Anywhere up to 400 mg of caffeine a day seems to be a safe amount for the majority of healthy adults. That equates to around the amount of caffeine present in 4 cups of brewed coffee, 2 energy drinks, or 10 cans of cola.
For the average human being, drinking 8 eight-ounce glasses of water a day should be enough. Drinking less than this amount may put you at risk of dehydration, while drinking over a gallon in a short amount of time may lead to water intoxication.
While there is absolutely no need to consume any added sugar, the American Heart Association (ASA) recommends that men should consume no more than 37.5g a day, while women should consume no more than 25g of sugar per day. For reference, a regular-sized Snickers bar contains 20g of sugar, while a 12oz can of Coca Cola contains a total of 39g of sugar.
Based on the average adult diet of 2,000 calories per day, adults can safely consume around 325g of carbohydrates each day without experiencing weight gain or other undesirable effects. However, you should be careful not to consume too little either, and the National Academy of Sciences' Institute of Medicine recommends that adults should consume no less than 130g of carbohydrates per day. A typical slice of white bread contains around 12g of carbohydrates, while 100g of steamed white rice contains 34g of carbohydrates.
When following a healthy and balanced diet, men should typically consume around 2,500 calories per day, while women should aim to consume around 2,000 calories. Of course, these values will vary depending on your level of physical activity, age, metabolism, and various other factors. Consuming a lot more or less calories than your body needs will cause changes in weight, and can lead to quite a staggering number of health complications. One medium-sized red apple typically contains around 80 calories, while a large pepperoni pizza can often contain well over 2,500 calories!
Consuming too much salt on a daily basis can lead to quite a number of health issues, and that's why the ASA recommends ideally limiting your salt intake to a maximum of 1,500mg a day. This equates to only around 3/5 of a teaspoon!
While it's very hard to eat too much protein, you certainly need to pay attention that you're eating enough since nutritionists recommend ingesting at least 0.8g of protein per kilogram of body weight. A 200g rump steak contains around 44g of protein, while 100g of cashews contains 18g of protein.
The Institute of Medicine recommends that adults should intake between 1,000mg and 2,000mg of calcium per day. Too little can leave you with a number of deficiency-related issues, while too much can cause heart issues. A cup of milk contains 305mg of calcium, while a cup of roasted soybeans contains around 237mg of calcium.
While it may be a good idea to cut alcohol out of your life entirely, if you really must drink, experts recommend an intake of no more than 14 units a week. This equates to around 6 glasses of wine, 6 pints of beer, 5 pints of cider, or 14 25ml measures of spirits.
Fish is generally a safe and healthy option to add to your diet, however, you should watch out for certain kinds of fish that contain mercury, such as salmon, tuna, swordfish, and marlin. Nutritionists recommend avoiding eating these kinds of fish more than twice a week, and for pregnant or breastfeeding women to avoid them altogether.
The American Institute for Cancer Research recommends eating no more than 18 ounces of red meat each week. They also recommend avoiding processed meat products, such as baloney and salami entirely due to their cancer-causing effects.
Consuming too little dairy can cause a whole host of health problems, including stroke, heart disease, and type 2 diabetes. You should try and consume at least 4 servings of dairy a day. One serving is equivalent to a glass of milk, 2 slices of cheese, half a cup of ricotta or 3/4 of a cup of yogurt.
By far the most unhealthy type of fat, you should limit your daily intake of trans fats to no more than 2g a day. That's equivalent to around an eighth of a chocolate chip cookie or 2 potato chips.
Saturated fats are a little less harmful to your body than trans fats, but not by much. That's why you shouldn't consume more than 16g a day. A slice of Italian pizza contains almost 5g of saturated fat, while a tablespoon of butter contains approximately 7g.
Unlike the other kinds of fats, your body needs a certain amount of unsaturated fat to keep you going, and experts recommend consuming between 44 and 78 grams of unsaturated fat each day for most healthy adults. A large smoked pork chop contains around 15g of unsaturated fat, while a tablespoon of olive oil contains about 11g of unsaturated fat.
BONUS: The Recommended Daily Intake of Vitamins and Minerals
Vitamin A - 600 µg
Vitamin B1 (thiamin) - 1.4 mg
Vitamin B2 (riboflavin) - 1.6 mg
Vitamin B3 (niacin) - 18 mg
Vitamin B5 (patothenic acid) - 6 mg
Vitamin B6 (pyridoxine) - 2 mg
Vitamin B12 (cobalamine) - 6 µg
Vitamin C (ascorbic acid) - 75 mg
Vitamin D (cholecalciferol) - 5 µg
Vitamin E (tocopherol) - 10 mg
Vitamin K - 80 µg
Biotin (B-complex) - 30 µg
Folate (B-complex) - 400 µg
Boron - < 20 mg
Calcium - 1000 mg
Chlorine - 3400 mg (in chloride form)
Chromium - 120 µg
Copper - 2 mg
Fluorine - 3.5 mg
Iodine - 150 µg
Iron - 15 mg
Magnesium - 350 mg
Molybdenum - 75 µg
Nickel - < 1 mg
Phosphorus - 1000 mg
Potassium - 3500 mg
Selenium - 35 µg
Sodium - 2400 mg
Vanadium - < 1.8 mg
Zinc - 15 mg