Myths

Photograph by Joanne Swallow©

Myth #1 “low-carb diets are better than low-fat diets”

The amount of fat vs the amount of carbs is not as important as the amount of calories for the purpose of weight loss. When two diets are equal in calories then they are called “isocaloric”. If a low-carb diet has the same number of calories as a low-fat diet, then they are isocaloric and equally effective for weight loss. However, people eating a low carb diet are generally more overweight that those on a low fat diet.1 In fact, high carbohydrate foods are often lower in calories compared to meat, eggs, and dairy, which are commonly eaten in a low carb diet. Fat has more calories per gram than carbohydrates.

Fat = 9 cal/g             Carb= 4 cal/g

In fact, fat has over twice the calories as carbs, therefore, low fat diets are better for satiety and overall health. High carb foods like fruits, vegetables, whole grains, and legumes are less fattening than low carb foods like meat, eggs, butter, and cheese. Vegetarians eat high carb diets and are leaner on average than meat-eaters.2

Myth #2 “vegetarians do not eat enough protein”

Eating sufficient calories to meet energy needs while not getting enough protein is implausible even on a vegan diet. If a vegan eats only broccoli all day then they can get 1638 calories by eating 30 cups of broccoli.  This 30 cups of broccoli has 111 grams of protein, which equals over 20% protein out of the total calories in one day.3 This kind of mono-diet is not recommended for anyone, however, the broccoli example illustrates how easily vegetarians can get protein from plant foods. Vegans and omnivores alike should eat a balanced diet including vegetables, fruits, grains, legumes, nuts, and seeds.

Myth #3 “soy is bad for men”

Soy foods or supplements do not affect the reproductive hormones of men. Neither testosterone nor sex hormone-binding globulin are affected by the consumption of soy protein.4 Soybean isoflavones do not have feminizing effects on men. Semen quality is not affected by dietary intake of soy protein regardless of the high or low isoflavone content.

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References:

1. Kennedy ET, Bowman SA, Spence JT, Freedman M, King J. Popular diets: correlation to health, nutrition, and obesity. J Am Diet Assoc. 2001 Apr;101(4):411-20.

2. Sabaté J, Wien M. Vegetarian diets and childhood obesity prevention. Am J Clin Nutr. 2010 May;91(5):1525S-1529S. Epub 2010 Mar 17.

3. USDA Nutrient Data Laboratory. Broccoli, cooked, boiled, drained without salt. National Nutrient Database for Standard Reference Release 24.

4. Hamilton-Reeves JM, Vazquez G, Duval SJ, Phipps WR, Kurzer MS, Messina MJ. Clinical studies show no effects of soy protein or isoflavones on reproductive hormones in men: results of a meta-analysis. Fertil Steril. 2010 Aug;94(3):997-1007. Epub 2009 Jun 12.

5. Messina M. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertil Steril. 2010 May 1;93(7):2095-104. Epub 2010 Apr 8.

6. Beaton LK, McVeigh BL, Dillingham BL, Lampe JW, Duncan AM. Soy protein isolates of varying isoflavone content do not adversely affect semen quality in healthy young men. Fertil Steril. 2010 Oct;94(5):1717-22. Epub 2009 Oct 12.