Can exercise make you smarter?

Can exercise make you smarter?

We all know that regular exercise can have dramatic effects on our physical health, as it helps protect us from preventable diseases, but what about our minds? The effects of physical fitness may extend beyond disease and obesity prevention, potentially impacting our intelligence from before birth well into old age.

Research on exercise and brain health

For fitness and brain health, the benefits may come early—perhaps as early as in the womb. A 2013 paper made a splash in health media when it claimed active pregnant mothers gave birth to smarter babies.

A review published in the CDC’s journal Prevention of Chronic Disease indicated that although longer-term and larger trials are needed, aerobic activity in children “is positively associated with cognition, academic achievement, behavior and psychosocial functioning outcomes.”

Some of the benefits of exercise (such as weight loss) come slowly and through repetition. But some research indicates the benefits of exercise on brain health and intelligence could come far more quickly.

One study, published in 2013 in the Journal of Clinical and Diagnostic Research, found that a single 30-minute session of moderate-intensity exercise could improve memory, planning, and reasoning, and shorten the amount of time needed to complete cognitive tests.

Similar research on 21 young adults identified increases in memory accuracy and recall speed following a half-hour workout, regardless of whether the exercise was aerobic or strength training.

How exercise affects the brain

Attempting to explain how acute exercise delivers these benefits, researchers from the University of Illinois analyzed 20 undergraduates and found a 30-minute treadmill workout increased neuroelectric activity and resulting cognitive functions, like reasoning and problem solving.

But neuroelectric activity is only part of the answer. Scientists have determined that exercise increases production of beneficial hormones like brain-derived neurotrophic factor (BDNF), for example. BDNF boosts communication between brain cells and stimulates the growth and development of blood vessels and neurons in the hippocampus, the region of the brain responsible for forming and organizing memories.

Several studies have linked exercise and the increased production of BDNF to increased hippocampal volume. The hippocampus, incidentally, shrinks with age and is the region of the brain that suffers the first and most profound damage when someone has Alzheimer’s disease.

Effects of exercise on brain health as we age

Earlier this year, researchers revealed findings that pointed at physical exercise in young adulthood improving cognition later in life. “Better verbal memory and faster psychomotor speed at ages 43 to 55 years were clearly associated with better CRF [cardiorespiratory fitness] 25 years earlier,” they concluded.

Researchers with King’s College London collected data on more than 9,000 people and found those who exercised at least once per week performed better on cognitive tests at age 50 than those who did not.

And much of the research indicates you can’t be too late to the party. Physical activity in midlife can reduce the risk of dementia in old age, according to the University of Eastern Finland. And a meta-analysis of 30 randomized control trials found exercise to have cognitive benefits for adults already suffering from dementia.

Shortcomings in the research

As with any growing field of study, the research is varied both in quality and results. Several of these studies involved very small groups of participants; others were limited in time and scope, or relied on participants to self-report their exercise habits. The research on fit pregnant mothers giving birth to smarter babies was criticized because it was promoted before even being accepted into a peer-reviewed journal.

Perhaps the best evidence for exercise and intelligence comes from firsthand experience. “Working out, for me, allows me to focus on what I need to do and block out distractions,” says LeeAnn Dillon, a fitness competitor and personal trainer from Raleigh, North Carolina, who spends an average of 10 hours in the gym each week when not training for a competition. And as a single mother who recently decided to go back to school, she relies heavily on focus and problem-solving.

People who exercise regularly report being better able to focus and perform on the days they work out; they report less stress and higher energy levels. “I think about… what bill needs to be paid, what my sons need, even the decision to go back to school while I’m working out,” Dillon says. “And in addition to giving me better focus, it gives me the confidence to take on new challenges.”

The Real Risk of Late Night Snacking

The Real Risk of Late Night Snacking

New research discovers late-night eating can wreak havoc on the part of our brains where memories are formed.

You’re pulling super late hours at work. You’re out drinking with your buddies. You’re spending long stretches of time traveling or commuting. Your grueling workout has tapped all the fuel in your tank. All these scenarios have one thing in common. (No, this isn’t an SAT question.) Each one has you raiding the fridge at midnight to quell the grumbling state of your stomach.

