By Sophie Egan

Soy milk can raise the risk of breast cancer. Fat-free foods are healthier than high-fat foods. Vegans and vegetarians are deficient in protein. Some false ideas about nutrition seem to linger like a terrible song stuck in your head.

So, to set the record straight, we asked 10 of the top nutrition experts in the United States a simple question: What is one nutrition myth you wish would go away — and why? Here’s what they said.

Myth No. 1: Fresh fruits and vegetables are always healthier than canned, frozen or dried varieties

Despite the enduring belief that “fresh is best”, research has found that frozen, canned and dried fruits and vegetables can be just as nutritious as their fresh counterparts.

“They can also be a money saver and an easy way to make sure there are always fruits and vegetables available at home,” said Sara Bleich, outgoing director of nutrition security and health equity at the US Department of Agriculture and a professor of public health policy at the Harvard T.H. Chan School of Public Health. One caveat: Some canned, frozen and dried varieties contain sneaky ingredients such as added sugars, saturated fats and sodium, Bleich said, so be sure to read nutrition labels and opt for products that keep those ingredients to a minimum.

Myth No. 2: All fat is bad

When studies published in the late 1940s found correlations between high-fat diets and high levels of cholesterol, experts reasoned that if you reduced the amount of total fats in your diet, your risk for heart disease would go down. By the 1980s, doctors, federal health experts, the food industry and the news media were reporting that a low-fat diet could benefit everyone, even though there was no solid evidence that doing so would prevent issues such as heart disease or overweight and obesity.

Dr. Vijaya Surampudi, an assistant professor of medicine at the UCLA Centre for Human Nutrition, said that as a result, the vilification of fats led many people — and food manufacturers — to replace calories from fat with calories from refined carbohydrates such as white flour and added sugar. (Remember SnackWell’s?) “Instead of helping the country stay slim, the rates of overweight and obesity went up significantly,” she said.

In reality, Surampudi added, not all fats are bad. Although certain types of fats, including saturated and trans fats, can increase your risk for conditions such as heart disease and stroke, healthy fats — such as monounsaturated fats (found in olive and other plant oils, avocados, and certain nuts and seeds) and polyunsaturated fats (found in sunflower and other plant oils, walnuts, fish and flaxseeds) — actually help reduce your risk. Good fats are also important for supplying energy, producing important hormones, supporting cell function and aiding in the absorption of some nutrients.

If you see a product labelled ‘fat-free’, don’t automatically assume it is healthy, Surampudi said. Instead, prioritize products with simple ingredients and no added sugars.

Myth No. 3: ‘Calories in, calories out’ is the most important factor for long-term weight gain

It’s true that if you consume more calories than you burn, you will probably gain weight. And if you burn more calories than you consume, you will probably lose weight — at least for the short term.

But the research does not suggest that eating more will cause sustained weight gain that results in becoming overweight or obese. “Rather, it’s the types of foods we eat that may be the long-term drivers” of those conditions, said Dr. Dariush Mozaffarian, a professor of nutrition and medicine at the Friedman School of Nutrition Science and Policy at Tufts University. Ultraprocessed foods — such as refined starchy snacks, cereals, crackers, energy bars, baked goods, sodas and sweets — can be particularly harmful for weight gain, as they are rapidly digested and flood the bloodstream with glucose, fructose and amino acids, which are converted to fat by the liver. Instead, what’s needed for maintaining a healthy weight is a shift from counting calories to prioritizing healthy eating overall — quality over quantity.

Myth No. 4: People with Type 2 diabetes shouldn’t eat fruit

This myth stems from conflating fruit juices — which can raise blood sugar levels because of their high sugar and low fibre content — with whole fruits.

But research has found that this isn’t the case. Some studies show, for instance, that those who consume one serving of whole fruit per day — particularly blueberries, grapes and apples — have a lower risk of developing Type 2 diabetes. And other research suggests that if you already have Type 2 diabetes, eating whole fruits can help control your blood sugar.

It’s time to bust this myth, said Dr. Linda Shiue, an internist and the director of culinary medicine and lifestyle medicine at Kaiser Permanente San Francisco, adding that everyone — including those with Type 2 diabetes — can benefit from the health-promoting nutrients in fruit such as fibre, vitamins, minerals and antioxidants.

