“Sugar, alcohol and tobacco,” economist Adam Smith once wrote, “are commodities which are nowhere necessaries of life, which have become objects of almost universal consumption, and which are, therefore, extremely popular subjects of taxation.”

    Two and a half centuries on, most countries impose (征税) sort of tax on alcohol and tobacco. With obesity levels putting increasing pressure on public health systems, governments around the world have begun to toy with the idea of taxing sugar as well.

    Whether such taxes work is a matter of debate. A preliminary review of Mexico's taxation found a fall in purchases of taxed drinks as well as a rise in sales of untaxed and healthier drinks. By contrast, a Danish tax on foods high in fats was abandoned a year after its introduction, during claims that consumers were avoiding it by crossing the border to Germany to satisfy their desire for cheaper, fattier foods.

    The food industry has, in general, been firmly opposed to such direct government action. Nonetheless, the renewed focus on waistlines means that industry groups are under pressure to demonstrate their products are healthy as well as tasty.

    Over the past three decades, the industry has made some efforts to improve the quality of its offerings. For example, some drink manufactures have cut the amount of sugar in their beverages (饮料).

    Many of the reductions over the past 30 years have been achieved either by reducing the amount of sugar, salt or fat in a product, or by finding an alternative ingredient. More recently, however, some companies have been investing money in a more ambitious undertaking: learning how to adjust the fundamental make-up of the food they sell. For example, having salt on the outside, but none on the inside, reduces the salt content without changing the taste.

    While reformulating (再制定) recipes is one way to improve public health, it should be part of a multisided (多边的) approach. The key is to remember that there is not just one solution. To deal with obesity, a mixture of approaches, which include reformulation, taxation and adjusting portion sizes, will be needed. There is no silver bullet.

    Soda is refreshing and delicious, but it is not part of a healthy, balanced diet. Most sodas are packed with sugar. In fact, a can of soda can be hiding up to 10 teaspoons of sugar! The sugar does make soft drinks delicious, but definitely not nutritious. Too much sugar in a person's diet can lead to diabetes (糖尿病), heart disease, and tooth problems. One of the biggest sugary soda problems is that drinking much can lead to weight gain and even obesity.

    There are diet options available for almost every kind of pop (汽水), which means that you don't have to drink all that sugar in order to enjoy a can of soda. Many studies have been done on whether or not aspartame (甜味剂), the sugar substitute in diet soda, is bad for you. Up to now, there are still conflicting opinions on this issue. The European Food Safety Authority recently concluded that aspartame is safe for most people, even in fairly large amounts. Aspartame still might not be good for you, though. Studies have shown that people who drink diet sodas may actually gain more weight than those who drink regular soda, perhaps because, strangely enough, drinks loaded with fake sugar may actually make you want to eat more.

    Maybe you've decided it's time to cut down on your soda drinking, but what should you drink instead? Water is absolutely the healthiest thing that you can drink. Your body needs water to stay hydrated (水合物) and function properly, and water contains no calories or fat. Drinking fruit juice occasionally is not a bad thing, but you should be careful what juice and how much juice you're drinking. Fruit juices can contain almost as much sugar as pop!

    As with most things to do with your health, moderation is really at the base of any healthy diet. You can totally drink soda, even the sugary kind just, make sure you're not drinking too much!

    Cold weather during winter months may keep many people from leaving home and running in the open air.

    However, a new study shows that the drop in temperature is a good reason to run. In fact, researchers say, running in cold weather helps improve one's performance.

    Many people say running in the winter can be difficult. Two reasons are the low temperatures and bitter winds. Yet many runners might find it easier than running in hot weather.

    That could be because lower temperatures reduce stress on the body. When you run in cold weather, your heart rate and the body's dehydration (脱水) levels are lower than in warmer conditions. The body needs less water on a cold day than in warm weather.

    This information comes from sports scientists at St. Mary's University in London. John Brewer is a professor of applied sport science at St. Mary's.

    For this study, he and other researchers put a group of people into a room they called an "environmental chamber." The researchers then recreated summer and winter weather conditions in the room. The test subjects were asked to run 10,000 meters under both conditions. Brewer says he and his team recorded biological measurements of the runners.

    "We've got a group of subjects into the environmental chamber, we've changed the conditions to replicate the summer or winter and we've got them to run a 10km under both of those conditions and taken various measurements on each runner while they've been completing their 10km."

    Brewer says every movement runners make produces heat. He explains that one way in which we lose heat is by sweating. The body loses heat through droplets of sweat. He says the body also loses heat by transporting the blood to the surface of the skin.

    Vinegar makes salad, fries and dumplings taste better, and you can even use it to clean your windows. And now, according to scientists, it may even the planet's population survive climate change.