We’ve all succumbed to the cravings, but a new University of California study finds the late-night behavior could be affecting us beyond disrupting our sleep or packing on the pounds (as if that isn’t bad enough). Researchers found that midnight snacks can wreak havoc on the hippocampus, the part of our brains where memories are formed.

In the study, which was conducted on mice, researchers allowed some mice to eat at night—which is part of their normal eating pattern—and prompted others to feed during the daytime. All the mice were kept in cages with wire grids that restricted their access to food, and given a six-hour window—depending on the day or night schedule—in which they could eat. The researchers monitored their nocturnal tendencies, sleep-wake behavior, and their contextual fear conditioning (whether they remembered getting the shock—and by consequence showed signs of fear of it happening again) by administering a mild shock to the mice after they ate.

The mice who had eaten during hours they normally slept showed a natural fear response, which indicated that they remembered the shock, while the mice who had eaten during their typical waking hours were less likely to react. In other words, the first group of mice basically “forgot” they had been shocked the last time they ate at that hour. Turns out, digesting food when the mice were meant to be asleep affected their long-term memory and mental function. The researchers theorize it’s because these mice had reduced levels of a protein called CREB, which is essential for the body’s internal clock and the brain’s ability to form memories.

So how does it influence us?

Lead study author Dawn Loh told the Daily Mail: “We have provided the first evidence that taking regular meals at the wrong time of day has far-reaching effects for learning and memory. Since many people find themselves working or playing during times when they’d normally be asleep, it is important to know that this could dull some of the functions of the brain.”

However, more studies need to be done in order to truly see how eating when we typically should be sleeping can impact our health—aside from raising blood sugar levels (enhancing the risk of diabetes and heart problems), which we already know. Take note if you’re a chronic night owl or frequent late-night fridge-raider.

7 Exercises for Killer Arms and Shoulders

7 Exercises for Killer Arms and Shoulders

Strong, toned arms and shoulders can make you feel like a total badass–whether you’re nailing those burpees during bootcamp or showing off your results in a racerback tank. Time to get lifting, pulsing, and pushing, ladies: These seven arm-shaking moves are totally worth the burn.

1. Rolling Push-Up

Start in a high plank with a 10- to 15-pound medicine ball under left hand.
Engage core and bend elbows, lowering into a low push-up position.
Push back up to high plank and roll ball to right hand (as shown), keeping elbows away from body.
Repeat in opposite direction for 1 rep. Do 12 reps.

2. Supergirl Soar

Lie facedown, a light weight in each hand, arms at sides.
Lift upper body and arms (as shown) to start.
Keeping upper body lifted, reach your arms straight in front of you, shoulders next to ears.
Pause; return to start. Do 12 reps.

3. Resistance Band X-Raise

Stand on a resistance band with feet hip-width apart.
Criss-cross it in front of you and hold handles at hips, palms in.
Step to left as you raise hands to chest, elbows out (as shown).
Return to start; repeat on opposite side for 1 rep. Do 20 reps.

4. Bow and Arrow

Stand with feet staggered wide, left foot in front, a heavy weight in each hand at sides.
Bend knees and lean forward as you reach right hand toward left foot (as shown).
Straighten legs, drawing right weight to waist.
Do 15 reps. Switch sides; repeat.

5. Triangle Push-Up

Start in a plank.
Walk hands together so thumbs and forefingers form a triangle.
Do a complete push-up (as shown) for 1 rep.
Too tough? Lower your knees. Do 12 reps.

6. Downward Dog Push-Up

Start in a downward dog position.
Bend at the elbows, sliding the shoulder blades down the back, and then pressing back up to the starting position for 1 rep.
Start with 10 reps; build up to 20.

7. Chair Dip

Sit on edge of a chair, hands on edge of seat, fingers forward, legs extended, feet flexed.
Use arms to lift yourself off chair.
Bend elbows, lowering body until upper arms are almost parallel to floor, hips directly under shoulders (as shown).
Push through hands to rise back up for 1 rep. Do 12 reps.

