Quick Dips

Watch that Food

Not everything in our food is good for us, but there are ways we can make things healthier. Lincoln University Masters student Sarah Noonan has been investigating oxalate compounds found in plants and the possible health effects these compounds produce.

Oxalates are chemicals which naturally occur in plants. Some people experience problems when they eat them because oxalates bind calcium and other minerals in the body. This can lead to mineral depletion and the formation of stones in the urinary tract. Noonan has been looking at ways in which these foods can be eaten while minimising any adverse effects.

"Oxalates are present in small amounts in a very wide range of plants, such as beets, sorrel, spinach, taro, tea and members of the buckwheat family", says Noonan, "but problems only occur when people eat very large amounts of foods containing oxalates, have very limited diets or have existing health problems."

They tend to occur in higher concentrations in the leafy parts of vegetables rather than in the roots or stalks. For most people, it is enough to cook foods or soak them in water before eating to leach out the oxalates. Soaking, however, can increase vitamin C losses.

In the UK, the mean daily intake of oxalates has been calculated to be 70-150mg, with most of this from tea. Rhubarb, spinach and beets are other common high-oxalate foods.

"Vegans and people who are lactose-intolerant should be aware that some foods contain high levels of oxalates," says Noonan. "Consuming greater amounts of vegetables will mean they have a high intake of oxalates, which may reduce the availability of calcium to the body."

Women, who as a group tend to be more susceptible than men to calcium deficiencies, would also be wise to eat dairy products which have no oxalates, or possibly dietary supplements, to satisfy their calcium intake, rather than vegetables.