Impact of food on health

By Runtian Wu

Introduction

As the ageing of populations occurs in many nations worldwide, people are increasingly looking for health-oriented diets to avoid diseases and increase the life span.¹ Various health claims are circulating in the daily communications, such as the benefit of vegetarian, tea, restricted food intake, and organic food. Although many of these claims are partially substantiated by scientific literature, they should be treated cautiously. Nevertheless, there is growing evidence that certain kinds and amounts of diet have great potential of increasing human lifespan. This paper will examine popular health claims and recent research to present the possibilities that how food can impact human life expectancy and health conditions.

Low meat intake

Many vegetarians would argue the benefit of low meat intake. Although the benefits are not conclusive, current research showed that low meat intake correlates positively with longer life expectancy. A study² that involved 6000 vegetarians (never eat meat and fish) and 5000 nonvegetarians that have similar lifestyle, social class, and health conditions found that vegetarians have significantly lower total cholesterol (often involved in heart disease) concentrations. An 11-year follow-up of 1,904 vegetarians in Germany³ also showed that mortality from all causes (such as cardiovascular and cerebrovascular diseases) was cut in half compared with the general population. However, as many critics pointed out, the improved health conditions in vegetarians are likely to do with their lifestyles. According to the report from Fraser⁴, most vegetarians never smoke cigarettes, seldom drink alcohol, and do not have chronic diseases. A 6-year study based on data collected from 34,198 members of a church⁵ explicitly excluded participants that ever smoked, drank alcohol, or had coronaryartery disease, stroke, and cancer. The study showed that fatal ischemic heart disease was reduced by 37% in male vegetarians compared with nonvegetarians. A review in 2003⁶ also found that long-term vegetarians (no meat intake for 17 years) have higher life expectancy than short-term vegetarians (no meat intake < 17 years). It is worth attention that all the research mentioned here was conducted in affluent countries where meatless diets are rare⁶, so it is hard to conclude whether low meat intake in some underdeveloped countries where populations can hardly have meat diets will have the same positive effect.

Dietary restriction

Compared with lowering meat intake, perhaps a more “extreme” claim would be the dietary restriction. Dietary restriction restricts nutrient intake without causing malnutrition.⁷ There is evidence that such removal of food will trigger an increase in stress resistance and autophagy and a decrease in translation and ribosome biogenesis, thereby contributing to longevity.⁸ Dietary restriction in Caenorhabditis elegans (C. elegans) showed a remarkable extension of life as well as an increase in thermotolerance.⁷

The mechanism of how Dietary restriction increases lifespan remains unclear; however, growing evidence suggested that at least some mechanisms may be conserved across species. For example, under dietary restriction, a loss of function mutations in daf-2 increased the lifespan of C. elegans by 49% compared with those without the mutation.⁷ Gene mutation increases lifespan additively with dietary restriction is also seen in other species. A study in Ames dwarf mice showed that although dietary restriction increased the life span of both wild-type mice and mutants with the gene Prop1^df, the mutants live about 50% longer than the wild type.⁹ It’s still unclear whether dietary restriction will have a similar effect on the longevity of humans, and arbitrary dietary restriction may come with health hazards. For example, there are suggestions that the increase of lifespan under dietary restriction is correlated with the loss of fecundity¹⁰, and experiments in flies have demonstrated that a reduction in female reproduction can lead to life extension under dietary restriction.¹¹ However, a direct causal link is yet to be established,¹² and subsequent research has shown that dietary restriction can increase lifespan in both male flies and sterile female flies.^12,13

Food choice

Instead of generally restricting food intake, a more advisable way toward a healthy life is carefully selecting the food. Reviews based on past research found that mortality of all-cause can be decreased by increasing intake of whole grains, vegetables, fruits, nuts, and fish and reducing intake of red and processed meat.^14,15,16 Consumption of certain food groups such as nuts, fruit, vegetables, and legumes was found to reduce the mortality of cardiovascular diseases and cancer.^17.18 There is also a significant effect of food on lifespan. A 13-year study using data from 1548 counties in the United States showed that populations with healthy diets have around 20 years longer life expectancy than those without healthy diets.¹⁹ Five healthy foods (whole grains, fresh fruits & vegetables, nuts, dairy, seafood) and three unhealthy foods (refined grains, red & processed meats, sugar-sweetened beverages) were used to construct a diet score with 1 average point given to a county if the average expenditure on a healthy food of the county was above the average; otherwise, the county received a 0 point.¹⁶ The total diet scores were then compared with the life expectancy in the county.