5 Fruits to Help You Lose Weight

5 Fruits to Help You Lose Weight

Tired of root vegetables and winter squash? As the weather gets warmer, fresh fruits are more likely to grace your refrigerator. Fruits are naturally low calorie, sweet, and nutritionally invaluable, as they provide a range of vitamins and minerals. These five fruits pack a powerful nutritional punch and can help blast away those last few winter pounds with their high fiber content.

Raspberries

Raspberries are chock full of fiber and contain essential nutrients including vitamins C, manganese, and vitamin K. Manganese helps burn fat by boosting your metabolism, while fiber helps slow down your digestive process, leaving you feeling full for longer. A single cup of raspberries packs 8 grams of belly-filling fiber, more than a 25 percent of your total daily needs, in only 64 calories.

Pears

There’s a reason why pears are considered a natural laxative – they’re packed with fiber! Just one medium-sized pear is loaded with 6 grams of fiber and only 100 calories. They’re also a great source of vitamin C and can help keep your cholesterol in check. The fiber acts like a sponge, absorbing the cholesterol and pulling it out of your body. Need a new, healthy dessert idea? Try poached pears!

5 Fruits to Help You Lose Weight

Blackberries

Blackberries are rich in antioxidants like catechins, which give them the natural ability to help activate fat-burning genes in belly-fat cells. They’re also loaded with polyphenols – chemical compounds that may prevent fat from forming. Just a cupful of blueberries packs 8 grams of fiber and more than a quarter of your daily needs for vitamins C and K. Vitamin K is important for bone health and blood clot formation.

Oranges

An orange a day can keep the doctor away, with 1 orange fulfilling more than 90% of your daily vitamin C recommendation. Vitamin C is important for maintaining collagen, an important structural component of connective tissue, bones, and skin. Vitamin C also has antioxidant properties, which aid in removing harmful substances from the body. Also, Oranges are 87% water, which makes them an incredibly hydrating fruit, giving you a natural energy boost.

Passion Fruit

Passion fruits tend to shy away from the public eye, but their delicious sweet and tart flavor are sure to impress. ¼ cup of passion fruit has over 6g of fiber, and a substantial amount of vitamin A and B vitamins. Vitamin A is essential for good eye sight and B vitamins aid in metabolism of foods, making sure you get the energy you need from the food you eat. Try scooping out the pulp of a passion fruit on top of plain Greek yogurt for natural sweetness and flavor.

Daily stretches to improve your flexibility

Daily stretches to improve your flexibility

What better way to loosen up than to incorporate some easy stretches into your daily routine? Stretching every day not only enhances the body’s range of motion, it also decreases the risk of injuries and improves your overall athletic performance. Check out these quick stretches that can be done any time, anywhere!

1. Overhead side lunge

Start by spreading your feet wide apart, bending one knee and keeping the opposite leg straight. As you lean to the side of the bent knee, reach your arm over top of your head to elongate your obliques. This stretch helps loosen up the hamstrings, hip flexors, hip adductors, obliques and lower back. Repeat this stretch on the opposite leg before moving onto the next stretch.

2. Shoulder stretch

Cross one arm over your chest, placing your hand or forearm onto your elbow. Taking deep exhales, apply pressure to your elbow, pushing your arm into your chest. Be sure to keep your hips and shoulders facing forward. Switch arms before moving onto the next stretch.

3. Reverse warrior stretch

Stand facing one direction and step your right foot back, almost as if you are preparing for a split. With your left knee bent, and your right hand resting on your right leg, stretch your left arm over the top of your head.

Be sure to stretch your fingers away from each other. If you’re a beginner, or you just want a deeper, more lengthy stretch, step that right foot back further, reach longer and sink more into the stretch with each breath. Perform on the opposite leg before moving onto the next stretch.

4. Reaching lower calf stretch

To start, stand with your feet less than hip-width apart. Reach both hands toward the ceiling and step one foot out in front of you with your heel on the ground and toe pointed up. Keeping your toe up, bend your opposite knee to bring your finger tips to meet your toe. Once you start to feel your calf muscle loosen up, switch and repeat the motion on the other leg.

