Soy contains an estrogen-like compound that weakly mimics human estrogen, which makes some men concerned that eating soy will cause enlarged breasts. Photo / 123rf

One of my favourite parts of being a dietitian is teaching group nutrition classes, whether at workplaces, hospital wellness clinics or community centres. I enjoy answering common food and health questions, and I often surprise people with facts that run counter to their long-held beliefs. Some nutrition questions are asked so frequently that I thought it would be helpful to share them and the answers here.

1. Is vegetarian (or keto, or . . . ) the best way to eat?

In any given class, the subject may be "keto" or "the Mediterranean diet" or "vegetarian," and the answer is always the same: There's not one best way to eat. We are all different, and it would be impossible to choose one plan that would be right for everyone. The best plan for you is the one that meets your medical and nutritional needs while also being affordable, accessible, enjoyable and something you can stick with for the long term. Sometimes that may not be clear, but seeing a dietitian can help you figure it out.

2. Is sugar (or salt, or fat) the biggest problem in our diets?

No single nutrient or ingredient is the cause of poor diets. We live in an environment where highly palatable and cheap food is available everywhere. Pizza, chips, pastries and soda are dietary staples, and the average American gets almost 60 per cent of their daily calories from such ultra-processed foods. What's most problematic is eating too much of those ultra-processed foods and not enough whole foods (such as vegetables, fish and nuts) over a long period of time.

3. Do microwaves cause cancer?

Many have asked about the safety of using these appliances to warm up last night's lasagna. They worry when they hear the word "radiation." Although radiation may be linked to damaged cells and an increased cancer risk when it's high frequency and there's prolonged exposure (think gamma rays and some ultraviolet radiation), microwaves use low-frequency radiation for short periods. Microwaves operate only when the oven is on and the door is shut - so they are not constantly emitting radiation. Well-functioning microwaves are deemed safe by the World Health Organization and the World Cancer Research Fund, as long as the door closes properly and the microwave has no dents or leaks.

4. Do I need to drink eight glasses of water daily?

Drinking water is vital because we lose fluid every day through sweating, urinating and breathing. But how can it be possible that each one of us - regardless of age, gender, size, activity level and diet - requires eight glasses per day? The answer: It's not. That number comes from a 1945 U.S. Food and Nutrition Board recommendation, which was not based on research. And it didn't recommend drinking only water for hydration; it noted that fluid can come from other beverages and food, too. So, there's no scientific basis for the "eight glasses" number. In most cases, thirst is your best indicator that you need a drink. If that sense is compromised, keep beverages visible so you remember to sip throughout the day. Exactly how much to drink is not a static number for everyone.

5. Is food labeled "organic" more nutritious?

Organic refers to a method of farming, but it's not a health claim. An organic logo tells you nothing about the calories, fat, salt, sugar or vitamin content of food. A cake made with organic white flour, organic sugar and organic butter is still cake - it's not suddenly "healthy cake" because the ingredients were grown using organic farming methods. Nutritious foods - whether conventionally or organically grown - are those that provide the body with fiber, vitamins, minerals, protein and other key nutrients.

6. Should I avoid fruit because it has too much sugar?

The No. 1 source of added sugar for Americans, providing 47 per cent of the sugar in their diet, is sweetened beverages - items such as soda, lemonade, fruit punch and energy drinks. Fruit provides 1 per cent of the added sugars Americans consume. (Note: Health advice to limit "added sugar" does not apply to the natural sugar in fruit.) Even if Americans met their daily fruit intake - and 88 per cent do not - it wouldn't come close to the volume of sugar we get from ultra-processed foods and beverages. If you need to cut back on sugar, swap sweetened beverages for water. Keep enjoying fruit, and aim for one or two cups per day.

7. Do I have to drink milk to get calcium?

Dairy products such as milk, cheese and yogurt are a great source of calcium, with about 250 to 350 milligrams per serving. (Adults require 1,000 to 1,200 milligrams of calcium per day, depending on age and gender.) Dairy products are certainly an easy and convenient way to get enough calcium, but they're not the only way. Fortified plant-based beverages (such as those made from almonds, oats, cashews, etc.) also have 300 milligrams of calcium per cup, as does a serving of canned salmon or sardines, as long as you eat the bones. Foods such as kale, almonds, white beans and tofu have about 100 milligrams of calcium per serving, and broccoli clocks in at 40 milligrams per cup. The bottom line: Milk is not essential, but calcium is. With some mindful planning, you can get enough calcium whether your diet includes dairy or not. Here's a quick tool to help you assess your usual calcium intake: calcium calculator.

8. Are fresh vegetables better than frozen?

The nutritional differences between fresh, frozen and canned vegetables is minuscule. Only 9 per cent of Americans get enough vegetables daily, so it's much more important to consume any vegetables, in any state. Vegetables are filled with vitamins, minerals and fibre, which help reduce the risk of developing heart disease, Type 2 diabetes and some types of cancer. The best advice is to buy whatever vegetables you can source and afford, and then prepare them in ways you enjoy most.

9. Is discarding the salt shaker enough to cut sodium intake?

People may be told to slash sodium consumption when battling heart or kidney problems, but skipping a sprinkle of salt is not enough. Only 11 per cent of the sodium we consume comes from salt that is added at the table or when cooking. A whopping 71 percent of sodium comes from processed, packaged and restaurant food. (The rest is naturally occurring in items such as milk, water and vegetables.) If you need to cut salt, choose fresh and whole foods over packaged products and fast foods. When that's not possible, compare food labels on similar products, and choose the option with lower sodium.

10. Will eating soy give men "man boobs"?

Soy contains an estrogen-like compound that weakly mimics human estrogen, which makes some men concerned that eating soy will cause enlarged breasts. We can trace this back to a 2008 case study in a medical journal, which described a man who did develop breasts after ingesting soy, but he was eating upward of 12 servings of soy foods daily. Once he reduced his intake, his breasts disappeared. Guidelines suggest that one or two servings of soy foods per day is fine, so feel free to enjoy some edamame or a tofu stir-fry, as long as the serving size remains moderate.

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Cara Rosenbloom, a registered dietitian, is president of Words to Eat By, a nutrition communications company specialising in writing, nutrition education and recipe development. She is the co-author of "Nourish: Whole Food Recipes Featuring Seeds, Nuts and Beans."

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