Should you take supplements? A practical guide to calcium and vitamin D

Supplements are not automatically necessary. They are not automatically sufficient either. Whether you need them, which ones, and in what doses depends on your diet, your blood levels, your medication, and your individual circumstances. The goal of this article is to help you answer that question for yourself informed by evidence, not marketing.

Calcium supplements - do you need one?

The answer depends on how much calcium you are getting from food. As covered in Articles 1 and 2 of this section, the daily target for post-menopausal women is approximately 1,200mg from all sources combined.

Before reaching for a supplement, estimate your dietary intake:

• Two to three serves of dairy or fortified plant milk per day provides approximately 600–900mg

• A varied diet with calcium-rich vegetables, nuts, legumes, and fortified foods can add a further 200–400mg

• Background calcium from bread, cereals, and other foods contributes approximately 200–300mg

If your dietary calcium is already close to 1,000mg, you may need only a small supplement, or none at all. If you are significantly below target, a supplement of 500–600mg per day is a reasonable addition.

Which form of calcium supplement is best?

The two most common forms are:

• Calcium carbonate - the most widely available and least expensive. Contains the highest proportion of elemental calcium (40 percent). Best absorbed when taken with food, as stomach acid aids dissolution

• Calcium citrate - better absorbed than carbonate, particularly in women with reduced stomach acid (more common after age 60 or in women taking proton pump inhibitors). Can be taken with or without food. More expensive and requires more tablets for the same dose

For most women, calcium carbonate with meals is adequate and cost-effective. For women who take acid-reducing medications or who experience digestive discomfort with carbonate, citrate is the better choice.

Vitamin D supplements - do you need one?

Given how common vitamin D deficiency is, particularly in women over 50 with osteoporosis, supplementation is often appropriate. The only way to know your status is a blood test. If you have not had one, ask your doctor.

If supplementation is needed, vitamin D3 (cholecalciferol) is the preferred form. It is more effective at raising blood levels than vitamin D2. Doses of 800–2,000 IU per day are typically used for maintenance in women with osteoporosis, depending on baseline levels.

Magnesium

Magnesium is involved in the activation of vitamin D and in the formation of bone crystals. Deficiency is common, partly because modern diets are lower in magnesium-rich foods (wholegrains, nuts, seeds, legumes, leafy greens) than historical diets were.

The evidence for magnesium supplementation specifically improving bone density is less robust than for calcium and vitamin D. However, adequate intake is important, and supplementation may be beneficial in women with low dietary intake or confirmed deficiency.

A typical supplemental dose of 200–400mg per day is generally well tolerated. Higher doses can cause loose stools. If this occurs, reducing the dose usually resolves it.

Vitamin K2

Vitamin K2 plays a role in directing calcium into bone and away from soft tissue, including arteries. It activates a protein called osteocalcin, which is involved in incorporating calcium into the bone matrix. Low vitamin K2 intake has been associated with lower bone density in some studies.

The evidence for K2 supplementation improving bone density is emerging but not yet as strong as for calcium and vitamin D. However, it is generally considered safe, and some researchers consider it a useful addition to a bone health supplement regimen.

K2 is found naturally in fermented foods, particularly natto (fermented soybeans), some aged cheeses, and egg yolks. For women who do not eat these foods regularly, supplementation is one way to ensure adequate intake. The form MK-7 (menaquinone-7) is considered the most bioavailable supplemental form.

What about collagen supplements?

Collagen supplements have become popular in recent years, with claims that they support bone health. Bone is approximately 30 percent collagen by weight. It provides the flexible framework into which calcium crystals are deposited. Some studies have shown that collagen peptide supplementation modestly improves bone density markers over time.

The evidence is promising but not yet conclusive. Collagen supplements are generally safe, and if you choose to take one, a dose of 5–10g per day of hydrolysed collagen peptides is what most studies have used. It is unlikely to replace calcium and vitamin D as the foundation of supplementation but it may be a useful addition for some women.

A practical framework

Before buying any supplement, work through these questions:

• Have I estimated my dietary calcium intake? Do I know whether I am meeting my daily target from food?

• Have I had my vitamin D level tested? Do I know my actual status?

• Has my doctor recommended specific supplements as part of my treatment plan? Am I taking them consistently?

• Am I on any medications that interact with supplements, particularly warfarin with vitamin K, or bisphosphonates with calcium (take at least two hours apart)?