5. Standing quad reach and stretch

Begin this stretch by kicking your heel back toward your butt (backside, glutes). Grab your ankle and place your hand out in front of you (or on a stable surface) for balance. Once you feel comfortable in this position, lean down as far as you can, reaching your fingertips toward your toe. This is a great way to stretch out the quads, hamstrings, calves and adductor muscles simultaneously. Not only does it improve your flexibility, this is also a great way to enhance your stability. Perform this stretch a few times on one leg before moving onto the other.

Small food changes that help you slim down

Small food changes that help you slim down

Eating is such a basic and pleasurable part of our lives that we often do it mindlessly.

Pay a little more attention and you might find you’re much more in control of how much you consume than you think. You’ll also discover how much things around you — like plate size — can influence your food decisions.

Little changes can mean a big difference for your waist line — something that fascinates researchers at the Cornell University Food and Brand Lab. They released a host of findings as part of “The Behavioral Science of Eating” in the January 2016 issue of the Journal of the Association for Consumer Research. Here are 10 insights that could change your eating habits:

1. Skip a meal if you’re not particularly hungry.

Are you heading for the fridge because your stomach is growling or just because you’re bored? Try to listen to your body. Eating when you’re not hungry causes your blood sugar to spike, which is not healthy.

2. Be careful around “healthy” food labels.

People tend to overeat food described as “healthy” because they think it’s less filling than “unhealthy” choices. Knowing this, pay attention to the recommended serving size and don’t overload your plate.

3. Install mirrors where you eat.

It turns out watching yourself devour chocolate cake makes the treat less tasty compared to eating it in a room where you can’t see your reflection. Mirrors in the kitchen and dining room add a bit of discomfort if you’re overindulging, but don’t change the taste of healthy food, researchers found.

Small food changes that help you slim down

4. Healthy meals can take a cue from “Happy Meals”.

In experiments, adults and children would rather eat a smaller portion of food paired with a toy or gift card than opt for a larger meal without a prize. Brain scans showed they responded to the prize in the same way they reacted to additional food.

5. Take a hint from Disney’s influence on diners.

When fruits and vegetables became default side dishes for kids’ meals at Walt Disney World restaurants, diners ate at least 11 percent more of them. Make healthy side dishes a default in your own kitchen.

6. Read nutrition labels carefully.

Don’t be seduced by a tasty treat that hides its true calorie count in a very small recommended serving size. Once you start, will you really stop yourself at two pieces or one thin slice? “Smaller recommended serving sizes will let all nutrition values on the label appear smaller too,” says lead author Dr. Ossama Elshiewy from the University of Goettingen. That can lead to overeating.

7. Use smaller plates.

RELATED: Master your munching: Simple ways to eat less every day

8. You’ll eat less from a less fancy plate.

We tend to throw away more food when we eat from paper plates than when we use ceramic dishware. Researchers think this is because we tend to associate food on disposable plates as more disposable, too. No one wants to waste food, but this research shows plate material plays a role in our consumption habits.

9. Choose a fork over a spoon.

This simple change can make a difference in how much you eat. People perceive a food as lower in calories and they want more of it when they eat it with a spoon than a fork. When it doubt, go for the fork!

10. Avoid negative messages.

Dieters who watched a “food police”-style video that bluntly told them “All sugary snacks are bad” ate 39 percent more cookies than those who saw a more positive clip. A gentler combination of negative and positive messages about food has a better effect, researchers say.

10 Ways to Beat Boredom on Your Run

10 Ways to Beat Boredom on Your Run

To fight boredom, engage your mind as well as your body. To accomplish this, I suggest mixing up your runs as much as you can. Avoid running the same route, at the same pace, day after day.

Run in different locations with varying mileage. Try diverse workouts, and do them with new running partners. Even better, find a local running group. Mixing it up helps get you out the door, keeps it fun, and boosts your fitness level.

