to reduce appetite. This results in a spontaneous decrease in calorie intake.
2. Saturated Fat Doesn’t Cause Heart Disease
For several decades, it was believed that eating saturated fat raised the risk of heart disease.
The theory was that saturated fat raised blood cholesterol levels and led to blocked arteries, which caused heart attacks.
In response to warnings from health organizations, many people replaced whole-milk dairy products with low-fat and fat-free versions. They also exchanged natural fats like butter for margarine made from vegetable oil.
However, in recent years, several systematic reviews and meta-analyses have found no connection between saturated fat intake and heart disease.
A 2014 review of 76 observational and randomized controlled studies with more than 650,000 participants found that those with a high saturated fat intake did not have an increased risk of heart disease.
On the other hand, some data suggests that replacing a portion of your saturated fats with unsaturated fats may slightly decrease your risk of heart problems.
However, the claim that eating saturated fat causes heart disease is not supported by the best available evidence to date.
3. Coffee and Green Tea Are Healthy Beverages
Coffee and green tea are two of the most popular beverages in the world.
A lot of evidence suggests they are also among the healthiest.
They contain caffeine, which several studies have shown increases alertness, mood, metabolic rate and exercise performance.
One analysis of 41 studies found that the most effective dosage to maximize caffeine’s benefits without causing side effects was 38–400 mg per day. This equals roughly 0.3 to 4 cups of coffee daily, depending on the strength.
Research has also shown a decreased risk of type 2 diabetes among coffee drinkers, particularly those who drink several cups per day on a daily basis.
In one large review of 18 studies with over 450,000 people, there was a 9% reduction in type 2 diabetes risk for each cup of regular coffee consumed per day. The reduction for decaffeinated coffee was 6% for each cup consumed daily.
In addition, coffee has been shown to protect against liver cancer and cirrhosis, a condition of liver inflammation and scarring that may occur in alcoholics or those with hepatitis.
Green tea contains antioxidants known as catechins, which help reduce inflammation, a driver of the aging process and many diseases.
Moreover, green tea is a rich source of epigallocatechin gallate (EGCG). This antioxidant has been shown to help reduce belly fat in several studies.
4. Sugary Drinks Are Fattening
Sugar is more than just empty calories. In excess, it can lead to health problems and weight gain, especially when consumed in liquid form.
Sugar (sucrose) contains 50% glucose and 50% fructose, while high-fructose corn syrup contains 45% glucose and 55% fructose. Fructose has been linked to obesity and several chronic diseases, such as type 2 diabetes and heart disease.
In observational and controlled studies, sugar-sweetened beverages have shown a strong relationship to weight gain, including abdominal or visceral fat surrounding the liver and other organs.
One study in children found that for each serving of soda or other sugar-sweetened beverage consumed per day, the risk of obesity increased by 60%.
In a controlled 10-week study, overweight people consuming 25% of calories in the form of fructose-sweetened beverages experienced a 14% gain in visceral fat.
Research suggests that calories consumed in liquid form don’t have the same appetite-suppressing effect as solid calories do. This leads to excess calories consumed throughout the day, which are then stored as fat.
5. Extra Virgin Olive Oil Is Good for You
Evidence supporting the benefits of extra virgin olive oil continues to mount.
Extra virgin olive oil contains oleic acid, a type of monounsaturated fat that has been shown to lower triglycerides, raise levels of HDL (the good cholesterol) and increase the fullness-promoting gut hormone GLP-1.
In a large analysis of 32 studies looking at different types of fat, oleic acid from olive oil was the only fatty acid linked to reduced risk of heart disease.
Extra virgin olive oil also contains antioxidants called polyphenols. These can fight inflammation, lower LDL cholesterol and protect it from damage, improve the function of the cells lining your arteries and reduce blood pressure.
Researchers who analyzed data from 5,800 people at an increased risk of heart disease found that the group treated with olive oil experienced a significant decrease in blood sugar levels and abdominal fat.
6. Cutting Carbs Improves Diabetes Management
Of the three macronutrients, carbs have by far the greatest impact on blood sugar. This is because they are broken down to sugar in the body.
Studies show low-carb diets lead to better blood sugar control in people with both type 1 and type 2 diabetes.
In a study of 21 people with type 2 diabetes who followed a diet containing 20 grams of carbs or less per day, 81% of subjects were able to eliminate or significantly reduce insulin or diabetes medication after 16 weeks.
Although very low-carb diets have been proven extremely effective at lowering blood sugar, several studies have shown that a more modest carb reduction can also produce excellent results.
In one study, men with type 2 diabetes who consumed a high-fiber diet with 100 grams of digestible carbs per day for 5 weeks had a nearly 30% reduction in fasting blood sugar, on average.
7. A High Protein Intake Is Beneficial for Weight Loss
Controlled studies have shown that eating a high-protein diet is one of the best ways to achieve and maintain a healthy weight.
A high protein intake decreases levels of the “hunger hormone” ghrelin and increases the release of fullness hormones PYY and GLP-1. This leads to a natural reduction in your calorie intake .
In one controlled study, people who ate a diet containing 30% of their calories from protein ended up consuming 441 fewer calories per day without consciously restricting their intake.
Furthermore, protein has a higher thermic effect than carbs or fats, meaning it raises your metabolic rate more for several hours after a meal.