Boning up on healthy options

Skeletal heath is nothing much to worry about, the odd broken bone, it takes care of itself. But when bones shatter after gentle impacts, something's wrong.

Every 30 seconds someone, somewhere in the EU suffers a fracture: one in three women over 50, one in eight men - the initial annual social cost is estimated at €2bn. And with an ageing population, that figure could double over the next 50 years unless preventative strategies are developed.

From birth, a flexible 30g skeleton toughens up to 1-1.5kg during its third decade. After a decade of stability, bone mass declines with age - loss in post-menopausal women can top 4% a year. The fracture threshold is reached when breaks result from minor trauma, such as a simple fall.

This tendency toward bone thinning is called osteoporosis (brittle bone disease) and levels are reaching epidemic proportions. Bone material is constantly turned over; tiny stress cracks from daily activity are repaired: osteoclasts remove damage, then osteoblasts reconstruct bone. An organic extra-cellular matrix, osteoid, (collagen/elastin fibres, plus glucosamine polymers) is laid down then impregnated with calcium and magnesium phosphates, creating bone. The matrix is activated principally by Vitamin K; and depends on other micro-nutrients for enzyme activity: vitamins C and B6, plus trace minerals zinc, copper and manganese.

Essential deposits: calcium

99% of the body's calcium comprises the teeth and bones, where it provides structural support, as a calcium phosphate compound, hydroxyapatite. Homeostasis maintains plasma calcium levels within narrow limits - and the bone reservoir is mobilised in response to falling levels, and vice versa.

Dairy products and green leafy vegetables are the richest readily available sources. Insoluble calcium carbonate, also a major component of antacids, is popularly consumed in supplements. Population studies reveal inadequate calcium intakes across all age groups and independent elderly and lactating women are most likely to benefit from supplements.

During growth spurts in childhood and puberty, high calcium intake is desirable to maximise the 'peak bone' mass, which extends the period up to the fracture threshold.

Firm evidence for this is debatable, as initial increases disappear when supplementation ceases. In contrast, weight-bearing exercise during childhood, and thereafter, significantly increases bone density. So keep active!

Oddly, osteoporosis is more prevalent in high-calcium European diets; whereas in communities in Africa whose food is low in calcium, prevalence is low. Put simply, we adapt to calcium intake.

High calcium intake from food or supplements is widely promoted to maintain bone health and prevent or treat osteoporosis. At best, calcium supplements slow bone loss in elderly women if dietary intake is low. When combined with vitamin D it may not prevent repeat fractures - but an earlier study suggests a similar combination reduces fracture risk in very elderly women. However, high calcium intake may compensate for diets deficient in vitamin D. The US RDA (recommended daily allowance) for over-50s is 1,200 mg/day - a level recommended by the UK's National Osteoporosis Society if osteoporosis is diagnosed.

As far as dietary risk factors are concerned, high salt consumption increases calcium loss; phosphoric acid in cola drinks has a similar counter-ion flushing effect; similarly if ingesting glucosamine, the hydrochloride is preferable to sulphate.

Magnesium

An important co-factor is magnesium, 60% of which is located in the bones. Most major metabolic processes have magnesium dependent enzymes. It is also required for hydroxylation of vitamin D: which suggests improved status might help prevent osteoporosis.

Good sources are leafy vegetables, whole grains and seafood. Supplements provide 100-500 mg/day, often with calcium and vitamin D. Nutritional intakes are frequently below the LRNI (lower reference nutrient intake), in up to 25% of the elderly.

Vitamin

D

Vitamin D is also an important co-factor that directly aids calcium absorption. Its primary function is to promote the synthesis of gut proteins essential for efficient calcium absorption.

Vitamin D3 (cholecalciferol) is activated by hydroxylation: in the liver then by the kidney, to become calcitriol. Calcitriol induces key proteins in the bone matrix and is required for bone development, mineralisation and remodelling. It also stimulates bone resorption by osteoclasts.

Acute deficiency leads to rickets in children or osteomalacia in adults - a disease prevalent 100 years ago in industrial towns in Northern Europe.

Vitamin K

Vitamin K plays a role in bone metabolism and insufficiency may be a factor in osteoporosis. Typically it activates the osteoclast protein, osteocalcin. This process is impaired in very elderly women: high concentrations of low activated osteocalcin correlate with low hip bone density and increased fracture risk.

Vitamin K1 (phylloquinone) is found in plants: leafy vegetables and some vegetable oils; food provides about 70 ?g/day; K2 is produced by intestinal bacteria and is essential for blood clotting.

Phyto-Oestrogens

Plant derived isoflavones, though not steroid hormones, are structurally similar to oestrogen, and bind at receptors, where they exert a small oestrogen-like effect. In post-menopausal women they boost overall oestrogenic activity. Derived from soy, the most active are diadzein and genistein (5mg/g soy flour). As an alternative to HRT they reduce post-menopausal mineral loss. In vitro genistein reduces bone resorption by osteoclasts and stimulates bone forming osteoblasts. South East Asian populations with high intakes of soy phyto-oestrogens have high bone mineral densities.

Ipriflavone is licensed for use as an osteoporosis medicine in Italy and Hungary. It prevents bone loss - slowing osteoclasts and increasing osteoblast growth. Overall it reduces bone resorption and enhances formation physiologically (600mg/day).

Formulation Options

An ideal anti-osteporosis supplement based on the observations above might include: 600mg calcium; 300mg magnesium; 8mg manganese; 2mg boron and copper; plus Vitamins K, D and B6 with, optionally, ipriflavone at 600-1200mg day.

When fortifying food and beverages, vitamins are added at minute levels - with minor impact on the formulation. But care is needed to meet processing knock-back and guarantee shelf-life nutritional claims.

Minerals are more robust, added at a level where their presence is felt. Even used sparingly, soluble (high pH) calcium minerals in food systems present developers with unexpected issues of complex formation, or even precipitation. The equivalent magnesium salt is usually more soluble, hence worse.

Insoluble minerals will come with manufacturers' evidence of 'bioavailability': absorption depends on gastric residence time for the acid to work, but this also depends on meal composition. Prebiotic inulin and oligofructose - such as Orafti's Beneo Synergy 1 - come with evidence of 20% improved calcium absorption in adolescents. Fermentation in the colon lowers pH, solubilising calcium, which aids uptake. The recommended amount is 8g per day, but it hydrolyses in low pH drinks and is not recommended for bread.

Marigot's Aquamin is a natural calcium source from seaweed that contains magnesium and other trace minerals including boron, copper, manganese and zinc, which help bone creation. It claims to provide better texture in gluten free bread.

Product development options are becoming more complex so single mineral suppliers face increasing competition from recent developments in soluble neutral minerals, such as Galam's NutraGal gluconate and lactate gluconates from Purac, Jungbunzlauer and Global Calcium.

Bulk addition increases along with cost, but benefits include improved taste, product stability and appearance, particularly at high inclusion levels.

While provision of a 'good source of calcium' is an on-pack claim consumers understand - skeletal health depends not merely on the presence of an essential nutrient, but on longer term investment in key combinations.

Paul Hart is general manager of ingredients consultancy Nutraceuticals. Contact him at: paul.m.hart@btopenworld.com