It can help to plan your runs for the week ahead. Keep in mind that every run you do should have a purpose to it. Runs can be easy for recovery, fast for speed, long run for endurance, or hill workouts to build strength. Plan your route and distance of the run with the purpose in mind.

And, most important of all, keep it fun. Regardless of how hard or easy, or how long or short, the run should be fun. Experiment! Find the workouts and the running routes you enjoy the most and incorporate them, but keep searching out new options to keep it fresh, exciting, and interesting.

Here are some suggestions for mixing up your week:

1. Run to a destination. For example, run to the gym or run to complete an errand—like going to the post office. You can meet up with friends so you have a ride home or plan to run back home.

2. Easy / medium / hard run. For a speed workout, run easy for three minutes, at a medium difficulty for two minutes, and hard for one minute. Repeat this sequence for the duration of your run.

3. Landmark runs. After a warmup, run hard for a short interval to a landmark like a mailbox, a driveway, or a streetlight along the route; then jog easy for recovery to the next landmark. Repeat.

4. Explore a new running area. Go to a park, or a new neighborhood popular with runners.

5. Try a trail run. The concentration needed for trail running engages your mind as you figure out how to traverse uneven terrain, rocks, roots, hills, water, and other obstacles. It’s a great strength builder, too. (Check out these 21 trail tips to get you started.)

6. Plan a hill repeat run. Find a hill in your area that is about a quarter mile in length with a nice incline. Run one mile for a warmup then tackle the hill. Run up the hill and jog easy down, then turn around and run up the hill again. Repeat several times. Run a one-mile cooldown afterward.

7. Try a track workout for speed. Run a one-mile warmup. Time yourself and run one lap at a hard pace; then, jog or walk one lap for recovery. Repeat four to six times. Set a consistent pace for the hard laps and stay within a five-second variance for each lap. Gradually increase the number of laps you run over the weeks.

8. Make running dates with friends. Nothing like good conversation to help pass the miles.

9. Running on a treadmill? Try using a pre-programmed hill run or interval run. The treadmill will automatically speed up or down or add an incline. Varying the pace and incline will engage your mind. (Our chief running officer, Bart Yasso, has a few favorite treadmill workouts you could try as well.)

10. Register for a race. There is nothing like making a race commitment to get you out the door and focused on training. Select a local race or go for a destination race. Finding a race somewhere you have always wanted to visit is a great motivator and a fun way to tour that area. If you have already done some races, select a race that presents a different challenge—like a new distance, a trail race, or an obstacle race.

Running as a Lifestyle for Weight Loss

Running as a Lifestyle for Weight Loss

Approaching a correct weight loss regimen that incorporates running and jogging as efficient exercises is of utmost importance, particularly because you can successfully lose those extra pounds without struggling too much with your workout routine.

We no longer need to pay expensive subscriptions at local fitness clubs, as we can easily attain the same performance by structuring a proper training schedule and following it exactly. If you aim to improve your appearance, health and lifestyle, consider the running program and ideas below.

Week One

Since you are just starting out, you have to know that you need to take things gradually in order to be efficient and attain the desired body shape. Begin with running only one mile during the first week, at a normal speed that will allow you to familiarize your body with this high-intensity exercise in a better way.

It is important not to try to exhaust yourself during this first week, so make sure to go running only four days, with one day pause in between them (for instance, Monday, Wednesday, Friday and Sunday). You can basically go anywhere you want to run, as long as the environment is appropriate and you feel comfortable there.

Week Two

During the second week, you have to think about increasing the amount of time you run instead of distance. Assuming that you can run a mile in 10 up to 15 minutes, you can run for 20-25 minutes during week two, making sure to keep your speed decent – not too fast, but not too slow either. Once you increase the amount of time you run, you analogically have to decrease the number of times you go running. Opt for Monday, Wednesday and Friday, or Thursday, Sunday and Saturday, so that your body will start gaining endurance.

Week Three

Continue with your running plan as you did during week two, not changing the amount of time you run or the number of times when you go running.

