This product is now recommended in a new nutrition book called It's Not the Cans: The Best Nutrient Balance for a Stronger and Healthier You UPDATE - Vitamin K2 in the form of MK7 prevents calcium from hardening your arteries. It also helps bind calcium to your skeletal tissue (bones). A couple of recommendations are: Solgar Natural Vitamin K2 (MK-7) Vegetable Capsules, 100 Mcg, 50 Count Now Foods Vitamin K-2 (MK7) Veg Capsules, 100 mcg, 60 Count Please try to ignore those who would have you mega-dose on Vitamin K2 (or any other nutrient) as they are the same people who suggested mega-dosing on Calcium and Vitamin D which has served to dramatically increase rates of Cardiovascular disease especially among women. Now the same people are suggesting mega-dosing on K2 in hopes of undoing the damage their initial "advice" has caused. Balance and consistancy will serve you far better than flooding your system with any nutrient. Please do not allow the bloggers and the one-off study scare you or your loved one into taking excessive doses of vitamins or minerals. END UPDATE - This is an excellent product! This product is Calcium Citrate. Here is what I know so far. Calcium Carbonate requires stomach acid to be absorbed so must be taking with a meal. Citracal contains Calcium Citrate which is more readily absorbed so it can be taken with or without food (very convenient) Calcium Carbonate is approx 40% elemental calcium whereas Calcium Citrate is approx 20% elemental calcium. So when only the "total" mg dose is displayed on the product you are actually only receiving 40% (carbonate) or 20% (citrate) real calcium per dose. Citrical displays the actual "elemental" (real) calcium dosage so you know exactly how much calcium you are receiving per dose vs trying to do the math (very convenient). Citrical includes Vitamin D3 (most recommended form of D is D3). Vitamin D is the mechanism that your cells need to absorb calcium (very beneficial). These are relatively small, square tablets with rounded edges (very convenient). PLEASE NOTE: You do NOT have to take four per day!!! We are all unique and have different requirements. 4 pills per day supply a concentrated dose of 80% of the RDA for calcium. Even that is a very generic statement. IMPORTANT: Evidence suggest that high levels of calcium hardens arteries over time. They think it is due to some of the excess being absorbed into the normal plaque we all have inside our arteries making it stiff over time (calcification). So the walls of the arteries become more narrow and less flexible which may result in a blockage that would have passed through if not for the hardened internal plaque. So please try to limit your supplemental calcium to no more than two pills per day taken several hours apart (half daily dosage). And then seek additional calcium via other means such as milk, brocholli, or what have you. If you take four of these per day (full dose) try to take them one at a time throughout the day so that you do not generate as much "excess" in your blood stream each time. I know this may be too much to remembe. However, this may help prevent the hardning artery plaque issue (not certain). GOOD NEWS: An increase in magnesium increase calcium absorption. So consider taking 200 to 400mg of magnesium each day (don't waste money on magnesium oxide as it does not absorb well). Also consider taking an additional 1000iu of vitamin D3. Basically, the more you actually absorb the less you need to take. Make sense? By the way, D is a "fat soluble" vitamin so it stores for several days in our liver. If you miss a few days your liver will release its stores to cover you like a camel's hump in the desert. There is zero need to megadose on any "fat soluble" vitamin. Doing so can become toxic. I would not exceed a total of 4000iu per day and I try to remain below 3000iu. Please note that Citracal has some D included. Simply add up all of your D3 sources then include additional D3 to total around 2000iu which is above the RDA yet far below the upper toxic limit. Studies show 10,000iu of D per day becomes toxic in some people after 3 months of that high daily dose. Also, please consider this: 1) Your unique body may require MORE than the RDA 2) Your unique body may require LESS than the RDA 3) The foods you eat on a regular basis are supplying SOME calcium (or ALL the calcium you need) 4) Too much concentrated calcium can lead to other problems (quote from Dr. Ox Calcium Fact Sheet) "A recently published study revealed that taking excess calcium can be bad for your heart. In one large study, researchers followed a cohort of over 60,000 women for nearly two decades. They found that those who got a lot of calcium in their diet and/or with a supplement had an increased risk of developing Cardiovascular disease or heart disease. The increased risk was more pronounced in those who got excess calcium and took a supplement." 5) Always try to spread supplements over the day (if taking 3 total, try to take them several hours apart). If you already have a calcium rich diet there is no need to take 4 of these pills per day (80% RDA). You may only wish to take 1 or 2 per day (20% or 40% RDA). If you are a petite person your unique body may require less calcium than someone twice your size. If you exercise intensely four days per week and eat a somewhat healthy diet you may only need 2 pills per day (40%). I've added a second glass of Horizon Organic 1% milk to my daily diet. Tastes great. Not only does it have calcium but each glass also has 400mg potassium, 15% protein, and a lot of other nutrients. This allowed me to lower my Citrical dose. I'm not suggesting you drink the milk I like. I'm just giving an example of an option I chose. CONCLUSION - This is an excellent product for the cost! There are a very few higher end products but those cost twice as much and are more for people with serious, medical calcium issues vs average people. SEARCH "too much calcium" or "calcium side effects" to help determine how much is too much. NEVER be a robot (not saying you would) and simply take the manufacturer's recommended daily dose. Be a little more comprehensive and take your unique size, activity level, diet, and medical history into account when determining the proper daily dosage for you. ALWAYS view this and every other supplement as just that, a SUPPLEMENT. This means try NOT to obtain 100% of your daily requirement via pills alone. Adjust your diet accordingly to get some (if not all) of the nutrients you need and then "SUPPLEMENT" the rest. The minimum goal is to get at least 50% of what you need through the foods you eat. In a perfect world you would try to get 100% from food yet minimal toxins and calories. You should not need to obtain 100% of anything via pills (exceptions of course for medical conditions). This is another reason why I suggest you consider only taking one or two of these per day (20% to 40% of RDA) and then seeking calcium rich foods to add to your diet (only if possible). That being said we all are unique so these are merely very loose guidelines to get us all to think a little more deeply about the foods we eat and the number of pills we take. Before I forget to mention it, THIS IS AN EXCELLENT PRODUCT!!