(Coral Plant Calcium used as Example)
Factual Marketing is one thing, but far too often marketing attempts to stretch and manipulate the facts to give greater significance to a product than it deserves. 
- Natural = Almost meaningless as currently used. B Vitamins are often called natural when over 95% are synthetic.
- Whole Food Vitamins = Usually mis-labeled. Again, very few are really natural or whole food derived, meaning synthetic vitamins are added to the product at some point rather than the vitamins being built by nature in living food.
Plant Source Calcium
Example: Plant source Calcium new on market called AlgaeCaltm.
Red algae cells use calcium in building the outer skeleton of the algae plant. When the algae plants which are attached to reefs die, they are often called coral, but are really different, they just exist in the same places, the reefs. The Algae "plants" can also break off from the reef and wash up on the beach. AlgaeCaltm gathers this source. While the marketing story truthfully says this is a natural plant source calcium, the form this calcium takes in algaes is calcium carbonate. This fact is seldom mentioned in marketing materials for this product. Well, on their website they do briefly mention it and simply say that AlgaeCal is 30% calcium and 70% other stuff.
Since calcium carbonate is 40% calcium and 60% carbonic acid, this means that while AlgaeCal has 25% less calcium, it has some extra room and contains other minerals such as magnesium (but not enough) and other nutrients. AlgaeCal claims this "extra stuff" not only enhances the absorption of the calcium but adds values of their own, plus the honeycomb structure also increases absorption. This added absorption may also be due to the fact that while limestone calcium carbonate is 100% calcite, the red algae adds small amounts of two other carbonate forms, aragonite and vaterite. It is the vaterite at about 12% that gives AlgaeCal an extra absorption advantage. Vaterite is more reactive and unstable while calcite and aragonite are low reactionary stable compounds.
Yes, calcium carbonate is the same calcium form found in limestone and in TUMStm. The company that holds the patent for this algae calcium brand uses complex tests with incredible sounding results such as 75% absorption. Well, not really absorption, but potential absorption as shown by solubility tests. They compare this 75% potential absorption solubility to calcium in foods that has between 8-67% solubility; pear is at 67% while cauliflower is 21%. What they don't tell you is that regular limestone calcium carbonate has a 69% solubility representing only a 12% difference between the 75% AlgaeCal. The actual in the body assimilation and absorption is still about 30-35%, like most other calcium sources. A study found no detectable effect of solubility on absorption.
Another test reveals a 200 - 250% increase over plain limestone (just calcium carbonate) and calcium citrate in generating one of the bone growth metabolites, alkaline phosphate activity. This was from an outside the body TEST TUBE study. If this same action transfers and happens in the body, algae calcium would be a miracle ingredient for bone building. But, the digestive system will tear apart the calcium carbonate from the algae plant material which includes other minerals and some proteins, items that may have influenced the test tube results. After the body separates the calcium from the carbonate, simply the nature of calcium digestion, it will behave just like any other calcium source, including limestone. The elemental calcium is the same. Plus, the ratio of magnesium to calcium is very low in natural algae which may jeopardize some body processes and the absorption of other minerals. One company, Garden of Lifetm, adds extra magnesium for a better balance while New Chaptertm does not. ref
Calcium carbonate uses up stomach acid in processing which could compromise protein digestion in Seniors who already might be low on digestive acid. In this situation, calcium citrate has some advantages since it uses far less acid for absorption preparation. Even though this red algae calcium can be called a plant source, the form is still a factor.
Calcium carbonate might not be appropriate for everyone, and still comes in at only about 30% actual absorption, not the 75% solubility percent often mentioned in ads. Body conditions really dictate calcium absorption percentages. It would also be of interest to know how this algae source calcium participates in generating calcium spikes in blood level. Food trickles in calcium since the elements in food act as buffers. Most supplements create rapid blood spikes of calcium which generate counter responses from the body. Evidently, long term effects of continual calcium spikes are not healthy. This is probably why studies comparing food sources versus calcium supplements find food sources do not exhibit the same negative effects long term, with the exception of milk. It is possible algae calcium has some buffering effects, similar to ground bone sources of calcium. While Milk has minerals and fats as buffers, the very low ratio of magnesium to calcium might be the factor generating increased fractures long term.
Now, how does this background calcium information about AlgaeCal's plant source calcium influence your perception of their marketing story?
Wrap UP
One further point needs clarification before leaving this topic. AlgaeCal calcium is slightly more absorbable, and may in the future show benefits due to it's solubility over other forms. But a current ongoing research study might misdirect this story in the future. This study is using an AlgaeCal calcium formula and a 680mg. strontium supplement. The halfway results appear remarkable and may be used to market this product. The AlgaeCal company is using this study result to make a guarantee that these products will grow bone and reduce fractures. But, these results are not new, and can almost totally be attributed to the uptake of strontium by bones which does increase density and prevent some fractures.
How? Strontium, which is double the weight of calcium, adds greater measurable density to bone due to the fact that it replaces some of the lighter weight calcium during bone rebuilding. There are some critical issues generating warnings you need to understand that are seldom mentioned in marketing information about strontium such as skin rashes, and increased heart attacks showing up over time. article article
CAUTIONARY NOTE: If you take a product with AlgaeCaltm, write to the company and ask if they check each production batch for lead content. Lead is commonly found in some mineral sources, including Red Algae.
Positives for Red Algae
UPDATE: A new study will be coming out soon for AlgaeCal which says this product reduces RANKL levels. RankL is a ligand protein involved in bone calcium metabolism by activating the development of bone tearing down cells. If RANKL levels get too high and out of balance with OPG, the element to control RANKL activity, lowering RANKL levels would have some favorable results. ref The RANKL pathway is very complex and related to a number of disease states. It will definitely play a significant role in future osteoporosis treatment protocols. BUT, it is also involved in immune functions so careful analysis is needed not to jump out of the frying pan and into the fire.
How does this calcium product lower RANKL levels? RANKL is triggered by an acid build up in the blood. RANKL is produced by bone building cells to activate bone tearing down cells causing them to release calcium out of bones to neutralize the acid blood. While all calcium sources will neutralize acids, the preferred mineral for buffering by the body is potassium. Increasing potassium foods in the diet would play a large role in regulating body acids so that using bone calcium to decrease RANKL levels would not be necessary. Only the levels needed for the proper amount of bone repair would be made.
Watch for more on this RANKL process and interaction with the Tumour Necrosis Factor pathway for immune activities soon. Here is another article with more insight.
Reduced Colon Cancer Cell Growth Rates in Test Tube Study.
Another aspect concerns the influence of AlgaeCal on colon tumor cell growth. It not only slows down colon tumors similar to limestone calcium, it also slows down tumor cell growth for cancers that do not respond to other calcium sources. This goes beyond just the calcium content. Maybe trace minerals. More research is needed to understand this potential benefit. ref ref