英语演讲稿关于饮食由刀豆文库小编整理，希望给你工作、学习、生活带来方便，猜你可能喜欢“饮食文化英语演讲稿”。
I shall be speaking today about
Before we start our presentation, let's take a brief look at
If you give a diet to laboratory animalit’s very common for animals to gain a good bit of weight when given acce to this diet.Even if they’re given healthy food at the same time, they’ll tend to ignore the healthy food and eat a diet like this.And there are two properties of this diet that help promote overeating and obesity in laboratory animals.What would you say the two features are?Sugar and fat.Sugar is what people usually gue first and that’s correct, fat is number two, so you guys are good so far.Who can gue what the third might be? Salt is a good gue, but that’s not the answer.But why would a lab animal seek out a diet, become very overweight, become nutritionally deficient in some things because it’s not eating the healthy foods to the extent that it becomes unhealthy? The fact is those lab animals have a hard-wired preference for foods that are high in fat and high in sugar, primarily because of the energy density that those foods bring to one, the seeking out fat and sugar is a highly evolved, adaptive evolutionary trait of animals and human.Today we’re going to talk the two big ones that people are usually concerned with: carbohydrates and fat.Let’s start with carbohydrates.Sugars, in other words.They’re used by the body for pretty immediate energy.There are three claes of sugar: monosaccharides, disaccharides, and polysaccharides.It’s not so important that you know which sugars fall under each of these categories, but it is important to know that there are different categories of sugars.Under the monosaccharides, glucose, fructose and galactose are the sugars.Disaccharides, where you have several sugars paired together, are maltose, sucrose, and lactose.Then the polysaccharides are the complex carbohydrates, and that’s starch, glycogen, and cellulose.If you look at sources of these different carbohydrates, the glucose comes from fruit.That’s not the only place but that’s a primary source of it.You see the lactose of course from milk, and then you get down to the celluloseand starches,cereals and vegetables become the primary source of these.Are we eating too much or too little of these different claes of sugars? Well, as you might gue, we eat too much of the simple sugars and the disaccharide sugars and we eat too little of the complex carbohydrates.So if you followed a diet where you ate le junk food and ate more fruits and vegetables, for example, just those two little rules you would help shift around this balance of sugars in a way that would benefit health.There’s sugar in a lot of foods where you don’t expect it.For example: peanut butter.Here’s a list of ingredients from skippy peanut butter and you see that sugar is the second most common ingredient.Here’s another example.Beef stew, you wouldn’t necearily expect to find sugar in beef stew but it’s there.Now it’s down the list of ingredients, it’s actually toward the end, but if you look at the marketing of this and look at the can it says, there’s fresh potatoes and carrots, but actually there’s more sugar in this than there is carrots.Okay, let’s talk about fat for a moment.Fat has twice the calories per unit weight as protein and carbohydrate.So it’s a very efficient way of securing energy.But if one is not deprived of calories,then having fat my not be so helpful.There are different kinds of fat that have different impacts on health.Several concepts that are relevant in the discuion of fat: cholesterol, saturation, and trans fat.First of all,cholesterol.There are different kinds of cholesterol, HDL and LDL.It was a major discovery when scientists in the last century found that HDL is good and LDL is bad, the HDL, that’s protective against things like heart disease and you want to have a higher level of that and a lower level of HDL.The saturation is interesting.You hear a lot about saturated fat and unsaturated fat.As you know, unsaturated fat is healthy and you want to have this in your diet.Trans fats have become a really interesting iue.There are groups of people who have studied the impact of trans fats on health for a number of years.They have found that trans fats were having a very negative impact on health.What are trans fats? They’re unsaturated fatty acids that get formed when foods are partially hydrogenated.When you see that partially hydrogenated oils on an ingredient list, that means there’s trans fat.Why would companies do this? Why would the food industry want to introduce trans fat in the first place? Well, it changes the food in ways that are commercially appealing for the industry.It gives foods a longer shelf life.They tend to stay stable during deep frying and then the palatability goes up and the foods taste better.Getting back to the concept that there are good and bad fats, if we look at the left hand side here, is a table or a graphic showing the fats that tend to have beneficial impacts on health.You have the unsaturated fat.The seafood, olive oils and some nuts are high in the unsaturated fats.So these kinds of rats are not necearily bad.The bad fats look like this, and those are the saturated fats and the trans fat.These bad fats raise the LDL levels, that’s not good for you.And they lower HDL.The trans fats that we mentioned before that you can see listed over here from margarine, shortenings, deep fried foods, a lot of fast foods and baked goods have a negative impact on health as well.So it’s important for the public health to change the portioning of fat so you move from bad to the better fats in the diets.
