Low carbohydrate diets: what are the potential short and long term health implications?

Low-carbohydrate diets for weight loss are receiving a lot of attention of late. Reasons for this interest include a plethora of low-carbohydrate diet books, the over-sensationalism of these diets in the media and by celebrities, and the promotion of these diets in fitness centres and health clubs. The re-emergence of low-carbohydrate diets into the spotlight has lead many people in the general public to question whether carbohydrates are inherently 'bad' and should be limited in the diet. Although low-carbohydrate diets were popular in the 1970s they have resurged again yet little scientific fact into the true nature of how these diets work or, more importantly, any potential for serious long-term health risks in adopting this dieting practice appear to have reached the mainstream literature. Evidence abounds that low-carbohydrate diets present no significant advantage over more traditional energy-restricted, nutritionally balanced diets both in terms of weight loss and weight maintenance. Studies examining the efficacy of using low-carbohydrate diets for long-term weight loss are few in number, however few positive benefits exist to promote the adoption of carbohydrate restriction as a realistic, and more importantly, safe means of dieting. While short-term carbohydrate restriction over a period of a week can result in a significant loss of weight (albeit mostly from water and glycogen stores), of serious concern is what potential exists for the following of this type of eating plan for longer periods of months to years. Complications such as heart arrhythmias, cardiac contractile function impairment, sudden death, osteoporosis, kidney damage, increased cancer risk, impairment of physical activity and lipid abnormalities can all be linked to long-term restriction of carbohydrates in the diet. The need to further explore and communicate the untoward side-effects of low-carbohydrate diets should be an important public health message from nutrition professionals.

Long-term effects of a reduced fat diet intervention on cardiovascular disease risk factors in individuals with glucose intolerance

The long-term effects on cardiovascular disease risk factors of a reduced fat (RF), ad libitum diet were compared with usual diet (control, CD) in glucose intolerance individuals.

Participants were 136 adults aged ≥40 years with ‘glucose intolerance’ (2 h blood glucose 7–11.0 mmol/l) detected at a Diabetes Survey who completed at 1 year intervention study of reduced fat, ad libitum diet versus usual diet. They were re-assessed at 2, 3 and 5 years. Main outcome measures were blood pressure, serum concentrations of total cholesterol, HDL and LDL cholesterol, total cholesterol:HDL ratio, triglycerides and body weight.

The reduced fat diet lowered total cholesterol (P<0.01), LDL cholesterol (P≤0.05), total cholesterol:HDL ratio (P≤0.05), body weight (P<0.01) and systolic blood pressure (P≤0.05) initially and diastolic blood pressure (P<0.01) long-term. No significant changes occurred in HDL cholesterol or triglycerides. In the more compliant 50% of the intervention group, systolic and diastolic blood pressure levels and body weight were lower at 1, 2 and 3 years (P<0.05).

It was concluded that a reduced fat ad libitum diet has short-term benefits for cholesterol, body weight and systolic blood pressure and long-term benefits for diastolic blood pressure without significantly effecting HDL cholesterol and triglycerides despite participants regaining their lost weight.

Omega 6 to omega 3 fatty acid imbalance early in life leads to persistant reductions in DHA levels in glycerophospholipids in rat hypothalamus even after long-term omega 3 fatty acid repletion

Failure to provide omega 3 fatty acids in the perinatal period results in alterations in nerve growth factor levels, dopamine production and  permanent elevations in blood pressure. The present study investigated whether changes in brain (i.e., hypothalamus) glycerophospholipid fatty acid profiles induced by a diet rich in omega 6 fatty acids and very low in alpha-linolenic acid (ALA) during pregnancy and the perinatal period could be reversed by subsequent feeding of a diet containing ALA. Female rats (6 per group) were mated and fed either a low ALA diet or a control diet containing ALA throughout pregnancy and until weaning of the pups at 3 weeks. At weaning, the pups (20 per group) remained on the diet of their mothers until 9 weeks, when half the pups were switched onto the other diet, thus generating four groups of animals. At 33 weeks, pups were killed, the hypothalamus dissected from the male rats and analysed for glycerophospholipid fatty acids. In the animals fed the diet with very little ALA and then re-fed the control diet containing high levels of ALA for 24 weeks, the DHA levels were still significantly less than the control values in PE, PS and PI fractions, by 9%, 18% and 34%, respectively. In this group, but not in the other dietary groups, ALA was detected in all glycerophospholipid classes at 0.2–1.7% of the total fatty acids. The results suggest that omega 6–3 PUFA imbalance early in life leads to irreversible changes in hypothalamic composition. The increased ALA and reduced DHA proportions in the animals re-fed ALA in later life are consistent with a dysfunction or down-regulation of the conversion of ALA to 18:4n-3 by the delta-6 desaturase.

