FOOD & DRINK
PHYTATES AND CEREALS Priya Tew Freelance Dietitian, running Dietitian UK, a dietetic and nutritional consultancy business
Priya runs Dietitian UK, a freelance dietetic service. She works with private patients, the media, brands, PR companies and is well known on social media.
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Wholegrains are something we often encourage people to eat more of, as they are considered highly nutritious and packed with fibre. Delving deeper, these cereal foods are also phytate-rich. Phytates are known to inhibit the absorption of some minerals, which begs the question how much of the nutrition in wholegrains does the body actually absorb. But there are ways to help increase absorption and to decrease the phytate content. Phytates (chemical name: inositol 6 phosphate) are mainly found in cereals and legumes, but also in seeds and nuts. They serve as the storage of phosphorus and minerals for the plant.1 Around 80% of phytate in cereals is found in the aleurone layers and the rest in the germ; the endosperm is almost phytate-free.1 Phytates form insoluble complexes with the minerals zinc, calcium, iron and magnesium. Thus, when they are present in a food, the full amount of these nutrients will not be absorbed. Phytate also negatively affects the absorption of lipids and protein because phytic acid inhibits enzymes that we need to digest our food, such as pepsin, amylases and trypsin, so it affects the absorption of lipids and protein.2 THE BENEFITS OF PHYTATES
Largely talked about due to their antinutrient, inhibitory effect on mineral absorption, phytates may have some health benefits. There is some research showing antioxidant and anticancer effects, specifically for prostrate, colon and breast cancers.1,3 Phytates can also prevent renal stone formation and some positive effects have been seen on blood glucose.1 Phytates may play a role in reducing the risk of heart disease through their effect on reducing blood cholesterol levels.3 Once phytate levels become too high in a food, these beneficial effects stop and the phytates work as anti-nutrients.3
The daily intake of phytate is estimated to be 0.3-2.6g/d in a Western diet, with a range of 504-844mg/d in the UK.1 It is obviously at the higher end in vegetarian diets. Vegetarians/vegans depend on many foods that are high in phytates for their iron and zinc, so the potential absorption issues that occur with phytates are especially of concern for them. There could also be a risk for infants who are weaned predominantly on cereals. After four months, infants have a reduced amount of minerals such iron in their body stores and breastmilk only provides low levels. If cereals are the main food intake it could potentially leave them deficient.2 CONTENT OF PHYTATES IN CEREALS
The amount of phytates in cereals varies due to differences in the variety of the cereal grown, the climate and environment, the stages of seed maturation and the method used to determine the phytate.3 DIGESTION OF PHYTATES
During digestion, phytase, found in plant foods, breaks down 37-66% of phytate to phytic acid in the stomach and small intestine.1 Phytic acid binds to minerals - iron, zinc and calcium - forming mineral complexes so the minerals cannot then be absorbed. Phytase can be inactivated by cooking and some processing methods, but even then some phytase is available in the gut from microbes in the large intestine and so is still able to degrade phytate.3 www.NHDmag.com May 2017 - Issue 124
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