Myth No. 5: Plant milk is healthier than dairy milk

There’s a perception that plant-based milks, such as those made from oats, almonds, rice and hemp, are more nutritious than cow’s milk. “It’s just not true,” said Kathleen Merrigan, a professor of sustainable food systems at Arizona State University and a former US deputy secretary of agriculture. Consider protein: Typically, cow’s milk has about 8 grams of protein per cup, whereas almond milk typically has around 1 or 2 grams per cup, and oat milk usually has around 2 or 3 grams per cup. While the nutrition of plant-based beverages can vary, Merrigan said, many have more added ingredients — such as sodium and added sugars, which can contribute to poor health — than cow’s milk.

Myth No. 6: White potatoes are bad for you

Potatoes have often been vilified in the nutrition community because of their high glycemic index — which means they contain rapidly digestible carbohydrates that can spike your blood sugar. However, potatoes can actually be beneficial for health, said Daphene Altema-Johnson, a program officer of food communities and public health at the Johns Hopkins centre for a Livable Future. They are rich in vitamin C, potassium, fibre and other nutrients, especially when consumed with the skin. They are also inexpensive and found year-round in grocery stores, making them more accessible. Healthier preparation methods include roasting, baking, boiling and air frying.

Myth No. 7: You should never feed peanut products to your children within their first few years of life

For years, experts told new parents that the best way to prevent their children from developing food allergies was to avoid feeding them common allergenic foods, such as peanuts or eggs, during their first few years of life. But now, allergy experts say, it’s better to introduce peanut products to your child early on.

If your baby does not have severe eczema or a known food allergy, you can start introducing peanut products (such as watered-down peanut butter, peanut puffs or peanut powders, but not whole peanuts) at around 4 to 6 months, when your baby is ready for solids. Start with 2 teaspoons of smooth peanut butter mixed with water, breast milk or formula, two to three times a week, said Dr. Ruchi Gupta, a professor of paediatrics and the director of the centre for Food Allergy & Asthma Research at the Northwestern Feinberg School of Medicine. If your baby has severe eczema, first ask your paediatrician or an allergist about starting peanut products at about 4 months. “It is also important to feed your baby a diverse diet in their first year of life to prevent food allergies,” Gupta said.

Myth No. 8: The protein in plants is incomplete

“‘Where do you get your protein?’ is the No. 1 question vegetarians get asked,” said Christopher Gardner, a nutrition scientist and professor of medicine at Stanford University. “The myth is that plants are completely missing some amino acids,” also known as the building blocks of proteins, he said. But in reality, all plant-based foods contain all 20 amino acids, including all nine essential amino acids, Gardner said; the difference is that the proportion of these amino acids isn’t as ideal as the proportion of amino acids in animal-based foods. So, to get an adequate mix, you simply need to eat a variety of plant-based foods throughout the day — such as beans, grains and nuts — and eat enough total protein. Luckily, most Americans get more than enough protein each day. “It’s easier than most people think,” Gardner said.

Myth No. 9: Eating soy-based foods can increase the risk of breast cancer

High doses of plant oestrogens in soy called isoflavones have been found to stimulate breast tumour cell growth in animal studies. “However, this relationship has not been substantiated in human studies,” said Dr. Frank Hu, a professor and the chair of the department of nutrition at the Harvard T.H. Chan School of Public Health. So far, the science does not indicate a link between soy intake and breast-cancer risk in humans. Instead, consuming soy-based foods and drinks — such as tofu, tempeh, edamame, miso and soy milk — may even have a protective effect toward breast-cancer risk and survival. “Soy foods are also a powerhouse of beneficial nutrients related to reduced heart disease risk, such as high-quality protein, fibre, vitamins and minerals,” Hu said. The research is clear: Feel confident incorporating soy foods into your diet.

Myth No. 10: Fundamental nutrition advice keeps changing — a lot

This is not the case, said Dr. Marion Nestle, a professor emerita of nutrition, food studies and public health at New York University. “In the 1950s, the first dietary recommendations for prevention of obesity, Type 2 diabetes, heart disease and the like advised balancing calories and minimizing foods high in saturated fat, salt and sugar. The current US Dietary Guidelines urge the same.” Yes, science evolves, but the bottom-line dietary guidance remains consistent. As author Michael Pollan distilled to seven simple words: “Eat food. Not too much. Mostly plants.” That advice worked 70 years ago, and it still does today, Nestle said. And it leaves plenty of room for eating foods you love.

-New York Times