A SPATIAL COMPARISON OF SHORT AND LONG TERM MIGRATION TRENDS IN CHINA

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Long-term risk factor control after a cardiac rehabilitation programme

This study examined the hypothesis that Phase II cardiac rehabilitation participants (CRP) had better long-term risk factor control, self-rated perception of health and return to work rates than non-participants (NP) between 18 and 36 months post myocardial infarction (MI). It was a comparative study in a 550 bed hospital.

Approximately half of both groups did not achieve a total cholesterol (TC) of 5.5mmol/L or less. Compared with NP, CRP were significantly more likely to have a TC<=6.5mmol/L (7% vs. 28%) (p=0.006). NP with TC>6.5mmol/L were significantly less likely to be on treatment (p=0.002). CRP were more likely to regularly exercise than NP (79% vs. 61%) (p=0.038). The success rate for blood pressure targets, return to work rates and self-rated perception of health were similar in both groups.

In conclusion, CRP had better long-term control of some risk factors than NP. The study provides comparative longer term patient outcomes after an Australian cardiac rehabilitation (CR) programme and forms the basis for further outcome measurement.

Making long-term economic growth more sustainable: evaluating the costs and benefits

Currently, traditional development issues such as economic stagnation, poverty, hunger, and illness as well as newer challenges like environmental degradation and globalisation demand attention. Sustainable development, including its economic, environmental and social elements, is a key goal of decisionmakers. Optimal economic growth has also been a crucial goal of both development theorists and practitioners. This paper examines the conditions under which optimal growth might be sustainable, by assessing the costs and benefits of growth. Key environmental and social aspects are considered. The Ecol-Opt-Growth-1 model analyses economic–ecological interactions, including resource depletion, pollution, irreversibility, other environmental effects, and uncertainty. It addresses some important issues, including savings, investment, technical progress, substitutability of productive factors, intergenerational efficiency, equity, and policies to make economic growth more sustainable—a basic element of the sustainomics framework. The empirical results support growing concerns that costs of growth may outweigh its benefits, resulting in unsustainability. Basically, in a wide range of circumstances, long term economic growth is unsustainable due to increasing environmental damage. Nevertheless, the model has many options that can be explored by policy makers, to make the development path more sustainable, as advocated by sustainomics. One example suggests that government supported abatement programs are needed to move towards sustainable development, since the model runs without abatement were infeasible. The optimal rate of abatement increases over time. Abatement of pollution is necessary to improve ecosystem viability and increase sustainability. Further research is necessary to seek conditions under which alternative economic growth paths are likely to become sustainable.

Evidence of high-skilled VET practitioners and high-performing VET organisations : findings from an evaluation of the long-term impacts of Framing the Future projects conducted in 1999-2000

Framing the Future is a major staff development initiative of the Australian National Training Authority (ANTA), designed to support the implementation of the National Training Framework (NTF). Since 1997 over 20,000 vocational education and training (VET) practitioners have participated in the program. The program was renamed Reframing the Future in 2001.

This study reports on research conducted on the long-term impacts of projects funded by Framing the Future in 1999 and 2000. John Mitchell and Sarah Wood from John Mitchell & Associates conducted the research from May 2000–May 2001.

Using twenty four case studies and the results of interviews and an extensive survey, the report provides evidence of high-skilled VET practitioners and high-performing VET organisations who ensure that their involvement in Framing the Future projects leads to long-term gains, particularly in support of the implementation of the NTF.

Nutrition surveys or surveillance : one-night stands or a long-term commitment?

Many disparate groups in Australia now concur about the need for continuous food and nutrition monitoring.