Vit D + Calcium: Too Much Of A Good Thing?
- Myth: you can’t get too much calcium!
- Myth: you must get as much vitamin D as possible!
Let’s tackle calcium first:
❝Calcium is good for you! You need more calcium for your bones! Be careful you don’t get calcium-deficient!❞
Contingently, those comments seem reasonable. Contingently on you not already having the right amount of calcium. Most people know what happens in the case of too little calcium: brittle bones, osteoporosis, and so forth.
But what about too much?
Hypercalcemia
Having too much calcium—or “hypercalcemia”— can lead to problems with…
- Groans: gastrointestinal pain, nausea, and vomiting. Peptic ulcer disease and pancreatitis.
- Bones: bone-related pains. Osteoporosis, osteomalacia, arthritis and pathological fractures.
- Stones: kidney stones causing pain.
- Moans: refers to fatigue and malaise.
- Thrones: polyuria, polydipsia, and constipation
- Psychic overtones: lethargy, confusion, depression, and memory loss.
(mnemonic courtesy of Sadiq et al, 2022)
What causes this, and how do we avoid it? Is it just dietary?
It’s mostly not dietary!
Overconsumption of calcium is certainly possible, but not common unless one has an extreme diet and/or over-supplementation. However…
Too much vitamin D
Again with “too much of a good thing”! While keeping good levels of vitamin D is, obviously, good, overdoing it (including commonly prescribed super-therapeutic doses of vitamin D) can lead to hypercalcemia.
This happens because vitamin D triggers calcium absorption into the gut, and acts as gatekeeper to the bloodstream.
Normally, the body only absorbs 10–20% of the calcium we consume, and that’s all well and good. But with overly high vitamin D levels, the other 80–90% can be waved on through, and that is very much Not Good™.
See for yourself:
- Hypercalcemia of Malignancy: An Update on Pathogenesis and Management
- Vitamin D-Mediated Hypercalcemia: Mechanisms, Diagnosis, and Treatment
How much is too much?
The United States’ Office of Dietary Supplements defines 4000 IU (100μg) as a high daily dose of vitamin D, and recommends 600 IU (15μg) as a daily dose, or 800 IU (20μg) if aged over 70.
See for yourself: Vitamin D Fact Sheet for Health Professionals ← there’s quite a bit of extra info there too