Week Four

Now is the time to increase the speed, decreasing the amount of time you have to run. During the first three weeks, you ran at a normal pace that was neither too fast nor too slow, but you have to increase the speed right now, particularly because your body has increased endurance and strength. Run only 20 minutes on three or four days of the week, with a break in between them. Make sure not to stop or slow down, otherwise you will make your exercise routine inefficient.

Week Five

Continue with your running plan of the fourth week, maintaining the same speed, running sessions and time interval.
Week Six

Your running routine has reached its peak during the fourth and fifth week, but it is time to go back to week one and run only 10-15 minutes at a normal pace. Go running four times a week as instructed for week one and make sure not to exhaust yourself.

Changes in Body Weight

Changes in Body Weight

To the layman one of the most obvious indices of the value of a given diet would be the changes in body-weight, for it is commonly believed that any increase in body-weight indicates ample, if not excessive, nourishment, and that a decrease is evidence of insufficient nourishment. For experiments of long duration, such as are commonly made on domestic animals when feeding or fattening for market, this is a remarkably good index.

With man, however, the experiments must of necessity be of short duration, since a routine diet can not be adhered to for so long a time as with animals, and fluctuations in body-weight are, therefore, by no means a proper index of gain or loss of body-material.

Index of Body Condition

Factors involved in change of body-weight.–An increase in body-weight is a resultant of a number of factors. There may have been actual additions to protein, fat, carbohydrate, and water, these four being the principal ingredients of the body, or there may have been an increase in two or three of these compounds with an actual decrease in the others, and there may have been losses from three of them compensated by a gain in the fourth.

It is evident, therefore, that a gain in body-weight is of real service only when it indicates increase of material other than water, and yet a large majority of the fluctuations in the body-weight can be attributed to material changes in the water-content of the body. When it is considered that some 60 per cent of the total weight of the body is water, and this water is easily lessened or increased, it can be seen that the gain or loss of a few pounds by the body may be very largely due to fluctuations in water-content and in no wise gives a true idea of the addition to or loss from the store of organic body-material.

This fact has frequently been the source of considerable error in experiments of short duration, in that a diet manifestly inadequate for maintenance has actually been partaken of for 3 or 4 days while the body-weight of the subject of the experiment has remained practically unchanged. As a result of this apparent constancy in body-weight, a diet obviously deficient has been thought ample for the needs of the body.

Influence of Diet on Body Weight

Nearly all experimental diets differ widely from the normal. In some diets there is a large preponderance of carbohydrates, or of fat; occasionally there is a large proportion of protein. Rarely is an experimental diet so evenly adjusted as to correspond exactly to the diet on which people commonly live. A striking series of experiments has demonstrated very clearly that a change from a diet poor in carbohydrates to one rich in carbohydrates is accompanied by a considerable retention of water by the tissues of the body.

Conversely, it is shown that when a change is made from the rich carbohydrate diet and a fat diet is substituted, there is a considerable loss of water to the body. It is obvious, therefore, that if a change is made from a normal diet to one containing an excessive proportion of carbohydrates, even though the total nutrients in the food may be insufficient for the maintenance of the body, the excess carbohydrates may cause the retention in the body of a sufficient amount of water to more than make up for the loss in body-material resulting from the decrease in the total food-supply.

Moreover, the body must draw upon its body-material, chiefly fat, and with a diet such as is under discussion, the loss of 100 grams of fat, furnishing some 900 calories of energy, may be compensated by the addition of 100 grams of water to the body. These facts will not be seen from a mere observation of change in body-weight, and one must be very careful in drawing deductions from such change charges, particularly in experiments of short duration.

Effect of Transition

The influence of marked changes in diet upon the body-weight has been shown in connection with a series of experiments conducted in the laboratory of Wesleyan University. 1 The diet of the subject in this series was for three days largely carbohydrate. It was then suddenly changed to a diet having equal energy which, however, was derived in large part from fat.