Flavonoids, tea, and organic food

The health effects of food such as tea and fruit are further substantiated with the understanding of an important substance called flavonoids. Flavonoids are a group of important plant pigments that can display colours in flowers. They are present in all plant parts and can be in any food with natural flavours and colourings or made from plants (20). Humans and other animals cannot synthesise flavonoids. It has been found that flavonoids have considerable effects on human health with their antiallergic, anti-inflammatory, antiviral, antiproliferative, and anticarcinogenic activities.²¹ The protective role of flavonoids against heart disease may also be explained by the ability to prevent lipoproteins from oxidation to an atherogenic form.²⁰ Tea, which is rich in flavonoids, showed positive effects against cancer, diabetes, cardiovascular and neurological diseases²², although further investigation is needed.

The popularity of organic food is driven by the perception that organic food is healthier, has greater nutritional value and fewer toxic chemicals.²³ Although such claims lack substantial scientific support, there is growing evidence that organic food is different from non-organic food in many aspects. For example, a review in 2010 analysed the data collected by French Agency for Food Safety (AFSSA) and concluded that organic food contained more dry matters and minerals (Fe, Mg), antioxidants such as phenols and salicylic acid, less nitrite in 50% of organic products and 94-100% without pesticide residues.²⁴ An animal study²⁵ found that rats fed with organic food exhibit a greater level of stimulated lymphocyte proliferation, while another study in the Netherlands²⁶ found that chicken fed with organic food had lower body weights and a more active immune system. However, these studies are insufficient to prove the benefits of organic food. Apart from the ongoing debate on the impact of the nutritional content of food on the health²⁷, the content of organic food is also subject to multiple factors such as fertiliser, weather and earth conditions.^28,29,30

Conclusions

This paper reviewed the research on impact of food on health, particularly on life expectancy. Low-meat intake and dietary restriction both showed a positive effect on life expectancy, although the arbitrary practice of dietary restriction is not recommended. Food choice can significantly impact human health, but the exact effect of many types of food remains unclear. Increasing evidence has pointed to the role of flavonoids in supporting critical functions in the human body. The benefits of organic food remain controversial, although there is some evidence suggesting the increased nutritional content in organic food. Current research on the health claims is still ongoing, so the interpretations in this paper should be taken cautiously as they are subject to change as new evidence are discovered.

References:

1.         Nocella G, Kennedy O. Food health claims – What consumers understand. Food Policy. 2012 Oct 1;37(5):571–80.

2.         Key TJ, Thorogood M, Appleby PN, Burr ML. Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17 year follow up. BMJ. 1996 Sep 28;313(7060):775–9.

3.         Chang-Claude J, Frentzel-Beyme R, Eilber U. Mortality pattern of German vegetarians after 11 years of follow-up. Epidemiology. 1992 Sep;3(5):395–401.

4.         Fraser GE. Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. Am J Clin Nutr. 1999 Sep;70(3 Suppl):532S-538S.

5.         Beeson WL, Mills PK, Phillips RL, Andress M, Fraser GE. Chronic disease among Seventh-day Adventists, a low-risk group. Rationale, methodology, and description of the population. Cancer. 1989 Aug 1;64(3):570–81.

6.         Singh PN, Sabaté J, Fraser GE. Does low meat consumption increase life expectancy in humans? The American Journal of Clinical Nutrition. 2003 Sep 1;78(3):526S-532S.

7.         Kaeberlein TL, Smith ED, Tsuchiya M, Welton KL, Thomas JH, Fields S, et al. Lifespan extension in Caenorhabditis elegans by complete removal of food. Aging Cell. 2006;5(6):487–94.

8.         Masoro EJ. Overview of caloric restriction and ageing. Mech Ageing Dev. 2005 Sep;126(9):913–22.

9.         Bartke A, Wright JC, Mattison JA, Ingram DK, Miller RA, Roth GS. Extending the lifespan of long-lived mice. Nature. 2001 Nov;414(6862):412–412.

10.      Partridge L, Gems D, Withers DJ. Sex and death: what is the connection? Cell. 2005 Feb 25;120(4):461–72.

11.      Rauser CL, Tierney JJ, Gunion SM, Covarrubias GM, Mueller LD, Rose MR. Evolution of late-life fecundity in Drosophila melanogaster. Journal of Evolutionary Biology. 2006;19(1):289–301.

