It's no secret that life in Hong Kong can be hectic. For a city where one in five employees work, on average, 11 hours a day, it's no wonder that at times we are left feeling tired and exhausted. But for the few that experience prolonged fatigue, it could be the warning signs of a deeper issue.
What’s causing my fatigue?
One of the main culprits of fatigue is a lack of iron in the body. Iron is necessary for the formation of haemoglobin, which carries oxygenated blood throughout your body. It's also necessary for several stages in converting glucose to energy in cells needed for metabolic functioning. Because the body is not able to circulate enough oxygen to your muscles and tissue, deficiency in iron will cause tiredness or fatigue and eventually lead to anaemia. Iron deficiency is also more common in adult women than in adult men (mostly attributed to menstruation).
The impact of iron deficiency
It’s not just adults — Iron deficiency is also of particular concern in children, for example:
- Children with Ferritin levels below 30 have been shown to correlate with attention deficit.1
- Several studies have shown that they also show poor cognitive development, particularly of verbal learning and memory.2
- Children with ADHD had lower levels of iron, which correlated with cognitive abnormalities.3
- Adolescent females with low iron levels have been shown to have cognitive impairment and lowered IQ.
Despite its small size, the brain accounts for 20% of the body's energy consumption, so it's rational to suggest that iron deficiency can cause cognitive impairment, especially in children whose brains can consume more energy as they grow. Fortunately, most of these impacts listed can be reversible and treatable by taking iron supplements.4
Testing for iron deficiency
You can test for iron stores in your body through a laboratory blood sample measuring Ferritin levels. At our local laboratory in Hong Kong, the Reference Range for Ferritin is set at 4.6 (4.6mcg/l) to 2014 for women5, and 21.8 to 274 for men. There is much debate surrounding the normal levels of Ferritin, but levels should be at least 30 (mcg/l) for optimal body function6, and we advise our athletes to maintain levels above 50 for maximum aerobic performance.
It’s not uncommon to see single-digit Ferritin levels in expatriate children living in Hong Kong. Having recently audited 40 consecutive Ferritin measurements in our expatriate paediatric patients, I found that the mean levels were 22 (range 5.3 to 61.5). By contrast, the mean Ferritin level was 37.9 in our Chinese paediatric patients (range 17.8 to 94). This may reflect the differences in cultural diets, as the western diet is not yet fully adopted by the Chinese population.
The historical shift in diets
So why are Ferritin levels so low today? It all comes down to dietary change and how we measure "normal" levels of iron. There is a body of evidence that indicates that what is considered normal iron levels in lab tests actually include iron deficient people. When we look at biological variables in populations, we can establish a set of "normal" values to measure against.
However, it's possible that the "normal" population does not fully represent a healthy population. Taking weight as an example, we see that in many western countries, what is considered “normal weight” is slightly overweight or obese. This isn't healthy as it can greatly increase risks for diseases like stroke, heart disease or cancer. The same can be said for measuring iron, iron deficiency could be "normal", but the reality is that it wouldn't be healthy.
Historically, iron deficiency hasn't always been problematic in humans. Ancestral diets were far more nutritious and had lower energy density. With the introduction of farming, the proportion of simple carbohydrates and fats in our diets have increased dramatically. Simple carbohydrates include rice, wheat, corn, potatoes, sugar and are all products of agriculture and wild animals. Studies show that:
- Between 1961 and 1985, consumption of fruit fell by a quarter and green vegetables by half.7
- In America, 17% of respondents ate no vegetables on the day of the survey.8
- 90% of UK females of childbearing age do not achieve the recommended daily intake of elemental iron (14.8 mg) from their diet.9
In contrast to today, where in Hong Kong the population is increasingly adopting the low micronutrient and high-energy density western diet. The modern diets contain high levels of phytate and phosphate acids that prevent the absorption of iron.
We are also seeing increasing numbers of patients with gut health problems that lead to poor absorption of essential nutrients like iron. For example, Irritable Bowel Syndrome, leaky gut and Gluten Intolerance can all impair iron absorption. In cases like this, the modern western diet is just not adequate.
How can I fight fatigue?
Iron is just one of several important trace elements including Zinc and Selenium. If you have a deficiency in one trace element, you are likely to have a deficiency in another (especially among children).
The main way to tackle fatigue would be through improving your lifestyle and diet, such as eating more nutritious foods and regular exercise. If you’re seeing a Functional Medicine practitioner, they will carefully assess all patients with fatigue, and children with developmental delay or behavioural problems for iron deficiency. Iron supplements can be advised as necessary.
So yes, if we look at the population data for a “normal” iron range, it can be normal to be fatigued, but it might not be healthy.
1. Archives of Pediatrics and Adolescent Medicine (2004;158:1113-5).
2. Oski et Al, Pediatrics, 1983, 171:877
3. Dillmann E, Johnson DG, Martin J, Mackler B, Finch CA. Catecholamine elevation in iron deficiency. Am J Physiol 1979; 237: 337-81R.
4. Bruner et Al, 1996, 344:821
5. To note: the lower limit for women levels of Ferritin has recently been adjusted downwards
6. Visual Textbook of Visual Medicine, Dr Igor Tabrizian
7. Ministry of Agriculture Fisheries and Food. Annual Reports of the National Food Survey Committee. HMSO, 1961 - 1990
8. Block G. Am J Clin Nutr 1991:53: 356S-357S
9. Ministry of Agriculture, Fisheries and Food. The dietary and nutritional survey of British adultsfurther analysis. London: HMSO, 1994:72-75.