The changes in body-weight during the series were most remarkable and interesting. The series consisted of work experiments, and the amount of energy in the diet was, therefore, large. During the carbohydrate period there were ingested about 970 grams of solid matter each day and sufficient water in food and drink to make the total weight of food and drink about 4500 grams per day. During 3 days on this diet, the body-weight as determined by a platform balance increased on the average 61 grams per day. The more accurate determinations of the gains and losses of body-material calculated from the amounts of protein, fat, carbohydrates, water, and ash katabolized showed an average gain of 88 grams per day.

On the fourth day of the series, the diet was so changed that the greater part of the energy came from the fat rather than the carbohydrates. The fat diet contained about 750 grams of solid matter and sufficient water to make the total weight of the materials ingested equal 3860 grams on the first day and 4900 grams on each of the other 2 days, the average for the 3 days being 4550 grams per day.

Although the total weight of food and drink ingested during the fat period was somewhat greater than during the carbohydrate period, there was actually a very marked loss to the body, averaging 914 grams per day, as determined by the balance with which the subject was weighed. The computations of the gains and losses of protein, fat, carbohydrate, water, and ash showed an average daily loss of 974 grams.

That this loss in weight was in large part water is shown by an examination of the data, by which it is seen that during the fat period there was an average loss from the body of 12 grams of protein, 47 grams of fat, 2.5 grams of carbohydrate, 906 grams of water, and 7 grams of ash per day. Even on the third day of the period the results show a loss of some 800 grams of water.

Although there are differences between the balance as found by means of the actual weights of the subject and that calculated from the materials gained or lost, it is reasonable to suppose from a careful inspection of the analytical data, that the losses in weight as computed from the gains and losses of material are somewhat more accurate than those obtained from the weights of the man. The apparatus then in use for weighing the man, while satisfactory for long experiments, has since been much improved, as its accuracy was by no means all that could be desired in studying such a problem as this. Fortunately, we have the direct chemical data indicating the katabolism of the protein, fat, carbohydrates, water, and ash.

The total energy furnished by both diets was substantially the same and the amount of external work performed was identical in both experiments. The heat eliminated by the body was on the average 70 calories larger in the experiment with the fat diet. It is significant that during the 6 days with the two diets, the body sustained a continuous loss of energy approximating 500 calories per day, and that during the 3 days with the carbohydrate diet the subject gained on the average about 60 grams per day.

Introducing Vitamin A

Introducing Vitamin A

There are three vitamins– A, D, and E-which dissolve readily in fats and are found only in certain fats which our foods contain. They do not, in general, occur together. Vitamin A is abundant in cod liver oil, butter fat, and milk fat; in the glandular organs of animals, such as the liver, kidney, sweetbread, etc.; and in all yellow pigmented vegetables. It never occurs in white vegetables, such as the potato, white turnip, apple.

This substance is now identified with the yellow pigment of vegetable foods, a compound known as carotin, from its abundance in carrots; or at least it seems to be demonstrated that carotin is the mother substance of the vitamin into which it is readily converted in the body. The latter seems the more probable, since the liver of an animal may be nearly freed from vitamin A by feeding a diet free from it, and become rich in the vitamin when an abundance of carotin is provided. Such a liver is still nearly free from yellow pigment. This is interpreted as meaning that the yellow pigment is converted into the vitamin, and is not itself the vitamin A.

It has recently been stated, on experimental evidence, that plants are all practically free from the vitamin A, but that they furnish carotin from which it is made in the body. Liver fats, egg yolk fats, and cod liver oil contain the vitamin instead of carotin. Little is known about the chemical nature of carotin and less about that of vitamin A. The former is a highly unsaturated hydrocarbon containing 40 carbon and 56 hydrogen atoms in its molecule. It is an unsaturated molecule and takes on oxygen readily, losing in the process its yellow color and its value as the mother substance of the vitamin.

Effects of Deficiency of Vitamin A

Much research has been done on the effects of deprivation of animals of this vitamin. The injury to the body which results from this kind of specific starvation is limited to the epithelial tissues. Since these line the ducts of the tear glands, salivary glands, and other digestive glands, and constitute other glandular tissues of major importance, vitamin A deficiency quickly undermines health.