12.      Mair W, Goymer P, Pletcher SD, Partridge L. Demography of dietary restriction and death in Drosophila. Science. 2003 Sep 19;301(5640):1731–3.

13.      Magwere T, Chapman T, Partridge L. Sex differences in the effect of dietary restriction on life span and mortality rates in female and male drosophila melanogaster. The journals of gerontology Series A, Biological sciences and medical sciences. 2004 Feb 1;59:3–9.

14.      Schwingshackl L, Schwedhelm C, Hoffmann G, Lampousi A-M, Knüppel S, Iqbal K, et al. Food groups and risk of all-cause mortality: A systematic review and meta-analysis of prospective studies. American Journal of Clinical Nutrition. 2017;105(6):1462–73.

15.      Zheng Y, Li Y, Satija A, Pan A, Sotos-Prieto M, Rimm E, et al. Association of changes in red meat consumption with total and cause specific mortality among US women and men: two prospective cohort studies. BMJ. 2019 Jun 12;365:l2110.

16.      Li Q, Yuan S, Yu Z, Larsson SC, He Q. Association of food expenditure with life expectancy in the United States, 2001–2014. Nutrition. 2021 Nov 1;91–92:111310.

17.      Miller V, Mente A, Dehghan M, Rangarajan S, Zhang X, Swaminathan S, et al. Fruit, vegetable, and legume intake, and cardiovascular disease and deaths in 18 countries (PURE): a prospective cohort study. The Lancet. 2017 Nov 4;390(10107):2037–49.

18.      Aune D, Keum NN, Giovannucci E, Fadnes LT, Boffetta P, Greenwood DC, et al. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: A systematic review and dose-response meta-analysis of prospective studies. BMC Medicine. 2016;14(1).

19.      Dwyer-Lindgren L, Bertozzi-Villa A, Stubbs RW, Morozoff C, Mackenbach JP, van Lenthe FJ, et al. Inequalities in life expectancy among US counties, 1980 to 2014: temporal trends and key drivers. JAMA Internal Medicine. 2017 Jul 1;177(7):1003–11.

20.      YAO LH, JIANG YM, SHI J, TOMÁS-BARBERÁN FA, DATTA N, SINGANUSONG R, et al. Flavonoids in food and their health benefits. Plant Foods Hum Nutr. 2004 Jul 1;59(3):113–22.

21.      Ren W, Qiao Z, Wang H, Zhu L, Zhang L. Flavonoids: promising anticancer agents. Med Res Rev. 2003 Jul;23(4):519–34.

22.      Dou QP. Tea in health and disease. Nutrients. 2019 Apr 25;11(4):E929.

23.      Crinnion WJ. Organic foods contain higher levels of certain nutrients, lower levels of pesticides, and may provide health benefits for the consumer. Altern Med Rev. 2010 Apr;15(1):4–12.

24.      Lairon D. Nutritional quality and safety of organic food. A review. Agron Sustain Dev. 2010 Mar 1;30(1):33–41.

25.      Finamore A, Britti MS, Roselli M, Bellovino D, Gaetani S, Mengheri E. Novel approach for food safety evaluation. Results of a pilot experiment to evaluate organic and conventional foods. J Agric Food Chem. 2004 Dec 1;52(24):7425–31.

26.      Huber M, van de Vijver LPL, Parmentier H, Savelkoul H, Coulier L, Wopereis S, et al. Effects of organically and conventionally produced feed on biomarkers of health in a chicken model. Br J Nutr. 2010 Mar;103(5):663–76.

27.      Dangour AD, Lock K, Hayter A, Aikenhead A, Allen E, Uauy R. Nutrition-related health effects of organic foods: a systematic review. Am J Clin Nutr. 2010 Jul;92(1):203–10.

28.      Brandt K, Mølgaard JP. Organic agriculture: does it enhance or reduce the nutritional value of plant foods? Journal of the Science of Food and Agriculture. 2001;81(9):924–31.

29.      Chassy AW, Bui L, Renaud ENC, Van Horn M, Mitchell AE. Three-year comparison of the content of antioxidant microconstituents and several quality characteristics in organic and conventionally managed tomatoes and bell peppers. J Agric Food Chem. 2006 Oct 18;54(21):8244–52.

30.      Jørgensen H, Brandt K, Lauridsen C. Year rather than farming system influences protein utilization and energy value of vegetables when measured in a rat model. Nutr Res. 2008 Dec;28(12):866–78.