I’m a vegan and have been for the last 8 months or so. During this time, I have been constantly harasssed by many people I know, saying that I was clearly not getting enough vitamins and nutrients to keep HEALTHY. The biggest concern is usually calcium. I have a history of osteoperosis in my family, so I have tried to make sure and get the daily recommended amount of calcium. I get it from various things such as soy milk, vegan cheese, brocoli, etc., and I also take a vitamin every day which says it contains 50% of the recommended daily intake of calcium. I have told my Dad this, and he claims that the vitamin doesn’t really contain that much calcium. He says that taking calcium through a vitamin is no where near as effective as eating things with calcium–and that it is probably more like 15 or 20% of the daily recommended amount even though it says 50% 
. I am sure that getting calcium directly IS better, but is it really true that the percentage is diminished that much? I have looked at a few online websites that have given me conflicting data on how effective vitamin supplements are. It seems hard to imagine that a vitamin company could survive if they were misleading the publicso greatly in regards how much of their daily calcium intake they were recieving, but I suppose it has been done before. Does anyone know the truth behind this?
Well, there is this little thing the federal government has about truth in labelling. If you are buying a reputable brand, I don’t think you have to worry. My doctor told me that my calcium 600 mg tablet twice a day is quite sufficient. I take the kind that also has vitamin D; the doctor says that you need the D to use the calcium.
If you have a risk of osteoporosis, be sure to get a bone scan to see if there is any bone density decrease. I don’t know how old you are, but I’ve been told that by at least 40 you should get a baseline test. Ask your doctor.
Nitpick: Calcium is a mineral, not a vitamin.
For calcium, take a TUMS once a day. As long as you are being reasonably carefull with your diet there is no reason you can’t be completely vegan and be healthy.
People that harass you about what you choose to eat aren’t thinking about you, they are thinking about themselves. This works in the other direction as well. You have no business telling non-vegitarians why they shouldn’t eat meat either. Nevertheless, I can not remember being more offended than when the people I was with were deliberately letting a co-worker of mine unknowingly eat crab dip.
Your choice is yours, my choice is mine. I love steak.
There is such a thing as bioavailability. It’s a measure of how the body deals with incoming nutrients, vitamins, or medications. It’s quite real and the results vary enormously. Some foods do deliver a higher bioavailability of their nutrients than pills. Some forms of minerals do get better absorbed than others.
Exactly how this all works in the extremely complex environment of any individual’s food and digestive system is a different question.
Most nutritionists recommend getting nutrients from foods because we don’t yet know enough about micronutrients and the interaction of nutrients to know how to duplicate all the good effects of food in a pill.
OTOH, you can find any number of studies that have done investigations and come up with no differences. One such is Relative bioavailability of calcium-rich dietary sources in the elderly, which concludes:
Now, as for the OP. If a pill says that it has 50% of your RDA for calcium, then it almost certainly does. In theory. How well it will be absorbed by the body is a different question that may defend on things as simple as whether you take the pill with a meal or not. Or whether the pill uses calcium citrate instead of calcium carbonate. Or several other things, including vitamin D, which is a concern of the elderly or those who don’t get enough sun, but not a real problem for those who are active and outdoors regularly.
Google bioavailability of calcium if you really want to get into this.
However, the general advice is that if you try to get enough calcium from your diet, taking a supplement should be sufficient without worrying too much about the exact number of milligrams of calcium you absorb.