The epithelial cells keratinize, becoming like the outer layers of the skin, and lose their normal functions. Plaques of these cells desquamate and tend to plug the ducts of glands. In vitamin A deficiency the earliest symptoms are deficiency of tears, dryness of the eyes, and dryness of the mouth. The skin becomes dry and scaly, the germinal epithelium in the testes degenerates, and the animals become sterile.

Attention has repeatedly been called to the occurrence of large numbers of calculi in the kidneys and bladders of rats suffering from deficiency of vitamin A. Rats develop deposits of phosphates and oxalates in the urinary tract very rapidly, and almost invariably when fed diets deficient in this vitamin. When chickens are fed an A-deficient diet, there accumulate in the kidneys great numbers of crystals of urates, or salts of uric acid, so that the kidneys feel sandy between the fingers. There is also some evidence that gall stones are more likely to develop under conditions of vitamin A insufficiency than otherwise. Plaques of epithelial cells desquamate and form nuclei upon which cholesterol deposits.

One of the earliest observed effects of vitamin A deficiency was the appearance of an ophthalmia characterized by drying of the cornea followed by ulceration and perforation of the eyeball. This has been shown to be a secondary result of injury to the tear glands. The gland atrophies and loses its power to secrete tears; the eyeball thereupon becomes dry, and cornification of the cornea soon develops.

A number of papers have been published which refer to the incidence of a similar ophthalmia in human subjects subsisting upon diets of poor quality. There is much reason to believe that the occurrence of night blindness is sometimes attributable to chronic deficiency of vitamin A. In the intestinal tract there may be impaired absorption due to injury to the epithelial cells of the wall.

In rats, when the diet is impoverished in vitamin A, the vaginal mucosa forms cornified epithelial cells continuously. Under normal nutrition there is a similar cornification limited to a brief period during which there is growth, maturation, and rupture of Graafian follicles, after which it disappears; but in A-deficient rats the desquamation of cornified cells is continuous and obscures all ovarian cycles that may be present.

Vitamin A deficiency does not create a malfunction of the ovaries, for they continue to secrete hormones similar to those in estrus. This effect on the vaginal mucosa of the rat is so pronounced that Evans and Bishop report their ability to detect vitamin A deficiency in otherwise apparently healthy animals receiving enough A to prevent ophthalmia. Raising the level of A in the diet may abolish the persistent cornification of the vaginal epithelium and restore normal conditions.

In vitamin A deficiency this transformation of epithelium into stratified, squamous keratinizing epithelium is especially pronounced in the upper respiratory tract, and in the renal pelvis, urinary bladder, seminal vesicles, epididymis, prostate, salivary glands, and pancreas.

When there is deficiency of vitamin A, the intestinal flora is markedly changed as respects gram-negative and gram-positive bacteria in the faeces. The faeces of rats on the deficient diet are dry and hard, which may account for the disappearance of streptococci; otherwise there is no change in the proportion of bacteria which ferment glucose, lactose, and sucrose. The proportion of hydrogensulphide-forming bacteria remains constant.

Under deficiency of vitamin A, rats frequently die of bacterial invasion of the ear and nasal cavities before the appearance of ophthalmia. As the infection advances, it leads to nutritional disaster in which the animal is not restored to a normal condition by feeding rations containing vitamin A. Werkman has reported that a deficiency of vitamin A in the diet increased the susceptibility of rats to anthrax and pneumonia.

An interesting observation reported by Howe is the reversion of the odontoblasts to osteoblasts when animals are deprived of vitamin A. The odontoblastic membrane surrounds the pulp of the tooth and lies in apposition to the under surface of the dentine. From each odontoblast a fiber extends through a tubule in the dentine to the base of the enamel.

The odontoblast forms dentine. Howe states that when animals are deprived of vitamin A, the odontoblasts revert to osteoblasts, or bone-forming cells, and that subsequently bone deposits may be formed by these cells. The frequent occurrence of pulp stones in the teeth of animals deprived of vitamin A supports this view. The importance of this vitamin for the health of the teeth appears, therefore, to be very great.