    Researchers from the RIKEN Center for Sustainable Resource Science （CSRS） in Japan found that growing plants in vinegar makes them more resistant to droughts. This could mean that in the future, worries about climate change affecting the world's supply of food will be much lower. The discovery was made after the researchers studied the Arabidopsis, a plant known for its ability to survive in dry weather. It was found that when the plant was placed in drought﹣like conditions, it produced a chemical called acetate（醋酸盐）﹣the main component of vinegar.

    After discovering this, the scientists experimented further by adding acetate to the soil of other plants, before they stopped giving them water completely. After leaving the plants for 14days, they found that the ones treated with acetate had survived, while the untreated plants had dried up and died.

    It's hoped that this simple method of survival could soon be used to help farmers in dry countries keep their crops alive. "In the experiment, we targeted the staple foods of the world﹣rice, wheat and maize﹣and the basic plant of breeding species, rapeseed（油菜籽）," Jong Myong Kim, co﹣author of the study, told Popular Science magazine.

    Kim also told the magazine he's already been in touch with people all over the world who are interested in trying this simple and cost﹣effective method out for themselves from flower growing companies to amateur gardeners. Although at this point keeping thirsty plants alive isn't as easy as just pouring vinegar over them, Kim said he and his team are working on making the process as simple as possible. "Now we are trying to cooperate with some farmers, and also some companies, to make a method to apply this system, "he said. And for those of us who always forget to ask our neighbors to water our plants when we go away, hopefully this means the end of returning home from a trip to find our favorite flowers have died.

    While faking and fierce looks are among animals great defenses, many species know that everyone runs from a big stink (臭气) too.

    Vulture (秃鸳)

    Vultures, are street sweepers that feast on the rotting flesh of dead animals, which benefits us by ridding our highways and landscapes of animal bodies and the bacteria they might carry. When vultures feel threatened they vomit, and the smell of vomited-on dead bodies puts of most predators. Throwing up allows the vulture to fly away more quickly-and the vomit can hurt the aggressor's eyes and face.

    Opossum (负鼠)

    In some ways opossums have it easy. In order to become "dead", they don't have to fax anyone a death certificate. They just lie there with their tongues hanging out with the smell of dead flesh, sometimes for hours, effectively convincing potential predators they can find a much fresher meal elsewhere. Even if they keep getting attacked, they won't move any more than a human statue until the threat has passed.

    Hoatzin (磨雉)

    Hold your nose and meet the hoatzin, a bird of distinctions, not the least of which is that it smells like fresh cow shit. The animal mostly eats leaves and it's the only bird known to digest by fermentation, like a cow. This process is what causes its smell and has earned it the nickname the "stink bird

    Millipedes (千足虫)

    Millipedes are tricky. For starters they look wormy. Their name is deceptive, too: Their legs number about 750. Their major defense is to curl up into a ball. They, though, also release a harm eyes, and leave a horrible smell on their attackers.

    Sea Hare (海兔)

    The graceful sea hare is plain in taste in the first place, so it's not the most popular dish in the seafood chain. Nonetheless this type of sea creature has a pretty creative smell-related defense that is almost the opposite of its smelly companions on this list. The sea hare gives out a slimy, purple ink, the substance which makes food less palatable to predators.

    Researchers using lobsters (2-f) as model predators found that the sea blocks the lobsters receptive mechanism. In other words, the sea hare gives its attacker the equivalent of a stuffy nose so they don't know how appealing it is.

    Yellowstone National Park is the flagship of the National Park Service and a favorite to millions of visitors each year. The park is a major destination for all members of the family. By driving the grand loop road, visitors can view the park from the comfort of their vehicle and also take a rest at one of the many roadside picnic areas.

    How much is the entrance fee?

    $25 - Private, noncommercial vehicle;

    $20 - Motorcycle or snowmobile (winter);

    $12 - Visitors 16 and older entering by foot, bike, ski, etc.

    This fee provides the visitor with a 7-day entrance permit for both Yellowstone and Grand Teton National Parks.

    A $50 park annual pass provides entrance for a single private non-commercial vehicle at Yellowstone and Grand Teton National Parks. The $10 Interagency Senior Pass (62 and older) is a lifetime pass available to U.S. citizens or permanent residents.

    Where can you stay?

    Inside Yellowstone, you can choose to stay in modern or historic hotels and cabins inside the park like the Old Faithful Inn, the world's largest log structure. For those who want to be a little closer to nature, there are 12 campgrounds with a range of services from primitive pit toilets to shower and laundry facilities. There's also RV camping with and without dumping stations.

    Staying outside the park gives you unique Old West experiences but still keeps you close to park attractions.

    If you're taking a road trip to Yellowstone, you'll want to check out our Hotels and Cabins On The Road section.