There are many mixed opinions in nutrition science.
Dozens of studies are published every week, but most of them are of a low quality. 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. Keep in mind, common sense and personal experience both play a major role when formulating a nutritious diet.
Here are 10 nutrition facts that are supported by strong evidence.
1. Low-Carb Diets Promote Weight Loss
Low-carb diets are undeniably effective for losing weight. 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 are satiating. High carb diets keep you hungry due to spikes in blood sugar followed by inevitable low blood sugar and carb cravings.
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. The claim that eating saturated fat causes heart disease is not supported by the best available evidence to date. Remember, however, that the fat you consume must be of the highest quality.
3. 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 sugar calories consumed in liquid form don’t have the same appetite- suppressing effect as solid calories do. This leads to excess sugar calories consumed throughout the day, which are then stored as fat.
4. 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.
Keep in mind that not all olive oil is created equal. Choose a high quality, cold pressed, pure, extra virgin olive oil.
5. 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. For best results and health benefits, the carbs you do eat should come from vegetables and fruit, not processed grains.
6. 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. As with all food, it is the quality that matters most. Choose only the highest quality protein.
7. Nuts Are Healthy and Weight Loss Friendly
Nuts are delicious and provide many health benefits. Several observational studies have shown a link between high nut consumption and a reduced risk of heart disease. One study found that people who consumed nuts more than 4 times per week had a 37% lower risk of heart disease than people who ate nuts less often. Almonds, pistachios, walnuts and Brazil nuts have been found to lower markers of inflammation, improve cholesterol levels and improve the function of the cells that line your arteries.
Also, despite their relatively high calorie content, many studies have found that nuts tend to prevent weight gain and in some cases promote weight loss. Since nuts contain anti-nutrients such as phytic acid and enzyme inhibitors, it is best to consume only sprouted nuts.
8. Vegetables and Fruits Are Healthy
Eating vegetables and fruits on a regular basis is considered a very healthy practice.Large studies from around the globe have found a significantly decreased risk of many chronic diseases in people who eat the most fruits and vegetables. Researchers who analyzed data from over 65,000 people found that those who ate at least seven servings of fruit or vegetables per day had a 42% lower risk of early death than those who ate less than one serving daily.
Certain vegetables and fruits may be especially protective against cancer. These include blueberries, vegetables high in beta-carotene such as spinach and carrots, and cruciferous vegetables such as broccoli and cauliflower. Controlled studies in both healthy people and those with diabetes have found that increasing fruit and vegetable consumption boosts antioxidant levels in the blood and improves heart disease risk factors. Keep in mind that high sugar fruit may not be the best options for those with diabetes or cancer since sugar drives both diseases.
9. Omega-3 Fatty Acids Lower Triglycerides
Eating enough omega-3 fatty acids is very important. They are good for the brain and have been shown to improve several risk factors, including blood triglycerides. In fact, dozens of studies have shown that omega-3 fats significantly reduce blood triglyceride levels. In one systematic review of 18 studies of more than 800 diabetics, taking 3-18 grams per day of fish oil led to a significant decrease in triglycerides. Additionally, some studies have found that supplementing with these omega-3 fats may also reduce inflammation, increase HDL cholesterol and improve function of the arteries. Make sure to buy high quality Omega 3 supplements since these oils are very fragile and can oxidize and turn rancid when exposed to heat, light or oxygen.
10. Dietary Cholesterol and Whole Eggs Aren’t Bad For You
For several decades, dietary cholesterol was believed to raise blood cholesterol and increase the risk of heart disease. However, studies show that when you eat more cholesterol, your body produces less. The result is that your blood cholesterol levels remain stable or only increase slightly. Studies have shown that consuming 1–3 eggs per day doesn’t raise LDL cholesterol levels or increase heart disease risk factors in most people. In fact, eating eggs has been shown to improve some risk factors for heart disease, including raising HDL levels and promoting beneficial changes in the size and shape of LDL cholesterol.
A small number of people, who are considered “hyper-responders” to cholesterol, have been found to experience a large increase in blood cholesterol levels in response to a high dietary cholesterol intake. However, for most people, regularly eating eggs has been shown to be very healthy. Importantly, you should eat the whole egg, including the yolk. That’s where almost all the nutrients are found, and of course the eggs should come from pastured hens.
Since we now have excellent controlled studies to back these nutritional facts many people feel more comfortable eating these healthful foods. Always use common sense and select the highest quality foods available to you. When in doubt, consult a nutritionist.