The nutritional quality of gluten-free diets
Outline of issues associated with gluten free diets
Gluten-free diets have become increasingly popular over the past 5 years. With this, the quality and range of gluten-free (GF) products has also increased. What used to be the one, hidden, gluten-free option on the bottom shelf of the bread aisle, is now a wide range of healthy and nutrient-dense substitutes.
Traditionally, a gluten-free diet was most commonly adopted as a treatment for coeliac disease, a disease where the body’s reaction to gluten destroys the lining of the bowel, rendering it unable to absorb important nutrients. Eliminating gluten from the diet entirely reverses this damage and relieves people of their symptoms. In more recent times, people without coeliac disease have adopted GF diets, either due to a gluten intolerance or as a general lifestyle choice.
Coeliac disease (CD) or not, there are many people who report feeling healthier on a GF diet. However, it is important to be aware that a gluten-free diet can be associated with a higher risk of nutritional deficiencies.
The majority of the scientific studies in this area are based on people with coeliac disease rather than gluten intolerance. Most of the statistics and facts described in this article are taken from these studies. While there are some significant differences between the nutritional status of those with CD and those without, most of the results can be generalised to a gluten-free diet, regardless of the reason for the diet.
It is estimated that as many as 20-38% of patients with coeliac disease have some form of nutritional deficiency (1-4). Most commonly, this deficiency is detected at diagnosis, prior to treatment and is reversed with adherence to a GF diet. However, some deficiencies can remain.
Without a concerted effort to incorporate a wide range of nutrients into the diet, a GF diet is less likely to contain the essential fiber, vitamin and mineral requirements. This is because many gluten-free substitutes are lower in important vitamins and minerals than their gluten-rich counterparts, which may also be fortified (with folate for example).
The most common replacement for GF staples such as wheat, are called ‘pseudo-cereals’ - buckwheat, quinoa and amaranth. These pseudo-cereals are actually naturally much higher in vitamins and minerals than refined wheat, however the large majority of processed gluten-free products are higher in fat, sugar and salt than gluten-containing counterparts. The specific nutritional deficiencies associated with a GF diet are highlighted below.
Note about Coeliac disease:
At the time of diagnosis, nutritional deficiencies are very common in patients with coeliac disease. The malabsorption of iron, folate and calcium are common problems, potentially leading to anaemia and if left untreated, osteoporosis. Some patients with coeliac disease may also be lactose intolerant, leading to a decreased intake of calcium and phosphorous. Studies have shown that the deficiencies due to malabsorption resolve following adoption of a GF diet, and any subsequent deficiency is usually due to inadequate dietary intake.
Inadequate fiber intake is one of the most common nutritional deficiencies in a gluten-free diet (5). This is because grains are very rich in fiber and GF products are usually made with starches and refined flours. The process of refining the grains to produce the inner starch removes a large part of the outer shell which contains most of the fiber. It is well documented that adequate fiber intake is very important in the prevention of bowel cancer, diabetes and heart disease. Fiber-enriched food and pseudocereals such as quinoa, buckwheat and amaranth are all good sources of fiber that a GF diet can accommodate.
Typically, a GF diet tends to be slightly lower in protein than the average, gluten-containing diet but the good news is that the protein content of pseudo-cereals is higher than wheat and the quality of the protein is much better. The availability of the protein to the body is also significantly higher in pseudo-cereals than wheat. As long as people are making a deliberate effort to replace their gluten with pseudo-cereals and eating protein-rich food in other parts of their diet, they are at a low risk of protein deficiency.
With an improvement in the quality of GF substitutes, the fat content in many GF alternatives has reduced. Many years ago, a GF diet tended to be much higher in fat than a normal diet (6), putting people with CD at greater risk of heart problems and obesity. This is less likely to be the case in this current food climate where many GF alternatives may actually contain less fat than usual. However, it remains important to be aware of the risk of increased fat content of GF alternatives.
GF diets are associated with lower folate, vitamin C and vitamin B12 compared with a normal diet. This of course does not mean that a GF diet inevitably leads to these deficiencies. Rather, it shows that there is a tendency for us to get many of our vitamins from foods that contain gluten, which may seem counterintuitive, as we don’t commonly associate wheat and grains with vitamins. However, they too are an important source of vitamins.
Most significantly it seems, gluten-free substitutes are commonly lower in folate than their gluten-rich alternatives. The good news is that the pseudocereals; quinoa, buckwheat and amaranth are higher in folate than wheat. They are also a good source of riboflavin, vitamin C and E.
Eating at least 5 portions of fruit and vegetables a day is particularly important for people on a GF diet, as this is another good source of vitamins.
One study found that as many as 1 in 10 men and women on a GF-diet (for CD) had an inadequate intake of minerals (6), particularly magnesium and calcium, as well as zinc in men and iron in women. The majority of this is due to low levels of minerals in GF products. Again, higher quality GF products and pseudo-cereals are higher in minerals than wheat and are an effective way of increasing mineral intake. Meat and other iron-rich foods are an important source of iron for people on a GF diet.
Overall, gluten-free diets are becoming increasingly popular and the gluten-replacements such as quinoa, buckwheat and amaranth are healthy, nutrient-rich alternatives to wheat. However, it is important to be mindful that much of our fiber, vitamins and minerals come from wheat-based products that often GF alternatives may be lacking. As long as a deliberate effort is made to maintain adequate intake of nutrients from other sources, people can maintain very healthy, nutrient-rich gluten-free diets.
1. Kemppainen, T.; Uusitupa, M.; Janatuinen, E.; Järvinen, R.; Julkunen, R.; Pikkarainen, P. Intakes of nutrients and nutritional status in coeliac patients. Scand. J. Gastroenterol. 1995, 30, 575-579
2. Kinsey, L.; Burden, S.T.; Bannerman, E. A dietary survey to determine if patients with celiac disease are meeting current healthy eating quidelines and how their diet compares to that of British general population. Eur. J. Clin. Nutr. 2008, 62, 1333-1342
3. Bode S, Gudmand-Hoyer E. Symptoms and haemotological features in consecutive adult coeliac patients. Scand. J. Gastroenterol. 1996, 31, 54-60
4. Kemppainen T. Oat meal as a component of a gluten-free diet, nutrient intakes, nutritional status and osteopenia in coeliac patients; Kuopio University publications D, Medical Sciences: Kuopio, Finland, 1997; p. 188.
5. Saturni, Letizia, Gianna Ferretti, and Tiziana Bacchetti. "The Gluten-Free Diet: Safety And Nutritional Quality". Nutrients 2.1 (2010): 16-34. Web. 24 June 2016.
6. Vici, Giorgia et al. "Gluten Free Diet And Nutrient Deficiencies: A Review". Clinical Nutrition (2016): n. pag. Web. 24 June 2016.